ELECTRONICELECTRONICELECTRONICELECTRONICELECTRONICCOMMUNICATIONCOMMUNICATIONCOMMUNICATIONCOMMUNICATIONCOMMUNICATION

Sanjeeva Gupta

Revised by :

Prof. Ashok RajB.Tech., (I.I.T., Delhi), M.Phil. (JNU)

Engineering Consultant

KHANNA PUBLISHERS4575/15, Onkar House, Ground Floor

Darya Ganj, New Delhi-110002Phones : 23243042, 27224179; Fax : 23242043

E-mail : khannapublishers@yahoo.inWeb site : www.khannapublishers.in

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Published by :Romesh Chander Khanna &Vineet Khannafor KHANNA PUBLISHERS2-B, Nath Market, Nai SarakDelhi- 110 006 (India)

© All Rights Reserved

This book or part thereof cannot be translated or reproduced in any form (except for reviewor criticism) without the written permission of the Author and the Publishers.

ISBN No. 978-81-7409-313-4

Third Edition : 2012

Price : Rs. 350.00

Computer Typset & Figures Designed by :Steps Computers,D-2/77, Dayal Pur, Delhi - 110094

Printed at :Print India,4/14, Site IV, Sahibabad, Ghaziabad (U.P.)

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With the widening of the communication systems in the last one decade or so, the worldnow has become like a global village. This has been facilitated by the rapid emergence of awhole set of new digital technologies, which have now made the analog systems of communicationlargely obsolete.

This completely revised edition of the Book has sought to present the massive transitionthat has taken place from largely analog communication systems to all-encompassing digitalsystems. This has been done in two ways.

Firstly, all the chapters in the earlier editions have been totally revised and updated makingthem technologically relevant to the current status of technologies being deployed.

Secondly, sixteen new chapters dealing with digital communication theory and systemshave been added. These are Electromagnetic Theory, Information Theory, Coding Theory,Semiconductor Microwave Devices, Pulse Communication, Pulse Code Modulation (PCM), OpticalFibre Communication, Direct Consequence Spread Spectrum Technologies, Digital Telephony,Audio Engineering, Global Positioning System, Data Communication, Digital SatelliteCommunication, VSAT, Internet and Wireless Communication. These additions have madethe book as the first ever comprehensive work on modern electronic communications.

Other significant features of the Book are that it contains a large number of solved examples,and multiple-choice questions at the end of each chapter. The number of multiple-choicequestions is more than 1000.

This way, the Book hopes to meet the requirements of the students studying varioustelecommunication courses being taught at the engineering colleges in the country. The Bookwill be highly useful for the students preparing for UPSC Engineering Services Examination.

This Book has been revised after consulting vast literature in the field of communicationengineering. The authors acknowledge with the due courtesy the sources consulted in thepreparation of this book.

The authors are grateful to Shri Ravi Kashyap (an alumni of IIT Delhi) for his excellenthelp in proof reading of the manuscript. They are also thankful to Shri Pritam Negi for takingup the difficult task of computer typesetting the book over several revisions and proofs.

The authors are also highly grateful for the highly spirited co-operation provided by ShriRomesh Chander Khanna and Shri Vineet Khanna and for the very useful suggestions by themduring the course of preparation of this book.

Finally, the authors will be highly obliged for any positive criticisms and suggestions fromthe readers for improving this book with an object to serve the student community in betterway.

— Authors

Preface

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Contents

1. Introduction to Communication Systems 1—161.1 Introduction 11.2 Communication Systems 1

1.2.1 Information 11.2.2 Transmitter 21.2.3 Channel 21.2.4 Receiver 2

1.3 Amplifiers 21.4 Modulation 31.5 Need for Modulation 31.6 Contaminations 31.7 Noise 31.8 The audio Spectrum 41.9 Signal Power Units 4

1.10 Volume Unit 71.11 Signal-to-noise Ratio 71.12 Analog and Digital Signals 71.13 Baseband and Carrier Communication 9

1.13.1. Types of Modulation 91.14 the Bandwidth Constraint 10

1.14.1 the Bandwidth S/N Ratio Trade-off 111.15 Number Systems 11

1.15.1 Conversion of a Decimal Number of Binary Number 121.15.2 Conversion of Decimal Fraction to Binary 121.15.3 Sign Bit 131.15.4 Binary Codes. The 8421 Code 14

2 Electromagnetic theory 17—542.1 Electromagnetic Wave 172.2 Electromagnetic Field theory : Maxwell’s Equations 17

2.2.1 Time-varying Fields and Maxwell’s Equations 172.2.2 Maxwell’s Equations 202.2.3 Interpretation of Curl in the Maxwell’s Equations 20

2.3 Fields at a Boundary Surface 212.3.1 Current Density in a Perfect Conductor 21

2.4 Electromagnetic Waves in a Homogeneous Medium : The Wave Equation 222.4.1 Uniform Plane-wave Propagation 232.4.2 Definition of Uniform Plane-wave 232.4.3 Transverse Nature of Uniform Plane Wave 232.4.4 Relation Between E and H in a Uniform Plane Wave 24

2.5 Wave Equations : Conducting Medium 262.6 Sinusoidal Time Variations 27

2.6.1 Relationship Between Time-varying and Phasor Quantities 272.6.2 Maxwell’s Equations in Phasor Notation 27

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2.6.3 Wave Equation for Sinusoidal Time Variations 282.6.4 Wave Propagation: Lossless Medium 282.6.5 Wave Propagation : Conducting Medium 29

2.7 Conductors and Dielectrics 302.7.1 Wave Propagation in Good Dielectrics 312.7.2 Wave Propogation in a Good Conductor. 322.7.3 Depth of Penetration. 33

2.8 Polarisation 332.8.1 Circular Polarisation. 342.8.2 Elliptical Polarisation. 342.8.3 Direction Cosines. 352.8.4 Wave Length and Phase Velocity. 36

2.9 Reflection and Refraction of Uniform Plane Waves 362.9.1 Normal incidence on a Perfect Conductor. 362.9.2 Oblique incidence on a Perfect Conductor. 38

2.9.2.1 Electric Field Perpendicular to the Plane of incidence. 392.9.2.2 Electric Field (E) Parallel to the Plane of incidence 40

2.9.3 Normal incidence on a Perfect Dielectric 412.9.4 Oblique incidence on a Perfect insulator 42

2.9.4.1. Perpendicular (Horizontal) Polarisation. 432.9.4.2. Parallel (Vertical) Polarisation. 442.9.4.3. Brewster angle. 45

2.9.5 Total internal Reflection. 462.9.6 Normal incidence on the Surface of a Conductive Medium. 46

2.10 Surface Impedance 462.10.1 Surface Impedance of Good Conductors. 47

2.11 Poynting theorem 482.11.1 Powers Flow for a Plane Wave. 482.12.3 Power Loss in Plane Conductor. 49

3 Noise 54—803.1. External Noise 54

3.1.1 Atmospheric Noise 543.1.2 Extraterrestrial Noise 553.1.3 Man-made Noise 55

3.2. Internal Noise 563.2.1 Shot Noise 573.2.2 Flicker Noise 583.2.3 Transit-time Noise 583.2.4 Partition Noise 58

3.3. Noise Calculations 583.3.1 Addition of Noise from Several Sources 583.3.2 Noise in Reactive Circuits 60

3.4 White Noise: Autocorrelation Function 623.4.1 Filtered White Noise 623.4.2 Equivalent Noise Bandwidth 633.4.3 Narrowband Noise 643.4.4 Equivalent Circuit of a Noisy Complex Impedance 653.4.5 Resistors in Series 65

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3.4.6 Resistor in Parallel 663.4.7 Noise in Passive Network: Nyquist formula 663.4.8 The RC Parallel Circuit 67

3.5 Noise Figure 683.5.1 Signal to Noise Ratio 683.5.2 Noise Figure 683.5.3 Calculation of Noise Figure 69

3.6 Noise Temperature 713.7 Noisy Two-port Network 72

3.7.1 Matched Two-port Noisy Network: Effective Noise Temperature 743.7.2 Attenuators 75

3.8 Receiver—Noise Calculations 753.8.1 Noisy Communication System 76

3.9 Noise in Pn Junction: Current Noise 773.9.1 Noise in Junction Diodes 773.9.2 Noise in Junction Transistors 77

4 Information theory 80-1044.1 Information Theory Analysis 80

4.1.1 Discrete Messages 804.1.2 the Concept of Amount of information 80

4.2 Average information and Entropy 814.2.1 Values of Entropy 824.2.2 Maximum Entropy 824.2.3 Entropy Variation of a Binary Source 834.2.4 Redundancy and Error-free Communication 844.2.5 information Rate 85

4.3 Channel Capacity: Discrete Channel 854.3.1 Discrete Noiseless Channel 864.3.2 Discrete Noisy Channel 874.3.3 The Entropy Rate 884.3.4 Signaling Speed 88

4.4 Calculation of Channel Capacity: Hartley Shannon Law 884.4.1 Capacity of Gaussian Channel 89

4.5 Signal Space and Signal Vectors : Continuous Channel 914.5.1 Properties of Signal Space 914.5.2 Signal Vector for Noisy Channel: Alternate Proof of Hartley-shannon Law 93

4.6 Optimum Bandwidth - Power Exchange 944.7 System Comparison 954.8 r—ary Communication 96

5 Coding theory 105–1185.1 Source Encoding 1055.2 Parity Check Coding 106

5.2.1 algebraic Codes 1075.2.2 Examples of Algebraic Codes 1085.2.3 The r-ary Code 1115.2.4 Fano Method of Code Construction 1115.2.5 Huffman Code 112

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5.2.6 Code Efficiency 1135.2.7 Huffman r-ary Code 113

6 Amplitude Modulation 119–1656.1 Theory of Amplitude Modulation 119

6.1.1 Frequency Spectrum of A.M. Wave. 1206.1.2 Location of A.M. Sidebands on Frequency Spectrum. 1206.1.3 Power Relations in A.M. Signal. 1216.1.4 Current Calculations for A.M. Wave. 1236.1.5 Modulation by Several Sine Waves Simultaneously. 1236.1.6 Graphical Representation of amplitude Modulated Wave. 124

6.2 AM Generation 1276.2.1 Gradual Nonlinear AM Modulator 1276.2.2 Piecewise Linear Modulator 1296.2.3 Low and High Level Modulation 1306.2.4 Modulator Circuits 1316.2.5 Class C Modulators 1316.2.6 Collector Class-C Modulator 1316.2.7 Base Modulator 1326.2.8 Transistor Vendor Biji Modulator 133

6.3 Double-Sideband Supressed-Carrier Modulation 1336.3.1 Generation of DSB: the Ring Modulator 1346.3.2 Generation of DSB: Product Modulator 135

6.4 Description of Single-Side-Band (SSB) 1366.4.1 Saving of Power in SSB 137

6.5 Carrier Suppression 1396.5.1 Effect of Non-linear Resistance on Addition of Signals 1396.5.2 Balanced Modulator 141

6.6 Unwanted Sideband Suppression 1436.6.1 Filter System 1436.6.2 Phase-Shift Method 1446.6.3 Weaver Method 1456.6.4 Comparison of SSB Generation Systems 1466.6.5 Comparsion of the Systems 147

6.7 Other Forms of Amplitude Modulation Systems 1486.7.1 Carrier Reinsertion System (Pilot Carrier System) 1496.7.2 Independent Sideband Systems (ISB) 1506.7.3 Vestigial Sideband Transmission 151

6.8 Demodulation of AM 1526.8.1 Synchronous Detection 1536.8.2 The Nonlinear Demodulator 1546.8.3 Suppressed Carrier AM Demodulator: The Problem of Absence of Carrier 1556.8.4 Homeodyne Detection: Injected Carrier Method 1566.8.5 Effect of Asychronism in DSB and SSB 157

6.9 Envelope Detection 1586.9.1 Envelope Or Diode Detection 1586.9.2 Distortion in Diode Detectors 160

6.10 Principle of Demodulation of SSB 1626.10.1 Product Demodulator 1626.10.2 Detection Using Diode Balanced Modulator 162

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7 Angle Modulation: FM and PM 166—2127.1 Frequency and Phase Modulation Theory 166

7.1.1 Description 1667.1.2 Mathematical analysis of FM Signal 1677.1.3 Frequency Spectrum of FM Wave 1687.1.4 Multi-tone Modulation 171

7.2 Frequency Modulation Bandwidths 1727.2.1 Significant Sideband Bands 1727.2.2 Transmission Bandwidth and Deviation Ratio 174

7.3 Narrowband and Wideband Frequency Modulation (NBFM and WBFM) 1747.4 Phase Modulation 1767.5 Generation of Frequency Modulation 176

7.5.1 Direct FM Modulator 1847.5.2 Frequency Stabilization : Automatic Frequency Controlled Modulator 1857.5.3 Disadvantages of Direct Method 1877.5.4 Indirect FM Modulator : From PM to FM 1877.5.5 RC Phase-Shift Modulator 1887.5.6 Armstrong Method 1897.5.7 FM Using a Phasitron 191

7.6 FM Demodulation : AM-Based Method 1927.6.1 Limiters 1927.6.2 Double-Tuned Demodulator 1937.6.3 Balanced Slope Detector 1947.6.4 Faster-Seely Phase Discriminator 1947.6.5 Ratio Detector 1987.6.6 Advantages of Ratio Detector and Phase Discriminator 200

7.7 Pulse-Based Detector 2017.8 Narrowband Phase Modulation (NBPM) 2027.9 Detection of Phase Modulation 202

7.9.1 Fixed-Reference Detection 2027.9.2 Differential Detection. 2037.9.3 Comparison between FM and PM Systems 2047.9.4 Comparison between FM and AM Systems 205

7.10 Frequency Modulation and Noise 2057.10.1 Effects of Noise on Carrier (Noise Triangle) 2057.10.2 Per-emphasis and De-emphasis 2087.10.3 Other Types of Interference 2097.10.4 Comparison of Narrowband and Wideband FM Systems 2097.10.5 Stereophonic FM Multiplex Broadcasting System 210

8 Radio Receivers: AM, SSBB and FM 213—2468.1 Various Types of Receivers 213

8.1.1 TRF Receiver 2138.1.2 Superherodyne Receiver 214

8.2 AM Receivers 2158.2.1 Radio Frequency Section Characteristics 2158.2.2 Frequency Changing 2198.2.3 Superheterodyne Tracking 2218.2.4 Local Oscillator 221

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8.2.5 Intermediate Frequencies and IF Amplifiers : Choice of IF andIntermediate Frequencies used 2228.2.6 Detection: Theory of a Diode Detector 2238.2.7 Automatic Gain Control (AGC): Principle of Operation 226

8.3 Communication Receivers 2268.3.1 Input Stage. 2278.3.2 Double Conversion 2278.3.3 Bandspread. 2278.3.4 Delayed AGC 2288.3.5 Blocking 2288.3.6 Variable Sensitivity and Selectivity 2298.3.7 Beat Frequency Oscillator (BFO) 2298.3.8 Tuning Calibration. 2298.3.9 Noise Limiter. 2308.3.10 Squelch (Muting) 2318.3.11 Automatic Frequency Control (AFC) 2328.3.12 the Tuning Eye 2328.3.13 S-meters 2338.3.14 Diversity Reception 233

8.4 FM Receivers 2368.4.1 Common Circuits Between AM and FM Receivers 2368.4.2 Amplitude Limiter 237

8.5. Stereophonic FM Broadcasting 2388.6. Single and independent Sideband Receivers 240

8.6.1 Demodulator of SSB Product Demodulator 2408.6.2 Types of Receivers 241

9 Transmission Lines 247—2739.1 Transmission Line analysis 247

9.1.1 Distributed Parameters 2479.1.2 Basic Transmission Line Equation 2489.1.3 Characteristic Impedance 2519.1.4 Propagation Constant 252

9.2 Distortions on Transmission Line 2529.2.1 Condition for Frequency Distortion to be Absent 2539.2.2 Condition for Phase Distortion to be Absent 2539.2.3 Loading of Transmission Lines 255

9.3 Standing Waves 2569.3.1 Lossless Open and Short Circuited Line 2569.3.2 Standing Wave Pattern 2599.3.3 Standing Wave Ratio (SWR) 259

9.4 Properties of Lines of Various Lengths 2619.4.1 Quarter Wavelength Line 2619.4.2 Half Wavelength Line 261

9.5 Matching 2629.5.1 Single Stub-matching 2639.5.2 Smith Chart 264

9.6 Types of Transmission Lines 270

Electronic Communication Digital,Analog and Wireless

Publisher : KHANNAPUBLISHERS ISBN : 9788174093134 Author : Sanjeeva Gupta

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