Practical Digital Wireless Signals Do you need to know what signal type to select for a wireless application? Quickly develop a useful expertise in digital modulation with this practical guide, based on the author’s experience of over 30 years in indus trial design. You will understand the physical meaning behind the mathematics of wireless signals and learn the intricacies and tradeoffs in signal selection and design. Key features: Six modulation families and 12 modulation types are covered in depth A quantitative ranking of relative cost incurred to implement any of 12 different modulation types Extensive discussions of the Shannon Limit, Nyquist filtering, efficiency measures and signal-to-noise measures Radio wave propagation and antennas, multiple access techniques, and signal coding principles are all covered Spread spectrum and wireless system operation requirements are presented. Earl McCune is a practicing engineer and Silicon Valley entrepreneur. A graduate of UC Berkeley, Stanford University, and UC Davis, he has over 30 years of post-graduate industry experience in wireless communications circuits and systems. Now semi-retired, he has founded two successful start-up companies, each of them winning industrial awards for their technical innovation. the cambridge rf and microwave engineering series Series Editor Steve C. Cripps, Visiting Professor, Cardiff University Peter Aaen, Jaime Pla´ and John Wood, Modeling and Characterization of RF and Microwave Power FETs Dominique Schreurs, Máirtín O’Droma, Anthony A. Goacher and Michael Gadringer, RF Amplifier Behavioral Modeling Fan Yang and Yahya Rahmat-Samii, Electromagnetic Band Gap Structures in Antenna Engineering Enrico Rubiola, Phase Noise and Frequency Stability in Oscillators Forthcoming Sorin Voinigescu, High-Frequency Integrated Circuits J. Stephenson Kenney and Armando Cova, RF Power Amplifier Design and Linearization Stepan Lucyszyn, Advanced RF MEMS Patrick Roblin, Nonlinear FR Circuits and the Large-Signal Network Analyzer Dominique Schreurs, Microwave Techniques for Microelectronics John L. B. Walker, Handbook of RF and Microwave Solid-State Power Amplifiers Practical Digital Wireless Signals EARL MCCUNE cambridge university press Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, Sa˜ o Paulo, Delhi Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title: www.cambridge.org/9780521516303 © Cambridge University Press 2010 This publication is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 2010 Printed in the United Kingdom at the University Press, Cambridge A catalog record for this publication is available from the British Library Library of Congress Cataloguing in Publication data ISBN 978-0-521-51630-3 Hardback Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party Internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. Dedicated to my father Earl McCune Sr. for instilling in me the great value of intuitive understanding of technical fundamentals Contents Preface page xvii Digital wireless signals: physical intuition and practical comparsions xx Definitions and acronyms xxi Terminology and notation xxvi 1 Keying, states, and block diagram construction 1 1.1 Radio communications: what really happens? 2 1.2 Modulation states: “keyed” 3 1.3 DWC signal representations 6 1.3.1 “Digital” modulations of an analog signal 6 1.3.2 Polar representation 6 1.3.3 Quadrature representation 7 1.3.4 Transformations between signal representations 9 1.4 Frequency domain representations 11 1.5 Implementing a DWC system 13 1.5.1 Symbol construction 13 1.5.2 Symbol-to-signal-state mapping 14 1.5.3 State transitions 15 1.5.4 Modulator 17 1.5.5 Power amplifier (PA) 17 1.5.6 Radio front-end 18 Simplex 18 Duplex 19 Duplexer vs. dipl exer 20 References 22 For further reading 22 2 Common issues and signal characterization 23 2.1 Power spectral density (PSD) 23 2.2 Occupied bandwidth 28 2.2.1 Useful signal-bandwidth measures 30 Bounded power-spectral-density (B-PSD) bandwidth 30 Fractional power-containment bandwidth 31 Transmitter mask 33 2.2.2 Bad signal-bandwidth measures 33 Null-to-null bandwidth 33 Equivalent white-noise signal bandwidth 34 2.3 Bandlimiting filtering 35 2.3.1 Exact vs. good enough 37 2.3.2 Filtering pulses 37 Full response 38 Partial response 38 2.3.3 Superposition 38 2.3.4 Intersymbol interference (ISI) 40 2.3.5 Nyquist filters 40 2.3.6 Matched filtering 43 2.4 Informational diagrams 47 2.4.1 Constellation diagram 47 2.4.2 Vector diagram 48 2.4.3 “Eye” diagram 48 2.5 Interference and near-far interference (NFI) 50 2.6 Signals and noise 52 2.6.1 Signal-to-noise ratio (SNR) 53 2.6.2 Carrier-to-noise ratio (CNR) 53 2.6.3 Information bit-energy-to-noise-density (IBEND) E b /N 0 53 2.7 Channel (Shannon) capacity 56 2.8 Important DWC signal measures 58 2.8.1 Efficiency measures 58 Bandwidth efficiency 58 Energy (DC) efficiency 59 Output efficiency 61 Peak efficiency 61 Backoff efficiency 61 Supply-referenced efficiency 62 Power-added efficiency 63 Overall transmitter efficiency 63 Power efficiency 63 2.8.2 Error vector 65 2.8.3 Off-channel power ratio 66 2.8.4 Envelope dynamics 67 Signal power 67 Peak-to-average power ratio (PAPR) 67 PDF/CDF/CCDF curves 68 2.9 Circuitry impacts from the signal selection 70 Constant-envelope (CE) signals 71 Envelope-varying (EV) signals 71 viii Contents Output-power control 72 Duplex method 72 Slew rate 72 References 72 For further reading 72 3 Important details on results from Shannon, Nyquist, and others 75 3.1 DWC channel capacity – the fundamental work of Claude Shannon 75 3.1.1 Basic capacity relationships to SNR 76 3.1.2 Basic capacity relationships to IBEND 79 3.1.3 Finite available power 82 3.1.4 Power vs. bandwidth for a set capacity 82 3.1.5 Signal design regio n: adaptive modulation 84 3.2 Equivalent noise bandwidth (ENB) 86 3.2.1 ENB of filters 87 3.2.2 Limitations of the ENB concept 88 3.3 Digital bandlimiting filtering 89 3.3.1 Conventional digital filtering 89 Finite-impulse-response (FIR) filters 89 Infinite-impulse-response (IIR) filters 89 3.3.2 Generalized Nyquist filter construction (GNFC) 90 3.3.3 The DZ (derivative-zeroed) pulse family 96 3.3.4 Superposition lowpass filtering (SLPF) 99 References 101 For further reading 101 4 Digital amplitude modulation (ASK) 103 4.1 Signals and characteristics 103 4.1.1 Amplitude shift keying definition 103 4.1.2 Modulation index and envelope dynamic range 104 Important special case: on-off keying (OOK) 105 4.1.3 ASK constellation diagrams 105 4.1.4 Spectrum and signal bandwidth 105 4.1.5 ASK bandwidth efficiency 107 4.1.6 ASK power efficiency 108 4.1.7 PAPR characteristics 109 4.1.8 Additive noise 110 4.2 ASK signal generation 112 4.2.1 Variable gain amplifier (VGA) 112 4.2.2 PA DC-power modulation 113 4.2.3 Complete-power keying for OOK 114 4.2.4 Transmitter efficiency characteristics 115 Contents ix 4.3 ASK signal demodulation principles 115 4.3.1 Diode 119 4.3.2 Demodulating logam p/received signal-strength indication (RSSI) 120 4.3.3 Automatic gain control (AGC) 121 4.3.4 Coherent 122 References 124 For further reading 124 5 Digital frequency modulation: FSK 125 5.1 Signals and characteristics 125 5.1.1 Frequency shift keying definition 125 5.1.2 Modulation index 128 Important special case: minimum shift keying (MSK) 131 5.1.3 Spectrum and signal bandwidth 132 Important special cases: gaussian-filtered FSK 137 5.1.4 FSK bandwidth efficiency 139 5.1.5 FSK power efficiency 141 5.1.6 Doppler shift 141 5.1.7 Additive noise 143 Threshold effect 143 Clicks and double ts 144 5.2 FSK signal generation 146 5.2.1 Switched oscillators 146 5.2.2 Voltage-controlled oscillator (VCO) 147 5.2.3 Fractional-division loop 148 5.2.4 Two-point modulation 14 9 5.2.5 Opened-loop modulation 150 5.2.6 Direct digital (frequency) synthesis (DDS, or also DDFS) 151 5.2.7 Transmitter energy-efficiency characteristics 152 5.3 FSK signal demodulation principles 152 5.3.1 Limiters: compression and capture effects 153 5.3.2 Slope demodulation 156 5.3.3 Frequency discriminators 156 5.3.4 D-flipFlop (DFF) 158 5.3.5 Phaselock loop (PLL) 159 References 159 For further reading 160 6 Digital phase modulation: PSK 161 6.1 Signals and characteristics 161 Authors dilemma 161 6.1.1 Phase shift keying 161 x Contents [...]... of the electromagnetic spectrum The most obvious way to 2 Practical Digital Wireless Signals facilitate this sharing is to ensure that the digital wireless communication signal uses a minimum amount of bandwidth But the many users of these digital wireless communication signals usually want to maximize the information transferred by the digital wireless communication, which tends to require a larger... construction Just to be absolutely clear – even though this book is about digital wireless communication (DWC) signals, the wireless signal itself is analog All wireless signals, and actually all signals whether wireless or not, are single, real, continuous-time analog waveforms The characteristic which makes us consider them as digital signals is that the information in the signal is only available at particular... the digital wireless communication signal meets regulatory requirements While certainly not exhaustive, these measures are usually sufficient to ensure that the digital wireless communication meets its overall objectives Further, while sufficient measures are almost always specified for digital wireless communication signals, experience shows that these measures are not uniformly enforced The digital wireless. .. enjoyed writing it Earl McCune Digital wireless signals: physical intuition and practical comparisons This book presents the principles of signals used in digital wireless communications systems Intended to be a side-by-side complement to any of the excellent theoretical texts in use, this book explains physical meanings behind the theoretical mathematics of communications signals Whereas a theoretical... digital wireless communication is one-way (simplex), two-way (duplex), or multi-way (multiplex) A huge amount of effort, and product cost, depends on the approach taken to this time aspect of digital wireless communication Finally, following nearly a century of experience with digital wireless communications, a particular set of measures has evolved to both determine the quality of the digital wireless. .. is doing at all times So let us begin by examining what makes us consider that these signals are digital No matter if signal phase, frequency, amplitude, or some combination is used for modulation, all digital wireless communication signals are a sequence of states This simply means that the information in the digital wireless communication signal can only be represented by a (usually short) finite list... general public good, these sharing rules usually focus on having the digital wireless communication signal use a minimum amount of the electromagnetic spectrum This is to insure that a greater number of users may also be using digital wireless communication signals at the same time – certainly a public good Furthermore, each of these signals must not harmfully interfere with another Since harmful interference... all digital wireless communication signal designers, and is the major part of this book Both the selection of the signal state set and the specific behavior of the digital wireless communication signal between states and state times are critical to successful resolution of this inherent conflict Signal operating times are also of critical importance One particular issue here is whether the desired digital. .. of the available signal parameters of amplitude, frequency, and phase The digital communication signal is made up of a sequence of individual state values, each of them holding constant for the defined state duration, and having some type of transition from one to the next as shown in Figure 1.2 4 Practical Digital Wireless Signals Figure 1.1 Example of a common telegraph key, the J38 State Duration... within this book the use of these terms shall be clear and unambiguous 1.3 DWC signal representations 1.3.1 Digital modulations of an analog signal All actual signals used for digital wireless communication are purely analog in their nature Time is not quantized at all for propagating DWC signals The actual signal therefore is one continuous-time electromagnetic wave Generalizing (1.1) to explicitly . McCune Preface xix Digital wireless signals: physical intuition and practical comparisons This book presents the principles of signals used in digital wireless communications systems Practical Digital Wireless Signals Do you need to know what signal type to select for a wireless application? Quickly develop a useful expertise in digital