Abstract: A countermeasures system technique for destroying threat radar frame of reference. Automatic change of false target pattern is accomplished by any one of three different switching schemes or by any combination of them. The switching schemes comprehend (a) changing polarity of digital counts delivered to system range position program matrix inputs; (b) alternately enabling and disabling selected outputs of the range position program matrix, and (c) interchanging selected input gates of the system angle position program matrix.

Abstract: A pulse repetition frequency (PRF) detection system is provided for indicating the existence of pulse trains having predetermined repetition frequencies in a composite signal containing pulse trains of different pulse repetition frequencies. The system includes a plurality of independent sorters to which the composite signal is sequentially applied. Each of the sorters is operable to detect a pulse train having a predetermined pulse repetition frequency, to indicate the detection, and to produce pulses for inhibiting or blocking the application of the corresponding pulses of the composite signal on a pulse-by-pulse basis. The sorters may be arranged and interconnected in a decreasing order of frequency detection whereby the signal applied to each successive sorter has all higher frequency detected pulse trains removed therefrom.

Abstract: A feed which is stationary relative to a parabolic reflector is located in close proximity to a prime focus of the reflector along its central axis. A moving element which is opaque to r.f. energy is moved along a path of revolution about the reflector axis, the path of revolution being located between the reflector and the stationary feed. The shape of the opaque element and the path of revolution are such that different portions of the aperture of the feed are masked as the element travels along the path of revolution. This imparts predictable scanning motion to the beam pattern which is coupled into the stationary feed. One highly useful embodiment of this invention is a construction in which the stationary feed is a secondary feed installed in a nutating feed antenna, and the nutating feed itself constitutes the opaque moving element.

Abstract: A circuit for detecting the occurrence of incoming pulses at a predetermined repetition rate while remaining unresponsive to pulses occurring at an even harmonic of such rate, the circuit including a clock pulse generator and resettable counter arranged to count the pulses produced by the generator and to produce an output representing its current count, resetting means for resetting the counter to its "0" count state when an incoming pulse arrives at a time after the arrival of a preceding pulse which started the clock pulse generator which is equal to or greater than the time between pulses occurring at the repetition frequency to be detected, signal producing means for producing an output signal only when the time of arrival between such incoming pulses is equal to the time between pulses at the repetition frequency to be detected, and output signal suppressing means arranged to prevent the production of an output signal when an incoming pulse arrives at a time after the arrival of an incoming pulse which