As outlined in Chapter 1, a bistatic hitchhiking receiver uses a cooperative or non-cooperative monostatic radar as the bistatic transmitter and operates at the pleasure of the host radar. Specifically, the radar must be on, illuminating regions of interest to the bistatic receiver and transmitting a useful waveform at adequate power leveis. Furthermore, the bistatic receiver must locate the host radar to solve the bistatic triangle, operate with adequate target LOS and establish time synchronization for range measurements and phase synchronization for coherent operation and clutter suppression. Both time and phase synchronization are often established by receiv-ing host radar sidelobe transmissions o ver the direct path. While these requirements are more difficult to satisfy and cannot be satisfied ail the time, when compared to operation with a dedicated transmitter (a transmitter that is designed for use with, and under the operational control of, the bistatic receiver), potentially useful applications for this concept exist. In fact, the concept has been deployed at least once as the German Klein Heidelberg, which is detailed in Chapters 1 and 2.
A utility assessment of the hitchhiking concept typically Starts with the cal-culation of its coverage area, the region of thermal noise-limited target detections. This area is calculated via the usual range equations and ovals of Cassini, Chapter 4, for selected host radar-to-bistatic receiver baseline ranges, L. The coverage area is then truncated by (1) the LOS-constrained coverage area, Section 5.5.2; (2) spatial nulling, time gating, or doppler filtering of the direct...