Abstract: A clutter filter which reduces by (N-1) the number of input pulses required or operation of an N-pulse MTI canceler when L>N consecutive filtered outputs are desired. The clutter filter includes the two channels of an N-pulse MTI canceler which weight and sum the in-phase and quadrature-phase components of N radar returns, and a pair of delay circuits which introduce a delay of N interpulse time periods to the N and subsequent in-phase and quadrature-phase components of the radar returns. The stored outputs of the two channels of the canceler and the consecutive outputs of the delay circuits are combined in a complex multiplier to generate the consecutive in-phase and quadrature-phase outputs of the filter. The clutter filter has utility in a multiple-stage filter system employing a Doppler filter as the last stage.

Abstract: A system and method for monitoring the operability of a radar system having phased-array antenna system. During an initial radiation pattern, a portion of the signals radiated from each radiating element of the array (except, in general, a center element, if any) is fed to a manifold network which combines the signals received from radiating elements which are symmetrically located with respect to the center of the array so that they differ by 180.degree. at the single manifold output. Radio-frequency energy is added to the manifold output to adjust it to approximately zero. While the radio-frequency energy added to the manifold network is maintained at this value, the phase-shift settings of pairs of radiating elements having equal amplitude-weighting are varied from the initial setting through 360.degree.. Failures are located by correlating the phase-shift settings and the adjusted output of the manifold network.

Abstract: A digital technique is disclosed for filtering clutter in a pulse doppler I radar which allows a filter notch to be set for different doppler frequencies. In particular, the system includes two or more MTI filters cascaded to cancel different kinds of clutter signals that interfere with target signal reception. In each filter a digital detection circuit senses the mean-clutter-doppler frequency for a particular clutter type and automatically places a notch at that frequency. Each notch is fixed by treating the radar samples as complex numbers and replacing the conventional filter coefficients with complex coefficients indicating amplitude and phase as derived from the radar returns.

Abstract: A partially adaptive array which compensates for jamming. The array is comprised of more than 1000 elements and uses a bootlace lens to form a family of beams from which an adaptive array chooses at least one beam of the family of beams that most closely represents the jamming, and subtracts the beam from a main beam. In this way jamming of the beam is compensated for.