The Signal and Interference Environment in Passive Bistatic Radar

We present a review of the properties of some signals that may be used as illuminators of opportunity in passive bistatic radar systems. It is shown that such signals are not ideal for radar purposes, though modern digital modulation formats are to be preferred, since their ambiguity performance is better and in general does not vary with time. However, with any type of signal the ambiguity performance is also a strong function of bistatic geometry. We also consider the direct signal, multipath and interference environment, and show both by analysis and experiment that this will in general be severe, requiring of order 80 dB or more of suppression to achieve acceptable target detection results, and even then an effective receiver noise figure of order 20 -30 dB should be used in performance calculations.