This discussion of the fundamentals of bistatic radar follows that of Willis, who provides a history of many bistatic radar proposals and programs and a summary of many technical analyses. Figure 13.1 introduces some basic terminology. Instead of two locations of interest (the radar and the target), we now have three (transmitter, Tx; receiver, Rx; and target) forming the vertices of the bistatic triangle, which defines the bistatic plane. All three vertices may vary with time, as in an air warfare scenario. The line between Tx and Rx isthe baseline. From the target location, the angle between the vector to the Tx and the vector to the Rx is the bistatic angle.