Electronic Communication System (4th Edition) by Kennedy & Davis.pdf PDF

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Contents PREFACE xv 1 INTRODUCTION TO COMMUNICATIONS SYSTEMS 1 1-1 COMMUNICATIONS 1 1-2 COMMUNICATIONS SYSTEMS 2 1-2.1 Information 2 1-2.2 Transmitter 3 1-2.3 Channel-Noise 4 1-2.4 Receiver 4 1-3 MODULATION 5 1-3.1 Description 5 1-3.2 Need for modulation 5 1-4 BANDWIDTH REQUIREMENTS 6 1-4.1 Sine wa...

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Contents xv

PREFACE

1 INTRODUCTION TO COMMUNICATIONS

1

1-1 COMMUNICATIONS 1-2 COMMUNICATIONS 1-2.1 Information 1-2.2 Transmitter 1-2.3 Channel-Noise 1-2.4 Receiver

1

SYSTEMS

SYSTEMS

2 2 3 4 4 5 5 5

1-3 MODULATION 1-3.1 Description 1-3.2 Need for modulation 1-4 BANDWIDTH REQUIREMENTS 1-4.1 Sine wave and Fourier series review 1-4.2 Frequency spectra of nonsinusoidal waves

6 7 11

14

2 NOISE 2-1 EXTERNAL

NOISE

2-1.1 Atmospheric noise 2-1. 2 Extraterrestrial noise 2-1.3 Industrial noise 2-2 INTERNAL 2-2.1 2-2.2 2-2.3 2-2.4

NOISE

Thermal agitation noise Shot noise Transit-time noise Miscellaneous noise

15 15 16 16 17 17 19 20 20

2-3 NOISE CALCULATIONS 2-3.1 Addition of noise due to several sources 2-3.2 Addition of noise due to several amplifiers in cascade 2-3.3 Noise in reactive circuits

21 21 21 23

2-4 NOISE FIGURE

25 25 25

2-4.1 Signal-to-noise ratio 2-4.2 Definition of noise figure

v

vi CONTENTS 2-4.3 Calculation of noise figure 2-4.4 Noise figure from equivalent noise resistance 2-4.5 Noise figure from measurement 2-5 NOISE TEMPBRATURE

26 27 29 30

3 AMPLITUDE MODULATION

35

3-1 AMPLITUDE MODULATION THEORY 3-1.1 Frequency spectrum of the AM wave 3-1.2 Representation of AM 3-1.3 Power relations in the AM wave

35 36 38 39

3-2 GENERATION OF AM 3-2.1 Basic requirements-Comparison of levels 3-2.2 Grid-modulated class C amplifier 3-2.3 Plate-modulated class C amplifier 3-2.4 Modulated transistor amplifers 3-2.5 Summary

43 43 46 47 50 52

4 SINGLE-SIDEBAND

56

TECHNIQUES

4-1 EVOLUTION AND DESCRIPTION OF SSB

57

4-2 SUPPRESSION OF CARRIER 4-2.1 Effect of nonlinear resistance on added signals 4-2.2 The balanced modulator

59 60 62

4-3 SUPPRESSION OF UNWANTED SIDEBAND 4-3.1 The filter system 4-3.2 The phase-shift method 4-3.3 The "third" method 4-3.4 System evaluation and comparison 4-4 EXTENSIONS OF SSB 4-4.1 Forms of amplitude modulation 4-4.2 Carrier reinsertion-Pilot-carrier systems 4-4.3 Independent-sideband (ISB) systems 4-4.4 Vestigial-sideband transmission 4-5 SUMMARY

64 64 65 67 68 69 69 71 71 73 75

5 FREQUENCY MODULATION 5-1 THEORY OF FREQUENCY AND PHASE MODULATION 5-1.1 Description of systems 5-1.2 Mathematical representation of FM 5-1.3 Frequency spectrum of the FM wave 5-1.4 Phase modulation 5-1.5 Intersystem comparisons

79 80 81 82 85 89 89

CONTENTS "il 5-2 NOISE AND FREQUENCY MODULATION 5-2.1 Effects of noise on carrier-Noise mangle 5-2.2 Pre-emphasis and de-emphasis 5-2.3 Other forms of interference 5-2.4 Comparison of wideband and narrowband FM 5-2.5 Stereophonic FM multiplex system 5-3 GENERATION OF FREQUENCY MODULATION 5-3.1 FM methods 5-3.2 Direct methods 5-3.3 Stabilized reactance modulator-AFC 5-3.4 Indirect method 5-4 SUMMARY

92 92 95 97 98 98 100 101 101 108 109 113 118

6 RADIO RECEIVERS 6-1 RECEIVER TYPES 6-1.1 Tuned radio-frequency (TRF) receiver 6-1.2 Superheterodyne receiver 6-2 AM RECEIVERS 6-2.1 RF section and characteristics 6-2.2 Frequency changing and tracking 6-2.3 Intermediate frequencies and IF amplifiers 6-2.4 Detection and automatic gain control (AGC) 6-3 COMMUNICATIONS RECEIVERS 6-3.1 Extensions of the superheterodyne principle 6-3.2 Additional circuits 6-3.3 Additional systems 6-4 FM RECEIVERS 6-4.1 Common circuits-Comparison with AM receivers 6-4.2 Amplitude limiting 6-4.3 Basic FM demodulators 6-4.4 Radio detector 6-4.5 FM demodulator comparison 6-4.6 Stereo FM multiplex reception 6-5 SINGLE- AND INDEPENDENT-SIDEBAND RECEIVERS 6-5.1 Demodulation of SSB 6-5.2 Receiver types

7 TRANSMISSION 7-1 BASIC PRINCIPLES 7-1.1 Fundamentals of transmission lines 7-1.2 Characteristic impedance

119 119 120 122 122 128 134 136 141 141 146 151 158 158 159 162 169 173 173 174 175 176

185

LINES 185 186 188

vjii CONTENTS192 193 196 199

7-1.3 Losses in transmission lines 7-1.4 Standing waves 7-1.5 Quarter- and half-wavelength lines 7-1.6 Reactance properties of transmission lines 7-2 THE SMITH CHART AND ITS APPLICATIONS 7-2.1 Fundamentals of the Smith chart 7-2.2 Problem solution

202 202 206

- 7=3 TRANSMISSION-LINE 7-3.1 7-3.2 7-3.3 7-3.4

214 214 215 216 217

COMPONENTS The double stub Directional couplers Baluns The slotted line

8 RADIATION

AND PROPAGATION

OF WAVES

222

8-1 ELECTROMAGNETIC RADIATION 8-1.1 Fundamentals of el~ctromagnetic waves 8-1.2 Effects of the environm~nt

223 223 229

8-2 PROPAGATION OF WAVES 8-2.1 Ground (surface) waves ~-2.2 Sky-wave propagation-The ionosphere 8-2.3 Space waves 8-2.4 Tropospheric scatter propagation 8-2.5 Extraterrestrial communications

236 237 239 246 248 249

9 ANTENNAS 9-1 BASIC CONSIDERATIONS 9-1.1 Electromagnetic radiation 9-1.2 The elementary doublet (Hertzian dipole) 9-2 WIRE RADIATORS IN SPACE 9-2.1 Current and voltage distributions 9-2.2 Resonant antennas, radiation patterns, and length calculations 9-2.3 Nonresonant antennas (Directional antennas) 9-3 TERMS AND DEFINITIONS 9-3.1 Antenna gain and effective radiated power 9-3.2 Radiation measurement and field intensity 9-3.3 Antenna resistance 9-3.4 Bandwidth, beamwidth, and polarization 9-4 EFFECTS OF GROUND ON ANTENNAS 9-4.1 Ungrounded antennas 9-4.2 Grounded antennas

255 256 256 257 258 258 259 261 262 262 264 264 265 266 267 267

CONTENTS ix 268 269

9-4.3 Grounding systems 9-4.4 Effects of antenna height 9-5 ANTENNA COUPLING AT MEDIUM FREQUENCIES 9-5.1 General considerations 9-5.2 Selection of feed point 9-5.3 Antenna couplers 9-5.4 Impedance matching with stubs and other devices

272 272 272 273 274

9-6 DIRECTIONAL HIGH-FREQUENCY ANTENNAS 9-6.1 Dipole arrays 9-6.2 Folded dipole and applications 9-6.3 Nonresonant antennas-The rhombic

275 276 278 280

9-7 UHF AND MICROWAVE ANTENNAS 9-7. 1 Antennas with parabolic reflectors 9-7.2 Horn antennas 9-7.3 Lens antennas

281 281 290 293

9-8 WIDEBAND AND SPECIAL-PURPOSE ANTENNAS 9-8.1 Folded dipole (bandwidth compensation) 9-8.2 Helical antenna 9-8.3 Discone antenna 9-8.4 Log-periodic antennas 9-8.5 Loop antennas 9-8.6 Phased arrays 9-9 SUMMARY

295 296 297 298 300 301 302

10 WAVEGUIDES,

RESONATORS

303

310

AND COMPONENTS

I0-1 RECTANGULAR WAVEGUIDES 10-1.1 Introduction 10-1.2 Reflection of waves from a conducting plane 10-1.3 The parallel-plane waveguide 10-1.4 Rectangular waveguides 10-2 CIRCULAR AND OTHER WAVEGUIDES 10-2.1 Circular waveguides 10-2.2 Other waveguides 10-3 WAVEGUIDECOUPLING, MATCHING AND ATTENUATION 10-3.1 Methods of exciting waveguides 10-3.2 Waveguide couplings 10-3.3 Basic accessories 10-3.4 Multiple junctions 10-3.5 Impedance matching and tuning 10-4 CAVITY RESONATORS 10-4.1 Fundamentals 10-4.2 Practical considerations

311 312 314 318 324 331 331 334 335 335 338 340 343 "347 353 353 355

x CONTENTS 10-5 AUXILIARY COMPONENTS 10-5.1 Directional couplers 10-5.2 Isolators and circulators 10-5.3 Mixers, detectors and detector mounts 10-5.4 Switches

11 MICROWAVE

357 357 358 365 367

377

TUBES AND CIRCUITS

11-1 MICROWAVE TRIODES 11-1.1 Frequency limitations of gridded tubes 11-1.2 UHF triodes and circuits

378 378 380

11-2 MULTICAVITY KLYSTRON 11-2.1 Operation 11-2.2 Practical considerations

381 382 384

11-3 REFLEX KLYSTRON 11-3.1 Fundamentals 11-3.2 Practical considerations

387 387 389

11-4 MAGNETRON 11-4.1 Introduction 11-4.2 Operation 11-4.3 Practical cQnsiderations 11-4.4 Types, performance and applications

390 391 394 396 398

11-5 TRAVELING-WAVETUBE (TWT) 11-5.1 TWT fundamentals 11-5.2 Practical considerations 11-5.3 Types, performance and applications 11-6 OTHER MICROWAVE TUBES 11-6.1 Crossed-field amplifier 11-6.2 Backward-wave oscillator 11-6.3 Miscellaneous tubes

400 401 403 405

12 SEMICONDUCTOR

408 408 410 411

, MICROWAVE DEVICES AND CIRCUITS

12-1 PASSIVE MICROWAVECIRCUITS 12-1.1 Stripline and microstrip circuits 12-1.2 SAW devices

417 417 419

12-2 TRANSISTORS AND INTEGRATED CIRCUITS 12-2.1 High-frequency limitations 12-2.2 Microwave transistors and integrated circuits 12-2.3 Microwave integrated circuits 12-2.4 Performance and applications of microwave transistors and MIC$

420 421 422 424 425

416

CONTENTS xi 12-3 VARACTOR AND STEP-RECOVERY DIODES AND MULTIPLIERS 12-3.1 Varactor diodes 12-3.2 Step-recovery diodes 12-3.3 Frequency multipliers 12-4 PARAMETRIC AMPLIFIERS .

12-5

12-6

12-7

12-8

427 427 430 430 432

12-4.1 Basic principles

432

12-4.2 Amplifier circuits TUNNEL DIODES AND NEGATIVE-RESISTANCE AMPLIRERS 12-5.1 Principles of tunnel diodes 12-5.2 Negative-resistance amplifiers 12-5.3 Tunnel-diode applications GUNN EFFECT AND DIODES 12-6.1 Gunn effect 12-6.2 Gunn diodes and applications AVALANCHEEFFECTS AND DIODES 12-7.1 IMPATT diodes 12-7.2 TRAPATT diodes 12-7.3 Performance and applications of avalanche diodes OTHER MICROWAVE DIODES 12-8.1 PIN diodes 12-8.2 Schottky-barrier diode 12-8.3 Backward diodes

435 440 440 444 446 448 448 451 454 455 458 '459 461 462 463 464

12-9 STIMULATED-EMISSION (QUANTUM-MECHANICAL) AND ASSOCIATED DEVICES 12-9.1 Fundamentals of masers 12-9.2 Practical masers and their applications 12-9.3 Fundamentals of lasers 12-9.4 CW lasers and their communications applications 12-9.5 Other optoelectronic devices

465 465 469 470 472 475

13 PULSE COMMUNICATIONS B-1 INFORMATION THEORY 13-1.1 Information in a communications system 13-1.2 Coding 13-1.3 Noise in an information-carrying channel 13-2 PULSE MODULATION 13-2.1 Introduction-Types J3-2.2 Pulse-width modulation 13-2.3 Pulse-position modulation (PPM) 13-2.4 Pulse-code modulation (PCM)

484 485 485 487 491 494 494 496 498 499

xii CONTENTS 13-3 PULSE SYSTEMS 13-3.1 Telegraphy (and Telex) 13-3.2 Telemetry

507 508 510

14 DIGITAL COMMUNICATIONS

516

14-1 DIGITAL TECHNOLOGY 14-1. 1 Digital fundamentals 14-1.2 The binary number system 14-1.3 Digital electronics 14-2 FUNDAMENTALS OF DATA COMMUNICATIONS SYSTEMS 14-2.1 The emergence of data communications systems 14-2.2 Characteristics of data transmission circuits 14-2.3 Digital codes 14-2.4 Error detection and correction

517 517 519 523

14-3 DATA SETS AND INTERCONNECTION REQUIREMENTS 14-3.1 Modem classification 14-3.2 Modem interfacing 14-3.3 Interconnection of data circuits to telephone loop~ 14-4 NETWORK AND CONTROL CONSIDERATIONS 14-4.1 Network ~rganizations 14-4.2 Switching systems 14-4.3 Network protocols 14-5 SUMMARY

547 548 550 552

15 BROADBAND COMMUNICATIONS

528 528 530 535 541

553 553 556 557 559

SYSTEMS

562

15-1 MULTIPLEXING 15-1.1 Frequency-division multiplex 15-1.2 Time-division multiplex 15-2 SHORT- AND MEDIUM-HAUL SYSTEMS 15-2.1 Coaxial cables 15-2.2 Fiber optic links 15-2.3 Microwave links 15-2.4 Tropospheric scatter links 15-3 LONG-HAUL SYSTEMS 15-3.1 Submarine cables 15-3.2 Satellite communications

563 564 566

15-4 ELEMENTS OF LONG-DISTANCE TEhEPHONY 15-4.1 Routing codes and signaling sy*ms 15-4.2 Telephone exchanges (switcheS) and routing 15-4.3 Miscellapeous practical aspects . 15-4.4 IntroductiOn to traffic engineering

592 592 593 594 595

568 569 571 571 575 576 576 581

CONTENTS xiii

16 RADAR SYSTEMS

600

16-1 BASIC PRINCIPLES 16-1.1 Fundamentals 16-1.2 Radar performance factors 16-2 PULSED SYSTEMS 16-2.1 Basic pulsed radar system 16-2.2 Antennas and scanning 16-2.3 Display methods 16-2.4 Pulsed radar systems 16-2.5 Moving-target indication (MTI) 16-2.6 Radar beacons

601 601 606 612 612 617 620 623 626 632

16-3 OTHER RADAR SYSTEMS 16-3.1 CW Doppler radar 16-3.2 Frequency-modulated CW radar 16-3.3 Phased array radars 16-3.4 Planar array radars

634 634 637 638 642

17 TELEVISION FUNDAMENTALS 17-1 REQUIREMENTS AND STANDARDS 17-1.1 Introduction to television 17-1.2 Television systems and standards 17-2 BLACK-AND-WHITE TRANSMISSION 17-2.1 Fundamentals 17-2.2 Beam Scanning 17-2.3 Blanking and synchronizing pulses 17-3 BLACK-AND-WHITE RECEPTION 17-3.1 Fundamentals 17-3.2 Common, video and sound circuits 17-3.3 Synchronizing circuits 17-3.4 Vertical deflection circuits 17-3.5 Horizontal deflection circuits

·

17A COLOR TRANSMISSION AND RECEPTION 17-4. 1 Introduction 17-4.2 Color transmission 17-4.3 Color reception

18 INTRODUCTION

648 649 649 651 655 655 657 660 664 664 665 670 674 679 682 682 684 689

TO FIBER OPTIC TECHNOLOGY

701

18-1 HISTORY OF FIBER OPTICS

702

18-2 WHY FIBER OPTICS?

703

xiv CONTENTS 18-3 INTRODUCTION TO LIGHT 18-3.1 Reflection and Refraction 18-3.2 Dispersion, Diffraction, Absorption, and Scattering 18-4 THE OPTICAL FIBER AND FIBER CABLES 18-4.1 Fiber Characteristics and Classification 18-4.2 Fiber Losses

703 704 705 709 712 716

18-5 FIBER 18-5.1 18-5.2 18-5.3 18-5.4 18-5.5 18-5.6

717 717 718 718 719 721 722

OPTIC COMPONENTS AND SYSTEMS The Source Noise Response Time The Optical Link Light Wave The System

18-6 INSTALLATION, TESTING, AND REPAIR 18-6.1 Splices 18-6.2 Fiber Optic Testing 18-6.3 Power Budgeting 18-6.4 Passive Components 18-6.5 Receivers

722 723 727 731 732 733

18-7 SUMMARY

735

APPENDIX: LIST OF SYMBOLS AND ABBREVIATIONS

INDEX

741

745

to Communications Systems Introduction

This chapter serves to introduce the reader to the subject of communications systems, and also this book as a whole. In studying it, you will be introduced to an information source, a basic communications system, transmitters, receivers and noise. Modulation methods are introduced, and the absolute need to use

them in conveying information will be made clear. The final section briefly discusses bandwidth requirements and shows that the bandwidth needed to transmit some signals and waveforms is a great deal more than might be expected.

OBJECTIVES Upon completing the material in Chapter 1, the student will be able to: Derme the word information as it applies to the subject of communications. Explain the term channel noise and its effects. Understand the use of modulation, as it applies to transmission. Solve problems using Fourier series and transforms. Demonstrate a basic understanding of the term bandwiifth and its application in communications.

1..1

COMMUNICATIONS In a broad sense, the term communications refers to the sending, receiving and processing of information by electronic means. Communications started with wire telegraphy in the eighteen forties, developing with telephony some decades later and radio at the beginning of this century. Radio communication, made possible by the invention of the triode tube, was greatly improved by the work done during World War II. It subsequently became even more widely used and refined through the invention and use of the transistor, integrated circuits and other semiconductor devices. More recently, the I

2 ELECTRONIC COMMUNICAnON SYSTEMS use of satellites andfiber optics has made communications even more widespread, with an increasing emphasi? on computer and other data communications. A modem communications system is first concerned with the sorting, processing and sometimes storing of information before its transmission. The actual transmission then follows, with further processing and the filtering of noise. Finally we have reception, which may include processing steps such as decoding, storage and interpretation. In this context, forms of communications include radio telephony and telegraphy, broadcasting, point-to-point and mobile communications (commercial or military), computer communications, radar, radiotelemetry and radio aids to navigation. All these are treated in turn, in following chapters. In order to become familiar with these systems, it is necessary first to know about amplifiers and oscillators, the building blocks of all electronic processes and equipment. With these as a background, the everyday communications concepts of noise, modulation and information theory, as well as the various systems themselves, may be approached. Any logical order may be used, but the one adopted here is, basic systems, communications processes and circuits, and more complex systems, is considered most suitable. It is also important to consider the human factors influencing a particular system, since they must always affect its design, planning and use.

1-2

COMMUNICATIONSSYSTEMS Before investigating individual systems, we have to define and discuss important terms such as information, message and signal, channel (see Section 1-2.3), noise and distortion, modulation and demodulation, and finally encoding and decoding. To correlate these concepts, a block diagram of a general communications system is shown in Figure I-I.

1-2.1 Information The communications system exists to convey a message. This message comes from the information source, which originates it, in the sense of selecting one message from a group of messages. Although this applies more to telegraphy than to entertainment broadcasting, for example, it may nevertheless be shown to apply to all forms of communications. The set, or total number of messages, consists of individual mes-

Encoding modulation(dIstortion)

FIGURE I-I

(distortion) .

Decoding demodulation (distortion)

Block diagram of communications system.

INTRODUCTION TO COMMUNICATIONS SYSTEMS 3 sages which may be distinguished from one another. These may be words, groups of words, code symbols or any other prearranged units. Information itself is that which is conveyed. The amount of information contained in any given message can be measured in bits or in dits. which are dealt with in Chapter 13, and depends on the number of choices that must be made. The greater the total number of possible selections, the larger the amount of information conveyed. To indicate the position of a word on this page, it may be sufficient to say that it is on the top or bottom, left or right side, i.e., two consecutive choices of one out of two possibilities. If this word may appear in anyone of two pages, it is now necessary to say which one, and more information must be given. The meaning (or lack of meaning) of the information does not matter, from this P9int of view, only the quantity is important. It must be realized that no real information is conveyed by a redundant (i.e., totally predictable) message. Redundancy is not wasteful under all conditions. Apart from its obvious use in entertainment, teaching and any appeal to the emotions, it also helps a message to remain intelligible under difficult or noisy conditions.

1-2.2 Transmitter Unless the message arriving from the information source is electrical i...