Bandwidth and amplitude insensitive frequency discriminator

摘要

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. The sequence of amplitude signals are non-uniformly weighted in accordance with their position in the sequence and added together to form a first composite signal. In addition, the sequence of amplitude signals are also uniformly weighted, preferably by a weighting factor of unity, and added together to form a second composite signal. The first composite signal is divided by the second composite signal in the frequency discriminator to generate an output error signal which is utilized by the clutter tracking loop to render the frequency centroid of the clutter signal spectrum substantially at the tuned frequency of a clutter signal filter.