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FIGURE 4.2 Basic antenna parameters: (a) schematic diagram <strong>of</strong> a transmission linkbetween transmitting T x <strong>and</strong> receiving R x antennas; (b) antenna radiation pattern, wherey is the depointing angle.Assume that a transmitter T x in Fig. 4.2(a) is equipped with a hypotheticalisotropic antenna that radiates spherically in space. At a distance R fromthe hypothetical isotropic source, the flux density F, crossing the sphericalsurface, with distance R taken as its radius, may be written asF ¼ P T4pR 2 W=m 2 ð4:1Þwhere P T is the total radiated by the transmitting source.Because the transmitting antenna would have a gain G T in the receiverR x direction, the flux density at the receiver isF ¼ G T P T4pR 2 W=m 2 ð4:2ÞCopyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.

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