RF Components and Circuits

RF Components and Circuits

RF Components and Circuits Joseph J. Carr Newnes OXFORD AMSTERDAM BOSTON LONDON NEW YORK PARIS SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO

Newnes An imprint of Elsevier Science Linacre House, Jordan Hill, Oxford OX2 8DP 225 Wildwood Avenue, Woburn, MA 01801-2041 First edition 2002 Copyright Joseph J. Carr and Elsevier Science Ltd 2002. All rights reserved The right of Joseph J. Carr to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1T 4LP. Applications for the copyright holder s written permission to reproduce any part of this publication should be addressed to the publishers British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN 0 7506 48449 Published in conjunction with Radio Society of Great Britain, Lambda House, Cranborne Road, Potters Bar, Herts, EN6 3JE. UK www.rsgb.org.uk For information on all Newnes publications visit our website at: newnespress.com Cover illustration supplied by Coilcraft Europe Ltd Composition by Genesis Typesetting, Rochester, Kent Printed and bound in Great Britain

Foreword...? Remembering Joe Carr, K4IPV...? Preface...? Part 1 Introduction... 1 1 Introduction to radio frequencies... 1 What are the radio frequencies?... 1 Why are radio frequencies different?... 1 What this book covers... 1 2 Signals and noise... 2 Types of signals... 2 Static and quasistatic signals... 2 Periodic signals... 2 Repetitive signals... 2 Transient signals and pulse signals... 9 Fourier series... 9 Waveform symmetry... 11 Transient signals... 17 Sampled signals... 18 Noise... 21 Signal-to-noise ratio (SNR or Sn)... 27 Noise factor, noise figure and noise temperature... 29 Noise factor (FN)... 29 Noise figure (NF)... 30 Noise temperature ( Te)... 30 Noise in cascade amplifiers... 31 Noise reduction strategies... 31 Noise reduction by signal averaging... 32 Example... 32 3 Radio receivers... 3 Signals, noise and reception... 3 The reception problem... 35 Strategies... 37 Radio receiver specifications... 38 Origins... 38 Crystal video receivers... 3.4 Tuned radio frequency (TRF) receivers... 3.4

Superheterodyne receivers... 3.4 Heterodyning... 42 Front-end circuits... 44 Intermediate frequency (IF) amplifier... 44 Detector... 44 Audio amplifiers... 44 Receiver performance factors... 44 Units of measure... 45 Input signal voltage... 45 dbm... 45 dbmv... 46 db... 46 V... 46 Noise... 46 Signal-to-noise ratio (SNR or Sn)... 46 Receiver noise floor... 47 Static measures of receiver performance... 47 Sensitivity... 47 Selectivity... 50 Front-end bandwidth... 52 Image rejection... 53 1st IF rejection... 54 IF bandwidth... 54 IF passband shape factor... 55 Distant frequency ( ultimate ) rejection... 57 Stability... 57 AGC range and threshold... 58 Dynamic performance... 58 Intermodulation products... 59-1 db compression point... 60 Third-order intercept point... 60 Dynamic range... 62 Blocking... 63 Cross-modulation... 63 Reciprocal mixing... 64 IF notch rejection... 64 Internal spurii... 65 Part 2 Circuits... 2 4 RF amplifiers... 4 Noise and preselectors/preamplifiers... 70

Amplifier configurations... 70 Transistor gain... 70 Classification by common element... 72 Common emitter circuits... 72 Common collector circuits... 73 Common base circuits... 73 Transistor biasing... 73 Collector-to-base bias... 74 Emitter bias or self-bias... 74 Frequency characteristics... 75 JFET and MOSFET connections... 75 JFET preselector... 76 VHF receiver preselector... 79 MOSFET preselector... 79 Voltage-tuned receiver preselector... 81 Broadband RF preamplifier for VLF, LF and AM BCB... 81 Push-pull RF amplifiers... 84 Types of push-pull RF amplifiers... 84 Actual circuit details... 86 Broadband RF amplifier (50 ohm input and output)... 88 5 Mixers... 5.1 Linear-vs-non-linear mixers... 5.1 Simple diode mixer... 94 The question of balance... 95 Unbalanced mixers... 95 Single balanced mixers... 95 Double balanced mixers... 95 Spurious responses... 95 Image... 95 Half IF... 96 IF feedthrough... 96 High-order spurs... 97 LO harmonic spurs... 98 LO noise spurs... 98 Mixer distortion products... 98 Third-order intercept point... 99 Calculating intercept points... 101 Mixer losses... 101 Noise figure... 102 Noise balance... 102 Single-ended active mixer circuits... 103

Balanced active mixers... 104 Gilbert cell mixers... 113 Passive double-balanced mixers... 114 Diplexers... 116 Bandpass diplexers... 117 Double DBM... 5.36 Image reject mixers... 5.36 VHF/UHF microwave mixer circuits... 124 6 Oscillators... 6 Feedback oscillators... 6 General types of RF oscillator circuits... 126 Piezoelectric crystals... 128 Piezoelectricity... 129 Equivalent circuit... 129 Crystal packaging... 129 Temperature performance... 133 Room temperature crystal oscillators... 133 Temperature-compensated crystal oscillators... 133 Oven-controlled crystal oscillators... 133 Short-term stability... 134 Long-term stability... 134 Miller oscillators... 134 Pierce oscillators... 136 Butler oscillators... 138 Colpitts oscillators... 143 Overtone oscillators... 145 Frequency stability... 147 Temperature... 149 Thermal isolation... 149 Avoid self-heating... 150 Other stability criteria... 150 Use low frequencies... 150 Feedback level... 150 Output isolation... 150 DC power supply... 150 Vibration isolation... 153 Coil core selection... 153 Coil-core processing... 153 Air core coils... 154 Capacitor selection... 154 Tempco circuit... 155

Varactors... 155 Frequency synthesizers... 157 Reference section... 159 Frequency synthesizer section... 159 Output section... 159 Automatic level control (ALC)... 160 7 IF amplifiers and filters... 7 IF filters: general filter theory... 7 L C IF filters... 163 Crystal filters... 165 Crystal ladder filters... 167 Monolithic ceramic crystal filters... 170 Mechanical filters... 170 SAW filters... 171 Filter switching in IF amplifiers... 173 Amplifier circuits... 174 Cascode pair amplifier... 175 Universal IF amplifier... 175 Coupling to block filters... 178 More IC IF amplifiers... 179 MC-1590 circuit... 179 SL560C circuits... 180 FM IF amplifier... 180 Successive detection logarithmic amplifiers... 180 8 Demodulators... 8.2 AM envelope detectors... 8.2 AM noise... 190 Synchronous AM demodulation... 190 Double sideband (DSBSC) and single sideband (SSBSC) suppressed carrier demodulators... 190 Phasing method... 197 FM and PM demodulator circuits... 197 Foster Seeley discriminator... 197 Ratio detector... 200 Pulse counting detector... 8.23 Phase-locked loop FM/PM detectors... 206 Quadrature detector... 206 Part 3 Components... 3

9 Capacitors... 9 Units of capacitance... 9 Breakdown voltage... 211 Circuit symbols for capacitors... 211 Fixed capacitors... 212 Paper dielectric capacitors... 212 Mylar dielectric capacitors... 212 Ceramic dielectric capacitors... 213 Mica dielectric capacitors... 214 Other capacitors... 214 Variable capacitors... 215 Air variable main tuning capacitors... 217 Capacitor tuning laws SLC-vs-SLF... 219 Special variable capacitors... 220 Split stator capacitors... 221 Differential capacitors... 221 Transmitting variable capacitors... 222 Variable capacitor cleaning note... 222 Using and stabilizing a varactor diode... 223 Varactor tuning circuits... 223 Temperature compensation... 9.21 Varactor applications... 230 10 Inductors... C Inductor circuit symbols... C Inductance and inductors... 233 Inductance of a single straight wire... 234 Combining two or more inductors... 235 Air-core inductors... 236 Solenoid wound air-core inductors... 237 Adjustable coils... 237 Winding your own coils... 239 Amidon Associates coil system... 239 Using ferrite and powdered iron cores... 240 Materials used in cores... 240 Powdered iron... 241 Ferrite materials... 242 Making the calculations... 242 Toroid cores... 244