TQ Delta Exhibit 2016
`
`Cisco Systems, Inc. v. TQ Delta, LLC
`
`IPR2016-01466
`
`1
`
`

`

`MODERN DIGITAL AND
`ANALOG
`COMMUNICATION
`SYSTEMS
`
`2
`
`

`

`THE OXFORD SERIES IN ELECTRICAL AND COMPUTER ENGINEERINGJHEUVATYRYbeeeeeeeeSee_00ESso—m™—"]
`
`AdelS. Sedra, Series Editor
`
`Allen and Holberg, CMOS Analog Circuit Design, 2nd Edition
`Bobrow, Elementary Linear Circuit Analysis, 2nd Edition
`Bobrow, Fundamentals ofElectrical Engineering, 2nd Edition
`Burns and Roberts, An Introduction to Mixed-Signal IC Test and Measurement
`Campbell, The Science and Engineering ofMicroelectronic Fabrication, 2nd Edition
`Chen, Linear System Theory and Design, 3rd Edition
`Chen, Signals and Systems, 3rd Edition
`Chen,Digital Signal Processing
`Comer, Digital Logic and State Machine Design, 3rd Edition
`Comer, Microprocessor-based System Design
`Cooper and McGillem, Probabilistic Methods ofSignal and System Analysis, 3rd Edition
`DeCarlo-and Lin, Linear Circuit Analysis, 2nd Edition
`Dimitrijev, Understanding Semiconductor Devices
`Fortney, Principles ofElectronics: Analog & Digital
`Franco, Electric Circuits Fundamentals
`Ghausi, Electronic Devices and Circuits: Discrete and Integrated
`Guru and Hiziroglu, Electric Machinery and Transformers, 3rd Edition
`Houts, Signal Analysis in Linear Systems
`Jones, Introduction to Optical Fiber Communication Systems
`Krein, Elements ofPower Electronics
`Kuo, Digital Control Systems, 3rd Edition
`Lathi, Modern Digital and Analog Communication Systems, 3rd Edition
`Lathi, Signal Processing and Linear Systems
`Lathi, Linear Systems and Signals, 2nd Edition
`Martin, Digital Integrated Circuit Design
`Miner, Lines and Electromagnetic Fieldsfor Engineers
`Parhami, Computer Arithmetic
`Parhami, Computer Architecture
`“
`Roberts and Sedra, SPICE, 2nd Edition
`Roulston, An Introduction to the Physics ofSemiconductor Devices
`Sadiku, Elements ofElectromagnetics, 3rd Edition
`Santina, Stubberud, and Hostetter, Digital Control System Design, 2nd Edition
`Sarma, Jntroduction to Electrical Engineering ~
`Schaumann and Van Valkenburg, Design ofAnalog Filters
`Schwarzand Oldham,Electrical Engineering: An Introduction, 2nd Edition
`Sedra and Smith, Microelectronic Circuits, 5th Edition
`Stefani, Savant, Shahian, and Hostetter, Design ofFeedback Control Systems, 4th Edition
`Tsividis, Operation and Modeling ofthe MOS Transistor
`Van Valkenburg, Analog Filter Design
`Warner and Grung, Semiconductor Device Electronics
`Wolovich, Automatic Control Systems
`Yariv, Optical Electronics in Modern Communications, 5th Edition
`Zak, Systems and Control
`
`3
`
`

`

`MODERN DIGITAL AND
`ANALOG _
`COMMUNICATION
`SYSTEMS
`
`B. P. LATHI
`
`xfo
`
`OXFORD UNIVERSITY PRESS
`
`4
`
`

`

`Oxford University Press
`Oxford New York
`Athens Auckland Bangkok Bogota Bombay BuenosAires
`Calcutta CapeTown Dares Salaam Delhi Florence Hong Kong
`Istanbul Karachi Kuala Lumpur Madras Madrid Melbourne
`Mexico City Nairobi Paris Singapore Taipei Tokyo Toronto Warsaw
`and associated companies in
`Berlin Ibadan
`
`Copyright © 1998 by Oxford University Press,Inc.
`Published by Oxford University Press, Inc.,
`198 Madison Avenue, New York, New York 10016
`http://www.oup-usa.org
`1-800-334-4249
`
`All rights reserved. No part of this publication may be reproduced,stored in a retrieval
`system,or transmitted, in any form or by any means,electronic, mechanical, photocopying,
`recording,or otherwise, withoutthe priorpermission of Oxford University Press.
`
`Library of Congress Cataloging-in-Publication Data
`
`)
`
`Lathi, B. P. (Bhagwandas Pannalal)
`Moderndigital and analog communication systems / B.P. Lathi—
`3rd ed.
`cm.—(The Oxfordseries in electrical and computer
`p.
`engineering)
`Includes bibliographical references (p.
`ISBN-13: 978-0-19-511009-8
`ISBN 0-19-511009-9 (cloth)
`1. Telecommunication systems.
`3, Statistical communication theory.
`TKS5101.L333
`1998
`621.382—de21
`
`2. Digital communications,
`I. Title
`II. Series.
`
`97-16040
`CIP
`
`19 18
`Printed in the United States of America
`Onacid-free paper
`
`5
`
`

`

`even for a small frequency difference. The effect of this distortion even for a small frequency
`mismatch, say Af = 1 Hz,is similar to the output when somerestless kid is fiddling with its
`volume control knob up and down continuously twice a second.
`To ensure identical carrier frequencies at the transmitter and the receiver, we can use
`quartz crystal oscillators, which generally are very stable. Identical crystals are cutto yield the
`same frequency at the transmitter andthe receiver. At very high carrier frequencies, wherethe
`crystal dimensions become too small to match exactly, quartz-crystal performance may not
`be adequate. In such a case,a carrier, orpilot, is transmitted at a reducedlevel(usually about
`—20 dB) along with the sidebands. The pilot is separated at the receiver by a very narrow-band
`filter tuned to the pilot frequency. It is amplified and used to synchronize the local oscillator,
`The phase-locked loop (PLL), which plays an importantrole in carrier acquisition, will now
`be discussed.
`The nature of the distortion caused by asynchronouscarrier in SSB-SC is somewhat
`different than that in DSB-SC. In SSB-SC,whenthecarrierat the receiveris 2 cos[(@,. + Aw)t],
`the output is m(t) with all its spectral components shifted (offset) by Aw (see Prob. 4.5-5),
`Such a shift of every frequency component by a fixed amount Aw destroys the harmonic
`relationship between frequency components. For instance, if Af = 10 Hz, then the components
`of frequencies 1000 and 2000 Hzwill be shifted to frequencies 1010 and 2010: This destroys
`their harmonic relationship. But unless Af is very large, such a change does not destroy
`intelligibility of the output (as the beating effect does in the case of DSB-SC). For audio
`signals Af < 30 Hz does not significantly affect the signal quality. Af > 30 Hzresults ina
`sound quality similar to that of Donald Duck. Butthe intelligibility is not completely lost.
`Whenthe carrier is cos (w,t + @), the output is the signal m(t) with the phases ofall
`its spectral components shifted by @ (see Prob, 4.5-5). The phase distortion in SSB-SC also
`gives rise to the Donald Duck sound effect. This discussion showsthat the problem of carrier
`synchronization is morecritical in DSB-SC than in SSB-SC.
`
`Phase-Locked Loop (PLL)
`The phase-locked loop (PLL) can be used to track the phase and the frequency ofthe carrier
`componentof an incomingsignal. It is, therefore, a useful device for synchronous demodulation
`of AM signals with suppressed carrier or withalittle carrier (the pilot). It can also be used for
`the demodulation of angle-modulated signals, especially under low SNR conditions. Forthis
`reason, the PLL is used in such applications as space-vehicle-to-earth data links, where there
`is a premium on transmitter weight, or wheretheloss alongthe transmission path is very large;
`and, more recently, in commercial FM receivers.
`A PLLhasthree basic components:
`
`1. A voltage-controlled oscillator (VCO)
`2. A multiplier, serving as a phase detector (PD) or a phase comparator
`3. A loop filter H(s)
`The operation of the PLL is similar to that of a feedback system (Fig. 4.25a). Inatypical
`feedback system, the signal fed back tends to follow the input signal. If the signal fed back
`is not equal to the input signal, the difference (knownasthe error) will change the signal fed
`back until it is close to the input signal. A PLL operates on a similar principle, exceptthat the
`quantity fed back and comparedis not the amplitude, but the phase. The VCO adjusts its own
`
`6
`
`

`

`Figure 4.25
`
`Phase-locked loop operation.
`
`A sin (@, + 8;)
`
`Loopfilter
`
`
`
`B cos (@,¢ + 8,)
`
`
`(a)
`
`
`
`frequencyuntil it is equal to that of the input sinusoid. Atthis point, the frequency and phase
`of the two signals are in synchronism (exceptfor a possible difference of a constant phase).
`
`Voltage-Controlled Oscillator (VCO): An oscillator whose frequency can be con-|
`trolled by an external voltage is a voltage-controlled oscillator (VCO). In a VCO,the
`oscillation frequency varies linearly with the input voltage. If a VCO input voltageis e,(f), its
`outputis a sinusoid of frequency w given by
`(4.25)
`.
`w(t) = w. + ceo(t)
`where c is a constant ofthe VCO and a,is the free--running frequency ofthe VCO [the VCO
`frequency when e,(t) = 0]. The multiplier outputis further low--pass-filtered by theloopfilter
`and then applied to the input of the VCO. This voltage changes the frequencyofthe oscillator
`and keepsthe loop locked.
`~
`
`Letthe input to the PLL be A sin (wt + 6;), and let the VCO
`How the PLL Works:
`output be a sinusoid B cos (Wet + 65). The multiplier output x(t) is given by
`AB
`x(t) = AB sin (w,t + 0;) cos (wet + 95) = “> [sin (0; — 8.) + sin (2w,t + 0; + )]
`The last term on the right-hand side, being a high-frequencysignal, is suppressed by the loop
`filter, which is a low-pass narrow-band filter. Hence, e,(t), the input to the VCO,is given by
`AB
`c= sinbe
`
`8 = 6 — 6
`
`(4.26)
`
`* It is not-necessary for the VCO input and output frequencies to be equal. All that is needed is to set the VCO
`free-running frequencyasclose as possible to the incomingfrequency.If the VCO output is B cos (@,t + 9,), we can
`express it as B cos (w,t + 6,), where 6, = [(@ — @)t + 4].
`
`7
`
`

`

`where6, is the phase error (0; — 6,). Figure 4.25b showstheplotof e, vs. @e. Usingthis plot,
`we can explain the tracking mechanism asfollows.
`Supposethat the loop is locked, meaningthat the frequencies of both the input andthe
`output sinusoidsare identical. This meansthingsare in the steadystate, and 6;, 0, and @, are
`constant. Figure 4.25b showsa typical operating point a andthe correspondingvaluesof e, and
`9, on the é, vs. 6, plot. Suppose further that the input sinusoid frequency suddenly increases
`from @, to w,+k. This means the incoming signal is A cos [(@, + k)t + 0;] = Acos (wt + 6),
`where 6; = kt +6;. Thus, the increase in the incoming frequencycauses 9; to increase to 6; + kt,
`thereby increasing 0,. The operating point a now shifts upward alongthee, vs. @, characteristic
`in Fig. 4.25b. This increases e,, which, in turn, increases the frequency of the VCO output to
`match the increase in the input frequency. A similar reasoning showsthatif the input sinusoid
`frequency decreases, the PLL output frequency will also decrease correspondingly. Thus, the
`PLLtracks: the input sinusoid. The two signals are said to be mutually phase coherentor in
`phase lock. The VCOthustracksthe frequency and the phase of the incoming signal. A PLL
`can track the incoming frequency only overa finite range of frequency shift. This range is
`called the hold-in or lock range. Moreover, if initially the input and output frequencies are
`not close enough, the loop may not acquire lock. The frequency range over whichthe input
`will cause the loop to lock is called the pull-in or capture range. Also if the input frequency
`changes toorapidly, the loop maynotlock.
`Although we assumed 6; and 9, to be constants, the preceding analysisis also valid if
`these angles are varying slowly with time.It is clear that the angle 0, tendsto follow the input
`angle 0; closely when the PLL tracks the inputsignal; the difference 0, = 6; — @,is either a
`constant or a small number — 0.
`If the input sinusoid is noisy, the PLL not only tracks the sinusoid, but also cleansit
`up. The PLL can also be used as an FM demodulator and frequency synthesizer. Frequency
`multipliers and dividers can also be built using PLL. The PLL,beinga relatively inexpensive
`integratedcircuit, has become oneof the most frequently used communication circuits.
`In space vehicles, because of the Doppler shift and the oscillator drift, the frequency
`of the received signal has a lot of uncertainty. The Doppler shift of the carrier itself could
`be as high as +75 kHz, whereas the desired modulated signal band may be just 10 Hz. To
`receive such a signal by conventional receivers would require a filter of bandwidth 150 kHz,
`when the desired signal has a bandwidth of only 10 Hz. This would cause an undesirable
`increase in the noise received (by a factor of 15,000), because the noise poweris proportional
`to the bandwidth. The PLL proves conyenient here becauseit tracks the received frequency
`continuously, and the filter bandwidth required is only 10 Hz.
`Being a nonlinear system, the detailed analysis of PLL is rather involved and beyond
`our scope. Complete analysis of two specialcasesis carred out in Chapter 5.
`
`Carrier Acquisition in DSB-SC
`Weshall now discuss two methodsofcarrier regeneration at the receiver in DSB-SC: signal
`squaring and Costas loop.
`
`An outline of this scheme is given in Fig. 4.26. The
`Signal-Squaring Method:
`incomingsignal is squared and then passed through a narrow (high Q) bandpassfilter tuned to
`2w,. The outputofthisfilter is the sinusoid k cos 2w,t, with some residual unwanted signal. This
`signal is applied to a PLL to obtain a cleaner sinusoid of twice the carrier frequency, which
`
`8
`
`