Non-linear non-adaptive clutter cancellation for airborne early warning radar

The present paper introduces a new non-linear filter for the cancellation of clutter echoes and the target detection in modern airborne early warning radar (AEW) systems. It is assumed that the radar is equipped with a digital beam-forming so that the clutter (and, possibly, the jammer) cancellation is obtained by a two-dimensional (2D) filter that operates in the angle and Doppler frequency domains. The performance of the following interference filters are compared: (a) optimum linear filter, (b) linear filter with Chebyshev tapering, (c) DPCA (Displaced Phase Centre Antenna), and (d) the non-linear filter which takes the minimum between the outputs of few linear filters which process the same radar signals with properly selected weights. The nonlinear filter offers a performance advantage, with respect to the widely used filters (b) and (c), in terms of detection capability of a target with Doppler frequency and direction of arrival (DOA) close to those of the clutter. The non-linear filter is much less computationally expensive than the optimum linear filter (a) and does not require the large region of homogeneous clutter, which is needed for the estimation of the clutter covariance matrix.