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View File - University of Engineering and Technology, Taxila

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FIGURE 4.1A simplex link.baseb<strong>and</strong> channels, which also meets constraints on satellite transmitter power<strong>and</strong> RF b<strong>and</strong>width.We saw in Chap. 3, Sec. 3.2, that, for digital transmission, energy pernoise density ratio ðE b =N 0 Þ in a baseb<strong>and</strong> channel depends on several factors:carrier-to-noise ratio ðC=NÞ <strong>of</strong> the receiver, the type <strong>of</strong> modulation used toimpress the baseb<strong>and</strong> signal onto the carrier, <strong>and</strong> the channel’s b<strong>and</strong>width.This chapter is concerned mainly with the design <strong>and</strong> analysis <strong>of</strong> satellitecommunication links in terms <strong>of</strong> the carrier-to-noise ratio ðC=NÞ plus interference.As a consequence, a logical step is to calculate (1) the carrier(received) power in an earth station receiver, as well as (2) the noise plusinterference power in the receiver, to establish the combined C=N.4.1 LINK EQUATIONSThe link equations deal with the calculation <strong>of</strong> the available carrier-to-noiseratio over a satellite link. The calculation <strong>of</strong> the power an earth terminalreceives from a satellite transmitter is fundamental to underst<strong>and</strong>ing satellitecommunications <strong>and</strong> the development <strong>of</strong> the link equations. A good start is todevelop the link equations from the transmission theory perspective.Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.

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