tomasi outlined
TRANSCRIPT
Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
CHAPTER 1 :Introduction to Electronic Communications
the transmission, reception and processing of information between two or more locations using electronic circuits electronic
communications
signals that are time-varying voltages or currents that are continuously changing, such as cosine and sine waves. It contains an infinite number of values
analog signals
signals that are voltages or currents that change in discrete steps or levels
digital signals
he invented the first workable telegraph Samuel Finley Breese Morse (1837)
it is used to transfer information in the form of dots, dashes and spaces between a simple transmitter and receiver using a transmission line consisting of a length of metallic wire
electromagnetic induction
they were the first to successfully transfer human conversation over a crude metallic-wire communication system using a device they called telephone
Alexander Graham BellThomas A. Watson
a logarithmic unit that can be used to measure ratios of virtually anything
decibel (dB)
a transmission-measuring unit used to express relative gains and losses of electronic devices and for describing relationships between signals and noise
decibel
another name for power loss attenuation a collection of one or more electronic devices or circuits that
converts the original source information to a form more suitable for transmission over a particular transmission medium transmitter
it provides a means of transporting signals between a transmitter and a receiver and can be as simple as a pair of copper wires
transmission medium or communications channel
any unwanted electrical signals that interfere with the information signal
system noise
a collection of electronic devices and circuits that accepts the transmitted signals from the transmission medium and then converts those signals back to their original form
receiver
higher-frequency analog signal carrier
the process of changing one or more properties of the analog carrier in proportion with the information signal
modulation
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
a system in which energy is transmitted and received in analog form, both the information and the carrier are analog signals
Analog communication system
it covers a broad range of communication techniques including digital and digital radio
Digital communication system
a true digital system where digital pulses are transferred between two or more points in communication system digital transmission
the transmittal of digitally modulated analog carriers between two or more points in communication system digital radio
the information signal is analog and the amplitude of the carrier is varied proportional to the information signal Amplitude modulation
(AM)
the frequency is varied proportional to the information signal Frequency modulation (FM)
a circuit performing modulation in a transmitter modulator
a carrier that has been acted on by an information signal modulated wave or modulated signal
the reverse process of modulation and converts the modulated carrier back to the original information demodulation
it is often used to refer to a specific band of frequencies allocated a particular service
channel
another name for information signal intelligence signal
the process of converting a frequency or band of frequencies to another location in the total frequency spectrum
frequency translation
it can propagate as a voltage or current along a metallic wire as emitted radio waves through free space or as light waves down an optical fiber
electromagnetic energy
simply the number of times a periodic motion such as sine wave of voltage or current occurs in a given period of time frequency
an international agency in control of allocating frequencies and services with the overall frequency spectrum
International Telecommunications Union (UTI)
signals in the 30-Hz to 300-Hz range and include ac power distribution signals (60Hz) and low frequency telemetry signals Extremely low
frequencies
signals in the 300-Hz to 3000-Hz range and include frequencies generally associated with human speech, standard telephone channels
Voice frequencies
signals in the 3-kHz to 30-kHz range which include the upper end of the human hearing range, specialized government and Very low frequencies
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
military system (submarine communications)
signals in the 30-kHz to 300-kHz range and used primarily for marine and aeronautical navigation Low frequencies
signals in the 300-kHz to 3-MHz range and are used primarily for commercial AM radio broadcasting (535 kHz to 1605 kHz) Medium frequency
signals in the 3-MHz to 30-MHz range and are used for two-way radio communications, Voice of America and Radio Free Europe broadcast, amateur radio and citizens band (CB) radio
High frequencies
signals in the 30-MHZ to 300-MHz and are used for mobile radio, marine, and aeronautical communications, commercial FM broadcasting (88 MHz to 108 MHz), and commercial television broadcasting of channels 2 to 13 (54 MHz to 216 MHz)
Very high frequencies
signals in the 300-MHz to 3-GHz range and are used by commercial television broadcasting of channels 14 to 83, land mobile communication services, cellular telephones, certain radar and navigation systems, and microwave and satellite radio systems
Ultrahigh frequencies
signal in the 3-GHz to 30-GHz range used for microwave and satellite radio communication system Superhigh frequencies
signals in the 30-GHz to 300-GHz range and seldom used for radio communication system
Extremely high frequencies
signal in the 0.3-THz to 300-THz range. It refers to electromagnetic radiation generally
associated with heat
Infrared
the length that one cycle of an electromagnetic wave occupies in space. It is inversely proportional to the frequency of the wave and directly proportional to the frequency of the wave and directly proportional to the velocity of propagation
wavelength
speed of light 3 x 108 m/s the two most significant limitations on the performance of a
communication system noise bandwidth
simply the difference between the highest and lowest frequencies in the information
bandwidth of an information signal
the difference between the highest and lowest frequencies that the channel will allow to pass through
bandwidth of a communication channel
a highly theoretical study of the efficient use of bandwidth to propagate information through electronic communications system
Information theory
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
a measure of how much information can be propagated through a communications system and is a function of bandwidth and transmission time
Information capacity
simply the number of bits transmitted during one second and is expressed in bit per second Bit rate
any undesirable electrical energy that falls within the passband signal
Electrical noise
implies a relationship between the signal and the noise. Exist only when a signal is present
correlated
noise present all the time whether there is signal or not uncorrelated
noise that is generated outside the device or circuit external noise
naturally occurring electrical disturbances that originate within Earth’s surface like lightning
Atmospheric noise
another name for atmospheric noise Static electricity
frequency of atmospheric noise 30 MHz
consists of electrical signal that originate from outside Earth’s atmosphere
Extraterrestrial noise
another name for extraterrestrial noise Deep-space noise
continuously distributed throughout the galaxies Cosmic noise
another name for cosmic noise Black-body noise
simply noise that is produced by mankind Man-made noise
another name for man-made noise Industrial noise
electrical interference generated within a device or circuit internal noise
caused by random arrival of carriers at the output element of an electronic device such as diode, field effect transistor or bipolar transistor
Shot noise
any modification to a stream of carriers as they pass from the input to the output of a device produces an irregular random variation
Transit-time noise
the rapid and random movement of electrons within a conductor due to thermal agitation
Thermal noise
another names for thermal noise: white noise Brownian noise Johnson noise
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
occurs when unwanted harmonics of a signal are produced through nonlinear amplification
Harmonic distortion
integer multiples of the original signal Harmonics
another name for harmonic distortion Amplitude distortion
the generation of unwanted sum and difference frequencies produced when two or more signals mix in a nonlinear device Intermodulation
distortion
characterized by high-amplitude peaks of short duration in the total noise spectrum
Impulse noise
a form of external noise meaning to disturb or detract from Interference
when information signals from one source produce frequencies that fall outside their allocated bandwidth and interfere with information signals from another source
Electrical interference
the ratio of the signal power level to the noise power level Signal-to-noise power ratio
CHAPTER 2: Signal Analysis and Mixing
the only two levels possible in a digital signal
binary signal
four-level signals quaternary digital signal
the voltage- or current-time variations that can be represented by a series of sine or cosine waves
Electrical signals
a waveform which repeats at a uniform rate Periodic
a description of a signal with respect to time Time domain
a time-domain instrument Oscilloscope
an amplitude-versus-time representation of the signal
Signal waveform
a description of a signal with respect to its frequency
Frequency-domain representation
a frequency-domain instrument Spectrum analyzer
any repetitive waveform that is comprised of more than one harmonically related sine or cosine wave
Sinusoidal wave
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
any periodic waveform that is not a sinusoid such as square waves, rectangular waves and triangular waves
Complex wave
a French physicist and mathematician who used a mathematical series to analyze a complex periodic wave
Baron Jean Fourier
a mathematical tool that allows us to move back and forth between time and frequency domains. It is used in signal analysis to represent the sinusoidal components of non-sinusoidal periodic waveforms
Fourier analysis
it describes the symmetry of a waveform in the time domain, that is, its relative position with respect to the horizontal (time) and vertical (amplitude) axes
Wave symmetry
a periodic voltage waveform in symmetric about vertical axis that have axes, or mirror, symmetry
Even symmetry
a periodic voltage waveform that said to have point, or skew, symmetry
Odd symmetry
a periodic voltage waveform such that the waveform for the first half-cycle repeats itself except with the opposite sign for the second half cycle
Half-wave symmetry
a waveform consists of all the frequencies contained in the waveform and their respective amplitudes plotted in the frequency domain
Frequency spectrum
range of frequencies contained in the spectrum the difference between the highest and lowest
frequencies contained in the information the difference between the highest and lowest
frequencies that the channel will allow to pass through
Bandwidth
the rate at which energy is dissipated, delivered, or used and is a function of the square of the voltage or current
Electrical power
a time-domain signal is sampled at discrete times Discrete Fourier transform
the computing time is proportional to n log 2n rather that n2
Fast Fourier series
it reduces the information capacity of the system Bandlimiting the process of combining two or more signals and is
an essential process in electronic communicationsMixing
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
two ways in which signals can be combined or mixed:
linearly nonlinearly
it occurs when two or more signals combine in a linear device, such as passive network or a small-signal amplifier
Linear summing (linear mixing)
occurs when two or more signals are combined in a nonlinear device such as a diode or large-signal amplifier
Nolinear mixing
undesired harmonics Harmonic distortion
desired harmonics Frequency multiplication
CHAPTER 3 : Oscillators, Phase-Locked Loops,and Frequency Synthesizers
to fluctuate between two states or conditions, to vibrate or to change
Oscillate
a device that produces oscillations Oscillator
an amplifier with a feedback loop (i.e., a path to propagate from the output back to input)
Feedback oscillators
four requirements for a feedback oscillator: amplification positive feedback frequency-
determining components
power source
an untuned oscillator RC phase shift oscillator that uses both positive and negative feedback
Wien-bridge oscillator
oscillator circuits that utilize tuned LC tank circuits for the frequency-determining components
LC oscillators
the ability of an oscillator to remain at a fixed frequency and is of primary importance in communication systems
Frequency stability
feedback oscillator circuits in which the LC tank circuit is replaced with a crystal for the frequency-determining component
Crystal oscillators
the study of the form, structure, properties, and classifications of crystals. It deals with lattices, bonding and the behavior of slices of crystal material that have been cut at various angles with respect to the crystal’s axes
Crystallography
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
it occurs when oscillating mechanical stresses applied across a crystal lattice structure generate electrical oscillations and vice versa
Piezoelectric effect
another name for mechanical vibrations Bulk Acoustic Waves (BAWs)
it is consist of a crystal-controlled oscillator and a voltage-variable component such as varactor diode
Crystal oscillator module
it is often used when describing varactor diode fabrication
Graded junction
CHAPTER 4 : Amplitude Modulation Transmission
the process of impressing low-frequency information signal onto a high-frequency
Modulation
the reverse process where the received signals are transformed back to their original form
Demodulation
the process of changing the amplitude of a relatively high frequency carrier signal in proportion with the instantaneous value of the modulating signal
Amplitude Modulation (AM)
frequencies that are high enough to be efficiently radiated by an antenna and propagated through free space
Radio frequency
the most commonly used amplitude modulation AM double side-band full carrier (AM DSBFC)
a term used to describe the amount of amplitude change present in an AM waveform
Coefficient of modulation
gives the percentage change in the amplitude of the output wave when the carrier is acted on by a modulating signal
Percent modulation
it use a unique arrangement of transistors and FETs to perform signal multiplication, which is a characteristic that makes them ideally suited for generating AM waveforms
Linear integrated-circuit function generators
typically a sensitive class A linear voltage amplifier with a high input impedance
Preamplifier
a low-gain, high-input impedance linear amplifier used to isolate the oscillator from the high-power amplifiers
Buffer amplifier
it is sometimes called upward or downward
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
modulation and has absolutely nothing to do with the frequency of the carrier. A form of amplitude distortion introduced when positive and negative alternations in the AM modulated signal are not equal
Carrier shift
are complex waveforms comprised of two or more frequencies
Nonsinusoidal signals
are complex waves made up of two or more harmonically related sine waves and include square, rectangular and triangular waves
Complex repetitive
a form of amplitude modulation where signals from two separate information sources modulate the same carrier frequency at the same time without interfering with each other
Quadrature amplitude modulation
CHAPTER 5 : Amplitude Modulation Reception
several parameters commonly used to evaluate the ability of a receiver to successfully demodulate a radio signal
selectivity bandwidth sensitivity dynamic range fidelity insertion loss noise temperature
a receiver parameter that is used to measure the ability of the receiver to accept a given band of frequencies and reject all others
Selectivity
the noise reduction ratio achieved by reducing the bandwidth
Bandwidth Improvement (BI)
the corresponding reduction in the noise figure to the reduction in bandwidth
Noise Figure Improvement
the minimum RF signal level that can be detected at the input to the receiver and still produce a usable demodulated information signal
Sensitivity
another name for receiver sensitivity Threshold
the difference in decibels between the minimum input level necessary to discern a signal and the input level that will overdrive the receiver and produce distortion
Dynamic range
the output power when the RF amplifier response is 1 dB less than the ideal linear-gain response
1-dB compression point
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
a measure of the ability of a communication system to produce at the output of the receiver, an exact replica of the original source information
Fidelity
three forms of distortion that can deteriorate the fidelity of a communication system:
amplitude frequency phase
the predominant cause of phase distortion Filtering
the total phase shift encountered by a signal and can generally be tolerated as long as all frequencies undergo the same amount of phase delay
Absolute phase shift
it occurs when different frequencies undergo different phase shifts and may have a detrimental effect on a complex waveform
Differential phase shift
it occurs when the amplitude-versus-frequency characteristics of a signal at the output of a receiver differ from those of the original information signal
Amplitude distortion
it occurs when frequencies are present in a received signal that were not present in the original source information
Frequency distortion
a parameter associated with the frequencies that fall within the passband of a filter and is generally defined as the ratio of the power transferred to a load with a filter in the circuit to the power transferred to a load without the filter
Insertion Loss (IL)
a hypothetical value that cannot be directly measured. An indication of the reduction in the signal-to-noise as a signal propagates through a receiver
Equivalent Noise Temperature (Te)
two basic types of radio receivers: coherent (synchronous) noncoherent (asynchronous)
a type of receiver wherein the frequency generated in the receiver and used for demodulation are synchronized to oscillator frequencies generated in the transmitter
Coherent
a type of receiver where either no frequencies are generated in the receiver or the frequencies used for demodulation are completely independent from the transmitter’s carrier frequency
Noncoherent
another name for noncoherent detection because the information is recovered from the received waveform by detecting the shape of the modulated
Envelope detection
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
envelope
one of the earliest types of AM receivers and probably the simplest designed radio receiver available
Tuned Radio-frequency (TRF)
it means to mix two frequencies together in a nonlinear device or to translate one frequency to another using nonlinear mixing
Heterodyne
five sections of the superheterodyne receiver:
RF section Mixer/converter section IF section Audio detector section Audio amplifier section
a broad-tuned bandpass filter with an adjustable center frequency that is tune to the desired carrier frequency. It reduce the noise bandwidth of the receiver
Preselector
it determines the sensitivity of the receiver RF amplifier
its purpose is to convert the IF signals back to the original source
Detector
the ability of the local oscillator in a receiver to oscillate either above or below the selected radio frequency carrier by an amount equal to the intermediate frequency throughout the entire radio frequency band
Tracking
the difference between the actual local oscillator frequency and the desired frequency
Tracking error
any frequency other than the selected radio frequency carrier that if allowed to enter a receiver and mix with the local oscillator will produce a cross-product frequency that is equal to the intermediate frequency
Image frequency
a numerical measure of the ability of a preselector to reject the image frequency
Image-frequency rejection ratio
it occurs when a receiver picks up the same station at two nearby points on the receiver tuning dial
Double spotting
its purpose is to down-convert the incoming radio frequencies to intermediate frequencies
Mixer / converter
the most common technique used for coupling IF amplifiers where the voltage that is applied to the primary windings of a transformer is transferred to the secondary windings
Inductive or transformer coupling
the ability of a coil to induce a voltage within its own windings
Self-inductance
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
the ability of one coil to induce a voltage in another coil
Mutual inductance
the ratio of the secondary flux to the primary flux Coefficient of coupling
the transfer of flux from the primary to the secondary windings
Flux linkage
a circuit that compensates for minor variations in the received signal level where it automatically increases the receiver gain weak RF input levels and automatically decreases the receiver gain when a strong RF signal is received
Automatic Gain Control (AGC)
when the receiver becomes less sensitive Automatic desensing
a circuit that has the purpose to quiet a receiver in the absence of a received signal. It keeps the audio section of the receiver turned off or muted in the absence of a received signal
Squelch circuit
used for removing sporadic, high amplitude noise transients of short duration such as impulse noise
Diode limiters or clippers
another circuit option commonly used for reducing the effects of high amplitude noise pulses where it detects the occurrence of a high-amplitude, short duration noise spike then mutes the receiver by shutting off a portion of the receiver for the duration of the pulse
Blanking circuit
the ratio of the demodulated signal level at the output of the receiver to the RF signal level at the input to the receiver
Net Receiver Gain
samples of receiver losses: preselector loss mixer loss detector loss
it includes all the gains and losses incurred by a signal as it propagates from the transmitter output stage to the output of the detector in the receiver and includes antenna gain and transmission line and propagation losses
System gain
the adjustment for the center frequency of the preselector and the adjustment for the local oscillator
Gang tuned
it offers higher gain and less noise than conventional cascaded amplifiers
Cascoded amplifier
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
CHAPTER 6 Single-Sideband Communications System
a form of amplitude modulation in which the carrier is transmitted at full power but only one of the sidebands is transmitted. It requires only half as much bandwidth as conventional double sideband AM
AM Single-sideband Full Carrier (SSBFC)
a form of amplitude modulation in which the carrier is totally suppressed and one of the sidebands removed and considerably less transmitted power
AM Single-sideband Suppressed Carrier (SSBSC)
a form of amplitude modulation in which one sideband is totally removed and the carrier voltage is reduced to approximately 10% of its unmodulated amplitude
AM Single Side-band Reduced Carrier (SSBRC)
a form of amplitude modulation in which a single carrier frequency is independently modulated by two different modulating signals
AM Independent Sideband (ISB)
a form of amplitude modulation in which the carrier and one complete sideband are transmitted but only part of the second sideband is transmitted
AM Vestigial Sideband (VSB)
the rms power developed at the crest of the modulation envelope when the modulating-signal frequency components are at their maximum amplitudes
Peak envelope power (PEP)
advantages of single-sideband transmission: power conservation bandwidth conservation selective fading noise reduction
disadvantages of single-sideband transmission: complex receivers tuning difficulties
a circuit that produces a double-sideband suppressed-carrier signal
Balanced Modulator
another name for balanced modulator Balanced Lattice Modulator
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
a small carrier component always present in the output signal
Carrier Leak
the typical amount of carrier suppression between 40 dB and 60 Db
three transmitter configurations used for single-sideband generation:
phase-shift method filter method third method
it is made from lead zirconate-titanate which exhibits the piezoelectric effect
Ceramic filters
a mechanically resonant transducer that when it receives electrical energy, it converts to mechanical vibrations and then converts the vibrations back to electrical energy at its output
Mechanical filter
four elements that comprise a mechanical filter: input transducer series of mechanical
resonant metal disks coupling rod output transducer
filters that use acoustic energy rather than electromechanical energy to provide excellent performance for precise bandpass filtering
Surface Acoustic Wave (SAW) filters
the basic SAW filter Bidirectional
it launches the acoustic wave in only one direction Unidirectional
a narrow band PLL that tracks the pilot carrier in the composite SSBRC receiver signal and uses the recovered carrier to regenerate coherent local oscillator frequencies in the synthesizer
Recovery circuit
a system that provide narrowband voice communications for land-mobile services with nearly the quality achieved with FM systems and do it using less than one-third the bandwidth
Amplitude-compandoring Single-sideband (ACSSB)
a device that performs compression and expansion Compandor(compressor-expander)
process of combining transmissions from more than one source and transmitting them over a common facility, like metallic or optical fiber cable or a radio-frequency channel
Multiplexing
an analog method of combining two or more analog sources that originally occupied the same frequency band in such a manner that the channels do not interfere with each other
Frequency-division Multiplexing (FDM)
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
a multiplexing method that uses double-sideband suppressed-carrier transmission to combine two information sources into a single composite waveform that is then transmitted over a common facility without the two channels interfering with each other
Quadrature Multiplexing (QM)
CHAPTER 7 Angle Modulation Transmission
it results whenever the phase angle modulation of a sinusoidal wave is varied with respect to time
Angle modulation
varying the frequency of a constant-amplitude carrier directly proportional to the amplitude of the modulating signal at a rate equal to the frequency of the modulating signal
Direct Frequency Modulation (FM)
varying the phase of a constant-amplitude carrier directly proportional to the amplitude of the modulating signal at a rate equal to the frequency of the modulating signal
Direct Phase Modulation (PM)
the relative angular displacement of the carrier phase in radians in respect to the reference phase
Phase deviation (Δθ)
the relative displacement of the carrier frequency in hertz in respect to its unmodulated value
Frequency deviation (Δf)
four terms with reference to angle-modulation
instantaneous phase deviation
instantaneous phase instantaneous
frequency deviation instantaneous
frequency
the instantaneous change in the phase of the carrier at a given instant of time and indicates how much the phase of the carrier is changing with respect to its reference phase
Instantaneous phase deviation
the precise phase of the carrier at a given instant of time
Instantaneous phase
the instantaneous change in the frequency of the carrier and is defined as the first time derivation of the instantaneous frequency deviation
Instantaneous frequency deviation
the precise frequency of the carrier at a given instant of time and is defined as the first derivative of the instantaneous phase
Instantaneous frequency
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
it can be defined as angle modulation in which the instantaneous phase deviation is proportional to the amplitude of the modulating signal voltage and the instantaneous frequency deviation is proportional to the slope or first derivative of the modulating signal
Phase modulation
an angle modulation in which the instantaneous frequency deviation is proportional to the amplitude of the modulating signal and the instantaneous phase deviations is proportional to the integral of the modulating signal voltage
Frequency modulation
the output-versus-input transfer functions for the modulators which give the relationship between what output parameter changes in respect to specified changes in the input signal
Deviation sensitivities
peak phase deviation Modulation index the change in frequency that occurs in the carrier
when it is acted on by a modulating-signal frequencyFrequency deviation
peak-to-peak frequency deviation Carrier swing
the ratio of the frequency deviation actually produced to the maximum frequency deviation allowed by law stated in percent form
Percent Modulation
a circuit in which the carrier is varied in such a way that its instantaneous phase is proportional to the modulating signal
Phase modulator
a single-frequency sinusoid
Unmodulated carrier (rest frequency)
a circuit in which the carrier is varied in such a way that its instantaneous phase is proportional to the integral of the modulating signal
Frequency modulator (frequency deviator)
differentiator followed by an FM modulator PM Modulator
FM demodulator followed by an integrator PM demodulator
integrator followed by a PM modulator FM modulator
PM demodulator followed by a differentiator FM demodulator
rule that approximates the bandwidth necessary to transmit an angle-modulated wave as twice the sum of the peak frequency deviation and the highest modulating-signal frequency, it defines a bandwidth that includes approximately 98% of the total power in the modulated wave
Carson’s rule
the worst-case modulation index and is equal to the maximum peak frequency deviation divided by the Deviation Ratio (DR)
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
maximum modulating-signal frequency
the interference produced when the highest side frequencies from one channel are allowed to spill over into adjacent channels
Adjacent Channel Interference
the noise voltage at the output of a PM demodulator is constant with frequency, whereas the noise voltage at the output of an FM demodulator increases linearly with frequency
Noise Triangle
a high-pass filter
Preemphasis Network
a low-pass filter Deemphasis Network
an angle modulation in which the frequency of the carrier is varied directly by the modulating signal
Direct FM
an angle modulation in which the frequency of the carrier is deviated indirectly by the modulating signal
Direct PM
a circuit that compares the frequency of the noncrystal carrier oscillator to a crystal reference oscillator and then produces a correction voltage proportional to the difference between two frequencies
Automatic Frequency Control (AFC)
a purpose to achieve near-crystal stability of the transmit carrier without using a crystal in the carrier oscillator
AFC loop
meaning cancel of the deviation thus removing the modulation from the FM wave
wipe off
transmitters that produce an output waveform in which the phase deviation is directly proportional to the modulating signal therefore the carrier oscillator can be a crystal because the oscillator itself is not a
modulator
Indirect FM transmitters
the low-pass filter that is simply 1/f filter
Predistorter (frequency correction network)
advantages of angle modulation:
noise immunity FM thresholding capture effect power utilization and
efficiency
it allows a receiver to differentiate between two signal received with the same frequency
Capture effect
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
CHAPTER 8 : Angle Modulation Reception and FM Stereo
it rejects the image frequency Preselector
it establishes the signal-to-noise ratio and noise figure RF amplifier
down-converts RF to IF Mixer/converter
it provides most of the gain and selectivity of the receiver
IF amplifiers
it removes the information from the modulated wave Detector
it is a frequency-dependent circuits designed to produce an output voltage that is proportional to the instantaneous frequency at its input
FM Demodulators
the most common circuits used for demodulating FM signal
slope detector Foster-Seeley
discriminator ratio detector PLL demodulator quadrature detector
it converts FM to AM and then demodulate the AM envelope with conventional peak detectors
tuned-circuit frequency discriminators
it is the simplest form of tuned-circuit frequency discriminators that has the most nonlinear voltage-versus-frequency characteristics
Single-ended slope detector
a simply two single-ended slope detectors connected in parallel and fed 180º out of phase
Balanced slope detector
a tuned-circuit frequency discriminator whose operation is very similar to that of the balanced slope detector
Foster-Seeley discriminator (phase shift discriminator)
it is relatively immune to amplitude variations in its input signal, it has a single tuned circuit in the transformer secondary
Ratio Detector
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
it requires no tuned circuits and automatically compensates for changes in the carrier frequency due to instability in the transmit oscillator
Phase-Locked Loop (PLL) FM Demodulator
it extracts the original information signal from the composite IF waveform by multiplying two quadrature (90º out of phase) signals
Quadrature FM Demodulator (coincidence detector)
the minimum dB difference in signal strength between two received signals necessary for the capture effect to suppress the weaker signal
Capture Ratio
the inherent ability of FM to diminish the effects of interfering signals
Capture Effect
it is used rather than a simple mechanical switch to reduce the static noise associated with contact bounce in a mechanical switches
Electronic push-to-talk (PTT)
CHAPTER 9: Digital Modulation
the transmission, reception, and processing of information with the use of electronic circuits
Electronic communications
the transmittal of digitally modulated analog signals (carriers) between two or more points in a communication system
Digital modulation
sometimes called for digital modulation because digitally modulated signals can be propagated through Earth’s atmosphere and used in wireless communications systems
Digital radio
a digitally modulated signal where in the information signal is digital and the amplitude of the carrier is varied proportional to the information signal
Amplitude Shift Keying (ASK)
if the frequency is varied proportional to the information signal
Frequency Shift Keying (FSK)
if the phase of the carrier is varied proportional to the information signal
Phase Shift Keying (PSK)
a highly theoretical study of the efficient use of bandwidth to propagate information through electronic communications systems
Information theory
a measure of how much information can be propagated through a communication system and is a function of bandwidth and transmission time
Information capacity
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
the most basic digital symbol used to represent information
Binary digit, bit
simply the number of bits transmitted during one second and is expressed in bits per second (bps)
Bit rate
he published a paper in the Bell System Technical Journal relating the information capacity of a communication channel to bandwidth and signal-to-noise ratio
Claude E. Shannon, 1948
a term derived from the word binary M-ary
a term that is often misunderstood and commonly confused with bit rate (bps). Like bit rate, is also a rate of change; however it refers to the rate of change of a signal on the transmission medium after encoding and modulation have occurred
Baud
another name for amplitude-shift keying Digital Amplitude Modulation (DAM)
a form of constant-amplitude angle modulation similar to standard frequency modulation except the modulating signal is a binary signal that varies between two discrete voltage levels rather than a continuously changing analog waveform
Frequency-Shift Keying(FSK)
the most common circuit used for demodulating binary FSK signals
Phase-locked Loop (PLL)
another form of angle-modulated, constant-amplitude digital modulation; an M-ary digital modulation scheme similar to conventional phase modulation except with PSK the input is a binary digital signal and there are a limited number of output phases possible
Phase-shift Keying (PSK)
simplest form of PSK; a form of square-wave modulation of a continuous wave signal
Binary Phase-shift Keying (BPSK)
other names for BPSK: phase reversal keying (PRK)
biphase modulation
it acts as a phase reversing switch in a BPSK transmitter
Balanced modulator
similar to a phasor diagram except that the entire phasor is not drawn, only the relative positions of the peaks of the phasors are shown
Constellation diagram, sometimes called signal state-space diagram
a balanced modulator wherein the output signal is the product of the two input signals
Product modulator
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
another form of angle-modulated constant-amplitude digital modulation. An M-ary encoding scheme where N = 2 and M = 4; four output phases are possible for a single carrier frequency
Quaternary Phase Shift Keying (QPSK), or Quadrature PSK
group of two bits Dibits
a modified form of QPSK where the waveforms on the I and Q channels are offset or shifted in phase from each other by one-half of a bit time
Offset QPSK (OQPSK)
a bit in QPSK transmitter that modulates a carrier that is in phase with the reference oscillator
I bit (hence the name “I” for “in phase” channel)
a bit in QPSK transmitter that modulates a carrier that is 90° out of phase or in quadrature with the reference carrier
Q bit (hence the name “Q” for “quadrature” channel)
three bits are encoded, forming bits, forming tribits and producing eight different output places; there are eight possible output phases
8-PSK
a code used to reduce the number of transmission errors
Gray code (maximum distance code)
a form of digital modulation similar to PSK except the digital information is contained in both the amplitude and the phase of the transmitted carrier; amplitude and phase-shift keying are combined; this reduce the likelihood or error occurring
Quadrature-amplitude Modulation (QAM)
less bandwidth is required to propagate a given bit rate
Bandwidth compression
often used to compare the performance of one digital modulation technique to another; the ratio of the transmission bit rate to the minimum bandwidth required for a particular modulation scheme
Bandwidth efficiency (information density or spectral efficiency)
the process of extracting a phase-coherent reference carrier from a receiver signal
Carrier recovery (phase referencing)
the binary data were encoded as a precise phase of the transmitted carrier
Absolute Phase Encoding
the function to determine the absolute phase of the received carrier necessary to produce a carrier at the receiver that is phase coherent with the transmit reference oscillator
Carrier Recovery Circuit
methods of carrier recovery squaring loop Costas loop remodulator
an alternative form of digital modulation where the binary input information is contained in the difference
Differential Phase-sift Keying (DPHK)
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
between two successive signaling elements rather than the absolute phase
combines encoding and modulation to reduce the probability of error, thus improving the bit error performance
Convolutional (tree) codes
the manner in which signal-state transitions are allowed to occur, and transitions that do not follow this pattern are interpreted in the receiver as transmission errors
Trellis Coding
an encoding technique used for over standard telephone circuits
Trellis Code Modulation (TCM)
the ratio of the average carrier power (the combined power of the carrier and its associated sidebands)
Carrier-to-noise Power Ratio
the energy of a single bit of information Energy per bit
the thermal noise power normalized to a 1-Hz bandwidth
Noise power density
used to compare two or more digital modulation systems that use different transmission rates (bit rates) modulation schemes
Energy per Bit-to-noise Power Density
simply the ratio of the energy of a single bit to the noise power present in 1 Hz of bandwidth
Energy per Bit-to-noise Power Density
optimum signaling format Antipodal signaling
the transmitter and receiver are not frequency or phase synchronized
Noncoherent FSK
local receiver reference signals are in frequency and
phase lock with the transmitted signalsCoherent FSK
CHAPTER 10: Digital Transmission
primary advantage of digital transmission Noise immunity
the processing of analog signals using digital methods and includes bandlimiting the signal with filters, amplitude equalization, and phase shifting
Digital Signal Processing (DSP)
one of the most important aspects of any communications system because it is costly and limited
Bandwidth
consists essentially of sampling analog information Pulse Modulation
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
signals and then converting those samples into discrete pulses and transporting the pulses from a source to a destination over a physical transmission medium
sometimes called pulse duration modulation (PDM) or pulse length modulation (PLM), as the width of a constant amplitude pulse is varied proportional to the amplitude of the analog signal at the time the signal is sampled
Pulse Width Modulation (PWM)
the position of a constant-width pulse within a prescribed time slot is varied according to the amplitude of the sample of the analog signal
Pulse Position Modulation (PPM)
the amplitude of a constant width, constant-position pulse is varied according to the amplitude of the sample of the analog
Pulse Amplitude Modulation (PAM)
the analog signal is sampled and then converted to a serial n-bit binary code for transmission; each code has the same number of bits and requires the same length of time transmission
Pulse Code Modulation (PCM)
he is credited with inventing PCM in 1937 while working for AT&T at its Paris laboratories
Alex H. Reeves
the function to periodically sample the continually changing analog input voltage and convert those samples to a series of constant-amplitude pulses that can more easily be converted to binary PCM code
Sampling circuit in a PCM transmitter
when tops of the sample pulses retain their natural shape during the sample interval making it difficult for an ADC to convert the sample to a PCM code
Natural Sampling
introduces less aperture distortion than natural sampling and requires a slower analog-to-digital converter
Flat-top sampling
the gradual discharge across the capacitor during conversion time caused by the capacitor discharging through its own leakage resistance and the input impedance of voltage follower
Droop
establishes the minimum sampling rate (fs) that can be used for a given PCM system
Nyquist sampling theorem
an impairment that occurs if minimum Nyquist sample rate is less than two times maximum analog input frequency
Alias or foldover distortion
the process of converting an infinite number of possibilities to a finite number of conditions
Quantization
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
type of code wherein the codes on the bottom half of the table are a mirror image of the codes on the top half, except for the sign bit
Folded binary code
the magnitude difference between adjacent steps Quantization interval or Quantum
it occurs if the magnitude of the sample exceeds the highest quantization interval
Overload distortion (peak limiting)
the magnitude of a quantum Resolution
any round-off errors in the transmitted signal are reproduced when the code is converted back to analog in the receiver
Quantization Error (Qe)
another name for quantization error Quantization Noise (Qn) the ratio of the largest possible magnitude to the
smallest possible magnitude that can be decoded by the digital-to-analog converter in the receiver
Dynamic Range (DR)
a numerical indication of how efficiently a PCM code is utilized; the ratio of the minimum number of bits required to achieve a certain dynamic range to the actual number of PCM bits used
Coding Efficiency
the magnitude change between any two successive code is the same
Linear codes
occurs when the input signal is at its minimum amplitude
Signal voltage-to-quantization noise voltage ratio (SQR)
during times when there is no analog input signal, the only input to the PAM sampler is random, thermal noise
Idle Channel Noise
the first quantization interval is made larger in amplitude than the rest of the steps
Midtread quantizing
the lowest-magnitude positive and negative codes have the same voltage range bas all the other codes
Midrise quantization
this type of coding compares the PAM signal to a ramp waveform while a binary counter is being advanced at a uniform rate; it requires a very fast clock
Level-at-a-time coding
this type of coding determines each digit of the PCM code sequentially; analogous to a balance where known reference weights are used to determine an unknown weight
Digit-at-a-time coding
flash encoders and are more complex; however they are more suitable for high-speed applications
Word-at-a-time coding
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
the process of compressing and then expanding Companding
amplified less than the lower-amplitude signals Compressed
amplified more than the lower-amplitude signals Expanded
it was implemented with diodes that were placed just after the low-pass filter in the PCM receiver
Analog expansion
it involves compression in the transmitter after the input sample has been converted to a linear PCM code and then expansion in the receiver prior to PCM decoding
Digital companding
a single integrated-circuit chip function to encode and decode
Codec
refers to the most of the more recently developed codecs as they include an antialising (bandpass filter), a sample-and-hold circuit, and an analog-to-digital converter in the transmit section and a digital-to-analog converter, a hold circuit, and a bandpass filter in the receive section
Combo chips
special voice encoders/decoders; are designed to reproduce only the short-term power spectrum, and the decoded time waveforms often only vaguely resemble the original input signal
Vocoders
three vocoding techniques: channel vocoder formant vocoder linear predictive coder
he developed the first channel vocoder Homer Dudley, 1928
the spectral power of most speech energy concentrates at three or four peak frequencies
Formants
a vocoder that compressed conventional speech waveforms into an analog signal with a total bandwidth of approximately 300 Hz
First channel vocoder
a vocoder that takes advantage of the fact that the short term spectral density of typical speech signals seldom distributes uniformly across the entire voice-band spectrum; it simply determines the location of
Format vocoders
a vocoder that extracts the most significant portions of speech information directly from the time waveform rather than from the frequency spectrum as with the channel and formant vocoders
Linear predictive coders
simply the data rate at which serial PCM bits are locked out of the PCM encoder onto the transmission line; it is dependent on the sample rate and the
Line speed
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
number of bits in the compressed PCM code
it uses a single-bit PCM code to achieve digital transmission of analog signals
Delta modulation
the slope of the analog signal greater than the delta modulator
Slope overload
when the original analog input signal has a relatively constant amplitude, the reconstructed signal has variation that were not present in the original signal
Granular noise
a delta modulation system where the step size of the DAC is varied, depending on the amplitude characteristic of the analog signal
Adaptive delta modulation
secondary lobes Ringing tails
an important consideration in the transmission of pulses over circuits with a limited bandwidth and a nonlinear phase response
Intersymbol interference (ISI)
it equalize the distortion for all frequencies, creating a uniform transmission medium and reducing transmission impairments
Equalizers
placed in a communication channel to bandlimit signals and reduce or eliminate predicted noise and interference; also used to produce specific pulse response
Filters
it resulted when the frequency characteristics of a communication channel depart from the normal or expected values; occurs when the peaks of pulses are reduced causing improper ringing frequencies in the time domain
Pulse distortion
simply the superposition of a series of harmonically related sine waves with specific amplitude and phase relationships
Pulse
it occurs if the relative phase relations of the individual sine waves are altered
Phase distortion
a convenient technique for determining the effects of the degradations introduced into the pulses as they travel to the regenerator
Eye pattern
CHAPTER 11 : Digital T- Carriers and Multiplexing
the transmission of information from one or ore source to one or more destination over the same transmission medium; the transmission medium may
Multiplexing
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
be a metallic wire pair, a coaxial cable, a PCS mobile telephone, a terrestrial microwave radio system, a satellite microwave system, or an optical fiber cable
a rather unsophisticated form of multiplexing that simply constitutes propagating signals from different sources on different cables that are contained within the same trench
Space-division multiplexing (SDM)
transmissions from multiple sources occur on the same facility but not at the same time; transmissions from various sources are interleaved in the time domain
Time division multiplexing
a communication system that uses digital pulse rather than analog signals to encode information
Digital carrier
stands for transmission one and specifies a digital carrier system using PCM-encoded analog signals
T1
occurs once per frame and is recovered in the receiver where it is used to maintain frame and sample synchronization between the TDM transmitter and receiver
Additional bit (framing bit)
consists of 24 193-bit frames totaling 4632 bits, of which 24 are bits
Extended superframe format
a digital interface that provides the physical connection to a digital carrier network
Data service unit/channel service unit (DSU/CSU)
can handle bit-rate conversions on both directions Multiplexers/demultiplexers (muldem)
provides a convenient place to make patchable interconnects and perform routine maintenance and troubleshooting
Digital cross-connect (DSX)
a low-quality video transmission for use between nondedicated subscribers
Picturephone
involves converting standard logic levels to a form more suitable to telephone line transmission
Digital line encoding
can be used to categorize the type of transmission Duty cycle
if the binary pulse is maintained for the entire bit time Nonreturn to zero (NRZ)
if the active time of the binary pulse is less than 100% of the bit time
Return to zero (RZ)
a condition when a long string of either logic 1s or 0s produces a condition in which a receive may lose its amplitude reference for optimum discrimination between received 1s and 0s
DC wandering
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
a popular type of line encoding that produces a strong timing component for clock recovery and does not cause dc wandering
Digital biphase (Manchester code or diphase)
used for encoding SMPTE (Society of Motion Picture and Television Engineers) time-code data for recording on videotapes
Biphase M
forms of delay-modulated codes where a logic 1 condition produces a transition in the middle of the clock pulse and a logic 0 produces no transition at the end of the clock intervals unless followed by another logic 0
Miller codes
used for the transmission of PCM-encoded time-division multiplexed digital signals
T carriers
filters and shapes the incoming digital signal and raises its power level so that the regenerator circuit can make a pulse-no pulse decision
Amplifier/equalizer
reproduces the clocking information from the received data and provides the proper timing information to0 the regenerator
Timing clock recovery
simply a threshold detector that compares the sampled voltage received to a reference level and determines whether the bit is a logic 1 or logic 0
Regenerative repeater
were designed to combine PCM and TDM techniques for short-haul transmission of 24 64-kbps channels with each channel capable of carrying digitally encoded voice-band telephone signals or data
T1 carrier systems
a technique used to ensure that sufficient transitions occur in the data to maintain clock synchronization
Binary eight zero substitution (B8ZS)
the same as added-digit framing except that digits are added in groups or words instead of as individual bits
Added-channel framing
2 methods of interleaving PCM transmissions: bit interleaving word interleaving
a large-scale integration chip designed for use in the telecommunications industry for private branch exchanges, central office switches, digital handsets, voice store-and-forward systems and digital echo suppressors
Codec
combined codec chips; provide the analog-to-digital and the digital-to-analog conversions and the transmit and receive filtering necessary to interface a
Combo chip
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
full-duplex (four wire) voice telephone circuit to the PCM highway of a TDM carrier system
multiple sources that originally occupied the same frequency spectrum are each converted to a different frequency band and transmitted simultaneously over a single transmission medium
Frequency-division multiplexing (FDM)
describes the modulating signal (intelligence) in a communications system
Baseband
a double side-band suppressed carrier modulator Balanced modulator
a void band of frequencies that is not included within any supergroup band
Guard bands
involves the transmission of multiple digital signal using several wavelengths without their interfering with one another
Wavelength division multiplexing (WDM)
separate signals with different wavelengths in a manner similar to the way filters separate electrical signals of different frequencies
Demultiplexers or splitters
direct signals of a particular wavelength to a specific destination while not separating while not separating all the wavelengths present on the cable
WDM routers
specific wavelengths are separated from the other optic signal by reflecting them at different angles
Diffraction gratings or prisms
a mirror with a surface that has been coated with a material that permits light of only one wavelength to pass through while reflecting all other wavelengths
Dichroic filter
CHAPTER 12: Metallic Cable Transmission Media
two general category of transmission media guided unguided
transmission media with some form of conductor that provides a conduit in which electromagnetic signals are contained
Guided transmission media
it transports signals using electric current Copper
a guided transmission medium and can be any Cable transmission medium
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
physical facility used to propagate electromagnetic signals between two locations in a communication system
include open wire, twin lead and twisted-pair copper wire as well as coaxial cable
Metallic transmission medium
the most common means of interconnecting devices in local area networks transmission of digital signals
Cable transmission medium
a metallic conductor system used to transfer energy from one point to another using electrical current flow; two or more electrical conductors separated by a nonconductive insulator (dielectric); can be as short as a few inches or span several thousand miles; can be used to propagate dc or low-frequency ac or to propagate very high frequencies
Transmission lines
the displacement (amplitude) is in the direction of propagation; surface wave of water
Longitudinal waves
the direction of propagation of displacement is perpendicular to the direction of propagation; electromagnetic
Transverse waves
propagation of electrical power along a transmission line occurs in the form of ______________________
Transverse electromagnetic (TEM) waves
the E and H fields are perpendicular to each other (at 90° angles) at all points
Space quadrature
electromagnetic waves that travel along a transmission line from the source to the load
Incident waves
those that travel from the load back toward the source
Reflected waves
it travel at approximately 1100 feet per second in the normal atmosphere
Sound waves
the rate at which the periodic wave repeats Frequency
the distance of one cycle occurring in space Wavelength
with two-wire balanced lines, both conductors carry current; however, one conductor carries the signal, and the other conductor is the return path
Differential or Balanced signal transmission
currents that flow in opposite directions in a balanced wire pair
Metallic circuit currents
currents that flow in the same direction Longitudinal currents
cancellation of common mode signals Common mode rejection
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
with an unbalanced transmission line, one wire is at ground potential, whereas the wire is at signal potential
Single-ended or Unbalanced signal transmission
a circuit device used to connect a balanced transmission line to an unbalanced load
Balun (balanced to unbalanced)
are comprised of two or more metallic conductors separated by a nonconductive insulating material called a dielectric
Parallel-wire transmission lines
two-wire parallel conductors; consist simply of two parallel wires, closely spaced and separated by air; its advantage is its simple construction; there is no shielding, radiation losses are high, and the cable is susceptible to picking up signals through mutual induction
Open-wire transmission lines
occurs when a signal on one cable interferes with a signal on an adjacent cable
Crosstalk
it is called if the sleeve is woven into a mesh Braid
it is given in dB of loss per 100 meters of cable with respect to frequency
Attenuation
given in dB of attenuation between the transmit signal and the signal is returned due to crosstalk with higher dB values indicating less crosstalk
Crosstalk
the name given to the area between the ceiling and the roof in a single building or between the ceiling and the floor of the next higher level in a multistory building
Plenum
plenum cables that coated with Teflon, which does not emit noxious chemicals when ignited, or special fire-resistant PVC
Plenum-grade PVC
a coaxial cable with one layer of foil insulation and one layer of braided shielding
Dual shielded
consist of two layers of foil insulation and two layers of braided metal shielding
Quad shielding
cables that are relatively expensive to manufacture and to minimize losses, the air insulator must be relatively free of moisture
Rigid-air filled coaxial
have lower losses than hollow cables and are easier to construct, install and maintain
Solid coaxial cables
sometimes referred to as “bayonet mount” as they can be easily twisted on or off
BNC connectors
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
are threaded and must be screwed on and off n-type connectors
the transmission characteristics of a transmission line Secondary constants
defined as the impedance seen looking into an infinitely long line or the impedance seen looking into a finite length of line that is terminated in a purely resistive load with a resistance equal to the characteristic impedance of the line
Characteristic impedance (surge impedance)
used to express the attenuation (signal loss) and the phase shift per unit length of a transmission line
Propagation constant (propagation coefficient)
defined simply as the ratio of the actual velocity of propagation of an electromagnetic wave through a given medium to the velocity of propagation through a vacuum (free space)
Velocity factor (velocity constant)
the relative dielectric constant of air 1.0006
transmission lines designed to intentionally introduce a time delay in the path of an electromagnetic wave
Delay lines
a phenomenon that when current flows through an isolated round wire, the magnetic flux associated with it is in the form of concentric circles surrounding the wire core
Skin effect
the ratio of the ac resistance to the dc resistance of a conductor
Resistance ratio
it caused a difference of potential between two conductors of metallic transmission line
Dielectric heating
the energy radiated if the separation between conductors in a metallic transmission is an appreciable fraction of a wavelength, the electrostatic and electromagnetic fields that surround the conductor cause the line to act as if it were an antenna and transfer energy to a nearby conductive material
Radiation loss
it occurs whenever a connection is made to or from a transmission line or when two sections of transmission line are connected together
Coupling loss
a luminous discharge that occurs between the two conductors of a transmission line when the difference of potential between them exceeds the breakdown voltage of the dielectric insulator
Corona
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
voltage that propagates from the source toward the load
Incident voltage
voltage that propagates from the load toward the source
Reflected voltage
a transmission line with no reflected power Flat or nonresonant line
defined as the ratio of the maximum voltage to the minimum voltage or the maximum current to the minimum current of a standing wave on a transmission lin
Standing Wave Ratio (SWR)
used to match transmission lines to purely resistive loads whose resistance is not equal to the characteristic impedance of the line
Quarter-wavelength
simply a piece of additional transmission line that is placed across the primary line as close to the load as possible; the susceptance is to tune out the susceptance of the load
Transmission-line stub
a technique that can be used to locate an impairment in a metallic cable
Time-domain reflectometry (TDR)
simply a flat conductor separated from a ground plane by an insulating dielectric material
Microstrip
simply a flat conductor sandwiched between two ground planes; less likely to radiate; losses are lower
Stripline
CHAPTER 13 : Optical Fiber transmission Media
the bandwidth of an analog communications system is expressed as a percentage of its carrier frequency
Bandwidth utilizations ratio
it was a device constructed from mirrors and selenium detectors that transmitted sound waves over a beam of light
Photophone
he successfully transmitted images through a single glass fiber
H. Lamm
they experimented with light transmission through A.C.S van Heel
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
bundles of fibers H.H. Hopkins N.S. Kapany
it was when the three scientists experimented on a bundle of glass fiber the transmission of light
1951
he coined the term fiber optics N.S. Kapany
they wrote a paper describing how it was possible to use stimulated emission for amplifying light waves as well as microwaves
Charles H. Townes Arthur L. Schawlow
defined as the maximum angle in which external light rays may strike the air/glass interface and still propagate down the fiber
Acceptance angle
other term used for acceptance angle Acceptance cone half-angle
closely related to acceptance angle and is figure of merit commonly used to measure the magnitude of the acceptance angle
Numerical aperture
the refractive index of a glass core 1.5
only one path for light rays to take down a cable Single mode
more than one path Multimode
the term that means path in fiber optics technology Mode
these parameters dictate how a light propagates mode or propagation index profile of fiber
the graphical representation of the magnitude of the refractive index across the fiber
Index profile
has a central core with a uniform refractive index Step-index fiber
no cladding and the refractive index of the core is nonuniform
Graded-index fiber
has a central core that is smaller in diameter that any of the multimode cables
Single-mode step-index fiber
type of fiber has a large light to fiber aperture and allows more external light to enter the cable
Multimode step-index optical fiber
the light rays that make up the pulse spread out in time, causing a corresponding reduction in the pulse amplitude and stretching of pulse width
Pulse spreading
other term used for pulse spreading Pulse-width dispersion
UPRZ is the acronym for _____ Unipolar return to zero
a condition wherein the energy from pulse a were UPNRZ transmission
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
to fall back one-half of a bit time, it would interfere with pulse b
UPNRZ is the acronym for _____ Unipolar nonreturn to zero
the light energy from pulse a were to fall back one bit time, it would interfere with pulse b and change what was a logic 0 to logic 1
UPRZ
the difference between the absolute delay times of the fastest and slowest rays of light propagating down a fiber of unit length
Pulse spreading constant
equal to the pulse spreading constant times the total fiber length
Total pulse spread
caused by imperfect physical connections Coupling losses
the other term used for gap displacement End separation
the typical value of loss for an angular displacement less than 2
Less 0.5 dB
these are the spectral widths of a standard LED 30 nm to 50 nm
the wavelength equivalent of bandwidth Linewidth
a pn junction diode usually made from a semiconductor material such as aluminum gallium arsenide or gallium arsenide phosphide
LED
a group iv atom used to produce light wavelengths in the 800 nm range
Arsenide
a small batterylike device that produced a dc output voltage proportional to the amount of light received
Photocell
a special high-intensity, single frequency light source. it produces a very narrow beam of brilliant light of a specific wavelength (color); it can penetrate atmospheric obstacles better than other type of light,
Laser
commonly used as a light source, this is a semiconductor device that puts out a low-intensity red light beam
LED
another commonly used light source, that generates an extremely intense single frequency light beam
Solid-state laser
light sensitive device, used to detect the light pulses; converts the light pulses to electrical signal
Photocell or light detector
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
CHAPTER 14: Electromagnetic Wave Propagation
a form of electromagnetic radiation that consist of traveling electric and magnetic fields
Radio waves
orientation of the electric field vector in respect to the surface of earth
Polarization
the polarization remains constant Linear polarization
a form of linear polarization when the electric field is propagating parallel to the Earth’s surface
Horizontal polarization
if the electric field is propagating perpendicular to the Earth’s surface
Vertical polarization
if the polarization vector rotates 360° as the wave moves one wavelength through the space and the field strength is equal at all angles of polarization
Circular polarization
when the field strength varies with changes in polarization
Elliptical polarization
shows a surface of constant phase of electromagnetic waves; formed when points of equal phase on rays propagated from the same source are joined together
Wavefront
a single location from which rays propagate equally in all directions
Point source
an invisible force field produced by a magnet, such as a conductor when current is flowing through it
Magnetic field
the rate at which energy passes through a given surface area in free space
Power density
also an invisible force fields produced by a difference in voltage potential between two conductors
Electric fields
a source that radiates power at a constant rate uniformly in all directions
Isotropic radiator
the power density is inversely proportional to the square of the distance from the source
Inverse square law
reduction in power density and occurs in free space as well as the Earth’s atmosphere
Attenuation
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
the reduction of power where in it contains particles that can absorb electromagnetic energy
Absorption loss
the reduction in power density due to nonfree-space propagation
Absorption
sometimes referred to as the bending of the radio-wave path
Refraction
the angle formed between the incident wave and the normal
Angle of incidence
the angle formed between the refracted wave and the normal
Angle of refraction
the ratio of the velocity of propagation of a light ray in free space to the velocity of propagation of a light ray in a given material
Refractive index
the ratio of the reflected to the incident voltage intensities
Reflection coefficient
a condition when an incident wavefront strikes an irregular surface, it randomly scattered in many directions
Diffuse reflection
reflection from a perfectly smooth surface Specular (mirrorlike) reflection
the fraction of power that penetrates medium two Absorption coefficient
states that a semirough surface will reflect as if it were a smooth surface whenever the cosine of the angle of incidence is greater than /8d, where d is the depth of the surface irregularity and is the wavelngth of the incident wave
Rayleigh criterion
defined as the modulation or redistribution of energy within a wavefront when it passes near the edge of an opaque object; the phenomenon that allows light or radio waves to propagate around corners
Diffraction
states that every point on a given spherical wavefront can be considered as a secondary point source of electromagnetic waves from which other secondary waves are radiated outward
Huygen’s principle
occurs whenever two or more waves simultaneously occupy the same point in space; states that the total voltage intensity at a given point in space is the sum of the individual wave sectors
Linear superposition
electromagnetic waves traveling within Earth’s atmosphere
Terrestrial waves
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
communications between two or more points on Earth
Terrestrial radio communications
direct and ground-reflected waves together Space waves
the cumulative sum of the direct, ground-reflected, and surface waves
Ground wave
depends on the presence of the ionized layers above the Earth that return some of the energy that otherwise would be lost in outer space
Sky wave
an earth-guided electromagnetic wave that travels over the surface of Earth;
Surface waves
travel essentially in a straight line between the transmit and received antennas
Direct waves
occurs when the density of the lower atmosphere is such that electromagnetic waves are trapped between it and Earth’s surface
Duct propagation
electromagnetic waves that are directed above the horizon
Sky waves
another term for sky wave propagation Ionospheric propagation
the lowest layer of the ionosphere and is located approximately between 30 miles and 60 miles above Earth’s surface
D layer
located approximately between 60 miles and 85 miles above the Earth’s surface; sometimes called Kennelly-Heavyside layer
E layer
made up of two layers F1 and F2 layers; during daytime, F1 layer is located between 85 miles and 155 miles above the earth’s surface; the F2 layer is located 85 miles to 185 miles above the Earth’s surface during winter and 155 miles to 220 miles in the summer
F layer
defined as the highest frequency that can be propagated directly upward and still be returned to earth by the ionosphere; depends on the ionization density and, therefore varies with the time of day and season
Critical frequency (fc)
the height above earth’s surface from which a refracted wave appears to have been reflected
Virtual height
the highest frequency that can be used for sky wave propagation between two specific points on Earth’s surface
Maximum usable frequency (MUF)
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
a law that assumes a flat Earth and a flat reflecting layer can never exist
Secant law
85% of the MUF that provides more reliable communications
Optimum working frequency (OWF)
defined as the minimum distance from a transmit antenna that a sky wave at a given frequency will be returned to Earth
Skip distance
usually of little significance, as it tends to be much weaker than the lower ray because it spreads over a much larger area than the lower ray
Pedersen ray
the area between where the surface waves are
completely dissipated and the point where the first sky wave returns to Earth
Quiet or skip zone
often defined as the loss incurred by an electromagnetic wave as it propagates in a straight line through a vacuum with no absorption or reflection of energy from nearby objects
Free-space path loss
it occurs simply because of the inverse square law Spreading loss
loss attributed to several different phenomena and can include both short- and long- term
Fading
an additional loss is added to the normal path loss to accommodate temporary fading
Fade margin
CHAPTER 15 : Antennas and Waveguide
the plane parallel to the mutually perpendicular lines of the electric and magnetic fields
Wavefront
the ratio of radiate to reflected energy Radiation efficiency
antenna wherein the conductors are spread out in a straight line to a total length of one-quarter wavelength
Quarter-wave antenna (vertical monopole sometimes called Marconi antenna)
a half wave dipole Hertz antenna
meaning two dipoles that is used to radiate more energy by simply spreading the conductors farther apart
Dipole
a basic antenna that cannot amplify a signal, at least not in the true sense of the word
Passive reciprocal device
a special coupling device that can be used to direct Diplexer
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
the transmit and receive signals and provide the necessary isolation
a polar diagram or graph representing field strength or power densities at various angular positions relative to an antenna
Radiation pattern
primary beam in a 90 direction Major lobe
represent undesired radiation or reception Minor lobe
the lobe that receives the most energy Front lobe
lobes adjacent to the front lobe (the 180 minor lobe)
Side lobes
lobes in a direction exactly opposite the front lobe Back lobe
ratio of the front lobe power to the back lobe power Front-to-back ratio
the ratio of the front lobe to a side lobe Front-to-side ratio
the line bisecting the major lobe, or pointing from the center of the antenna in the direction of maximum radiation
Line of shoot (point of shoot)
refers to the filed that is close to the antenna Near field
refers to the field pattern that is at great distance Far field
sometimes called to near field Induction field
sometimes called for far field because power that reaches the far field continues to radiate outward and is never returned to the antenna
Radiation field
an ac antenna resistance and is equal to the ratio of the power radiated by the antenna to the square of the current at its feedpoint
Radiation resistance
the ratio of the power radiated by an antenna to the sum of the power radiated and the power dissipated or the ratio of the power radiated by the antenna to the total input power
Antenna efficiency
the ratio of the power density radiated in a particular direction to the power density radiated to the same point by a reference antenna, assuming both antennas are radiating the same amount of power
Directive gain
the maximum directive gain Directivity
the same as directive gain except that the total power fed to the antenna is used; it is assumed that the given antenna and the reference antenna is lossless
Power gain
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
defined as an equivalent transmit power; the equivalent power that an isotropic antenna would have to radiate to achieve the same power density in the chosen direction at a given point as another antenna
Effective Isotropic Radiated Power (EIRP)
the power density in space and a somewhat misleading quantity
Captured power density
refers simply to the orientation of the electric field radiated from it.
Polarization of an antenna
simply the angular separation between the two half-power points on the major lobe of an antenna’s plane radiation pattern, usually taken in one of the “principal” planes
Beamwidth
vaguely defined as the frequency range over which antenna operation is “satisfactory”
Antenna bandwidth
normally taken as the difference between the half-power frequencies but sometimes refers to variations in the antenna’s input impedance
Bandwidth
the point on the antenna where the transmission line is connected
Feedpoint
the feedpoint presents an ac load to the transmission line
Antenna input impedance
an electrically short dipole Elementary doublet
a multiple of quarter-wavelength long and open circuited at the far end
Resonant antenna
a monopole antenna one-quarter wavelength long, mounted vertically with the lower end either connected to ground or grounded through the antenna coupling network
Marconi antenna
a wire structure placed below the antenna and erected above the ground; should be insulated from earth ground
Counterpoise
a technique wherein the physical length of an antenna remains unchanged although its effective electrical length is increased
Loading
a coil (inductor) added in series with a dipole antenna that effectively increases the antenna’s electrical length
Loading coil
a technique where in a metallic array that resembles a spoked wheel is placed on top of the antenna
Top loading
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
formed when two or more antenna elements are combined to form a single antenna
Antenna array
an individual radiator, such as a half- or quarter- wave dipole
Antenna element
elements that are directly connected to the transmission line and receive power from or are driven by source
Driven elements
not connected to the transmission line; they receive energy only through mutual induction with a driven element or another parasitic element
Parasitic element
a parasitic element that is longer than the driven element from which it receives energy; effectively reduces the signal strength in its direction and increases it in the opposite direction
Reflector
a parasitic element that is shorter than its associated driven element; increases field strength in its direction and reduces it in the opposite direction
Director
one of the simplest types of antenna rays; made by simply placing a several resonant dipoles of equal size in parallel with each other and in a straight line
Broadside array
essentially the same element configuration as the broadside array except that the transmission line is not crisscrossed between elements; as a result the field are additive in line with the plane of the array
End-fire array
a nonresonant antenna that is capable of operating satisfactorily over a relatively wide bandwidth making it ideally suited for HF transmission
Rhombic antenna
essentially a single antenna made up of two elements
Folded dipole
dipole elements larger in diameter; Fat dipole
antenna named after two Japanese scientists who invented it and describe its operation
Yagi-uda antenna
a linear array consisting of a dipole and two or more parasitic elements: one reflector and one or more directors
Yagi antenna
formed by placing two dipoles at right angles to each other 90° out of phase
Turnsile antenna
a class of frequency-independent antennas where in its primary advantage is the independence of their radiation and radiation pattern to frequency; from the initial work of V. H. Rumsey, J. D. Dyson,
Log-periodic antennas
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
R. H. DuHamel and D.E. Isbell
the ratio of the highest to the lowest frequency over which antenna will satisfactorily operate
Bandwidth ratio
simply a single-turn coil of wire that is significantly shorter than one wavelength and carries RF current
Loop antenna
a group of antenna or a group of antenna arrays that, when connected together function as a single antenna whose beamwidth and direction can be changed electronically without having to physically move any of the individual antennas or antenna elements within the array
Phased array antenna
a broadband VHF or UHF antenna that is ideally suited for applications for which radiating circular rather than horizontal or vertical polarized electromagnetic waves; used as a single element antenna or stacked horizontally or vertically in an array to modify its radiation pattern by increasing the gain and decreasing the beamwidth of the primary lobe
Helical antenna
electromagnetic radiation is in a direction at right angles to the axis of the helix
Normal mode
radiation is in the axial direction and produces a broadband, relatively directional pattern
Axial mode
defined as the ratio of its maximum gain in the forward direction to its maximum gain in its backward direction
Front-to-back ratio
used with point-to-point microwave systems Highly directional antennas
provide extremely high gain and directivity and are very popular for microwave radio and satellite communications skills
Parabolic reflector antennas
two main parts of parabolic antenna: parabolic reflector feed mechanism
resemble the shape of a plate or dish; a plane curve that is defined as the locus of a point that moves so that its distance from another point added to its distance from a straight line is of constant length
Parabolic reflectors (parabolic dish, dish antennas)
the ratio of the focal length to the diameter of the mouth of the parabola
Aperture ratio
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
the resulting curved surface dish Paraboloid
energy near the edge of the dish does not reflect but rather is diffracted around the edge of the dish
Spillover or leakage
considers both the radiation pattern of the primary radiator and the effect
Aperture efficiency
the ratio of the focal length of the antenna to the reflector diamtere
Aperture number
houses the primary antenna which radiates electromagnetic waves toward the reflector
Feed mechanism
three primary types of feed mechanism for parabolic antennas:
center feed horn feed cassegrain feed
the primary antenna is placed at the focus Center feed
the primary antenna is a small horn antenna rather than a simple dipole or dipole array
Horn feed
the primary radiating source is located in or just behind a small opening at the vertex of the paraboloid rather than at the focus
Cassegrein feed
consists of a cone that is truncated in a pice of circular waveguide; the waveguide in turn connects the antenna to either the transmitter or the receiver
Conical horn antenna
a hollow conductive tube, usually rectangular in cross section but sometimes circular or elliptical
Waveguides
the velocity at which a wave propagates; the velocity at which information signals of any kind are propagated; also the velocity at which energy is propagated; can be measured by determining the time it takes for a pulse to propagate a given length of a waveguide
Group velocity
velocity at which the wave changes phase; the apparent velocity of a particular phase of the wave; the velocity with which a wave changes phase in a direction parallel to a conducting surface; such as the walls of a waveguide
Phase velocity
minimum frequency of operation; the absolute limiting frequency; frequencies above the cutoff frequency will not be propagated by the waveguide
Cutoff frequency
maximum wavelength that they can propagate; defined as the smallest free-space wavelength that
Cutoff wavelength
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
is just unable to propagate in the waveguide
the travel of electromagnetic waves down a waveguide in different configurations
Propagation of modes
means that the electric field lines are everywhere transverse (perpendicular to the guide walls)
TE
waveguides used in radar and microwave applications when it is necessary or advantageous to propagate both vertically and horizontally polarized waves in the same waveguide
Circular waveguide
waveguide that is more expensive to manufacture than a standard rectangular waveguide; however it allows operation at lower frequencies for a given size
Ridged waveguide
consists of a spiral-wound ribbons of brass or copper; used extensively in microwave test equipment
Flexible waveguide
CHAPTER 16: Telephone Instruments and Signal
a part of global communications network which uses telephone or a data modem on a telephone network
Public telephone network (PTN)
PTN that interconnects subscribers through one or more switches
Public switch telephone network (PSTN)
the simplest and most straightforward form of telephone service which involves subscribers accessing the public telephone network through a pair of wires
Plain old telephone service (POTS)
simply an unshielded twisted-pair transmission line (cable pair) consisting of two insulated conductors twisted together; generally comprised of several lengths of copper wire interconnected at junction and cross-connect boxes located in manholes, back alleys, or telephone equipment rooms with large buildings and building complexes
Subscriber loop (local loop)
means to connect a telephone set at a subscriber’s location to the closest telephone office, which is commonly called an end office, local exchange office, or central office
Subscriber loop
enables the subscriber to access the public Electronic switching system
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
telephone network (ESS)
the quality of transmission over a telephone depends on:
received volume relative frequency
response of the telephone circuit
degree of interference
helps prevent the speaker from talking too loudly Sidetone/talkback
pair of wires connecting a subscriber to the closest telephone office
Local loop
one wire on the local loop Tip come from the ¼-inch-diameter two-conductor
phone plugs and patch cords used at telephone company switch-boards to interconnect and test circuits
Tip and Ring
standards for registered jacks and is sometimes called as RJ-XX; a series of telephone connection interfaces (receptacle and plug) that are registered with the U.S. FCC
RJ
the most common telephone jack in use today and can have up to six conductors
RJ-11
reasons why a dc voltage was used rather than an ac voltage
prevent power supply hum
allow service to continue in the event of a power outage
people were afraid of ac
voltage selected to minimize electrolytic corrosion on the loop wires; used for supervisory signaling and to provide talk battery for the microphone in the telephone set
-48 Vdc
examples of supervisory signals on-hook off-hook dial pulsing
placed directly across the tip and ring of the local loop; the purpose of the ringer is to alert the destination party of incoming calls
Ringer circuit
a simple single-throw, double pole (STDP) switch placed across the tip and ring; mechanically connected to the telephone is idle (on hook) is open; when the telephone is in use (off hook) is closed completing an electrical path through the microphone between the tip and ring of the local loop
On/off hook circuit (switch)
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
combinations of passive components that are used to regulate the amplitude and frequency response of the voice signals
Equalizer
the receiver for the telephone; converts electrical signals received from the local loop to acoustical signals (sound waves) that can be heard and understood by a human being; connected to the local loop through the hybrid network; typically enclosed in the handset of the telephone along with the microphone
Speaker
the transmitter for the telephone; converts acoustical signals in the form of sound pressure waves from the caller to electrical signals that are transmitted into the telephone network through the local subscriber loop
Microphone
a special balanced transformer used to convert a two-wire circuit (the local loop) into a four-wire circuit (the telephone set) and vice versa, thus enabling full duplex operation over a two-wire circuit
Hybrid network (hybrid coil or duplex coil)
enables the subscriber to output signals representing digits and this enables the caller to enter the destination telephone number; either an electronic dial-pulsing circuit or a Touch-Tone keypad which sends various combinations of tones representing the called digits
Dialing circuit
are acknowledgement and status signals that ensure the processes necessary to set up and terminate a telephone call are completed in an orderly and timely manner
Call progress tones and call progress signals
the exchange of signaling messages over local loops between stations (telephone) and telephone company switching machines
Station signaling
the exchange of signaling messages between switching machines
Interoffice signaling
indicate a request for service such as going off hook or ringing the destination telephone
Alerting signals
provide call status information, such as busy or ring-back signals
Supervising signals
provide information in the form of announcements such as number changed to another number, a number no longer in service
Controlling signals
provide the routing information such as calling and called numbers
Addressing signals
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
Call Progress Tone Summary
Tone or Signal
Frequency Duration/Range
Dial tone 350 Hz plus 440 Hz Continuous DTMF 697 Hz, 770 Hz, 852 Hz, 941
Hz, 1209 Hz, 1336 Hz, 1477 Hz, 1633 Hz
Two of eight tonesOn, 50-ms minimumOff, 45-ms minimum3-s minimum
MF 700 Hz, 900 Hz, 1100 Hz,1300 Hz, 1500 Hz, 1700 Hz
Two of six tonesOn, 90-ms minimum120-ms maximum
Dial pulses Open/closed switch On, 39 msOff, 61 ms
Station busy 480 Hz plus 620 Hz On, 0.5 sOff, 0.5 s
Equipment busy
480 Hz plus 620 Hz On, 0.2 sOff, 0.3 s
Ringing 20 Hz, 90 vrms (nominal) On, 2 sOff, 4 s
Ring-back 440 Hz plus 480 Hz On, 2 sOff, 4 s
Receiver on hook
Open loop Indefinite
Receiver off hook
Dc current 20 mA minimum80 mA maximum
Receiver-left-off- hook alert
1440 Hz, 2060 Hz, 2450 Hz, 2600 Hz
On, 0.1 sOff, 0.1 s
a 2600-Hz frequency tone placed on a circuit to indicate the circuit is not currently in use
IDLE signal
a multifrequency control tone comprised of 1100 Hz plus 1700 Hz ranging from 90 ms to 120 ms; used to indicate the beginning of a sequence of MF digits
Key Pulse (KP) signal
the method originally used to transfer digits from a telephone set to the local switch
Dial pulsing (rotary dial pulsing)
is sent from the switching machine back to the Station busy signal
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
calling station whenever the called telephone number is off hook; a two-tone signal comprised of 480Hz and 620 Hz
sent from the switching machine back to the calling station whenever the system cannot complete the call because of equipment unavailability
Equipment busy signal (congestion tone/no-circuits-available)
whenever the system is overloaded and more calls are being placed than can be completed
Blocking
sent from a central office to a subscriber whenever there is an incoming call; the purpose is to ring the bell in the telephone set to alert the subscriber that there is an incoming call
Ringing signal
sent back to the calling party at the same time the ringing signal is sent to the called party; the purpose is to give some assurance to the calling party that the destination telephone number has been accepted, processed, and is being rung
Ring-back signal
simply tones that operate cords attached to the handset; a full duplex, battery-operated , portable radio transceiver that communicates directly with a stationary transceiver located somewhere in the subscriber’s office
Cordless telephone
enables the destination of a telephone call to display the name and telephone number of the calling party before the telephone is answered; allows subscribers to screen incoming calls and decide whether they want to answer the telephone; a simplex transmission sent from the central office switch over the local loop to a caller ID display unit at the destination
Caller ID
simplex wireless communications system deigned to alert subscribers of awaiting messages; relay radio signals and messages from wire-line and cellular telephones to subscribers carrying portable receivers
Paging transmitters
CHAPTER 17 : The Telephone Circuit
the network bandwidth for a standard voice-band message channel
4 kHz
the only facility required by all voice-band circuits, as it is the means by which subscriber locations are
Local subscriber loop
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
connected to the local telephone company
a metallic transmission line comprised of two insulated copper wires (a pair) twisted together
Local loop
an actual loss of signal strength Attenuation
occurs when two or more frequencies undergo different amounts of phase shift
Phase distortions
depend on the wire diameter, conductor spacing, dielectric constant of the insulator separating the wires and the conductivity of the wire
Transmission characteristics
refers to the electrical characteristics of a cable uniformly distributed along its length
Distributed parameters
the largest cable used in a local loop, usually 3600 pair of copper wire placed underground or in conduit
Feeder cable (F1)
a cross-connect point used to distribute the larger feeder cable into smaller distribution cables
Serving area interface (SAI)
a smaller version of a feeder cable containing less wire pairs
Distribution cable (F2)
a device that serves as the demarcation point between local telephone company responsibility and subscriber responsibility for telephone service
Subscriber or standard network interface (SNI)
the final length of cable pair that terminates at the SNI
Drop wire
that portion of the local loop that is strung between poles
Aerial
the location where individual cable pairs within a distribution cable are separated and extended to the subscriber’s location on a drop wire
Distribution cable and drop-wire cross-connect point
an irregularity found in cables serving subscriber locations; unused sections of cable that are connected in shunt to a working cable pair
Bridge tap
the basic yardstick used for making power measurements in communications
Decibel, dB
defined as the optimum level of a test tone on a channel on a channel at some point in a communications system
Transmission level point (TLP)
the ratio in dB of the power of a signal at that point to the power the same signal would be at a 0-dBm transmission level point
Transmission level (TL)
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
a parameter used as a reference for data transmission
Data level point (DLP)
used primarily in Europe; assumes a perfect receiver; therefore, its weighting curve corresponds to the frequency response of the human ear only
Psophometric noise weighting
apply to dedicated private-line data circuits that utilize the private sector of the public telephone network – circuits with bandwidths comparable to those of standard voice-grade telephone channels that do not utilize the public switched telephone network
Transmission parameters
direct connections between two or more locations Private-line circuits
the difference in circuit gain of a reference frequency
Attenuation distortion (frequency response, differential gain and 1004-Hz deviation)
an indirect method of evaluating the phase delay characteristics of a circuit
Envelope delay distortion
the process used to improve a basic telephone channel; improves the high frequency response of a message channel and reduces power loss
Line conditioning
specifies the maximum limits for attenuation and envelope delay distortion; pertains to line impairments for which compensation can be made with filters and equalizers
C-type conditioning
telephone systems provided by local telephone companies dedicated to a single customer, usually with a large number of stations
Private switched networks
a relatively low-capacity switching machine where the subscribers are generally limited to stations within the same building or building complex
Private branch exchange (PBX)
the time delay encountered by a signal as it propagates from a source to a destination
Propagation time
delay measured in angular units, such as degrees or radians
Phase delay
the actual time required for a particular frequency to propagate from a source to a destination through a communications channel
Absolute phase delay
evaluate not the true phase-versus-frequency characteristics but rather the phase of a wave that is the result of a narrow band of frequencies
Envelope delay
the phase difference at the different carrier frequencies; indicates the relative delays of the various carrier frequencies with respect to the
Envelope delay distortion
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
reference frequency
neither reduces the noise on a circuit nor improves the signal-to-noise ratio; a requirement and does not add anything to the circuit and it cannot be used to improve a circuit; it simply places higher requirements on circuits used for high-speed data transmission
D-type conditioning
unwanted multiples of the transmitted frequencies Harmonic distortion
cross products [sums and differences] of the transmitted frequencies
Intermodulation distortion (fluctuation noise or cross-modulation noise)
the purpose is to simulate the combined signal power of a standard voice-band data transmission
1004-Hz test tone
determine the average weighted rms noise power C-message noise
differ from standard C-message noise measurements only in the fact that a holding tone is applied to the transmit end of the circuit while the noise measurement is taken
C-notched noise
ensures that the circuit operation simulates a loaded voice or data transmission
Holding current
a communications term that indicates the presence of a signal power comparable to the power of an actual message transmission
Loaded
characterized by high-amplitude peaks (impulses) of short duration having an approximately flat frequency spectrum; can saturate a message channel; the primary source of transmission errors in data circuits
Impulse noise
a sudden, random change in the gain of a circuit resulting in a temporary change in the signal level
Gain hit
a decrease in circuit gain of more than 12 dB lasting longer than 4 ms; characteristics of temporary open-circuit conditions and are generally caused by deep fades on radio facilities or by switching delays
Dropout
sudden, random changes in the phase of a signal; are classified as temporary variations in the phase of a signal lasting longer than 4 ms
Phase hits (slips)
a form of incidental phase modulation-a continuous, uncontrolled variation in the zero crossings of a signal; occurs at a 300 Hz rate or lower and its primary cause is low-frequency ac ripple in power supplies
Phase jitter
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
the presence of one or more continuous, unwanted tones within a message channel
Single-frequency interference
unwanted tones caused by crosstalk or cross modulation between adjacent channels in a transmission system due to system nonlinearities
Spurious tones
occurs in coherent SSBSC systems, such as those using frequency-division multiplexing when the received carrier is not reinserted with the exact phase relationship to the received signal as the transmit carrier possessed
Phase intercept distortion
used to match impedances and to provide isolation between the two directions of signal flow
Hybrid set
used to convert two-wire circuits to four-wire circuits similar to the hybrid coil found in standard telephone sets
Hybrid circuits
eliminate the echo electrically subtracting it from the original signal rather than disabling the amplifier in the return circuit
Echo cancellers
used to eliminate echo Echo suppressors
can be defined as any disturbance created in a communications channel by signals in other communications channels; a potential problem whenever two metallic conductors carrying different signals are located in close proximity to each other; was originally coined to indicate the presence of unwanted speech sounds in a telephone receiver caused by conversations on another telephone circuit
Crosstalk
crosstalk cause by inadequate control of the transfer characteristics or transmittance of networks
Transmittance crosstalk
electromagnetic coupling between two or more physically isolated transmission media;
Coupling crosstalk
crosstalk that occurs at the transmit end of a circuit and travels in the opposite direction as the signal in the disturbing channel
Near-end crosstalk (NEXT)
occurs at the far-end receiver and is energy that travels in the same direction as the signal in the disturbing channel
Far-end crosstalk (FEXT)
referenced to the level on the cable that is being interfered with
dBx for crosstalk
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CHAPTER 18 : The Public Telephone Network
identifies and connects the subscribers to a suitable transmission path
Switching functions
supply and interpret control and supervisory signals needed to perform the operation
Signaling functions
involves the actual transmission system of a subscriber’s messages and any necessary control signals
Transmission functions
referred to the leased lines designed and configured for their use only
Private-line circuits (dedicated lines)
equipment and facilities that are available to all the public subscribers to the network which includes transmission facilities and telephone switches
Common usage equipment
sometimes called to public telephone companies Service providers
simply the dedicated facility used to connect an instrument at a subscriber’s station to the closest telephone office
Local loop
similar to local loop except trunk circuits used to interconnect two telephone offices; a common usage connection; can be simple as a pair of copper wires twisted together or as sophisticated as an optical fiber cable
Trunk circuit
allows any telephone connected to it to be interconnected to any of the other telephones connected to the exchange without requiring separate cable pairs and telephones for each connection
Telephone exchange
the first telephone exchanges where manual interconnects were accomplished using patchcords and jacks
Switchboards
each telephone line that could have 10 or more subscribers connected to the central office exchange using the same loop
Party line
a programmable matrix that allows circuits to be connected to one another; interconnect input loop or trunk circuits to output loop or trunk circuits
Circuit switch
local exchanges centrally located within the area they serve; can directly interconnect any two
Central offices (CO)
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
subscribers whose local loops are connected to the same local exchange
a telephone call completed within a single local exchange
Intraoffice call (intraswitch call)
calls placed between two stations that are connected to different local exchanges
Interoffice calls
an exchange without any local loops connected to it Tandem office
called switcher’s switch Tandem switch
trunk circuits that terminate in tandem switches Tandem trunks (intermediate trunks)
was established to provide a telephone numbering system for the United States, Mexico, and Canada that would allow any subscriber in North America to direct dial virtually any other subscriber without the assistance of an operator
North American Telephone Numbering Plan (NANP)
allows many subscribers to share a limited number of lines to a central office switch
Concentrator
splits the two directions of signal propagation so that the actual long-distance segment of the route can be accomplished on a four-wire basis
Terminating set (hybrid)
allows a certain degree of route selection when establishing a telephone call
Switching hierarchy
simply a path between two subscribers and is comprised of one or more switches, two local loops, and possibly one or more trunk circuits
Route
an equipment busy signal received by the calling party if a call cannot be completed because the necessary trunks or circuits are not available
Blocking
a local exchange where subscriber loops terminated and received dial tone; end offices interconnected subscriber loop to other subscriber loops and subscriber loops to tandem trunks, interoffice trunks, and toll-connecting trunks
Class 5 end office
provided no operator assistance Class 3 primary center
provide service to geographical regions varying in size from part of a state to all of several states, depending on population density
Class 2 sectional center
the highest-ranking office in the DDD network in terms of the size of the geographical area serves
Class 1 regional center
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
and trunking options available
a global standard for telecommunications defined by the International Telecommunications Union (ITU) Telecommunications Sector (ITU-T); was developed as an alternate and much improved means of transporting signaling information through the public telephone network;
Common channel signaling no. 7 (SS7 or C7)
a telecommunications term that describes the legal boundaries for the responsibility of maintaining equipment and transmission lines; a demarcation point separating two companies
Point-of-presence
allows customers to change to a different service and still keep the same telephone number
Porting
store information about subscriber’s services, routing of special service numbers and calling card validation for fraud protection and provide information necessary for advanced call-processing capabilities
Databases
provides access from one level of the protocol to another level
Primitive
CHAPTER 19 : Cellular Telephone Companies
utilized frequency modulation and were generally assigned a single carrier frequency in the 35 MHz to 45 MHz range that was used by both the mobile unit and the base station
Mobile telephone systems (MTSs) (manual telephone system)
small handsets, easily carried by a person in their pocket or purse
Mobile telephone stations
suggested any radio transmitter, receiver, or transceiver that could be moved while in operation
Mobile
described a relatively small radio unit that was handheld, battery powered, and easily carried by a person moving at walking speed
Portable
similar to two-way mobile radio in that most communications occurs between base stations and mobile units; best describe by pointing out the primary difference between it and two-way mobile radio
Cellular telephone
push-to-talk PTT
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examples of two-way mobile radio citizen’s band (CB) public land mobile radio
Evolution of Cellular Telephone
July 28, 1945 : Saturday Evening Post, E. K. Jett, then the commissioner of the FCC hinted of a cellular
telephone scheme that he referred to as simply s small zone radio telephone system June 17, 1946 : in St. Louis Missouri, AT&T and Southwestern Bell introduced the first American
commercial mobile radio-telephone service to private customers. In the same year, similar services were offered to 25 major cities throughout the United States
early 1950s : the FCC doubled the number of mobile telephone channels by reducing the bandwidth to
60 kHz per channel1960 : AT&T introduced direct-dialing, full-duplex mobile telephone service with other
performance enhancements1966 : Don Adams, in a television show called Get Smart, unveiled the most famous mobile
telephone to date: the fully mobile shoe phone1968 : AT&T proposed the concept of cellular mobile system to the FCC with the intent of
alleviating the problem of spectrum congestions in the existing mobile telephone system1974 : the FCC allocated an additional 40-MHz bandwidth for cellular telephone service1975 : the FCC granted AT&T the first license to operate a development cellular telephone
service in Chicago1976 : the Bell Mobile Phone service for metropolitan New York City offered only 12 channels
that could serve a maximum of 543 subscribers. FCC granted authorization to the American Radio Telephone Service (ARTS) to install a second developmental system in the Baltimore- Washington, D.C., area
1983 : the FCC allocated 666 30 kHz half-duplex mobile telephone channels to AT&T to form the
first U.S. cellular telephone system called Advanced Mobile Phone System (AMPS)1991 : the first digital cellular services were introduced in several major U.S. cities, enabling a
more efficient utilization of the available bandwidth using voice compressionNovember 17, 1998 : a subsidiary of Motorola Corporation implemented Iridium, a satellite-based wireless
personal communications satellite system (PCSS)
the pattern that fits the cellular concept Honeycomb
defined by its physical size; its physical size varies depending on user density and calling patterns
Cell
the smallest cells used most often in high-density areas such as found in large cities and inside buildings; exhibit milder propagation impairments such as reflections and signal delays
Microcells
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
these is used in well-shielded areas or areas with high levels of interference
Picocells
normally used in center-excited cells (center of the cell)
Omnidirectional antennas
are used in edge- and corner- excited cells (three of the cell’s six vertices)
Sectored directional antennas
the process in which the same set of frequencies (channels) can be allocated to more than one cell, provided the cells are separated by sufficient distance
Frequency reuse
a geographic cellular radio coverage area containing three groups of cells
Clusters
when the area of a cell, or independent component coverage area of a cellular system is further divided, thus creating more cell areas; to increase the channel capacity and improve the availability and reliability of a cellular telephone network
Cell splitting
the point when a cell reaches maximum capacity occurs when the number of subscribers wishing to place a call at any given time equals the number of channels in the cell
Maximum traffic load
decreasing co-channel interference while increasing capacity by using directional antennas
Sectoring
placing two receive antennas; improves reception by effectively providing a larger target for signals radiated from mobile units
Space diversity
divides a group of channels into smaller groupings or segments of mutuality exclusive frequencies; cell sites, which are within the reuse distance, are assigned their own segment of the channel group; a means of avoiding co-channel interference, lowers the capacity of a cell by enabling reuse inside the reuse distance
Segmentation
means of avoiding full-cell splitting where the entire area would otherwise need to be segmented into smaller cells
Dualization
the locations of these radio-frequency transceivers; serves as central control for all users within that cell
Base stations
when mobile unit moves possibly from one company’s service area into another company’s service area
Roaming
the transfer of a mobile unit from one base Handoff (handover)
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station’s control to another base station’s control
a connection that is momentarily broken during the cell-to-cell transfer
Hard handoff
a flawless handoff; no perceivable interruption of service and normally takes approximately 200 ms which is imperceptible to voice telephone users although the delay may be disruptive when transmitting data
Soft handoff
a protocol aligns with a subprotocol of the SS7 protocol stack that facilitates communications among databases and other network entities; allow mobile units to roam and to perform handoffs of calls already in progress when a mobile unit moves from one cellular system into another without subscriber intervention
IS-41
the process where a mobile unit notifies a serving MTSO of its presence and location through a base station controller
Autonomous registration
operates under the direction o switching center (MTSO); manage each of the radio channels at each site, supervises calls, turns the radio transmitter and receiver on and off, injects data onto the control and voice channels and performs diagnostic tests
Cell-site controller
second part of the base station controllers Base transceiver station (BTS)
also a part of the base station subsystem; used with cellular telephone system voice channels can be either narrowband FM for analog system
Radio transceivers
generally used to connect switching centers to cell sites and to the public telephone network
Four-wire leased lines
governs the way telephone calls are established and is disconnected
Communications protocol
the actual voice channel where mobile users communicate directly with other mobile and wireline subscribers through a base station
User channel
is used for transferring control and diagnostic information between mobile users and a cellular telephone switch through a base station
Control channel
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CHAPTER 20 Cellular Telephone Systems
a standard cellular telephone service (CTS) initially placed into operation on October 13, 1983; the idea was to eliminate the possibility of a monopoly and provide the advantages that generally accompany a competitive environment
Advanced Mobile Telephone System (AMPS)
a transmission mode that simultaneously transmit in both directions
Duplexing
a 34-bit binary code comprised of a three-digit area code, a three-0digit prefix (exchange number), and a four-digit subscriber (extension) number
Mobile identification number (MIN)
a 32-bit binary code permanently assigned to each mobile unit
Electronic serial number (ESN)
indicates whether the terminal has access to all 832 AMPS channel ; specifies the maximum radiated power for the unit
Four-bit station class mark (SCM)
a 15-bit binary code issued by the FCC to an operating company when it issues it a license to provide AMPS cellular service to an area
System identifier (SID)
combination of cellular telephone networks and the Intelligent Network which is the entity of the SS7 interoffice protocol that distinguishes the physical components of the switching network
Personal Communications System (PCS)
a database that stores information about the user, including home subscription information and what supplementary services the user is subscribed to
Home location register (HLR)
a database that stores information about subscribers in a particular MTSO serving area
Visitor location register (VTR)
a database that stores information pertaining to the identification and type of equipment that exist in the mobile unit
Equipment identification registry (EIR)
allows all calls to pass through the network to the subscriber except for a minimal number of telephone numbers that can be blocked
Available mode
the PCS equivalent to caller ID; the name of the calling party appears on the mobile unit’s display, which allows PCS users to screen calls
Screen mode
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all calls except those specified by the subscriber are automatically forwarded to a forwarding destination without ringing the subscriber’s handset
Private mode
no calls are allowed to pass through to the subscriber
Unavailable mode
was originally intended to provide a short-term solution to the traffic congestion problem in the AMPS system
Narrowband AMPS (N-AMPS)
used by mobile units to request access to the cellular telephone system; a unidirectional channel specified for transmissions from mobile-to-base units only
RACH
used to transmit information from base stations to specific mobile stations;
SPACH
channels used to carry generic, system-related information; a unidirectional base station-to-mobile unit transmission shared by all mobile units
BCCH
an access method used with standard analog AMPS FDMA
was first used by the military to ensure reliable antijam and to secure communications in a battlefield environment; the fundamental concept is to break a message into fixed-size blocks of data with each block transmitted in sequence except on a different carrier frequency
Frequency-hopping spread spectrum
a high-bit rate pseudorandom code is added to a low-bit rate information signal to generate a high-bit-rate pseudorandom signal closely resembling noise that contains both the original data signal and the pseudorandom code
Direct-sequence spread spectrum
a second-generation cellular telephone system initially developed to solve the fragmentation problems inherent in first-generation cellular telephone system
Global System for Mobile Communications (GSM)
basic parameters of GSM GMSK modulation (Gaussian MSK)
50 MHz bandwidth FDMA/TDMA accessing eight 25-kHz channels
w/in each 200-kHz traffic channel
200 kHz traffic channel 992 full-duplex channels supplementary integrated
services digital network (ISDN) services
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a satellite-based wireless personal communications network designed to permit a wide range of mobile telephone services, including voice, data, networking, facsimile and paging
uses 66 satellites
Iridium
the unique key to the Iridium system and the primary differentiation between Iridium
Satellite cross-links
relay information to the terrestrial gateways and the system control segment located at the earth stations
Feeder links
CHAPTER 21: Introduction to Data Communications and Networking
are systems of interrelated computers and computer equipment and can be as simple as a personal computer connected to a printer or two personal computers connected together through the public telephone network
Data communications network
one of the earliest means of communicating electrically coded information when a proposal submitted to a Scottish magazine suggested running a communications line between villages comprised of 26 parallel wires
1753
Carl Friedrich gauss developed an unusual system based on a five by five matrix representing 25 letters
1833
the first successful data communications system was invented.
1832
the first practical data communications code. Morse code
Morse secured an American patent for the telegraph.
1840
the first telegraph line was established between Baltimore and Washington dc with the first message conveyed over this system.
1844
high speed printers were available 1860
Emile Baudot invented a telegraph multiplexer which allowed signals from up to six different telegraph machines to be transmitted simultaneously over a single wire.
1874
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the telephone was invented by Alexander graham bell
1875
Guglielmo Marconi succeeded in sending radio telegraph messages
1899
the first commercial radio stations carrying voice information were installed
1920
he demonstrated a computing machine sometime in the late 1930s
Konrad Zuis
the first special purpose computer using electromechanical relays for performing logical operations
1940
batch processing systems were replaced by on-line processing systems with terminals connected directly to the computer through serial or parallel communications lines.
1960s
the year introduced microprocessor controlled microcomputers.
1970s
personal computers became an essential item in the home and workplace.
1980s
ATM components routers and switches to connect carrier on global basis
backbone devices to connect all the lans within a large organization
switches and adapters which link desktop computers to high speed atm connection for running multimedia applications
ATM speeds 1.4 Gbps
a digital telecommunications technology that can simultaneously transmit voice and data over the same pair of telephone wires
ISDN
ISDN channels: B-channel (Bearer channel) D channel H channel
used to carry the digital information; build block of the ISDN; 64 kbps
B-channel
used to carry signaling and supervisory information to the network; kpbs (bri) or 64 kbps
D channel
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(pri)
provide for user information at higher bit rates; combination of several b channels
H channel
for business with larger data needs; American 23b + d(t1 = 1.544mbps); European 30b + d (e1= 2.048 mbps)
PRI
150 mbps; for future HDTV projects; h channels Broadband ISDN
CHAPTER 22: Fundamental Concepts of Data Communications
the first fixed-length character code developed for machines rather than for people; named after Emile Baudot, an early pioneer in telegraph printing; a fixed-length source code; all characters are represented in binary and have the same number of symbols (bits)
Baudot Code
the standard character set for source coding the alphanumeric character set that humans understand but computers do not; a seven-bit fixed length character set
United States of America Standard Code for Information Exchange (ASCII)
an eight-bit fixed-length character developed in 1962 by the International Business Machines Corporation (IBM); used almost exclusively with IBM mainframe computers and peripheral equipment
Extended Binary-Coded Decimal Interchange Code (EBCDIC)
are those omnipresent black-and-white striped
stickers that seem to appear on virtually every consumer item in the United States and most of the rest of the world; a series of vertical black bars separated by vertical white bars
Bar codes
has spaces or gaps between characters; each character within the bar code is independent of every other character
Discrete code
does not include spaces between characters Continuous code
stores data in two dimensions in contrast with a conventional linear bar code
2D code
uses an alphanumeric code similar to the ASCII code; consists of 36 unique codes representing the 10 digits and 26 uppercase letters
Code 39 (Code 3 of 9, 3 of 9 Code)
developed sometime in the early 1970s to identify the products of the grocery industry; found on
Universal Product Code (UPC)
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Electronics Systems and Technologies Engr. Jaime P. Licuanan, CCNA
virtually every grocery item from a candy bar to a can of beans
only one bit within a given data string is in error; affects only one character within a message
Single bit error
when two or more non-consecutive bits within a given data string are in error; can affect one or more characters within a message
Multiple bit error
the first fixed length character code developed for machines rather than people
Baudot code
a French postal engineer who developed the Baudot code
Thomas Murray
RTTY is the acronym for _____ Radio teletype
a fixed length source code Baudot code
the standard character set for source coding the alphanumeric character set that humans understand
ASCII
an eight bit fixed length character set developed in 1962 by IBM
EBCDIC
EBCDIC is the acronym for ___ Extended binary coded decimal interchange code
when two or more consecutive bits within a given data string re in error; can affect one or more characters within a message
Burst error
the process of monitoring data transmission and determining when errors have occurred; not to prevent errors from occurring but to prevent undetected errors from occurring
Error detection
duplicating each data unit for the purpose of detecting errors; an effective but rather costly means of detecting errors, especially with long messages
Redundancy
adding bits for the sole purpose of detecting errors Redundancy checking
probably the simplest error-detection scheme Vertical redundancy checking (VRC) (character parity, parity)
own error-detection bit Parity bit
the parity bit is always a 1; useful only when errors occur in a large number of bits
Marking parity
another relatively simple form of redundancy error Checksum
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checking where each character has a numerical value assigned to it; appended to the end of the message
a redundancy error detection scheme that use parity to determine if a transmission error has occurred with a message and is therefore sometimes called message parity
Longitudinal Redundancy Checking (LRC)
the bit sequence for the LRC Block check sequence (BCS) or Frame check sequence (FCS)
probably the most reliable redundancy checking technique for error detection; a convolutional scheme; approximately 99.999% of all transmission errors are detected
Cyclic redundancy checking (CRC)
include enough redundant information with each transmitted message to enable the receiver to determine when an error has occurred
Error-detecting codes
include sufficient extraneous information along with each message to enable the receiver to determine when an error has occurred and which bit is in error
Error-correcting codes
two primary methods used for error-correction: retransmission forward error correction
CHAPTER 23: Data-Link Protocols andData Communications Networks
the primary goal is to give users of a network the tools necessary for setting up the network and performing data flow control
Network architecture
arrangements between people or processes Protocols
a set of rules implementing and governing an orderly exchange of data between layer two devices such as line control units and front-end processors
Data-link protocol
all stations have equal access to the network, but when they have a message to transmit, they must contend with the other stations on the network for access to the transmission medium
Peer-to-peer network
determines which device is transmitting and which is receiving at any point in time
Line discipline
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coordinates the rate at which data are transported over a link and generally provides an acknowledgement mechanism that ensures that data are received at the destination
Flow control
a solicitation sent from the primary to a secondary to determine if the secondary has data to transmit
Poll
how the primary designates a secondary as a destination or recipient of data
Selection
the transmitting station sends one message frame and then waits for an acknowledgement before sending the next message frame
Stop-and-wait flow control
a source station can transmit several frames in succession before receiving an acknowledgement
Sliding window flow control
refers to imaginary receptacles at the source and destination stations with the capacity of holding several frames of data
Sliding window
interpret a frame of data as a group of successive bits combined into predefined patterns of fixed length usually eight bits
Character-oriented protocols
a discipline for serial-by-bit information transfer over a data communications channel
Bit-oriented protocol
are relatively simple, character-oriented generally used on two-point networks using asynchronous data and asynchronous modems
Asynchronous data-link protocols
remote stations can have more than one PC or printer
Synchronous data-link protocols
group of computers, printers, and other digital devices
Cluster
a synchronous character-oriented data-link protocol developed by IBM; sometimes called bisync or bisynchronous communications
Binary synchronous communications (BSC)
a synchronous bit-oriented protocol developed in the 1970s by the IBM for use in system network architecture environment
Synchronous data-link control (SLDC)
an information field is not allowed; cannot be used to transfer numbered information
Supervisory frame
causes all previously set functions to be cleared by the secondary
Clear
causes the secondary to turn on or turn off Beacon test
causes the addressed secondary station to place Monitor mode
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itself into the monitor mode
causes a secondary station to loop its transmission directly to its receiver input
Wrap
make a receiver transparent to all data located Transparency
a switched data communications network similar to the public telephone network except it is designed for transferring data only
Public switched data network (PDN or PSDN)
involves dividing data messages into small bundles of information and transmitting them through communications networks to their intended destinations using computer-controlled switches
Packet switching
logically equivalent to a two-point dedicated private-line circuit except slower
Permanent virtual circuit (PVC)
users send small packets of data into the network Datagram (DG)
the integrating of a wide range of services into a single multipurpose network; a network that proposes to interconnect an unlimited number of independent users through a common communication network
Integrated service digital network (ISDN)
provides the most economical and effective means of handling local data communication needs
Local area network (LAN)
the time it takes a signal to travel from a source to a destination
Propagation delay
CHAPTER 24: Microwave Radio Communications and System Gain
described as electromagnetic waves with frequencies that range from approximately 500 MHz to 300 GHz or more
Microwave
systems are those used to carry information for relatively long distances
Long-haul microwave systems
propagate signals through Earth’s atmosphere between transmitters and receivers often located on top of towers spaced about 15 miles to 30 miles apart
Microwave radios
the composite signal that modulates the FM carrier Baseband
a preemphasis network precedes the FM deviator; Microwave transmitter
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provides an artificial boost in amplitude to the higher baseband frequencies
a receiver and a transmitter placed back to back or in tandem with the system
Microwave repeaters
another name for local oscillator and is considerably lower in frequency than either the received or the transmitted radio frequencies
Shift oscillator
the reduction in signal strength Radio fade
it suggests that there is more than one transmission path or method of transmission available between a transmitter and a receiver; used to increase the reliability of the system by increasing its availability
Diversity
simply modulating two different RF carrier frequencies with the same IF intelligence, then transmitting both RF signals to a given destination
Frequency diversity
the output of a transmitter is fed to two or more antennas that are physically separated by an appreciable number of wavelengths
Space diversity
a single RF carrier is propagated with two different electromagnetic polarizations
Polarization diversity
using more than one receiver for a single radio-frequency channel
Receiver diversity
it combines frequency, space, polarization and receiver diversity into one system
Quad diversity
somewhat specialized form of diversity that consists of a standard frequency-diversity path where the two transmitter/receiver pairs at one end of the path are separated from each other and connected to different antennas that are vertically separated as in space diversity
Hybrid diversity
provide protection for a much larger section of the communications system that generally includes several repeaters spanning a distance of 100 miles or more
Protection switching arrangement
two types of protection switching arrangement: hot standby diversity
each working radio channel has a dedicated backup or spare channel
Hot standby protection
a single backup channel is made available to as many as 11 working channels
Diversity protection
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points in the system where baseband signals either originate or terminate
Terminals
points in a system where baseband signals may be reconfigured or where RF carriers are simply repeated or amplified
Repeater stations
a balanced modulator that when used in conjunction with a microwave generator, power amplifier, and bandpass filter, up-converts the IF carrier to an RF carrier and amplifies the RF to the desired output power
Transmit modulator (transmod)
a unidirectional device often made from a ferrite material; used in conjunction with a channel-combining network to prevent the output of one transmitter from interfering with the output of another transmitter
Isolator
this occurs when three stations are placed in a geographical straight line in the system
Multihop interference
preventing the power that leaks out the back and sides of a transmit antenna from interfering with the signal entering the input of a nearby receive antenna
Ring around
the line-of-sight path directly between the transmit and receive antennas
Free-space path
the portion of the transmit signal that is reflected off Earth’s surface and captured by the receive antenna
Ground-reflected wave
consists of the electric and magnetic fields associated with the currents induced in Earth’s surface
Surface wave
the portion of the transmit signal that is returned back to Earth’s surface by the ionized layers of Earth’s atmosphere
Sky wave
often defined as the loss incurred by an electromagnetic wave as it propagates in a straight line through a vacuum with no absorption or reflection of energy from a nearby objects
Free-space path loss
a phenomena where in no electromagnetic is actually lost or dissipated – it merely spreads out as it propagates away from the source resulting in lower relative power densities
Spreading loss
the reduction in receive signal level; reduction in signal strength at the input to a receiver; it applies
Fading
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to propagation variables in the physical radio path that affect changes in the path loss between transmit and receive antennas
the difference between the nominal output power of a transmitter and the minimum input power to a receiver necessary to achieve satisfactory performance; must be greater than or equal to the sum of all gains and losses incurred by a signal as it propagates from a transmitter to a receiver
System gain
essentially a fudge factor included in system gain equations that considers the nonideal and less predictable characteristics of radiowave propagation, such as multipath propagation and terrain sensitivity; these characteristics cause temporary, abnormal atmospheric conditions
Fade margin (link margin)
the minimum wideband carrier power at the input to a receiver that will provide a usable baseband output
Receiver threshold (receiver sensitivity)
simply a ratio of input signal-to-noise ratio to output signal-to-noise ratio
Noise factor
indicates how much the signal-to-noise ratio deteriorates as a waveform propagates from the input of a circuit
Noise figure
CHAPTER 25 : Satellite Communications
in astronomical terms, a celestial body that orbits around a planet; in aerospace terms, a space vehicle launched by humans and orbits Earth or another celestial body
Satellites
a microwave repeater in the sky that consists of a diverse combination of one or more of the following: receiver, transmitter, amplifier, regenerator, filter, onboard computer, multiplexer, demultiplexer, antenna, waveguide and about nay other electronic communications circuit ever developed
Communications satellite
called a transponder Satellite radio repeater
consists of one or more satellite space vehicles, a ground-based station to control the operation of the system and a user network of earth stations that provides the interface facilities for the transmission and reception of terrestrial communications traffic
Satellite system
includes control mechanisms that support the payload operation
Bus
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the actual user information conveyed through the system
Payload
a continuously transmitted unmodulated carrier that an earth station can lock on to and use to determine the exact location of a satellite so the earth station can align its antennas
Beacon
accomplished the first transatlantic transmission Echo
meaning lightning Molniya
Kepler’s laws: the planets move in ellipses with the sun at one focus
the line joinining the sun and a planet sweeps out equal areas in equal intervals of time (laws of areas)
the square of the time of revolution of a planet divided by the cube of its mean distance from the sun gives a number that is the same for all planets (harmonic law)
closest approach to the earth Perigee
farthest point from earth Apogee
rotate around the Earth in an elliptical or circular pattern
Orbital satellites (nonsynchronous)
the orbit if the satellite is orbiting in the same direction as Earth’s rotation (counterclockwise) and at an angular greater than that of earth
Prograde or posigrade orbit
the orbit if the satellite is orbiting in the opposite direction of Earth’s rotation or in the same direction with an angular velocity less than that of Earth
Retrograde orbit
a system utilizing a 66-satellite constellation orbiting approximately 480 miles above Earth’s surface; the main advantage is that the path loss between earth stations and space vehicles is much lower than for satellites revolving in medium- or high-altitude orbits
Low Earth Orbit
operate in the 1.2 GHz to 1.66 GHz frequency band and orbit between 6000 miles and 12000 miles above the Earth
Medium Earth Orbit
high-altitude earth-orbit satellites operating primarily in the 2 GHz to 18 GHz frequency
Geosynchronous satellites
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spectrum with orbits 22 300 miles above the Earth’s surface
the line joining the perigee and apogee the center of Earth
Major Axis (line of apsides)
the line perpendicular to the major axis and halfway between the perigee and apogee
Minor axis
half the distance of the minor axis Semiminor axis
all satellites rotate around Earth in an orbit that forms a plane that passes through the center of gravity of Earth
Geocenter
are virtually all orbits except those that travel directly above the equator or directly over the North and South Poles
Inclined Orbits
the angle between the Earth’s equatorial plane and the orbital plane of a satellite measured counterclockwise at the point in the orbit where it crosses the equatorial plane traveling from south to north
Angle of inclination
traveling from south to north Ascending node
the point where a polar or inclined orbit crosses the equatorial plane traveling from north to south
Descending node
the line joining the ascending an descending nodes through the center of Earth
Line of nodes
when the satellite rotates in an orbit directly above the equator, usually in a circular path
Equatorial orbit
when the satellite rotates in a path that takes it over the North and South poles in an orbit perpendicular to the equatorial plane
Polar orbit
causing elliptical orbits to rotate in a manner that causes the apogee and perigee to move around the Earth
Rotation of the line of apsides
satellites appear to remain in a fixed location above one spot on earth’s surface
Geosynchronous (stationary or geostationary)
the process of maneuvering a satellite within a preassigned window
Station keeping
the circumference of a geosynchronous orbit 264 790 km
the velocity of a geosynchronous satellite 6840 mph
sometimes referred to geosynchronous earth orbit Clarke orbit or Clarke belt
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direction of maximum gain of an earth station antenna
Boresight
azimuth and elevation angle are jointly referred to __________
Look angles
a point on the surface below the satellite Subsatellite point (SSP)
the vertical angle formed between the direction of travel of an electromagnetic wave radiated from an earth station antenna pointing directly toward a satellite and the horizontal plane
Angle of elevation
the horizontal angular distance from a reference direction either the southern or northern most point of the horizon
Azimuth
defined as the horizontal pointing angle of an earth station antenna
Azimuth angle
determine the farthest satellite away that can be seen looking east or west of the earth station’s longitude
Line-of-sight limits
uses the angular momentum of its spinning body to provide roll and yaw stabilization
Spinner satellite
the body remains fixed relative to Earth’s surface, while an internal subsystem provides roll and yaw stabilization
Three-axis stabilizer satellites
the geographical representation of a satellite antenna’s radiation pattern; the area on Earth’s surface that the satellite can receive from or transmit to
Footprint (footprint map)
the smallest beams; concentrate their power to very small geographical areas and, therefore, typically have proportionately higher EIRPs than those targeting much larger areas because a given output power can be more concentrated
Spot beams
typically target up to 20% of the Earth’s surface and, therefore, have EIRPs that are 3 dB or 50% lower than those transmitted by spot beams that typically cover only 10% of the Earth’s surface
Hemispherical downlink antennas
have a beamwidth of approximately 42% of Earth’s surface which is the maximum view of any one geosynchronous satellite
Earth coverage
increasing the size of an antenna, the beamwidth of the antenna is also reduced thus, different beams of the same frequency can be directed to different geographical areas of Earth
Frequency reuse
consists of an input bandlimiting device (BPF), an Satellite transponder
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input low-noise amplifier (LNA), a frequency translator, a low-level power amplifier, and an output bandpass filter
used when it is necessary to communicate between satellites
Cross-links or intersatellite links (ISLs)
high power amplifiers used in earth station transmitters and the traveling-wave tubes typically used in a satellite transponders
Nonlinear devices
the amount the output level is backed off from rated levels equivalent to a loss
Back-off loss
defined as an equivalent transmit power Effective isotropic radiated power (EIRP)
a hypothetical value that can be calculated but cannot be measured; often used rather than noise figure because it is more accurate method of expressing the noise contributed by a device or a receiver when evaluating its performance
Equivalent noise temperature
the noise power normalized to a 1-Hz band width, or the noise power present in a 1-Hz bandwidth
Noise density
the average wideband carrier power-to-noise density ratio
Carrier-to-noise density ratio
the combines power of the carrier and its associated sidebands
Wideband carrier power
the thermal noise present in a normalized 1-Hz bandwidth
Noise density
CHAPTER 26: Satellite Multiple Accessing Arrangements
sometimes called multiple destination because the transmission from each earth station are received by all the other earth stations in the system
Multiple accessing
method of assigning adjacent channels different electromagnetic polarization
Frequency reuse
an Eskimo word meaning “little brother” Anik
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a method required when three or more earth stations wish to communicate with each other
Multiple accessing
sometimes called to multiple accessing because the transmissions from each earth station are received by all the other earth stations in the system
Multiple destination
when it is used, a given number of the available voice-band channels from each other station are assigned a dedicated station
Preassignment
voice-channels are assigned on an as-needed basis; provides more versatility and more efficient use of the available frequency spectrum
Demand assignment
each earth station’s transmissions are assigned
specific uplink and downlink frequency bands within an allotted satellite; transmissions are separated in the frequency domain
FDMA
each earth station transmits a short burst of information during a specific time slot (epoch); transmissions are separated in the time domain; the entire transponder bandwidth and power are used for each transmission but for only a prescribed interval of time
TDMA
the entire satellite transponder bandwidth is used by all stations on a continuous basis; signal separation is accomplished with envelope encryption/decryption techniques
CDMA
an alternate channel allocation scheme Demand-assignment, multiple access (DAMA)
an acronym for single-channel-per-carrier PCM multiple-access demand-assignment equipment
SPADE
a time-division-multiplexed transmission that is frequency-division multiplexed into the spectrum below the QPSK-encoded voice-band channels with a 160 KHz bandwidth
Common signaling channel (CSC)
called when each stations can transmit only during their specified time slot although the incoming voice-band signals are continuous
Store-and-forward system
a unique binary word Chip code
produced when a bipolar data-modulated signal is linearly multiplied by the spreading signal in a special balanced modulator
Direct-sequence spread spectrum (DS-SS)
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a form of CDMA where a digital code is used to continually change the frequency of the carrier
Frequency hopping
there can be more TCs assigned than there are SCs Channel compression
a phenomenon when speech energy is detected on a TC and there is no SC to assign it to
Competitive clipping
a form of analog channel compression that has been used for suboceanic cables for many years
Time-assignment speech interpolation (TASI)
can be defined as the art or science of plotting, ascertaining, or directing the course of movements; knowing where you are and being able to find your way around
Navigation
the most ancient and rudimentary method of navigation; is simply continuing to travel about until you reach your destination
Wandering
direction and distance are determined from precisely timed sightings of celestial bodies including the stars and moon; a primitive technique that dates back thousand of years
Celestial navigation
another rudimentary method of navigation; fixing a position and direction with respect to familiar, significant landmarks, such as railroad tracks, water towers, barns, mountain peaks and bodies of water
Piloting
a navigation technique that determines position by extrapolating a series of measured velocity increments used quite successfully by Charles Lindbergh in 1927 during his historic 33 hour transatlantic journey and quite unsuccessfully by Amelia Earhart in 1937 during her attempt to make first around-the-world flight
Dead reckoning
the most accurate navigation technique; position is determined by measuring the travel time of an electromagnetic wave as it moves from a transmitter to a receiver
Radio or electronic navigation
consist of 24 operational satellites revolving around Earth in six orbital planes approximately 60° apart with four satellites in each plane; there are 21 working satellites and three satellites reserved as spaces
Space segment
this unique number is used to encrypt the signal from that satellite
Pseudorandom noise (PRN) code
a term generally associated with a table showing the position of a heavenly body on a number of dates in a regular sequence, in essence, an
Ephemeris
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astronomical almanac
the Navstar control segment which includes all the fixed-location ground-based monitor stations located throughout the world a master control station (MCS), and uplink transmitters
Operational control system (OCS)
makes GPS even more accurate; works by canceling out most of the natural and man-made errors that creep into normal GPS measurements
Differential GPS
-end-
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