초록

The invention provides an improved clutter filter for a Pulse Doppler Radar utilizing rapidly changing p.r.f.\s. The filter is designed to reduce the effect of spectrum spreading which has previously caused difficulties.

대표청구항 ▼

A clutter filter for a Pulse Doppler Radar in which the p.r.f. of the transmitted pulse is changed during the time taken to scan across a given target, the filter including a bandpass filter operative to receive signals derived from echo pulses and serving to reduce the frequency spectrum of the sig

A clutter filter for a Pulse Doppler Radar in which the p.r.f. of the transmitted pulse is changed during the time taken to scan across a given target, the filter including a bandpass filter operative to receive signals derived from echo pulses and serving to reduce the frequency spectrum of the signals, frequency changing means for reducing the frequency of the output signals of the bandpass filter such that the resultant signals have a frequency less than the lowest p.r.f. of the radar for all targets travelling at Less than a predetermined velocity, a sample-and-hold circuit arranged to sample the output of the frequency changing means at times related to the prevailing p.r.f. of the Radar and filter means for smoothing abrupt signals transition in the output signals of the sample-and-hold circuit and for attenuating frequency components resulting from undesired stationary and slow moving objects.