Coherent sidelobe canceller for radar

Claim 1

A coherent sidelobe canceller for a radar, comprising a plurality N + 1, where N is a positive integer, of antennas including a main antenna (200-0) and N auxiliary antennas (200-1 to 200-N), N + 1 receivers (210-0 to 210-N) connected to the antennas respectively to produce corresponding radar video signals, N + 1 analog to digital converters (220-0 to 220-N) connected to the receivers respectively to convert the video signals to digital signals, a weighting coefficient computing circuit (270, 280) responsive to signals derived from the said converters to calculate a set of weighting coefficients by operating on time- sequential digital signals from the converters to derive the weighting coefficients in dependence upon statistical properties of these signals, multiplier means (240-0 to 240-N) and adder means (250) operative to form a sum of products of signals multiplied by respective ones of the weighting coefficients, and memories (230-0 to 230-N) acting on digital delays which delay the digital signals fed to the multiplier means (240-0 to 240-N) in correspondence with the time taken to complete the weighting coefficient calculations, characterised in that the weighting coefficient computing circuit further includes clutter region detection means (260) responsive to the digital signal (CHo) obtained as an output of said analog-to-digital converter (220-0) connected to said main antenna (200-0) through the corresponding receiver channel (210-0) to determine a clutter region in the received signal, thereby to calculate said weighting coefficients utilizing digital signals outside of said clutter region.