The theory of radio waves was originated by:

The theory of radio waves was originated by:

MarconiBell MaxwellHertzThe person who sent the first radio signal across the Atlantic ocean was:

MarconiBell MaxwellHertzThe transmission of radio waves was first done by:

MarconiBell MaxwellHertzA complete communication system must include:

A. a transmitter and receiverB. a transmitter, a receiver, and a channelC. a transmitter, a receiver, and a spectrum analyzerD. a multiplexer, a demultiplexer, and a channelThe bandwidth required for a modulated carrier depends on: the carrier frequency the signal-to-noise ratio the signal-plus-noise to noise ratiothe baseband frequency rangeWhen two or more signals share a common channel, it is called:sub-channeling signal switching SINADmultiplexingTDM stands for:Time-Division Multiplexing Two-level Digital Modulation Time Domain Measurement None of the aboveFDM stands for:Fast Digital Modulation Frequency Domain MeasurementFrequency-Division MultiplexingNone of the aboveDistortion is caused by:creation of harmonics of baseband frequenciesbaseband frequencies "mixing" with each othershift in phase relationships between baseband frequenciesall of the aboveThe collection of sinusoidal frequencies present in a modulated carrier is called its:frequency-domain representation Fourier series spectrumall of the aboveThe baseband bandwidth for a voice-grade (telephone) signal is:approximately 3 kHz 20 Hz to 15,000 Hz at least 5 kHznone of the aboveNoise in a communication system originates in:A. the sender B. the receiver C. the channelD. all of the above"Man-made" noise can come from:A. equipment that sparks B. temperature C. staticD. all of the aboveThermal noise is generated in:a. transistors and diodes b. resistors c. copper wire d. all of the aboveThermal noise is dependent on temperature and its frequency content is spread equally throughout the usable spectrum. It is also called Brownian noise, Johnson noise, White noise, and Gaussian noise. Resistive components are the primary source of thermal noise.Noise power formula

k Boltzman constant (1.38 x 10-23 J/K) T Noise temperature B BandwidthNoise voltage formula

R Resistance generating the noiseA 300-ohm resistor is connected across the 300-ohm antenna input of a television receiver. The bandwidth of the receiver is 6 MHz, and the resistor is at room temperature (290 K or 20oC) . Find the noise power and noise voltage applied to the receiver input.a. 24.2 fW and 5.4 uVb. 18.6 fW and 4.9 uVc. 18.6 fW and 8.2 uVd. 24.2 fW and 4.9 uVShot noise is generated in:a. transistors and diodes b. resistors c. copper wired. none of the aboveShot noise consists of random fluctuations of the electric current in an electrical conductor which is caused by the fact that the current is carried by carried by discrete charges (electrons)In electronic devices, shot noise is due to shot effect, caused by random variations in the arrival of electrons or holes at the output electrode of an amplifying device and appearing as a randomly varying noise current superimposed on the output.The name shot noise is derived from the fact that when amplified, it is supposed to sound as though a shower of lead shots were falling on a metal sheet. Shot noise formulas for a diode:

rms shot noise current of a diode

charge of an electron (1.602x10-19C)

direct diode current reverse saturation current

A diode noise generator is required to produce 10 uV of noise in a receiver with an input impedance of 75 ohms, resistive and a noise power bandwidth of 200 kHz (these values are typical of FM broadcast receivers.) What must the current through the diode be?a. 230 mAb. 276 mAc. 320 mAd. 440 mAThe power density of "flicker" noise is:a. the same at all frequencies b. greater at high frequencies c. greater at low frequencies d. the same as "white" noiseFlicker noise is inversely proportional to frequency and may be completely negligible at about above 500 Hz. It is sometimes considered as low-frequency noise, modulation noise, excess noise, 1/f noise or pink noise.So called "1/f" noise is also called:a. random noise b. pink noise c. white noise d. partition noiseLight is pink when it contains more red than it does other colors, and red is at the low end of the visiblespectrum. Likewise, pink noise has higher power density at lower frequencies. "Pink" noise has:a. equal power per Hertz b. equal power per octave c. constant powerd. none of the aboveIn pink noise - a reduction of 50% (or 6dB ) of energy as you go up one octave When two noise voltages, V1 and V2, are combined, the total voltage VT is:a. VT = sqrt(V1 x V1 + V2 x V2) b. VT = (V1 + V2)/2 c. VT = sqrt(V1 x V2)d. VT = V1 + V2Suppose there is 30 mV from one noise source that is combined with 40 mV from another noise source.Calculate the total noise voltage.a. 20 mVb. 35 mVc. 45 mVd. 50 mVSignal-to-Noise ratio is calculated as:a. signal voltage divided by noise voltageb. signal power divided by noise powerc. first add the signal power to the noise power, then divide by noise powerd. none of the aboveIf you have 100 mV of signal and 10 mV of noise, both across the same 100-ohm load, what is the signalto-noise ratio in dB?a. 10 dBb. 20 dBc. 30 dBd. 40 dBSINAD is calculated as:a. signal voltage divided by noise voltageb. signal power divided by noise powerc. first add the signal power to the noise power, then divide by noise powerd. none of the aboveSINAD is a measurement that can be used for any radio communication device to look at the degradation of the signal by unwanted or extraneous signals including noise and distortion.

However the SINAD measurement is most widely used for measuring and specifying the sensitivity of a radio receiver.35A receiver produces a noise power of 200 mW with no signal. The output level increases to 5 W when a signal is applied. Calculate (S+N)/N.a. 25b. 30c. 35d. 40Noise figure is a measure of:a. how much noise is in a communications systemb. how much noise is in the channelc. how much noise an amplifier adds to a signald. signal-to-noise ratio in dBNoise Factor is used to specify how noisy a device is. It is defined as the ratio of the input S/N to the output S/N usually determined at the standard noise temperature of 290K.

The input to an amplifier has a signal-to-noise ratio of 100 dB and an output signal-to-noise ratio of 80 dB. Find the noise figure.a. 10 dBb. 20 dBc. 30 dBd. 40 dBA microwave receiver has a noise temperature of 145 K. Find its noise factor.a. 1.5b. 2.0 c. 2.5d. 3.0An amplifier has a noise figure of 2 dB. What is its equivalent noise temperature?a. 345.6 Kb. 169.6 Kc. 230.8 Kd. 168.9 KThe formula used to calculate the totalnoise factorof a cascade of stages, each with its ownnoise factorandgain(assuming that the impedances are matched at each stage).a. Johnsons Formulab. Friss Formulac. Brownians Formulad. Shockleys FormulaThe formula used to calculate the totalnoise factorof a cascade of stages, each with its ownnoise factorandgain(assuming that the impedances are matched at each stage).

Two cascaded amplifiers each have a noise factor of 5 and a gain of 10. Find the total NF for the pair.a. 3.2b. 5.4c. 6.9d. 8.5A three-stage amplifier has the following specifications:a. 3400, 2.316, 144b. 7500, 5.216, 382c. 7500, 2.316, 382d. 2800, 2.316, 382StagePower GainNoise Factor110222543305Calculate the power gain, noise figure, and noise temperature for the entire amplifier, assuming matched conditions:The part, or parts, of a sinusoidal carrier that can be modulated are:a. its amplitude b. its amplitude and frequency c. its amplitude, frequency, and direction d. its amplitude, frequency, and phase angleIDENTIFICATIONOne-way communications is called _______.

simplex

Simultaneous two-way communications is called ______________.

full duplexTransmission ModesGenerally, the mode of communication can be divided into 3 types :Simplex System: the system capable of sending information in one direction only. (e.g. TV & radio broadcasting) Also called receive-only, transmit-only, or one-way only lines.Half-duplex System: the system capable to carry information in both direction, but only one direction is allowed at a time. (e.g. walkie-talkie, 2-way intercom) Also called two-way-alternate or either-way lines.

50Full-duplex System: Information can be carried in both direction at the same time. The 2 directions of information travel are independent of each other. (e.g. ordinary/mobile phone systems, computer systems)Also called two-way simultaneous, duplex or both-way lines.Full/full duplex System: Transmission is possible in both direction at the same time but not between the same two stations.

51The frequency band used to modulate the carrier is called the _____band.base

The original electrical information signal to be transmitted is called the _______________.baseband signalThe process of modifying a high frequency carrier with the information to be transmitted is called ____________.modulationThe process of transmitting two or more information signals simultaneously over the same channel is called _______________.multiplexingContinuous voice or video signals are referred to as ___________ signals.basebandRecovering information from a carrier is known as _____________.detectionTransmission of graphical information over the telephone network is accomplished by _________________.

facsimileMeasuring physical conditions at some remote location and transmitting this data for analysis is the process of __________.telemetryReceiving electromagnetic emissions from stars is called radio ____________.astronomyA personal communications hobby for individuals is ________ radio.hamA frequency of 27MHz has a wavelength of approximately ______________. 11mRadio signals are made up of electric and ____________ fields. magneticThe voice frequency range is ________________. 300 to 3000 HzEM spectrum

30-300300-33-3030-300300-33-3030-300300-33-3030-300ELFVFVLFLFMFHFVHFUHFSHFEHFIRVISIBLE0.7-100m8000 -4000 navy/submarinesaeronautical and marine, subcarriersAMamateur radio, CB radioFM, TV (channels 2-13)TV (channels 14-83)satellites and radarssatellites and some specialized radars6730-300300-33-3030-300300-33-3030-300300-33-3030-300ELFVFVLFLFMFHFVHFUHFSHFEHFMyriametricKilometricHectometricDecametricMetricDecimetricCentimetricMillimetricMyKittenHasDMostDecentS...mell68High frequencies are generally known as _____________.shortwavesFrequencies above 1 GHz range are called _____________.microwavesThe audio frequency range is ________________. 20 to 20,000 HzThe sound above the audio frequency range is called ________________. ultrasoundAnother name for signals in the HF range is _____________.shortwavesTelevision broadcasting occurs in which frequency bands?VHF and UHF535-1605 kHzThe range of frequencies used for AM?What is that band called?MFThe range of frequencies used for FM?88-108 MHzWhat is that band called?VHFElectromagnetic waves produced primarily by heat are called _________ rays.infraredOne __________ is equivalent to one-millionth of a meter.micronThe frequency range of infrared rays is approximately ____________.0.7 to 100mLong infrared 0.01 mm to 1000 nmShort infrared 1000 nm to 700 nmIR ClassificationsA unit of length equivalent to 1 x 10 -10 meter.Angstrom ()The range of wavelength of visible light is ________________________.8000 (red) to 4000 (violet)In the united states, the electromagnetic spectrum is regulated and managed by ____.FCCWhat is the threshold of hearing?0 dB SPL10 dB SPL120 dB SPLNone of the choicesThe sound of leaves rustling is 10 dB SPLWhat is the threshold of pain?0 dB SPL10 dB SPL120 dB SPLNone of the choicesWhat is the frequency of visible light0.3 PHz to 3 PHz 0.4 PHz to 4 PHz 0.5 PHz to 5 PH 0.6 PHz to 6 PHz Flicker noise or excess noise, or 1/f noise is insignificantAbove 1 kHzAbove 10 kHzAbove 100 kHzAbove 1 MHzAtmospheric noise is insignificant above1 MHz30 MHz50 MHz80 MHz1 Neper is equal to 2.232 dB8.686 dB 5.232 dB10.454 dBThe fundamental frequency of typical human voice500 HzThe bandwidth to propagate voice-quality analog3 kHzThe bandwidth to propagate voice-quality digital telephone

32 kHzNoise Representation, Types & Source

Two General Categories of Noise :Correlated noise noise that exists only when a signal is present.Uncorrelated noise noise that presents all the time whether there is a signal or not96Uncorrelated noise

Two General Categories of Uncorrelated Noise :1. External noise noise that generated outside the device or circuit.Atmospheric noisenaturally occurring electrical disturbances that originate within earths atmosphere such as lightning.also known as static electricity.

Extraterrestrial noiseconsists of electrical signal that originate from outside earths atmosphere and therefore also known as deep-space noise.2 categories of extraterrestrial noise.i solar noise noise that generated directly from the suns heat.Sunspot activity follows a cyclic pattern that repeats every 11 years.ii cosmic noise / black-body noise noise that is distributed throughout the galaxies.

Man-made noise- noise that is produced by mankind.- source : spark-producing mechanism (commutators in electrical motors, automobile ignition systems, ac power generating/switching equipment, fluorescent lights).- sometimes known as industrial noise.

97Uncorrelated noise

2. Internal noise noise that generated within the device or circuit.Shot noise-described mathematically by W. Schottky and is sometimes called transistor noise-caused by the random arrival of carriers (holes and electrons) at the output element of an electronic device. shot noise is randomly varying and is superimposed onto any signal present.Transit-time noiseirregular, random variation due to any modification to a stream of carriers as they pass from the input to the output of a device.this noise become noticeable when the time delay takes for a carrier to propagate through a device is excessive.Thermal / random noise

98Correlated noise

A form of internal noise that is correlated to the signal and cannot be present in a circuit unless there is a signal.Produced by a nonlinear amplification resulting in nonlinear distortion.There are 2 types of nonlinear distortion that create unwanted frequencies that interfere with the signal and degrade the performance :1. Harmonic distortionoccurs when unwanted harmonics of a signal are produced through nonlinear amplification.harmonics are integer multiples of the original signal. The original signal is the first harmonic (fundamental harmonic), a frequency two times the fundamental frequency is the second harmonic, three times is the third harmonic and so on.Distortion measurements :99Correlated noise

1. Harmonic distortiondistortion measurements :- Nth harmonic distortion = ratio of the rms amplitude of Nth harmonic to the rms amplitude of the fundamental.- Total Harmonic Distortion (THD)

where all in rms value.

100Correlated noise

2. Intermodulation distortionintermodulation distortion is the generation of unwanted sum and difference frequencies produced when two or more signals mix in a nonlinear device (cross products).unwanted !

101Other type of noise

1. Impulse noisecharacterized by high amplitude peaks of short duration (sudden burst of irregularly shaped pulses) in the total noise spectrum.common source of impulse noise : transient produced from electromechanical switches (relays and solenoids), electric motors, appliances, electric lights, power lines, poor-quality solder joints and lightning.

2. Interferenceelectrical interference occurs when information signals from one source produces frequencies that fall outside their allocated bandwidth and interfere with information signal from another source.most occurs in the radio frequency spectrum.102