TQ Delta Exhibit 2016
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`Cisco Systems, Inc. v. TQ Delta, LLC
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`IPR2016-01466
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`1
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`MODERN DIGITAL AND
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`ANALOG
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`COMMUNICATION
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`SYSTEMS
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`2
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`THE OXFORD SERIES lN ELECTRICAL AND COMPUTER ENGINEERING
`
`Adel S. 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 ofSzgnal and System Analysis, 3rd Edition
`DeCarlo—and Lin, Linear Circuit Analysis 2nd Edition
`Dimitrij ev, 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
`2»
`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, Introduction to Electrical Engineering -
`Schaumann and Van Valkenburg, Design ofAnalog Filters
`Schwarz'and 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 of the 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
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`MODERN DIGITAL AND
`
`ANALOG *
`
`COMMUNICATION
`SYSTEMS
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`Third Edition
`
`B. P. LATHI
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`Oxford University Press
`Oxford New York
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`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 orby any means, electronic, mechanical, photocopying,
`recording, or otherwise, without the prior-permission of Oxford University Press.
`
`Library ofiCongress Cataloging-in-Publicalion Data
`
`Lathi, B. P. (Bhagwandas Pannalal)
`Modern digital and analog communication systems / B.P. Lathi.——
`3rd ed.
`
`)
`
`cm.—(The Oxford series 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.
`TK5101.L333
`1998
`621.382—dc21
`
`2. Digital communications.
`I. Title
`II. Series.
`
`97-16040
`CIP
`
`19 18
`Printed in the United States of America
`On acid—free paper
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`5
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`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 some restless 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 cut to yield the
`same frequency at the transmitter and the receiver. At very high carrier frequencies, where the
`crystal dimensions become too small to match exactly, quartz-crystal performance may not
`be adequate. In such a case, a carrier, or pilot, is transmitted at a reduced level (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 important role in carrier acquisition, will now
`be discussed.
`
`The nature of the distortion caused by asynchronous carrier in SSB—SC is somewhat
`different than that in DSB-SC. In SSB-SC, when the carrier at the receiver is 2 cos[(a)c + Aw)t],
`the output is m(t) with all its Spectral components shifted (offset) by Aa) (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 Hz will 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 Hz results in a
`sound quality similar to that of Donald Duck. But the intelligibility is not completely lost.
`When the carrier is cos (wet + 9), the output is the signal m(t) with the phases of all
`its spectral components shifted by 6 (see Prob. 4.5-5). The phase distortion in SSB-SC also
`gives rise to the Donald Duck sound effect. This discussion shows that the problem of carrier
`synchronization is more critical 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 of the carrier
`component of an incoming signal. It is, therefore, a useful device for synchronous demodulation
`of AM signals with suppressed carrier or with a little carrier (the pilot). It can also be used for
`the demodulation of angle-modulated signals, especially under low SNR conditions. For this
`reason, the PLL is used in such applications as space-vehicle-to-earth data links, where there
`is a premium on transmitter weight, or Whefe the loss along the transmission path is very large;
`and, more recently, in commercial PM receivers.
`
`A PLL has three basic components:
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`1. A voltage—controlled oscillator (VCO)
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`2. A multiplier, serving as a phase detector (PD) or a phase comparator
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`3. A loop filter H (s)
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`The operation of the PLL is similar to that of a feedback system (Fig. 4.25a). In a typical
`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 (known as the error) will change the signal fed
`back until it is close to the input signal. A PLL operates on a similar principle, except that the
`quantity fed back and compared is not the amphtude, but the phase. The VCO adjusts its own
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`A sin (u)C + 6,)
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`LOOP filter
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`B cos (cost + 80)
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`Figure 4.25
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`Phase-locked loop operation.
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`
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`frequency until it is equal to that of the input sinusoid. At this point, the frequency and phase
`of the two signals are in synchronism (except for a possible difference of a constant phase),
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`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 voltage is eo(t), its
`output is a sinusoid of frequency a) given by
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`(00‘) = coc + 660(1‘)
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`'
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`(4.25)
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`Where c is a constant of the VCO and we is the free-running frequency of the VCO [the VCO
`frequency when e0 (t) = 0]. The multiplier output is further low-pass-filtered by the loop filter
`and then applied to the input of the VCO. This voltage changes the frequency of the oscillator
`and keeps the loop locked.
`x
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`How the PLL Works: Let the input to the PLL be A sin (wct + 6,-), and let the VCO
`output be a sinusoid B cos (mgr + 90).* The multiplier output x(t) is given by
`AB
`x(t) = AB sin (coat + 6;) cos (6051’ + 90) = 75in (6,- — 80) + sin (2am + 9,- + 60)]
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`The last term on the right-hand side, being a high—frequency signal, is suppressed by the loop
`filter, which is a low-pass narrovy—band filter. Hence, ego), the input to the VCO, is given by
`AB
`e,, = 7 sin 6e
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`9e = 9,. — 90
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`(4.26)
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`* It is not necessary for the VCO input and output fi‘equeucies to be equal. All that is needed is to set the VCO
`free-running frequency as close as possible to the incoming frequency. If the VCO output is B cos ((Dct + 90). we can
`express it as B cos (wct + 9:), where 6:, = [((2)c — wc)t + 00].
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`where 9,; is the phase error (9, — 9a). Figure 4.25b shows the plot of ea vs. 95. Using this plot,
`we can explain the tracking mechanism as follows.
`Suppose that the loop is locked, meaning that the frequencies of both the input and the
`output sinusoids are identical. This means things are in the steady state, and 9,, 90, and 9,2 are
`constant Figure 4.25b shows a typical operating point a and the corresponding values of e0 and
`9 on the 6,, vs 9 plot. Suppose further that the input sinusoid frequency suddenlyincreases
`from a)fl to wc+k, This means the1ncoming Signal1s A cos [(wc + k)t + 9-]: A cos (wet + 9-),
`where 9—— kt + 9. Thus, theincrease in the1ncoming frequency causes 9 to increase to 9- + kt,
`therebyincreasing 9 . The operating point a now shifts upward along the ac vs 9 characteristic
`in Fig. 4.25b. This increases e0, which, in turn, increases the frequency of the VCO output to
`match the increase in the input frequency. A similar reasoning shows that if the input sinusoid
`frequency decreases, the PLL output frequency will also decrease correspondingly. Thus, the
`PLL tracks the input sinusoid. The two signals are said to be mutually phase coherent or in
`phase lock. The VCO thus tracks the frequency and the phase of the incoming signal. A PLL
`can track the incoming frequency only over a 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 which the input
`will cause the loop to lock is called the pull-in or capture range. Also if the input frequency
`changes too rapidly, the loop may not lock.
`Although we assumed 91 and 90 to be constants, the preceding analysis is also valid if
`these angles are varying slowly with time. It is clear that the angle 90 tends to follow the input
`angle 9,- closely when the PLL tracks the input signal; the difference Ge : 9,- — 90 is either a
`constant or a small number -—> 0.
`
`If the input sinusoid is noisy, the PLL not only tracks the sinusoid, but also cleans it
`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, being a relatively inexpensive
`integrated circuit, has become one of 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 :l: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 power is proportional
`to the bandwidth. The PLL proves convenient here because it 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 special cases is carred out in Chapter 5.
`
`Carrier Acquisition in DSB-SC
`We shall now discuss two methods of carrier regeneration at the receiver in DSB—SC: signal
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`squaring and Costas loop.
`
`An outline of this scheme is given in Fig. 4.26. The
`Signal-Squaring Method:
`incoming signal is squared and then passed through a narrow (high Q) bandpass filter tuned to
`2mg. The output of this filter is the sinusoid lc cos Zth, with some residual unwanted signal. This
`signal is applied to a PLL to obtain a cleaner sinusoid of twice the carrier frequency, which
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