Cancellation of diffuse jammer multipath by an airborne adaptive radar

Airborne surveillance radars need to operate in an environment that can include the presence of ground clutter, standoff jammers, and diffuse jammer multipath. It is demonstrated here that a phased-array radar that employs adaptive spatial degrees of freedom, plus two different sets of adaptive temporal degrees of freedom can effectively cancel the aforementioned interference to an acceptable level. The two different sets of temporal taps required for each antenna element consist of one set spaced by the pulse repetition interval, so as to cancel ground clutter, and another spaced by about one-half of the reciprocal of the radar bandwidth, so as to cancel the diffuse jammer multipath which may enter through the main beam of the radar, as well as its sidelobes. Using the ideal covariance matrix, a simulation has been developed, and the necessary conditions for cancellation are analyzed and discussed. It is also shown that the cancellation can be performed either with the antenna elements or a set of beams, but that the beam space approach requires fewer space-time degrees of freedom for nearly the same level of cancellation as the element space approach.<>