The bistatic radar cross section of a target, ? B, is a measure as is the monostatic RCS, ? M, of the energy scattered from the target in the direction of the receiver. Bistatic cross sections are more complex than monostatic cross sections because ? B is a function of aspect angle and bistatic angle.
Three regions of bistatic RCS are of interest: pseudomonostatic, bistatic, and forward-scatter (sometimes called near-forward-scatter). Each region is defined by the bistatic angle. The extent of each region is set primarily by physical characteristics of the target.
The Crispin and Siegel monostatic-bistatic equivalence theorem applies in the pseudomonostatic region [36]: For vanishingly small wavelengths, the bistatic RCS of a sufficiently smooth, perfectly conducting target is equal to the monostatic RCS measured on the bisector of the bistatic angle. Sufficiently smooth targets typically include spheres, elliptic cylinders, cones, and ogives. Figure 8.1 shows the theoretical bistatic RCS of two perfectly conducting spheres as a function of bistatic angle [1, 92 95]. For the larger sphere (near the optics region), the pseudomonostatic region extends to ? ? 100 , with an error of 3 dB. Even for the smaller sphere (in the resonance region), the pseudomonostatic region extends to ? ? 40 .
For targets of more complex structure, the extent of the pseudomonostatic region is considerably reduced, and a variation of the equivalence theorem developed by Kell...
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