Pulse doppler surveillance post signal processing and scan to scan correlation
First Claim
Patent Images
1. A method of processing detected signals from a pulse Doppler radar system for automatically tracking targets, wherein said system has a directional antenna that scans in azimuth repetitively collecting return signals from respective targets during successive scans of the antenna, said method comprising:
- determining the range and Doppler shift of each return signal exceeding a selected threshold level during each dwell of the antenna to constitute a detected signal;
correlating detected signals on successive dwells of the antenna;
forming candidate target reports having an unambiguous range and ambiguous ranges in accordance with the number of correlated detected signals;
selecting target reports from the candidate target reports, said target reports selected having an amplitude sum of correlated signals meeting a criterion corresponding to a predetermined beam-shaped modulation; and
tracking the movement of selected unambiguous and ambiguous range target reports during successive scans of the antenna.
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Abstract
Post detection processing for a pulse doppler surveillance radar is disclosed wherein target reports having ambiguous ranges along with those containing unambiguous ranges are used for tracking targets. The tracking includes a maneuver recognition mechanism for adaptively weighting the range, range rate, and X and Y coordinate driving errors as a function of the maneuvering and non-maneuvering operations of the target.
23 Citations
25 Claims
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1. A method of processing detected signals from a pulse Doppler radar system for automatically tracking targets, wherein said system has a directional antenna that scans in azimuth repetitively collecting return signals from respective targets during successive scans of the antenna, said method comprising:
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determining the range and Doppler shift of each return signal exceeding a selected threshold level during each dwell of the antenna to constitute a detected signal; correlating detected signals on successive dwells of the antenna; forming candidate target reports having an unambiguous range and ambiguous ranges in accordance with the number of correlated detected signals; selecting target reports from the candidate target reports, said target reports selected having an amplitude sum of correlated signals meeting a criterion corresponding to a predetermined beam-shaped modulation; and tracking the movement of selected unambiguous and ambiguous range target reports during successive scans of the antenna. - View Dependent Claims (2, 3, 4)
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5. A method of processing signals for a pulse Doppler surveillance radar system, comprising:
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determining the range and Doppler shift of each return signal exceeding a selected threshold level during each dwell of the antenna; correlating successive detected signals from different PRF'"'"'s to form categories of target reports, said categories including a (3/3) category of candidate target reports formed by three consecutive detected signals, a (2/2) category of candidate target reports formed by two consecutive detected signals, a (2/3) category of candidate target reports formed by two detected signals out of three dwells of the antenna, said (2/2) and (2/3) categories of candidate target reports having up to four ambiguous ranges; linking selected combinations of said categories of candidate target reports having the same range and Doppler in accordance with the number of missed detections in successive modulation periods between each candidate target report, the selected combination of target links including the extension of said categories in accordance with the difference between the number of modulation periods from the beginning of a first report (M) to the beginning of the next report (N) in accordance with the formula N-M as follows;
space="preserve" listing-type="tabular">______________________________________ Modulation Periods Extensions Between Report Types ______________________________________ (3/3) to (3/3) 1 (3/3) to (2/3) 1 (2/3) to (3/3) 2 (2/3) to (2/2) 1 (2/3) to (2/3) 2 (2/2) to (2/3) 2 (2/2) to (2/2) 4 ______________________________________and resolving in azimuth closely spaced targets in accordance with said linked combinations. - View Dependent Claims (6, 7, 8, 9)
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10. A method of processing detected signals from a pulse Doppler radar system for automatically tracking targets wherein said system has a directional antenna that scans in azimuth repetitively collecting return signals from respective targets during successive scans of the antenna, said method comprising:
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determining the range and Doppler shift of each return signal exceeding a selected threshold level using successive PRF detected signals to form candidate target reports; identifying candidate target reports having the same Doppler and either ambiguous or unambiguous ranges within one range gate of each other; and rejecting one of said identified candidate target reports in accordance with a predetermined criterion to reject range ghosts occurring as a result of multiple detections at the same Doppler, said rejecting step including the substeps of comparing unambiguous target reports to determine adjacent range gates of individual detections; and eliminating ambiguous target reports occupying identical range gates at times when an unambiguous pair of target reports has consecutive detections in adjacent range gates. - View Dependent Claims (11, 12)
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13. A method of automatically tracking detected targets in a pulse Doppler surveillance radar having a directional antenna that scans in azimuth for detecting targets during successive scans, said method comprising the steps of:
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comparing uncorrelated ambiguous and unambiguous target reports from a current scan of the antenna with uncorrelated target reports formed during preceding scans of the antenna to initiate a tentative track in response to a correlation of said reports; comparing said target reports from the current scan of the antenna with tentative tracks initiated during preceding scans of the antenna to form an established track in response to correlation of a target report with a tentative track; and eliminating tentative tracks failing to correlate with a target report within a selected azimuth zone after a selected number of scans of the antenna, said eliminating step including the substeps of eliminating a tentative track failing to correlate with a target report having an unambiguous range after a first selected number of scans at times when said track is initiated by a pair of target reports having ambiguous ranges; and eliminating a tentative track failing to correlate with an ambiguous range target report after a second selected number of scans less than said first selected number at times when said tentative track is initiated by ambiguous range target reports. - View Dependent Claims (14, 15, 16)
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17. A method of tracking targets in a pulse Doppler radar surveillance system having a directional antenna that scans in azimuth for collecting return signals from respective targets during successive scans, said method comprising the steps of:
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detecting for each range the Doppler of each detected signal having a selected threshold level; correlating for each range the Doppler of successive detected signals during each scan of the antenna; correlating successive detected returns to provide candidate target reports having ambiguous and unambiguous ranges; processing candidate target reports to provide selected target reports meeting a preselected criterion for outputting both ambiguous and unambiguous range type target reports; processing in selected azimuth zones successively output target reports of both range types during a current scan of the antenna and output target reports formed during preceding scans of the antenna for initiating tentative tracks; associating tentatively in said azimuth zones output target reports produced during a current scan with tracks initiated during a preceding scan; selecting a tentative association to provide a firm track correlation, said step of selecting including the substep of prioritizing the output target reports for a respective tentative track at times when more than one target output report is tentatively associated with such track; predicting the coordinates of an output target report for a respective track in a succeeding scan in accordance with selected weight values of the range, range rate, X coordinate and Y coordinate driving errors of the output target report selected for the firm correlation of such track on the current scan, said step of predicting in accordance with selected weight values including the substeps of storing a plurality of non-maneuvering weight values, each corresponding to range, range rate, position and velocity for tracking a target in the smoothing mode; storing a plurality of maneuver weight values, each corresponding to range, range rate, position and velocity for tracking a target in the maneuver mode; checking during each current scan of the antenna the mode utilized in predicting the coordinates of the target report for a respective track in a preceding scan of the antenna; comparing to respective first distinct values during each scan of the antenna the computed driving error values for each output target report having the non-maneuver weight values utilized in predicting the coordinates; comparing to respective second distinct values during each scan of the antenna the computed driving error values for each output target report having the maneuver weight values utilized in predicting the coordinates; using maneuver weight values in predicting coordinates for target reports having at least one driving error exceeding said first distinct values for at least two successive scans of the antenna, and exceeding said second distinct values subsequent to said two successive scans, and having all driving error values less than said second distinct values for a selected number of successive scans of the antenna; and selecting the weight values in accordance with the weight values used on the preceding scan and the driving errors of the firmly correlated target report on the current scan of the antenna. - View Dependent Claims (18, 19, 20)
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21. A method of tracking targets in a surveillance radar system having a scanning antenna, said method comprising:
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sampling values of range, range rate, and azimuth angle for each target during successive scans of the antenna; storing a plurality of non-maneuver weight values, each corresponding to range, range rate, position, and velocity for tracking a target in a non-maneuver mode; storing a plurality of maneuver weight values, each corresponding to range, range rate, position, and velocity for tracking a target in a maneuver mode; computing a driving error value for each of the sampled target values during a current scan of the antenna by subtracting corresponding predicted target values for the current scan from said respective sampled target values; computing a predicted value for each of the sampled target values for a succeeding scan of the antenna by adding to a corresponding predicted value for a current scan of the antenna, the product of the computed driving error value and a corresponding weight value selected from one of said non-maneuver and maneuver plurality of stored weight values; selecting one of said non-maneuver and maneuver plurality of weight values for multiplying with a driving error value during a current scan of the antenna in accordance with the weight values used on the preceding scan and the magnitude of the computed driving error values during the current scan of the antenna, said selecting step including the substeps of checking during each current scan of the antenna the selected one of the non-maneuver and maneuver plurality of weight values utilized in computing the predicted target values during a preceding scan; comparing during the current scan of the antenna the computed driving error values for each target to respective first distinct predetermined values at times when the non-maneuver plurality of weight values are utilized in computing the predicted target values; and changing the weight values from the non-maneuver plurality to the maneuver plurality in computing the predicted target values of respective target for the succeeding scan at times when the driving error values of said target for said preceding scan and the current scan of the antenna are both of a predetermined comparison to said respective first distinct predetermined values; and tracking non-maneuvering and maneuvering targets during successive scans of the antenna in accordance with the correlation of the sampled target values and the corresponding computed predicted target values. - View Dependent Claims (22, 24, 25)
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23. selecting the number of subsequent consecutive scans of the antenna for using the maneuver plurality of weight values in predicting target values for said target in accordance with the determined relative magnitude;
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correcting the predicted target values made on a preceding scan with the use of non-maneuver weights to predicted values made with the maneuver weights; and recomputing the driving errors for the current scan in accordance with the corrected predicted target values.
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Specification