Electrical Spectrum & Network Analyzers: A Practical Approach

223 Pages·1991·21.81 MB·English

by  Albert D. Helfrick

Electrical Spectrum
and Network Analyzers
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Electrical Spectrum
and Network Analyzers
A Practical Approach
Albert D. Helfrick
Consulting Engineer
Kinnelon, New Jersey
Academic Press, Inc.
Harcourt Brace Jovanovich, Publishers
San Diego New York Boston London Sydney Tokyo Toronto
This book is printed on acid-free paper. @
Copyright © 1991 by ACADEMIC PRESS, INC.
All Rights Reserved.
No part of this publication may be reproduced or transmitted in any form or
by any means, electronic or mechanical, including photocopy, recording, or
any information storage and retrieval system, without permission in writing
from the publisher.
Academic Press, Inc.
San Diego, California 92101
United Kingdom Edition published by
Academic Press Limited
24-28 Oval Road, London NW1 7DX
Library of Congress Cataloging-in-Publication Data
Helfrick, Albert D.
Electrical spectrum and network analyzers: a practical approach
/ Albert D. Helfrick,
p. cm.
Includes bibliographical references and index.
ISBN 0-12-338250-5
1. Spectrum analysis. 2. Spectrum analyzers. I Title.
TK7879.4.H45 1991
621.382-dc20 90-49831
CIP
PRINTED IN THE UNITED STATES OF AMERICA
91 92 93 94 9 8 7 6 5 4 3 2 1
Contents
Preface ix
1
Spectra and Spectrum Analysis
1.1 Waveforms: A Review of Basics 1
1.2 The Fourier Transform 2
1.3 The Fourier Series 3
1.4 Measuring Spectra 8
1.5 Standards for Spectrum Analyzers 8
2
Methods of Spectrum Analysis
2.1 Overview 14
2.2 The Parallel Filter Analyzer 15
2.3 The Superheterodyne Analyzer 17
2.3.1 Determining the Internal Frequencies 20
2.3.2 Log IF Amplifiers 21
2.3.3 Multiple-Conversion Superheterodyne Analyzers 25
2.3.4 Local Oscillators 28
2.3.5 Frequency Linearizers 35
2.3.6 IF Filters 38
2.3.7 Mixers 46
Review Questions 47
Frequency Control, Phase Lock, and
Microprocessor-Controlled Spectrum Analyzers
3.1 Frequency Display 48
3.2 Phase-Locked Frequency Tuning 56
vi Contents
3.3 Microwave Spectrum Analyzers 69
3.4 Microprocessor Control of the Spectrum Analyzer 72
3.5 Digital Display Storage 73
Review Questions 76
4
Spectrum Analyzer Applications
4.1 Measuring Spectra 78
4.2 Measuring Wide-Band Spectra 80
4.3 Measuring Amplitude and Frequency Modulation 92
4.4 Spurious Responses 99
Review Questions 100
Advanced Spectrum Analyzer Applications
5.1 Transmitter Measurements 102
5.1.1 Spurious Outputs 102
5.1.2 Occupied Bandwidth 106
5.1.3 Frequency Stability 108
5.2 In-Circuit Troubleshooting Techniques 109
5.3 Radio Frequency Interference Measurements 112
Review Questions 114
The Tracking Generator and Scalar Network Analysis
6.1 Tracking Generator Basics 116
6.2 The Superheterodyne Tracking Generator 119
6.3 Network Analysis 129
6.4 Tracking Generator Applications 134
Review Questions 137
7
A Practical Spectrum Analyzer
7.1 Overview 139
7.2 Specifications 140
7.3 Attenuator 142
7.4 Input Low-Pass Filter 145
Contents vii
7.5 First Mixer and Local Oscillator 148
7.6 First IF Amplifier, Second Mixer, and Second
Local Oscillator 154
7.7 The IF Filters 155
7.8 Log IF Amplifier and Video Display Amplifier 159
7.9 Horizontal Sweep Generator and Amplifiers 161
7.10 Vertical Amplifiers and Video Filter 164
7.11 Frequency Readout and Control 167
Review Questions 174
8
Spectrum Analyzer Performance Determination
8.1 Overview 176
8.2 Spectrum Analyzer Tests 177
8.2.1 Center-Frequency Display Accuracy 177
8.2.2 Frequency Span Readout 178
8.2.3 Resolution Bandwidth Accuracy 179
8.2.4 Shape Factor 180
8.2.5 Display Vertical Accuracy 180
8.2.6 Frequency Response 182
8.2.7 Display Flatness 182
8.2.8 Sensitivity 183
8.2.9 Dynamic Range 183
8.2.10 Intermodulation Dynamic Range 184
8.2.11 No-Signal, Internally Generated Spurious Responses 185
8.2.12 Residual Frequency Modulation 185
8.2.13 IF Feedthrough 186
8.2.14 Other Tests 187
Review Questions 187
9
The Network Analyzer
9.1 Introduction 188
9.2 Group Delay Measurements 194
9.3 Network Analyzer Circuits 196
9.4 Network/Spectrum Analyzers 201
9.5 The Scalar Network Analyzer 203
Review Questions 206
Bibliography 207
Index 209
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Preface
This book fills the gap between the texts that provide all there is to know
about the theory of spectrum analysis and the glorified instruction books. For
most engineers and technicians, what is most necessary for the effective use of
the spectrum analyzer is the knowledge of how the instrument operates. The
physical basis for the displayed spectra, the Fourier and fast Fourier transforms,
and the rigorous theoretical foundations of spectral analysis are often beyond
what is needed to make effective use of the spectrum analyzer. On the other
hand, knowledge of the internal structure of an instrument helps in understanding
the proper operation of that instrument.
This text presents some theory and some theoretical circuits, but primarily
it provides a view of practical circuits and useful operational techniques. Insight
into some of the more specialized analyzers is presented so that the student will
appreciate the wide use of spectral analysis. The main thrust, however, is the use
of spectral analysis for radio frequency measurements. The operational tech-
niques described in this book go beyond those provided in the typical instruction
manual. Because operational techniques are generic and thus applicable to any
spectrum analyzer, techniques that extend beyond just the operation of an ana-
lyzer are given. Use of the spectrum analyzer for troubleshooting is discussed as
well as numerous accessories that make the analyzer more valuable.
The tracking generator, one of the more useful of these accessories, is
covered as is the network analyzer, a practical extension of the spectrum
analyzer-tracking generator combination. In some modern instruments both
functions are contained in a single instrument. Therefore, to keep the text mod-
ern and complete, the network and spectrum analyzers are covered in a similar
fashion.
Above all, this is a textbook. There are end-of-chapter review questions,
an extensive bibliography, and practical circuits that may be constructed and
investigated.
Albert D. Helfrick
ix