As outlined in Chapter 8, the bistatic RCS of a target becomes large as the bistatic angle, ?, becomes large, reaching the forward-scatter maximum, ? F, at ? = 180 , where
and A is the target's silhouette or shadow area, and ? is the wavelength. The target can be of simple or complex shape, and can be reflecting, absorbing, or a combination, as long as it "cuts a hole" in the transmitter beam. As a consequence, interest in forward-scatter bistatic fence operation has been revived [54, 101, 141, 142, 211, 212] as a counter to "stealth vehicles," which attempt to reduce their monostatic RCS by the use of shaping and radar absorbing materials (RAM).
References [1, 15, 16] show that operating exactly at ? = 180 yields information only that the target is somewhere between the transmitter and the reeeiver. Target range is indeterminate; target doppler shift is zero for all target velocity vec-tors; and both range and doppler resolution are lost. Implementation is also greatly complicated: The direct path signal and any forward-scattered clutter compete directly with the target signal, all at the same doppler frequency (zero doppler when the transmitter and reeeiver are stationary). Henee, doppler filtering cannot be used for clutter suppression. Of course, the reeeiver must also establish a LOS to the transmitting site. These problems are reduced as ? moves away from 180 . In this case, the forward-scatter RCS diminishes at ? < 180 ,...
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