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 monopulse radar receiver especially having off-boresite processing for a multiple target capability, there is included apparatus for compensating the receiver derived centroid and extent related signals for post hybrid interchannel imbalances in accordance with system parameter states. Generally, there is included in the sum and difference channel pairs of a monopulse radar receiver, attenuators which are operative in a plurality of attenuation states wherein a different error in the centroid and extent related signals may be rendered for each attenuation state. The compensating apparatus included in the receiver derives compensating signals for each of the attenuation states and stores the derived signals for use in compensating the centroid and extent related signals computed under mutually related attentuation conditions.