Passive Radar

Abstract

Passive radar may be defined as a set of techniques that exploit existing transmissions as radar illuminators, such as broadcast, communications, or radionavigation signals, rather than requiring a dedicated radar transmitter. Passive radar has a number of advantages, including the fact that it requires no additional spectrum and that the passive nature of the receiver makes it potentially covert. It may also offer advantages in detecting and tracking stealthy targets. There are also some disadvantages, notably that the signals are usually not optimum for radar purposes, so care has to be taken to choose the right signals and to process them in the right way. Also, the continuous nature of many such transmissions means that it is necessary to suppress the direct transmitted signal at the receiver, which may be difficult. In the past decade there has been a significant change in the level of maturity of the subject, and passive radar is now seriously considered for a number of applications. The article describes the properties of bistatic radar, the nature of a range of different signals that may be used as the basis of passive radar, some signal processing techniques that are particular to passive radar, some examples of systems and results, and finally some comments of future prospects.