Patent ID: 7079072

Claim:
A Doppler radar for discriminating detected targets as either helicopter targets or fixed-wing targets, comprising: a Doppler radar receiver for providing a sequence of N radar return data signal samples; means responsive to said sequence of return data signals for detecting the presence of a target, estimating its Doppler frequency and providing an estimate signal indicative of said estimated target Doppler frequency; a radar processor responsive to said Doppler frequency estimate signal, said processor comprising means for providing a plurality of sets of filter coefficients, means for processing said sequence of radar return data signals by each of said respective sets of filter coefficients to provide a plurality of filtered data sequence signals, and means for summing the squared magnitudes of the respective filtered data sequence signals to provide a processor detection statistic signal; each of said sets of filter coefficient sets being selected to pass components of said radar return signals resulting from a helicopter rotor hub and to substantially reject components of said radar return signals resulting from the target skin and ground clutter; and means for comparing said processor detection statistic signal to a predetermined threshold value to provide a target discrimination signal having a first state indicative of the “helicopter present” state and a second state indicative of the “helicopter absent” state, the particular state of said target discrimination signal depending on whether or not said threshold value is exceeded.