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FIGURE 4.9 Cross-link transmission data rate vs. antenna diameter. Parametersused: f ¼ 14.5 GHz, Z ¼ 65%, d c ¼ 9598 km, e b =N 0 ¼ 9.6 dB, T e ¼ 1000 K.can be transmitted across the cross-link at a 14.5-GHz frequency withacceptable probability <strong>of</strong> error (P e ¼ 10 5 ) for low transmitter powerðP t ¼ 0:1 WÞ, the computed data rate is tabulated in Table 4.3.Fig 4.10 demonstrates that increasing the antenna diameter sizeproduces increasing cross-link E b =N 0 until corresponding narrowing beamwidthsbegin to cause a rapid antenna gain fall-<strong>of</strong>f for a particular pointingerror. For the graphs in Fig. 4.10, the transmitting <strong>and</strong> receiving antennas areassumed identical, <strong>and</strong> the pointing error at each end <strong>of</strong> the antennas isassumed to be the same; that is, Y t ¼ Y r ¼ Y.TABLE 4.3PowerData Rate for LowD(m)r b (Mbps)0.5 0.6451.0 10.3131.5 52.2122.0 156.0152.5 402.8693.0 835.3903.5 1547.663Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.

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