Clutter covariance smoothing by subaperture averaging

Space-time processing has been proposed as an approach by which an airborne radar can adaptively detect small targets in the presence of ground clutter and jammers, provided the covariance matrix of the interference is available. One of the difficulties in estimating the covariance matrix is the need to obtain a sufficient number of independent samples, especially for high pulse-repetition-frequency (PRF) systems. It is shown here that this difficulty can be overcome by combining subaperture averaging, or spatial smoothing, of the received data with conventional range bin averaging