fy bsc-it communication
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this is also the document for telecommunication part for FY bsc-it , i hope you will get benefit , and good luck with examsTRANSCRIPT
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Semester II
• Mathematics I
• Fundamentals of Digital Computing
• Electronics and Tele Communication Systems
• Professional Communication Skill
• Programming with C++
CLASS: B. Sc (Information technology)
Semester – I
SUBJECT: Electronics and Communication Technology (USIT104)
Periods per week Lectures - 5 3 Credits
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ELECTRONICS• Unit – I• Concept of Conductor, Semiconductor, Insulator.
Semiconductor Diode, Forward bias, Reverse Bias, Application of Diode as Rectifier, Zener diode and its applications, Introduction to Transistor (BJT, FET), PNP, NPN Transistors their Characteristic. Application of Transistor as amplifier and as a Switch.
• Unit- II• Concept of amplification, amplifier notations, Av, Ai, Ap Zi, Zo),
Application of BJT as single stage Amplifier, Frequency response of single stage Amplifier. Multistage Amplifiers:-(Basics concepts) RC coupled, cascade, Darlington pair, DC amplifiers.
• Unit-III• Concept of Feedback:- Negative Feedback and its advantage
in Amplification, Positive Feedback :- Oscillators, RC Phase Shift Oscillator, LC Oscillator. Switching Circuits Multivibrators :
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COMMUNICATION TECHNOLOGY• Unit- IV
• Introduction:- Need for modulation system, Concept of Modulation. AM :-Definition of AM, Modulation index, Power relation in AM, Generation and Demodulation of AM. SSB:- Power requirement in comparison with AM, Advantages of SSB over AM, Concept of Balanced Modulator, Generation of SSB, Pilot Carrier System, Independent Side System, Vestigial Sideband Transmission.
• Unit- V
• FM: - Definition of FM, Bandwidth, Noise triangle, Per-emphasis and De-emphasis. PM: - Definition of PM. Difference between AM and FM. Radio receivers. Pulse Modulation:- Sampling Theorem, PAM, PTM, PWM, PPM, pulse code modulation, Quantization noise, companding, PCM system, differential PCM, Delta modulation. Multiplexing: - FDM/TDM. Television:-Scanning, Composite Video signal, Television Transmitter, television receiver.
• Unit-VI• Introduction to Digital Communication: PSK, ASK, FSK. • Introduction to fibre optics system:- Propagation of light in optical fibre; ray
model . Types of fibre : Single mode, steps index. Graded index. Signal
• Boylstead and Neshelesky , “Electronics Devices and Circuits”, 4th , PHI, 1999.
• Data communication & networking by Behroz Forouzan, 3rd edition
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Signals
Data
Leads to
Information
Leads to
Signal
Note:Note:
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To be transmitted, data must be transformed to electromagnetic
signals.
Note:Note:
3.1 Analog and Digital
Analog and Digital Data
Analog and Digital Signals
Periodic and Aperiodic Signals
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Signals can be analog or digital. Analog signals can have an infinite number of values in a range; digital
signals can have only a limited number of values.
Note:Note:
Figure 3.1 Comparison of analog and digital signals
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In data communication, we commonly use periodic analog signals and
aperiodic digital signals.
Note:Note:
3.2 Analog Signals
Sine WavePhaseExamples of Sine WavesTime and Frequency DomainsComposite SignalsBandwidth
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Frequency and period are inverses of each other.
Note:Note:
Figure 3.4 Period and frequency
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Table 3.1 Units of periods and frequenciesTable 3.1 Units of periods and frequencies
Unit Equivalent Unit Equivalent
Seconds (s) 1 s hertz (Hz) 1 Hz
Milliseconds (ms) 10–3 s kilohertz (KHz) 103 Hz
Microseconds (ms) 10–6 s megahertz (MHz) 106 Hz
Nanoseconds (ns) 10–9 s gigahertz (GHz) 109 Hz
Picoseconds (ps) 10–12 s terahertz (THz) 1012 Hz
Example 1Example 1
Express a period of 100 ms in microseconds, and express the corresponding frequency in kilohertz.
SolutionSolution
From Table 3.1 we find the equivalent of 1 ms.We make the following substitutions:100 ms = 100 × 10-3 s = 100 × 10-3 × 106 µs = 105 µs
Now we use the inverse relationship to find the frequency, changing hertz to kilohertz100 ms = 100 × 10-3 s = 10-1 s f = 1/10-1 Hz = 10 × 10-3 KHz = 10-2 KHz
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Frequency is the rate of change with respect to time. Change in a short span of time means high frequency. Change
over a long span of time means low frequency.
Note:Note:
If a signal does not change at all, its frequency is zero. If a signal changes
instantaneously, its frequency is infinite.
Note:Note:
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Phase describes the position of the waveform relative to time zero.
Note:Note:
Figure 3.5 Relationships between different phases
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Example 2Example 2
A sine wave is offset one-sixth of a cycle with respect to time zero. What is its phase in degrees and radians?
SolutionSolution
We know that one complete cycle is 360 degrees.
Therefore, 1/6 cycle is
(1/6) 360 = 60 degrees = 60 x 2π /360 rad = 1.046 rad
Figure 3.6 Sine wave examples
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Figure 3.6 Sine wave examples (continued)
Figure 3.6 Sine wave examples (continued)
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An analog signal is best represented in the frequency domain.
Note:Note:
Figure 3.7 Time and frequency domains (continued)
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Figure 3.7 Time and frequency domains (continued)
A single-frequency sine wave is not useful in data communications; we need to change one or more of its characteristics to make it useful.
Note:Note:
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When we change one or more When we change one or more characteristics of a singlecharacteristics of a single--frequency frequency signal, it becomes a composite signal signal, it becomes a composite signal
made of many frequencies.made of many frequencies.
Note:Note:
According to Fourier analysis, any composite signal can be represented as
a combination of simple sine waves with different frequencies, phases, and
amplitudes.
Note:Note:
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Figure 3.12 Signal corruption
The bandwidth is a property of a The bandwidth is a property of a medium: It is the difference between medium: It is the difference between
the highest and the lowest frequencies the highest and the lowest frequencies that the medium can that the medium can satisfactorily pass.satisfactorily pass.
Note:Note:
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In this book, we use the term In this book, we use the term bandwidth to refer to the property of a bandwidth to refer to the property of a
medium or the width of a single medium or the width of a single spectrum.spectrum.
Note:Note:
Figure 3.13 Bandwidth
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Example 3Example 3
If a periodic signal is decomposed into five sine waves with frequencies of 100, 300, 500, 700, and 900 Hz, what is the bandwidth? Draw the spectrum, assuming all components have a maximum amplitude of 10 V.
SolutionSolution
B = fh − fl = 900 − 100 = 800 HzThe spectrum has only five spikes, at 100, 300, 500, 700, and 900 (see Figure 13.4 )
Example 4Example 4
A signal has a bandwidth of 20 Hz. The highest frequency is 60 Hz. What is the lowest frequency? Draw the spectrum if the signal contains all integral frequencies of the same amplitude.
SolutionSolution
B = fB = fhh −− ffll
20 = 60 20 = 60 −− ffll
ffll = 60 = 60 −− 20 = 40 Hz20 = 40 Hz
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Example 5Example 5
A signal has a spectrum with frequencies between 1000 and 2000 Hz (bandwidth of 1000 Hz). A medium can pass frequencies from 3000 to 4000 Hz (a bandwidth of 1000 Hz). Can this signal faithfully pass through this medium?
SolutionSolution
The answer is definitely no. Although the signal can have The answer is definitely no. Although the signal can have the same bandwidth (1000 Hz), the range does not the same bandwidth (1000 Hz), the range does not overlap. The medium can only pass the frequencies overlap. The medium can only pass the frequencies between 3000 and 4000 Hz; the signal is totally lost.between 3000 and 4000 Hz; the signal is totally lost.
3.3 Digital Signals3.3 Digital Signals
Bit Interval and Bit RateAs a Composite Analog SignalThrough Wide-Bandwidth MediumThrough Band-Limited MediumVersus Analog BandwidthHigher Bit Rate
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Figure 3.16 A digital signal
Example 6Example 6
A digital signal has a bit rate of 2000 bps. What is the duration of each bit (bit interval)
SolutionSolution
The bit interval is the inverse of the bit rate.
Bit interval = 1/ 2000 s = 0.000500 s = 0.000500 x 106 µs = 500 µs
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Figure 3.17 Bit rate and bit interval
Figure 3.18 Digital versus analog
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A digital signal is a composite signal A digital signal is a composite signal with an infinite bandwidth.with an infinite bandwidth.
Note:Note:
Table 3.12 Bandwidth RequirementTable 3.12 Bandwidth Requirement
BitRate
Harmonic1
Harmonics1, 3
Harmonics1, 3, 5
Harmonics1, 3, 5, 7
1 Kbps 500 Hz 2 KHz 4.5 KHz 8 KHz
10 Kbps 5 KHz 20 KHz 45 KHz 80 KHz
100 Kbps 50 KHz 200 KHz 450 KHz 800 KHz
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The bit rate and the bandwidth are The bit rate and the bandwidth are proportional to each other.proportional to each other.
Note:Note:
3.4 Analog versus Digital3.4 Analog versus Digital
Low-pass versus Band-pass
Digital Transmission
Analog Transmission
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3.6 Transmission Impairment3.6 Transmission Impairment
Attenuation
Distortion
Noise
Figure 3.20 Impairment types
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Figure 3.24 Noise
3.7 More About Signals3.7 More About Signals
Throughput
Propagation Speed
Propagation Time
Wavelength
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Figure 3.25 Throughput
Figure 3.26 Propagation time
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Figure 3.27 Wavelength
Digital-to-analog modulation
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Figure 5.2 Types of digital-to-analog modulation
Figure 5.3 ASK
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Figure 5.9 PSK constellation
Figure 5.10 The 4-PSK method
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Figure 5.11 The 4-PSK characteristics
Figure 5.12 The 8-PSK characteristics
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Figure 5.14 The 4-QAM and 8-QAM constellations
Figure 5.15 Time domain for an 8-QAM signal
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Analog Analog ––to to -- AnalogAnalog
Amplitude Modulation (AM)
Frequency Modulation (FM)
Phase Modulation (PM)
Figure 5.24 Analog-to-analog modulation
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Figure 5.25 Types of analog-to-analog modulation
The total bandwidth required for AM can be determined from the bandwidth
of the audio signal: BWt = 2 x BWm.
Note:Note:
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Figure 5.26 Amplitude modulation
Figure 5.27 AM bandwidth
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BASIC COMMUNICATION SYSTEM
BLOCK DIAGRAM FOR BASIC COMMUNICATION SYSTEM
NOISE
INFORMATION OR
i/p SIGNALINPUT
TRANSDUCERTRANSMITTER
COMMUNICATION CHANNEL
OR MEDIUM
RECEIVER OUTPUTTRANSDUCER
Classification of communication systems• Whether the system is unidirectional or bidirectional
• Whether it uses an analog or digital information signal• Whether the system uses baseband transmission or
uses some kind of modulation
DIRECTION NATURE OF THE SIGNAL
TECHNIQUE OF
TRANSMISSION
SIMPLEX HALF DUPLEX
FULL DUPLEX
ANALOG
DIGITAL BASEBAND
MODULATION
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Bending of light ray
Optical fiber
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Figure 7.12 Propagation modes
Figure 7.13 Modes
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Table 7.3 Fiber typesTable 7.3 Fiber typesType Core Cladding Mode
50/12550/125 50 125Multimode, graded-
index
62.5/12562.5/125 62.5 125 Multimode, graded-index
100/125100/125 100 125Multimode, graded-
index
7/1257/125 7 125 Single-mode
Figure 7.14 Fiber construction
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Figure 7.15 Fiber-optic cable connectors
Why we need Modulation?
• To reduce the height of antenna• To avoid mixing of signals (distortion)• To increase the range of
communication(attenuation )• To make multiplexing possible• To improve quality of reception
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To reduce the height of antenna
• As per the Standards, for the transmission of radio signals, the antenna height must be multiple of ( ?/4)
• Here ? is wavelength. And ?=c/f• C= velocity of light • F = frequency of the signal to be transmitted
• So for f = 10kHz signals to get transmitted, we need:
• Height of antenna= ?/4 = c/4f
3x108
-------------- = 7500 meters=7.5km4x 10x103
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• Now assume the signal of frequency 1MHz. And do the calculation.
Height of antenna= ?/4 = c/4f
3x108
-------------- = 75 meters4x 1x106
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To make multiplexing possible