Abstract: A slow speed pulse chase apparatus in a bistatic radar system, wherein the receive antenna follows the transmit pulse out in space. The receive beam comprises many parallel beams that overlap all the possible positions of the transmit pulse as it travels into space. Slow speed chase apparatus provides a small group of beams which are held in a fixed location as the transmit pulse travels by and then is jumped in one large step to continue to the next position to remain there until the transmit pulse travels by.

Abstract: The present invention provides a system that cancels second time around clutter in a multiple pulse repetition frequency radar system which uses three groups of differently spaced pulses. The system processes returns from a clutter cancellation group of eight pulses from three different concatenated pulse repetition frequency groups, using two pulses from one group, all pulses from a central group and two pulses from a third group. The pulse returns are each multiplied by a different weight and the eight weighted returns are added together and output as the filtered return signal. As the weights of the outer pairs of pulses increase, as compared to the weights of the inner four pulses, the second time around clutter cancellation effects increase and the first time around clutter cancellation effects decrease.

Abstract: A recursive radar filter arranged to provide filtering of ground clutter signals from radar echoes in the form of short batches of pulses. The filter includes a feed-forward section with delay, adder, and fixed amplifier elements. The filter also includes a feedback section which includes similar elements. Two time-varying amplifiers are included in the filter which change gain as the pulses are applied to the input of the filter. In a three delay version of the filter, the gain of one of the time-varying amplifiers is such that the feed-forward section of the filter does not pass any pulses until the fourth pulse has been applied to the filter. After the third pulse, the gain of this time-varying amplifier increases on each successive input pulse. In another embodiment, the two time-varying amplifiers are eliminated by making all of the fixed gain amplifiers time-varying in relationship with the interpulse period of the pulse input signal.

Abstract: An airborne pulse doppler radar set generally includes a moving target indicator (MTI) system for detecting moving aircraft within its scanning purview. To avoid processing undesirable clutter, the MTI system includes a clutter cancelling type filter for rejecting doppler shift frequency signals reflected from objects moving at velocities below a predetermined minimum velocity value. Unfortunately, the doppler shift frequencies representative of the body velocity of most helicopters fall within this clutter repetition band and may go undetected by the MTI system. To detect these helicopters, a helicopter detection system which operates on the specular flash energy of the doppler shift frequency signals reflected from the rotating blades of a helicopter is provided.

Abstract: An electronically scanned phased array antenna system comprises a phase shift controller corresponding to each antenna array element for individually computing a phase shift value which governs the phase of the signal associated with the corresponding antenna element. The computed phase shift values of all the phase shift controllers effect a phased array on the signals of the antenna elements to point the antenna beam in a desired direction. Each of the phase shift controllers is programmed with a predetermined phase shift value increment for computing a sequence of phase shift values at specified intervals of a predetermined time pattern, each new phase shift value being preferably concurrently computed by the phase shift controllers at the specified time intervals.

Abstract: An airborne radar system and method for detecting and tracking slowly moving ground targets off the boresight of the antenna beam, is disclosed.

Abstract: 1.

Abstract: A bistatic radar system for detecting the presence of a slowly moving target by the use of an arrangement which provides a reduction in the frequency spread of the reflected clutter energy. A radar transmitter and a radar receiver are located aboard separate aircraft which fly with a predetermined speed and direction about the target area. The speed and direction of the two aircraft are such that the angular velocities of the aircraft about the target area are substantially equal and opposite. This arrangement reduces the spread of the reflected clutter energy caused by motion of the radar transmitter and receiver relative to the target area. The radar return signals are filtered and processed to determine when a signal is present which has been shifted in frequency due to the motion of the moving target. In one embodiment, the two aircraft fly directly toward each other at the same speed. In another embodiment, the two aircraft fly directly away from each other at the same speed.