Abstract: An adaptive pulse signal threshold detector is disclosed wherein detected signals are analyzed to determine the strength of the signals and the system is adapted for increased or decreased sensitivity on the basis of the detected signal strength. The adaptive pulse signal threshold detector subjects the detected signals to three threshold criteria during a signal validity analysis. The adaptive pulse signal threshold detector causes the system to be adaptive in so far as the system responds to detected signal strength to alter the detection criteria. The adaptive pulse signal threshold detector includes a binary detector.

Abstract: Apparatus for processing radar video signals and applying the processed signals to a radar display. The apparatus includes video extraction circuitry which removes random pulse interference and noise from the video signals. The improvement of the present invention comprises clutter transmission circuitry and a memory which transmits and stores clutter video signals provided by the video extraction circuitry. In addition, comparison circuitry is provided which compares the applied signals (present video) provided by the video extraction circuitry to time-averaged signals computed thereby. The comparison circuitry transmits the present video signals to the radar display when the difference between the present video signals and the time-averaged signals is greater than a predetermined value. In one specific embodiment, the comparison circuitry includes scan-to-scan correlation circuitry which provides time-averaged video signals which are averaged in a predetermined manner over a plurality of azimuth scans.

Abstract: A false alarm control processor that receives sampled input radar video data and provides an output signal having a zero mean value. The processor accumulates the sample video for a range sweep of range bins, then stores the value and resets a counter. The stored value is scaled to form an estimate of the mean and subtracted from the input video signals of the following sweep. To prevent the mean from being biased by strong targets, a target exclusion function may be included to prevent accumulation of video from strong targets. However, if the noise or jamming level has increased for more range bins than a target would occupy, the video is then sampled by the accumulator so that the mean is responsive to changes in the level of the noise. Thus, the system provides a constant false alarm rate and accurate azimuth estimation in the azimuth integrator filter as well as allowing the azimuth integrator to operate with a relatively small dynamic range.

Abstract: A processor for operating on video and azimuth signals from a radar system having an antenna which scans in azimuth. The processor enhances the signal-to-noise ratio of the video signals while imposing thereon a substantially constant azimuth delay error.The processor includes a first circuit for forming and storing a count indicative of the video signal history in each range zone. The processor also includes a second circuit for generating and removing a flag signal indicative of azimuth leading and trailing edges respectively of a target pulse in the video signal. A gating circuit is included to pass video signals, for a given range zone, to an output terminal during the presence of a flag signal associated with the zone.

Abstract: A receiving antenna connected to a surveillance sensor feeding a target detector. The target detector provides multiple inputs of target reports, azimuth, range and scan count data into a clutter mapper circuit which in turn feeds a track-while-scan circuit feeding a CRT display. The clutter mapper circuit provides improved clutter detection in the presence of scintillating clutter conditions.

Abstract: An automatic clutter detecting and mapping system in which the area being mapped is broken up into clutter mapping quantum areas with corresponding storage cells including reject codes for automatically rejecting clutter returns which may occur in intermittent or fading clutter occurring a small percentage of the time for example. For each clutter mapping cell a clutter count and a reject code are stored in a main memory and in a first mode which is searching for clutter the clutter count is incremented by eight in response to an input targert but is not decremented in the absence of a received target from that clutter mapping area. In any clutter mapping cell when the clutter count reaches a threshold within a selected number of scan periods, the reject code is set to the amplitude corresponding to the maximum amplitude target report received in that cell and provided by a temporary memory.

Abstract: A time sampling adaptive clutter processor that samples on a scan to scan basis rather than on an area basis and in response to signals received from the object being interrogated develops a mean level value and a standard deviation value. The mean value and the standard deviation value may be provided by recursive type filters operating with scan to scan memories. The mean level value is then combined with the standard deviation value to provide a threshold that provides improved clutter detection especially with a condition in which a clutter variation from scan to scan is less than the clutter variation between areas in any one scan. The system may also include a valid target control to eliminate the detrimental effects on the threshold that may be caused by targets being tracked.

Abstract: A system for detecting the presence of clutter utilizing an area overlap technique that effectively rejects scintillating position clutter near the boundaries of the area clutter map ACM cells. A first area clutter-mapper system is provided with its area ACM cells at a first position and a second clutter-mapper system is provided with its ACM cells in a second position with each cell displaced by about one-half ACM cell dimension in range and azimuth to overlap the original ACM cell boundaries. All of the clutter returns which were divided among the original set of ACM cells occur in one of the area overlap ACM cells so that when the clutter scintillates between ACM cells for any selected detection criterion, it is identified as clutter rather than a moving target. Separate detection history counts for clutter-identification and inhibit code for clutter rejection are provided in both the first and second clutter overlap map units.

Abstract: An antenna is connected to a surveillance sensor feeding a target detector. The target detector provides multiple inputs of target reports, azimuth, range and scan count data to a clutter mapper circuit which in turn feeds a track-while-scan circuit one output of which is fed back to a data input buffer also feeding the clutter mapper circuit. Another output of the track-while-scan circuit provides input to a CRT display.

Abstract: This invention relates to an improved signal processor that is insensitive to the type of clutter that is encountered by utilizing multiple parallel range sample intervals which vary in length from minimum to maximum so that the optimum sample size is provided for clutter or different range extents. By utilizing the correct range sample interval for the clutter, the detection threshold is accurately set as a result of an improved sample mean. The detection system includes a plurality of mean level processors operating in parallel in response to signal samples varying from minimum to maximum length in range and a selection circuit that selects the largest amplitude value of the clutter signal for use as the mean value in a signal comparator. When the mean value is the same for two or more sample sizes, one arrangement in accordance with the invention utilizes the larger sample size as the mean value.

Abstract: An improved video clutter processor utilizing a multiple moment detector that provides a constant false alarm rate regardless of the probability distribution of the radar clutter. The processor provides an adaptive threshold that is a function of multiple moments to compensate for variation in parameter of a selected number of parameter probability distributors. In accordance with the invention either moments around the origin may be combined to establish the threshold or central moments may be combined for the threshold level. In one arrangement of the invention, digital delay lines store the quantized sample video and the second, third and fourth powers of the quantized video which are the mean values about the origin are estimated by dividing the sum of the quantized videos by a number equal to the number of combined values to provide the moments about the origin.

Abstract: A digital detection criteria control device for use in a radar tracking system incorporating a memory that is electronically synchronized to a surveillance radar in a manner to perform video mapping and control functions. This memory is organized so that each small quantum area of the radar's surveillance area has code bits which are controlled primarily by inputs from valid and invalid video return detectors. These detectors examine quantized video returns from the radar for certain bit densities and bit patterns to determine whether the video returns are valid or invalid targets. The code bits provide a history of the type of video return for each quantum area thereby making a more accurate indication of the nature of the video return possible.