25.1 CONCEPT AND DEFINITIONS

Bistatic radar employs two sites that are separated by a considerable distance. A transmitter is placed at one site, and the associated receiver is placed at the second site. Target detection is similar to that of monostatic radar: target illuminated by the transmitter and target echoes detected and processed by the receiver. Target location is similar to but more complicated than that of a monostatic radar: total signal propagation time, orthogonal angle measurements by the receiver, and some estimate of the transmitter location are required to solve the transmitter-target-receiver triangle, called the bistatic triangle. Continuous-wave (CW) waveforms can often be used by a bistatic radar because site separation, possibly augmented by sidelobe cancellation, provides sufficient spatial isolation of the direct-path transmit signal.

When separate transmit and receive antennas are at a single site, as is common in CW radars, the term bistatic is not used to describe such a system since the radar has characteristics of a monostatic radar. In special cases, the antennas can be at separate sites and the radar is still considered to operate monostatically. For example, an over-the-horizon (OTH) radar can have site separation of 100 km or more. But that separation is small compared with the target location of thousands of kilometers,1 ^,2 and the radar operates with monostatic characteristics.

When two or more receive sites with common spatial coverage are employed and target data from each site is combined at...