Abstract: A frequency discriminator which generates an output signal characteristically representative of a predetermined frequency spectrum of an input signal, but insensitive to variations in the amplitude and spectral width thereof is disclosed. The frequency discriminator is adaptable for use in a radar receiver clutter tracking loop to improve the filtering of clutter signals from the radar returns by maintaining a measured centroid frequency of the clutter signal spectrum substantially at a desired frequency with a loop response which is invariant to both amplitude and spectral width of the clutter signals. More specifically, the frequency discriminator when included in a clutter tracking loop of a radar receiver discriminates from the clutter spectrum a plurality of frequency signals in accordance with a preselected sequence and computes the amplitudes thereof to generate a corresponding sequence of amplitude signals.

Abstract: In a radar system such as Doppler radar, clutter is eliminated without a requirement for somewhat sensitive frequency spectrum positioning. Processed returns are integrated over different halflook periods, where a look period is a period of constant pulse repetition frequency, and multiplexed into a postprocessor. The postprocessor measures the presence of clutter, and provides a blanking signal for clutter returns during portions of an operating cycle corresponding to clutter peaks.