analog communication - Kopykitab

A TEXT BOOK OF

AANNAALLOOGG

CCOOMMMMUUNNIICCAATTIIOONN FOR

SEMESTER – II

SSEECCOONNDD YYEEAARR DDEEGGRREEEE CCOOUURRSSEE IINN EELLEECCTTRROONNIICCSS//

EELLEECCTTRROONNIICCSS AANNDD TTEELLEECCOOMMMMUUNNIICCAATTIIOONN EENNGGIINNEEEERRIINNGG

Strictly According to New Revised Credit System Syllabus

of Savitribai Phule Pune University (w.e.f June 2016)

Dr. G. R. PATIL M.E. (Electronics), Ph. D. (E&TC)

Professor & Head, E & TC Department,

Army Institute of Technology,

Dighi, PUNE

Price `̀̀̀ 325.00

N3574

ANALOG COMMUNICATION (SE E & TC) ISBN 978-93-83750-97-9

First Edition : January 2017

© : Author The text of this publication, or any part thereof, should not be reproduced or transmitted in any form or stored in any computer storage system or device for distribution including photocopy, recording, taping or information retrieval system or reproduced on any disc, tape, perforated media or other information storage device etc., without the written permission of Authors with whom the rights are reserved. Breach of this condition is liable for legal action. Every effort has been made to avoid errors or omissions in this publication. In spite of this, errors may have crept in. Any mistake, error or discrepancy so noted and shall be brought to our notice shall be taken care of in the next edition. It is notified that neither the publisher nor the authors or seller shall be responsible for any damage or loss of action to any one, of any kind, in any manner, therefrom.

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PREFACE

It gives me great pleasure in publishing this text book on "Analog Communication"

for the students of Second Year Degree Course in Electronics/Electronics and

telecommunication Engineering. This book is strictly written according to New Revised

Credit System Syllabus of Savitribai Phule Pune University (2015 Pattern).

As per the policy of the University, Engineering Syllabi is revised every five years. Last

revision was in the year 2012. New revision is coming little earlier, as university has

introduced Online System of Examination from year 2012.

As per the New Credit System, the Online Examinations Phase-I will be conducted

based on First & Second Units and Phase II on Third & Fourth Units. The Online

examinations will have objective types of questions with multiple choices. End Sem. Theory

Examination will be based on all the six units and that will be conducted in traditional way

and the Theory Course will have 4 credits.

This book provides an introduction to the theory on Analog Communication. The concepts

of Analog Communication are presented with Numbers of Examples, are also given to test

the understanding of the students.

Unit 1 provides the Concept of AM Transmission

Unit 2 provides the Concepts of AM Receiver

Unit 3 provides the Concepts of FM Transmission

Unit 4 provides the Concepts of FM Receiver

Unit 5 provides the Concepts of Noise

Unit 6 provides the Concepts of Pulse Analog Modulation.

Main feature of this book is, Complete Coverage of the New Credit System Syllabus

with large number of Worked (Solved) Examples and Exercises.

I have given Separate Book of Multiple Choice Questions (MCQ’s) which will be

very useful to the students especially for Online Examinations.

I take this opportunity to express our sincere thanks to Shri. Dineshbhai Furia, Shri.

Jignesh Furia, Mrs. Nirali Verma and Shri. M. P. Munde and entire team of Nirali Prakashan

namely Mrs. Deepali Lachake (Co-ordinator), who really have taken keen interest and

untiring efforts in publishing this text.

The advice and suggestions of our esteemed readers to improve the text are most

welcomed, and will be highly appreciated.

Pune Author

SYLLABUS

Unit I : AM Transmission (08 Hrs)

Base band & Carrier communication, Generation of AM (DSBFC) and its spectrum,

Power relations applied to sinusoidal signals, DSBSC – multiplier modulator, Nonlinear

generation, switching modulator, Ring modulator & its spectrum, Modulation Index.

SSBSC, ISB & VSB, their generation methods & Comparison, Block Diagram of AM

Transmitter and Broadcast technical standards.

Unit II : AM Reception (8 Hrs)

Block diagram of TRF AM Receivers, Super Heterodyne Receiver, Dual Conversion Super

heterodyne Receiver, Concept of Series & Parallel resonant circuits for Bandwidth &

Selectivity. Performance Characteristics: Sensitivity, Selectivity, Fidelity, Image Frequency

Rejection and IFRR. Tracking, Mixers. AM Detection: Rectifier detection, Envelope

detection; Demodulation of DSBSC: Synchronous detection; Demodulation of SSBSC:

Envelope detection

Unit III : FM Transmission (8 Hrs)

Instantaneous frequency, Concept of Angle modulation, frequency spectrum& Eigen

Values, Narrow band & wide band FM, Modulation index, Bandwidth, Phase Modulation,

Bessel’s Function and its mathematical analysis, Generation of FM (Direct & Indirect

Method), FM stereo Transmitter, Two way FM Radio Transmitter, Comparison of FM and

PM.

Unit IV : FM Reception (6 Hrs)

Block diagram of FM Receiver, FM Stereo Receiver , Two way FM Radio Receiver, FM

detection using Phase lock loop(PLL) ,Slope detector, Balanced Slope detector etc.

Unit V : Noise (6 Hrs)

Sources of Noise, Types of Noise, White Noise, Thermal noise, shot noise, partition

noise, Low frequency or flicker noise, burst noise, avalanche noise, Signal to Noise Ratio,

SNR of tandem connection, Noise Figure, Noise Temperature, Friss formula for Noise

Figure, Noise Bandwidth, Behavior of Baseband systems and Amplitude modulated

systems i.e.DSBSC and SSBSC in presence of noise.

Unit VI : Pulse Analog Modulation (6 Hrs)

Band limited & time limited signals, Narrowband signals and systems, Sampling

theorem in time domain, Nyquist criteria, Types of sampling- ideal, natural, flat top,

Aliasing & Aperture effect. PAM PWM & PPM. Introduction to Pulse Code Modulation.

CONTENTS

Unit I – AM Transmission

Chapter 1 : AM Transmission 1.1-1.112

1.1 Baseband and Carrier Communication 1.1

1.1.1 The Elements of a Communication System 1.2

1.1.2 Baseband Signal Transmission and Bandwidth Requirement 1.4

1.1.3 Communication Channel or Medium 1.6

1.1.4 Types of Transmission Mediums 1.7

1.1.5 Modulation Techniques 1.7

1.1.6 Necessity of Modulation (Need of Modulation) 1.8

1.1.7 Types of Modulation 1.11

1.1.8 Summary of Baseband and Carrier Communication 1.16

1.2 Amplitude Modulation (AM) DSB-FC 1.17

1.2.1 Frequency Domain Description of AM (Spectrum of AM) 1.20

1.2.2 Power Relation in AM Wave 1.24

1.2.3 AM for Multiple Sinusoidal Signals 1.27

1.2.4 Over Modulation 1.30

1.2.5 Measurement of Modulation Index 1.30

1.3 Generation of AM Signal 1.33

1.3.1 Practical AM Generation Techniques 1.35

1.3.2 High Level Amplitude Modulators 1.36

1.3.3 Low Level Amplitude Modulators 1.40

1.4 Double Sideband Suppressed Carrier (DSB – SC) Modulation 1.41

1.5 Generation of DSB-SC 1.49

1.6 Single Sideband Suppressed Carrier (SSB-SC) Modulation 1.53

1.6.1 Methods of Generation of SSB-SC Signal 1.57

1.6.2 The "Third Method" 1.59

1.6.3 Comparison between Filter / Phase Shift / Third Method 1.61

1.7 Independent Side Band (ISB) 1.62

1.8 Vestigial Sideband (VSB) Modulation 1.63

1.8.1 VSB Application in TV Broadcasting 1.65

1.9 Comparison Between AM, DSB, SSB, ISB and VSB 1.67

1.10 AM Transmitters 1.67

1.10.1 High Level AM Transmitter 1.68

1.10.2 Low Level AM Transmitter 1.69

1.10.3 Comparison of High Level and Low Level Modulation 1.70

1.10.4 Different AM Techniques (Forms of AM) 1.70

1.11 Broadcast Technical Standards 1.72

• Exercise 109

• University Problems 1.110

• University Questions 1.112

Unit II – AM Reception

Chapter 2 : AM Reception 2.1-2.52

2.1 Introduction 2.1

2.2 Tuned Radio Frequency Receiver 2.1

2.3 Block Diagram of AM Receiver (Superheterodyne Receiver) 2.2

2.4 Dual or Double Conversion Superheterodyne Radio Receiver 2.4

2.5 Concept of Series and Parallel Resonance Circuits 2.7

2.6 Performance Characteristics of Receiver 2.13

2.7 RF Amplifiers 2.22

2.8 Local Oscillator 2.23

2.9 Intermediate Frequency Selection 2.24

2.10 Mixer 2.25

2.11 AM Detection 2.29

2.12 Automatic Gain Control (AGC) 2.34

2.13 Demodulation of DSB-SC 2.37

2.14 Demodulation of SSB-SC Signal 2.40

• Exercise 2.48



Unit III – FM Transmission

Chapter 3 : FM Transmission 3.1-3.64


3.2 Concept of Instantaneous Frequency 3.1

3.2.1 Phase Modulation and Instantaneous Frequency 3.3

3.2.2 Frequency Modulation and Instantaneous Frequency 3.3

3.2.3 Generalized Concept of Angle Modulated System 3.4

3.2.4 Modulation Indices 3.5

3.3 Frequency Spectrum and Bandwidth of Wideband Angle Modulated Wave 3.11

3.4 Narrowband FM and PM 3.19

3.4.1 Generation of Narrowband PM and FM signal 3.22

3.5 Generation of FM 3.23

3.5.1 Indirect Method or Armstrong Method 3.23

3.5.2 Direct Method of Generation of WBFM 3.25

3.5.3 WBFM using Varactor Diode 3.26

3.5.4 WBFM using Reactance Modulator 3.27

3.6 Comparison of FM and PM 3.29

3.7 FM Stereo Transmitter 3.29

3.8 Two Way FM Radio 3.32

3.9 Comparison Between AM and FM 3.35

3.10 Comparison Between WBFM and NBFM 3.37

• Exercise 3.60



Unit IV – FM Reception

Chapter 4 : FM Reception 4.1-4.20


4.2 FM Receivers 4.3

4.3 Practical Frequency Demodulators 4.7

4.4 FM Stereo Receiver 4.17

4.5 Two Way FM Receiver 4.18

• Exercise 4.19


Unit V – Nosie

Chapter 5 : Noise 5.1-5.44


5.1.1 Noise Sources / Types / Classification 5.1

5.2 Thermal Noise (Nyquist or Johnson’s Noise) 5.3

5.2.1 Thermal Noise Calculation for Resistors in Series 5.6

5.2.2 Thermal Noise Calculation for Resistors in Parallel 5.6

5.2.3 Thermal Noise for Reactive Circuits 5.7

5.2.4 Thermal Noise for Amplifiers in Cascade 5.8

5.3 Shot Noise 5.10

5.4 Partition Noise 5.12

5.5 Low Frequency or Flicker Noise 5.12

5.6 Burst Noise 5.13

5.7 Avalanche Noise (Due to Avalanche Breakdown) 5.14

5.8 White Noise 5.15

5.8.1 White Noise in Spatial Context 5.15

5.8.2 Statistical Properties 5.15

5.8.3 Additive White Gaussian Noise (AWGN) 5.17

5.8.4 Applications of White Noise 5.17

5.8.5 Power Spectral Density and Auto-Correlation Function of the

White Noise 5.18

5.9 Signal to Noise Ratio (SNR) 5.19

5.10 SNR of a Tandem Connection 5.20

5.11 Noise Factor and Noise Figure 5.21

5.11.1 Noise Figure Calculation for Receiver (Amplifier) System 5.22

5.11.2 Noise Figure from Equivalent Noise Resistance 5.24

5.11.3 Friss’s Formula 5.25

5.12 Noise Temperature 5.26

5.12.1 Equivalent Noise Temperature for Microwave Devices 5.26

5.13 Noise Figure, Noise Factor and Equivalent Noise Temperature

Conversion Table 5.28

5.14 Noise Equivalent Bandwidth 5.30

5.14.1 Technical Definition of Noise-Equivalent Bandwidth 5.31

5.14.2 Practical Design and Simulation for Noise Equivalent

Bandwidth of BPF 5.32

• Exercise 5.41



Chapter 6 : Behaviour of Analog Systems in Presence of Noise 6.1-6.28


6.2 Noise in Baseband Communication Systems 6.2

6.3 Noise in Amplitude Modulated Systems 6.5

6.4 Pre-Emphasis and De-Emphasis in FM 6.16

• Exercise 6.26



Unit VI – Pulse Analog Modulation

Chapter 7 : Pulse Analog Modulation 7.1-7.52


7.2 Band Limited and Time Limited Signals 7.1

7.3 Narrowband Signals and Systems 7.1

7.4 Sampling Theorem in Time Domain 7.2

7.4.1 Impulse or Ideal Sampling 7.2

7.4.2 Nyquist Criteria and Aliasing 7.7

7.5 Natural Sampling 7.14

7.6 Flat-Top Sampling 7.16

7.7 Comparison of Various Sampling Techniques 7.20

7.8 Introduction to Pulse Modulation 7.28

7.9 Pulse Amplitude Modulation (PAM) 7.29

7.10 Pulse Width Modulation (PWM) 7.33

7.11 Pulse Position Modulation (PPM) 7.38

7.12 Pulse Code Modulation (PCM) 7.44

7.12.1 Low Pass Filter 7.45

7.12.2 Sampling 7.45

7.12.3 Quantizing 7.45

7.12.4 Encoding 7.47

7.12.5 Regeneration 7.47

7.12.6 Decoding 7.48

7.12.7 Reconstruction Filters 7.48

7.12.8 Bandwidth Requirement of PCM 7.48

• Exercise 7.49



•••• Sample Question Paper for End. Sem. Theory Exam. P.1

��

Unit 1 | 1.1

UNIT - I

Chapter 1

AM TRANSMISSION

1.1 BASEBAND AND CARRIER COMMUNICATION

The Electronics field can be roughly categorized into three major areas :

1. Computers

2. Communication

3. Control

1440

1844-66

1876

1879

1887

1895

19010

1903-06

1923

1931

1940-45

1948

1954

1959

1962

2005

Invention of printing press

Telegraph communication

Telephone communication

Photographic film development

Discovery of Radio waves

Wiress Telegraphy

First Radio Transmission

Valve & Vaccum tube Invention

Television Invention

Discovery of Radio Astronomy

Radar Discovery & Implementation

Invention of transistor

Colour Television broadcast

Invention of integrated circuits

First satellite communications

All Advanced Communication Systems

Fig. 1.1 : Evolution of the Human Race's Communication Techniques

ANALOG COMMUNICATION (SE E&TC) AM TRANSMISSION

Unit 1 | 1.2

The computer field is the latest of the three, while communication field is the oldest one. The

field of communication is related with electronic equipments used for the transfer of

information like voice, video, digital data between two or more points.

Communication is the transfer of meaningful information from one location (the sender,

source, originator or transmitter) to other location (the destination or receiver). This

definition is a basic one that only requires that the term information be defined to complete

its meaning. Also, you can define the communication as the basic process of information

exchange between transmitter and receiver. Most communication in the past has been done

between one human and another. The communication systems in the past used two broad

techniques - visual and aural. The evolution of people's ability to use these techniques is

summarized in Fig. 1.1.

1.1.1 The Elements of a Communication System

The block diagram of the simplest possible electronic communication system is as shown in

Fig. 1.2.

Informationsource

Transmitter(TX)

Receiver(RX)

Communicationchannel or

medium

Noise /Interference

source

Destination

Fig. 1.2 : Block diagram of basic communication system

As seen from the Fig. 1.2, the basic components of a communication system are, transmitter,

a communication channel or medium and a receiver. Unwanted noise is inherently present in

the channel. The components of a communication system are as follows :

• Information

• Transmitter

• Medium or Communication Channel

• Unwanted Noise

• Receiver

Information or Input Signal :

The communication systems have been developed for communicating or transferring or

exchanging information from one location to other. The information can be as follows :

• human voice

• music

• picture or video signal

• data from computer

• or combinations of the above


Unit 1 | 1.3

Transmitter (Tx) :

Most of the times message coming from information source is not suitable for immediate

transmission. The task of transmitter block is to convert the electrical equivalent of the

information to a suitable form. Transmitter consists of electronic circuits such as amplifier,

oscillator and power amplifier for signal conditioning to cover the large range.

Communication Channel or Medium :

Depending on the type of communication medium, two types of communication systems will

be available, they are as follows :

Communication System

Wired Communication

or

Line Communication

Wireless Communication

or

Radio Communication

The wired communication medium can be conducting wires, cables and optical fibers. The

wireless communication medium can be free space.

1. Wired Communication : Wired communication systems use the communication

mediums like the simple wires, cables or optical fibers. The examples of wired

communication are telegraph system, telephone system, fax system, cable T.V. system,

Internet lines like leased lines, ISDN (Inter Services Digital Network) lines etc. This wired

medium cannot be used for the communication over long distances because of the

requirement of actual physical connection from one point of one location to other point

of other location.

2. Wireless Communication : Radio communication is the broad general term applied to

any form of wireless communication between two locations. Wireless communication

doesn't require any physical wire between transmitter (Tx) and receiver (Rx), instead the

signal is sent through air or free space via. transmitter antenna and received by receiver

antenna. Transmitter antenna radiates the signal in electromagnetic waveform and

received in the same form. For long distance communication like intercontinent

communication, Earth to Satellite, Earth to Moon, Earth to Planet etc., radio

communication is widely used.

Noise : Noise is random, unwanted electrical signal energy which gets added to the

transmitted signal via medium in electronic communication system. It is very much difficult to

separate the added noise from the transmitted signal. Also, receiver adds its own noise. So

overall signal quality degrades, hence degradeing the overall performance of communication

system. There are several ways of classifying noise. It may be subdivided according to type,

source, effect or relation to the receiver, depending on circumstances. It is most convenient

here to divide noise into two broad groups as follows :


Unit 1 | 1.4

Noise

External noise Internal noise

• Atmospheric noise

• Extraterrestrial noise

• Industrial noise

• Thermal agitation noise

• Shot noise

• Transit time noise

Atmospheric noise is caused by lightening discharges in thunderstorms and other natural

electrical disturbances occurring in the atmosphere. Extraterrestrial noise includes solar noise,

cosmic noise etc. Industrial noise is concerned with the sources such as automobile and

aircraft ignition, electric dc/ac motors and switching gear, high voltage transmission line

leakage etc. Thermal noise is due to thermal agitation in resistive component of system. Shot

noise is due to random variations in the arrival of electrons (or holes) at the output electrode

of amplifying device. Transit time noise is added due to the circuit operation above VHF

(Very High Frequency). Even though noise cannot be completely eliminated, its effect can be

minimized by using various noise reduction methods.

Receiver : The reception is exact opposite process of transmission. The received signal is

processed by the various circuits like pre-amplifier, mixer, oscillator, detector, demodulator,

driver amplifier and power amplifier.

Thus, we have studied the basic electronic communication system and its components.

Further the electronic communication systems can be categorized as Analog communication

systems and Digital communication systems. In Analog communication system, the

continuous varying signal such as sine wave is used. For example, audio and video signal

which is the output of microphone and video camera respectively. The data output from

computer is digital data representing the alphabets, characters, numerical etc. which is being

transmitted by digital communication system by either wired or wireless medium.

1.1.2 Baseband Signal Transmission and Bandwidth Requirement

Regardless of whether the original information signals are analog or digital, they are all

referred to as baseband signals. Following are the examples of the baseband signal

transmission given in Fig. 1.3 (a), (b), (c), (d).

Analog information

Baseband signal

(Parallel wire)

Telephone Telephone

(a) Voice as analog baseband signal

Analog Communication

Publisher : Nirali Prakashan ISBN : 9789383750979 Author : Dr. G. R. Patil

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