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Zeus Acquisition Radar (ZAR)

A target detector for an acquisition radar system wherein target data arriving at a high peak rate is received and stored. The stored data is released at a reduced sequential rate to a common processing unit. The target detector is a receiving means which receives the target data, and a buffer which stores the data temporarily. The buffer determines the sequential release of data, 2Q of the input equipment and the sorter and combiner of and a calculator for comparing the data and determining the presence or absence of a target.

A target detector of the Nike-Zeus acquisition radar must monitor the outputs of the numerous (180) receivers of the antenna system. In doing so, it must perform the following functions: Provide three dimensional digital target position information from the receiver analog video signals; determine if a signal is in fact a target or a noise pulse; average the individual target positions obtained from a given target during a "look" period; and determine the quality of data, i.e., the number of targets. In obtaining target position information, it must combine the antenna positional information with the monopulse interpolation signals which determine the target position within an antenna beamwidth. Because the target detector must process the outputs of 180 receivers each of which is capable of reporting targets at a peak rate of one target per 4 microseconds, it is extremely important that the most efficient use be made of circuitry to perform this task accurately and reliably.

In the Nike-Zeus radar system, initial contact with approaching targets is made by the acquisition radar. It continually revolves in azimuth and automatically scans out to very long range. The receivers of the acquisition radar get their signals from a symmetrical three antenna (three yokes) radar which rotates once every 15 seconds so that all 360° are scanned once every 5 seconds. The target detector is duplicated for each yoke so that the loss of one detector will still allow the radar system to function at a reduced rate. The target detectors monitor the outputs of the numerous receivers associated with the radar and report the average target positions associated with the number of pulses returned from each target as the antenna scans by it. It will distinguish targets from noise. In obtaining target position information the target detectors must combine the antenna positional information with the mono- pulse interpolation signals to determine the target position within an antenna beamwidth.

Systems solve the problems presented in a target detector for an acquisition radar system by a digital system which utilizes a common processor for the radar receivers of an antenna yoke. Target data arriving at a high peak rate is temporarily stored in individual receiver buffer stores from which it is sequentially released at a reduced rate to a common processing unit. The target detector takes advantage of the fact that the expected peak data rate is far below the theoretical peak data rate and the average data rate is even considerably lower. Storge space is provided for the maximum expected peak target densities, and a common processing unit is provided for each of the three antenna yokes of the radar system. The analog receiver data is converted to digital information at the receiver output and, thereafter, is processed in digital form.

Each target detector can be separated into three main functional areas. These are input equipment, sorter and combiner, and calculator. Input equipment The input equipment converts the received analog radar data to digital form. The input equipment consists primarily of 60 receivers, receiver gates 1-60, 60 receiver encoders, and a range unit. The individual receivers provide two kinds of data: antenna position data determined by which antenna cluster receives target information while the antenna scans in azimuth and monopulse interpolation data which specifies the target position within the beam of the particular antenna cluster which receives the target return. This data is contained in four input analog voltages representing a sum signal, an azimuth interpolation signal, an elevation interpolation signal, and a range mark. The range mark is used to mark receiver yoke azimuth, target range, and receiver number for storage in the control and program store unit by way of the range unit. The other three analog voltages from the receivers are gated into their encoder which converts them into binary words. The azimuth and elevation interpolation signals are encoded by the encoders 1-60 to 1 binary digits each. The sum signal, which provides a measure of the amplitude of the returned pulse, is encoded to 4 binary digits.