Monopulse radar apparatus

Claim 1

Monopulse radar apparatus for automatically tracking a moving target comprising a high-frequency pulse transmitter, means for receiving echo signals within receiving patterns relative to predetermined axes, comparator means coupled to said receiving means for converting said echo signals into a sum signal and at least one difference signal, a receiver coupled to said comparator means, said receiver comprising means for the coherent detection and filtering of the sum and difference signals to produce at least first and second low-frequency signals proportional to the Doppler shift of moving targets, said first and second Doppler-shifted signals being composed of desired, sampled and coarse filter Doppler signals, undesired noise signals caused by frequency instabilities inherent to the system, and undesired signals caused by signal and noise components falling within the passband of Doppler filters as a consequence of the internal clutter movement of fixed targets, at least one error detector coupled to received said first Doppler-shifted signals to produce error signals for tracking circuits of said radar apparatus, and a signal generator coupled to receive said second Doppler-shifted signals and produce third Doppler-shifted signals simulating desired filter Doppler signals equal in frequency and phase to the desired, sampled and coarse filter Doppler signals, said signal generator comprising control circuits for controlling the phase and frequency of said signal generator, and switching means coupled to said control means for supplying to said error detector as reference signals the third Doppler-shifted signals having said undesired signalS suppressed when the frequency and phase of said signal generator is equal to the frequency and phase of said second Doppler-shifted signals.