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FIGURE 1.1Intercontinental communication paths.The investment for a link in the illumination zone is independent <strong>of</strong> thedistance between the terminals.A provision for wide-area coverage for remote or inaccessible territoriesor for new services is made.This is ideally suited to medium, point-to-multiunit (broadcast) operations.A practical satellite comprises several individual chains <strong>of</strong> equipment called atransponder: a term derived from transmitter <strong>and</strong> responder. Transponders canchannel the satellite capacity both in frequency <strong>and</strong> in power. A transpondermay be accessed by one or several carriers. Transponders exhibit strongnonlinear characteristics <strong>and</strong> multicarrier operations, unless properly balanced,which may result in unacceptable interference. The structure <strong>and</strong> operation <strong>of</strong>a transponder are addressed in Chap. 2, <strong>and</strong> the techniques used to access thetransponder are examined in Chap. 5.Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.

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