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the baseband signal (more details appear in Chap. 3, Sec. 3.2.4). Anymeasurable property of such a signal can be used to transmit information bychanging this property in some known manner and then detecting whateverchanges at the receiver end. The signal that is modulated is called the carriersignal, because it carries the digital information from one end of thecommunication channel to the other end. The device that changes the signalat the transmitting end of the communication channel is called the modulator.The device at the receiving end of the channel, which detects the digitalinformation from the modulated signal, is called the demodulator. Thermal,device, cosmic, and terrestrial noise and other satellite interference corrupt thesatellite channel. It is the function of the demodulators, decoders, anddecompressors to recover the signal and produce the desired replica of thetransmitted signal. Coders (encoder and decoders) can be as standaloneequipment or can be integrated into a modularized modem: a contraction ofmodulation and demodulation (more is said of modems in Sec. 3.3.1). Theprimary function of the forward error correction (FEC) coding method is toensure low error rates over the satellite link. Error correction techniques areone subject of Chap. 6.2.9.1 Channel Filters and MultiplexersThe purpose of an input channel filter is to confine the bandwidth of the signalallowed into the transponder by rejecting unwanted signals such as thosegenerated by the transponder itself (e.g., spurii) and from other communicationsystems (e.g., noise and harmonics). Filters are electrical or microwave devicesdesigned to allow a selected range of signal frequencies to pass whileobstructing those outside the range. They also reduce the possibility ofinterference between transmitted signals.A generic type of channel filters is the bandpass filter—a filter with bothhigh- and low-frequency cutoffs. The channel filter in communicationspayload is a bandpass filter since it defines the usable bandwidth of thetransponder. A communications payload is divided into two parts: antennasand transponders, parts that have been previously discussed in this chapter.Figure 2.22 shows four types of bandpass filters.Figure 2.22(a) is a perfectly flat passband filter with infinite selectivity(or out-of-band rejection). It is purely theoretical. Figure 2.22(b) is theButterworth filter, which has a flat passband with slow rolloff and poorselectivity. It is rarely used in communications payloads. Figure 2.22(c) isthe response of the Chebychev filter, which solves the selectivity problems atCopyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.
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SatelliteCommunicationEngineeringMi
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This book is dedicated to my famili
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Because of the immense importance o
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means of a combination of applicati
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about my promise to my students, an
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2.3 Coverage Area and Satellite Net
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1Basic Principles of SatelliteCommu
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and voice (telephone) communication
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FIGURE 1.2Communication between two
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interpreting or uncovering the deci
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cryptographic keys K ti (where i ¼
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FIGURE 1.6Block ciphering technique
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FIGURE 1.7Part of block ciphering w
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Based on the ordering sequence of (
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TABLE 1.1 (continued )S612 1 10 15
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For an uncoded message x and the fe
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2. Your task is to develop a commun
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FIGURE 2.1Geometry of a satellite.
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Future trends in satellite antennas
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In the United States, the three sat
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TABLE 2.3Typical Links Frequency Ba
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FIGURE 2.4Satellite period and orbi
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FIGURE 2.6An illustration of covera
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FIGURE 2.7constellation.A sketch of
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width of 1:73 with reduced coverag
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y ¼ elevation angle of satellite f
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We can conclude that the antenna mu
Page 110: FIGURE 2.9Design flowchart of a sat
Page 114: Risk control and monitoring measure
Page 118: TABLE 2.4Antenna Selection Criteria
Page 122: Then the system availability can be
Page 126: In fact, MTBF is the reciprocal of
Page 130: 2.7 ANTENNASBased on function, sate
Page 134: Two kinds of horns in common use ar
Page 138: FIGURE 2.13Geometry of a parabolic
Page 142: FIGURE 2.14 Axisymmetric reflector
Page 146: A transceiver antenna is a single a
Page 150: The gain, in the axial mode, of a h
Page 154: angles, spacecraft may shadow the s
Page 158: 3. The probability of both parallel
Page 164: FIGURE 2.22(d) elliptic.Types of ba
Page 168: FIGURE 2.23A klystron. (Courtesy of
Page 172: FIGURE 2.25A simple block diagram o
Page 176: tional protection is required to en
Page 180: 3.1 BASIC PRINCIPLE OF EARTH STATIO
Page 184: 3.1.1 Technical and Operational Req
Page 188: excellent protection against noise
Page 192: FIGURE 3.3QPSK modulator.FIGURE 3.4
Page 196: TABLE 3.28-PSK Truth TableInput bit
Page 200: FIGURE 3.8An M-ary PSK demodulator
Page 204: where B is the allocated channel ba
Page 208: A frequently used function is the Q
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In view of (3.11), Eq. (3.18) can b
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Encoder and DecoderAn encoder is an
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Modulator and DemodulatorA modulato
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Zero Forcing Technique. Suppose the
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The adjoint of matrix A is obtained
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FIGURE 3.14The three-tap equalizer
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First, in the case of digital signa
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than 1=A. Whichever law is used, th
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FIGURE 3.16Block diagram for estima
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3.4.2 Antenna TrackingAn earth stat
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controlling antenna pointing. The m
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FIGURE 3.19A generalized model of a
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FIGURE 3.20Entropy of a binary sour
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whereHðYÞ¼output entropy, the av
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To have a feel for this expression,
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2. The system’s overall condition
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transmitted down the fiber as digit
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10. Kantor, L. Y. (ed). (1987). Han
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142. Simulate the probability of bi
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FIGURE 4.1A simplex link.baseband c
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Chapter 2, Sec. 2.7, discusses that
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From (4.6), the received power P r
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FIGURE 4.3A model of the combined-l
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4.1.2 Rain AttenuationRain attenuat
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FIGURE 4.5rates.Average rainstorm p
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FIGURE 4.6Adjacent satellite interf
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FIGURE 4.8Satellite separation dist
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inability of satellite A to accurat
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FIGURE 4.10 Cross-link E b =N 0 vs.
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Then using (4.41), the overall C=N
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(iv)(v)(vi)(vii)Calculate the recei
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5Communication Networks andSystemsC
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discriminate among carriers by temp
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FIGURE 5.2 Principle of FDMA system
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FIGURE 5.3 Operational concept of T
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FIGURE 5.5TDMA: bit rate r b for 1
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Copyright © 2002 by Marcel Dekker,
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5.2 CAPACITY COMPARISON OFMULTIPLE-
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Rearranging (5.11) in terms of ener
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The transmission bit rate isR r ¼
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6Error Detection and CorrectionCodi
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the channel and reconstruct the sou
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message sequence X . Thus, a system
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If we consider a message X ¼ð1010
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can be seen in Table 6.1 that the m
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FIGURE 6.1A (7, 4) cyclic code gene
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FIGURE 6.2Convolutional codes encod
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Alternative methods of describing a
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FIGURE 6.5 Code tree diagram of Fig
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FIGURE 6.8 Code tree diagram of rat
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consistent with the constraint leng
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trellis depth is approximated to 5L
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FIGURE P.1A convolutional coder.the
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7Regulatory Agencies andProceduresT
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of the radiofrequency spectrum, and
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The CCIR works through the medium o
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7.1.3 IFRBThe International Frequen
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The national or regional spectrum m
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3. The need to expand or enhance th
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The DSP will be responsible for res
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2. Provide a convenient framework w
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FIGURE 8.3Types of user-to-network
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H1-channels are designed to carry v
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information. The transfer cell prov
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The OSI layers are divided into two
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plane is denoted by U, the control
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interfacing, maintenance, and conne
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adjoining base station to scan the
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FIGURE 8.9Geometry of a polygon.The
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FIGURE 8.11Splitting cells into sma
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causes signal fading. Of course, th
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FIGURE 8.14TCP=IP suite and its rel
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access to an Internet point of pres
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message security via satellite is d
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REFERENCES1. Wu, W.W. (1989). Eleme
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Appendix ANotationsThe symbols have
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N sPP rP sP TRRðtÞR cR eR rR vSS
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g Central anglez Channel gainZ Ante
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AttenuationBandwidthBearer serviceB
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Frequency divisionmultiple accessFr
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MultiplexingNetworkOmnidirectionala
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UplinkUser-to-networkinterfaceThe e
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