US4095222A
Expired / Lapsed
US
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Post-detection stc in a medium prf pulse doppler radar
Assignee: Westinghouse Electric Corp
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Filing: 1976-05-27
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Granted: 1978-06-13
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Expires: 1996-05-27
Abstract
Abstract A method and apparatus is described for the post processing of return signal data in a single channel medium PRF pulse doppler radar receiver. The disclosure is directed to preventing sidelobe return signals from being displayed as "ghost" or "false" targets. The received signal data is preliminarily processed by a filter bank and a CFAR threshold circuit to remove main beam clutter and area sidelobe clutter returns. The preliminarily processed data is then temporarily stored as two parallel correlations are performed on a range cell by range cell basis to identify range cells which contain discrete sidelobe clutter return signals. One of the parallel correlations is performed on the data after it has passed an STC (Sensitivity Time Control) threshold circuit and the other parallel correlation is performed on the raw data. The outputs of the parallel correlators are compared. The identified range cell correlations in the raw data correlator are compared with corresponding range cells of the STC's correlations to identify range cell numbers which contain discrete sidelobe clutter return signals. Identified range cell numbers are blanked from the raw data before it is correlated for a third time. The output of the third correlator identifies the true target return signals and the corresponding unambiguous range thereof.
Inventors
- 👤 David H. Mooney, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 00:36
CPC Classifications
G; G01; G01S; G01S7/00; G01S7/02; G01S7/28; G01S7/2813; G01S13/00; G01S13/02; G01S13/06; G01S13/08; G01S13/10; G01S13/20; G01S13/50; G01S13/52; G01S13/522; G01S13/524; G01S13/5242; G01S13/5246
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
141 words
A single channel radar receiver responsive to return signals that include discrete sidelobe return signals and target return signals, said receiver comprising: first means for correlating said return signals to provide a first correlation signal; means for thresholding the return signals over a predetermined period of time to provide thresholded return signals; second means for correlating the thresholded return signals in response to the output of the thresholding means to provide a second correlation signal; means for detecting discrete sidelobe clutter returns in response to said first and second correlation signals to provide a blanking signal; means for blanking the discrete sidelobe return signals of said return signals in response to the blanking signal to provide target return signals; and means for determining the range of the target return signals in response to the target return signals of said blanking means.
Claim 2
Dependent Claim
141 words
A single channel radar receiver responsive to return signals that include discrete sidelobe return signals and target return signals, said receiver comprising: first means for correlating said return signals to provide a first correlation signal; means for thresholding the return signals over a predetermined period of time to provide thresholded return signals; second means for correlating the thresholded return signals in response to the output of the thresholding means to provide a second correlation signal; means for detecting discrete sidelobe clutter returns in response to said first and second correlation signals to provide a blanking signal; means for blanking the discrete sidelobe return signals of said return signals in response to the blanking signal to provide target return signals; and means for determining the range of the target return signals in response to the target return signals of said blanking means.
Claim 3
Independent Claim
244 words
A method of processing return signal data in a medium PRF radar receiver, to distinguish main beam true target return signals from sidelobe return signals over multiple transmitted PRF's, comprising the steps of: correlating said return signal data over a first predetermined number of unambiguous range cells for each PRF, to produce a first signal for each range cell indicative of a second predetermined number of corresponding range cells being occupied by return signal data; thresholding said return signal data over a predetermined time period corresponding to a predetermined range for each PRF, wherein the threshold level varies over said predetermined time period; correlating said thresholded returned signal data over said first predetermined number of unambiguous range cells for each PRF, to produce a second signal for each range cell indicative of said second predetermined number of corresponding range cells being occupied by said thresholded returned signal data; comparing said first and second signals to determine the range cell number in which a first signal is present and a second signal is not present; blanking said determined range cell number in said return signal data for each PRF to remove any said sidelobe return signals present in said return signal data; and correlating said blanked return signal data over a third predetermined number of unambiguous range cells for each PRF to produce a third signal indicative of the unambiguous range of any main beam true target return signals present in said return signal data.
Claim 4
Independent Claim
244 words
A method of processing return signal data in a medium PRF radar receiver, to distinguish main beam true target return signals from sidelobe return signals over multiple transmitted PRF's, comprising the steps of: correlating said return signal data over a first predetermined number of unambiguous range cells for each PRF, to produce a first signal for each range cell indicative of a second predetermined number of corresponding range cells being occupied by return signal data; thresholding said return signal data over a predetermined time period corresponding to a predetermined range for each PRF, wherein the threshold level varies over said predetermined time period; correlating said thresholded returned signal data over said first predetermined number of unambiguous range cells for each PRF, to produce a second signal for each range cell indicative of said second predetermined number of corresponding range cells being occupied by said thresholded returned signal data; comparing said first and second signals to determine the range cell number in which a first signal is present and a second signal is not present; blanking said determined range cell number in said return signal data for each PRF to remove any said sidelobe return signals present in said return signal data; and correlating said blanked return signal data over a third predetermined number of unambiguous range cells for each PRF to produce a third signal indicative of the unambiguous range of any main beam true target return signals present in said return signal data.
Claim 5
Dependent Claim
20 words
A method as in claim 2, wherein said steps of correlating to produce respective first and second signals, occur simultaneously.
Claim 6
Dependent Claim
35 words
A method as in claim 2, wherein said steps of correlating said return signal data and correlating said thresholded return signal data takes place prior to said steps of correlating said blanked return signal data.
Claim 7
Dependent Claim
55 words
A method as in claim 2, wherein said steps of correlating said return signal data and correlating said thresholded return signal data over a first predetermined number of unambiguous range cells is less than said third predetermined number of unambiguous range cells over which said step of correlating said blanked return signal data is performed.
Claim 8
Independent Claim
258 words
A system for processing return signal data in a medium PRF radar receiver to distinguish main beam true target return signals from sidelobe return signals over multiple transmitted PRF's comprising: first means for correlating said return signal data over a first predetermined number of unambiguous range cells for each PRF to produce a first signal for each range cell indicative of a second predetermined number of corresponding range cells being occupied by return signal data; means for thresholding said return signal data over a predetermined time period of each PRF, wherein the threshold level varies over said predetermined time period; means for correlating said thresholded return signal data over said first predetermined number of unambiguous range cells for each PRF, to produce a second signal for each range cell indicative of said second predetermined number of corresponding range cells being occupied by said thresholded return signal data; means for comparing said first and second signals and producing a third signal according to the range cell number in which a said first signal is present and a said second signal is not present; means for receiving said third signal and blanking said corresponding range cell number in said return signal data for each PRF to remove said sidelobe return signals present in said return signal data; and means for correlating said blanked return signal data over a third predetermined number of unambiguous range cells for each PRF and producing a fourth signal indicative of the unambiguous range for any true target return signals present in said returned signal data.
Claim 9
Independent Claim
258 words
A system for processing return signal data in a medium PRF radar receiver to distinguish main beam true target return signals from sidelobe return signals over multiple transmitted PRF's comprising: first means for correlating said return signal data over a first predetermined number of unambiguous range cells for each PRF to produce a first signal for each range cell indicative of a second predetermined number of corresponding range cells being occupied by return signal data; means for thresholding said return signal data over a predetermined time period of each PRF, wherein the threshold level varies over said predetermined time period; means for correlating said thresholded return signal data over said first predetermined number of unambiguous range cells for each PRF, to produce a second signal for each range cell indicative of said second predetermined number of corresponding range cells being occupied by said thresholded return signal data; means for comparing said first and second signals and producing a third signal according to the range cell number in which a said first signal is present and a said second signal is not present; means for receiving said third signal and blanking said corresponding range cell number in said return signal data for each PRF to remove said sidelobe return signals present in said return signal data; and means for correlating said blanked return signal data over a third predetermined number of unambiguous range cells for each PRF and producing a fourth signal indicative of the unambiguous range for any true target return signals present in said returned signal data.
Claim 10
Dependent Claim
51 words
A system for processing return signal data as in claim 6, wherein said means for thresholding said return signal data includes means for generating a threshold level which varies as a function of an R 4 power curve decaying over said first predetermined number of unambiguous range cells for each PRF.
Claim 11
Dependent Claim
47 words
A system for processing return signal data as in claim 6, including means for unfolding said return signal data in unambiguous range cells, for each PRF, and outputting said return signal data into said respective return signal data correlating means and said return signal data thresholding means.
Claim 12
Dependent Claim
70 words
A system for processing return signal data as in claim 6, wherein said return signal data correlating means comprises a delay line for receiving said return signal data in a first predetermined number of unambiguous range cells, for each PRF, and correlation logic circuitry for producing a said first signal for each range cell indicative of said second predetermined number of corresponding range cells being occupied by return signal data.
Claim 13
Dependent Claim
73 words
A system for processing return signal data as in claim 6, wherein said thresholded return signal data correlating means includes a delay line for receiving said thresholded return signal data in said first predetermined number of unambiguous range cells, for each PRF, and correlation logic circuitry for producing a said second signal for each range cell indicative of said second predetermined number of corresponding range cells being occupied by thresholded return signal data.
Claim 14
Independent Claim
385 words
A system for post-detection processing of return signal data over multiple PRF's subsequent to the removal therefrom of main beam clutter return signal data in a single channel medium PRF pulse doppler type radar receiver, comprising: means for temporarily storing said return signal data for each of a plurality of ambiguous range cells in each PRF: means for unfolding said data from said temporary storage means into unambiguous range cells for each PRF; means for correlating said unfolded data to determine at least a predetermined number of occurrences of data in corresponding unambiguous range cells of said multiple PRF's and producing a first output signal for each correlated range cell indicating said determination; means for amplitude thresholding said unfolded data along a predetermined decaying threshold corresponding to a first predetermined number of unambiguous range cells, for each PRF, and outputting said unfolded thresholded data; means for correlating said thresholded data over said first predetermined number of unambiguous range cells to determine at least said predetermined number of occurrences of thresholded data in corresponding unambiguous range cells of said multiple PRF's and producing a second output signal for each correlated cell indicating said determination; means for comparing said first and second output signals for each correlated cell and outputting a third signal, when said first signal indicates at least said predetermined number of occurrences and said second signal indicates less than said predetermined number of occurrences, indicating said compared range cell number; means for converting said third signal to an ambiguous range cell gate and blanking said corresponding ambiguous range cell in said data from said temporary storage means for each PRF; means for unfolding said data from said blanking means into unambiguous range cells for each PRF; and means for correlating said unfolded data from said blanking means over a second predetermined number of unambiguous range cells to determine at least said predetermined number of occurrences of data in corresponding unambiguous range cells of said multiple PRF's and producing a fourth output signal for each unambiguous range cell in which said data is determined to occur at least said predetermined number of times in said corresponding unambiguous range cells of said multiple PRF's, thereby indicating the unambiguous range of true target return signals as distinguished from all other return signals in said return signal data.
Claim 15
Independent Claim
385 words
A system for post-detection processing of return signal data over multiple PRF's subsequent to the removal therefrom of main beam clutter return signal data in a single channel medium PRF pulse doppler type radar receiver, comprising: means for temporarily storing said return signal data for each of a plurality of ambiguous range cells in each PRF: means for unfolding said data from said temporary storage means into unambiguous range cells for each PRF; means for correlating said unfolded data to determine at least a predetermined number of occurrences of data in corresponding unambiguous range cells of said multiple PRF's and producing a first output signal for each correlated range cell indicating said determination; means for amplitude thresholding said unfolded data along a predetermined decaying threshold corresponding to a first predetermined number of unambiguous range cells, for each PRF, and outputting said unfolded thresholded data; means for correlating said thresholded data over said first predetermined number of unambiguous range cells to determine at least said predetermined number of occurrences of thresholded data in corresponding unambiguous range cells of said multiple PRF's and producing a second output signal for each correlated cell indicating said determination; means for comparing said first and second output signals for each correlated cell and outputting a third signal, when said first signal indicates at least said predetermined number of occurrences and said second signal indicates less than said predetermined number of occurrences, indicating said compared range cell number; means for converting said third signal to an ambiguous range cell gate and blanking said corresponding ambiguous range cell in said data from said temporary storage means for each PRF; means for unfolding said data from said blanking means into unambiguous range cells for each PRF; and means for correlating said unfolded data from said blanking means over a second predetermined number of unambiguous range cells to determine at least said predetermined number of occurrences of data in corresponding unambiguous range cells of said multiple PRF's and producing a fourth output signal for each unambiguous range cell in which said data is determined to occur at least said predetermined number of times in said corresponding unambiguous range cells of said multiple PRF's, thereby indicating the unambiguous range of true target return signals as distinguished from all other return signals in said return signal data.
Claim 16
Dependent Claim
248 words
A pulse doppler radar receiver for detecting the range of a target from received signals which include target returns, main beam clutter returns, area sidelobe clutter returns and discrete sidelobe clutter returns, said receiver comprising: means for filtering the main beam clutter returns from said received signals; means for providing an adaptive threshold signal which varies in response to the amplitude of the area sidelobe clutter returns said providing means being responsive to said filtering means to remove said area sidelobe clutter returns from said received signals; means for unfolding the output of said providing means over a predetermined range, said unfolding means being responsive to the output of said providing means to provide an unambiguous range signal; means for thresholding the unambiguous range signal in response to the output of said unfolding means, the threshold being such that the discrete sidelobe clutter returns are rejected over a selected range of said unambiguous range signal; means for detecting discrete sidelobe clutter returns in the unambiguous range signal of said unfolding means said detecting means being responsive to said unfolding means and to said thresholding means to provide a blanking signal; means for blanking the discrete sidelobe clutter returns detected by said detecting means from the output of said providing means, said blanking means being responsive to said detecting means to provide the target returns of the received signals; and means for determining the range of the target in response to said target returns provided by said blanking means.
Claim 17
Dependent Claim
248 words
A pulse doppler radar receiver for detecting the range of a target from received signals which include target returns, main beam clutter returns, area sidelobe clutter returns and discrete sidelobe clutter returns, said receiver comprising: means for filtering the main beam clutter returns from said received signals; means for providing an adaptive threshold signal which varies in response to the amplitude of the area sidelobe clutter returns said providing means being responsive to said filtering means to remove said area sidelobe clutter returns from said received signals; means for unfolding the output of said providing means over a predetermined range, said unfolding means being responsive to the output of said providing means to provide an unambiguous range signal; means for thresholding the unambiguous range signal in response to the output of said unfolding means, the threshold being such that the discrete sidelobe clutter returns are rejected over a selected range of said unambiguous range signal; means for detecting discrete sidelobe clutter returns in the unambiguous range signal of said unfolding means said detecting means being responsive to said unfolding means and to said thresholding means to provide a blanking signal; means for blanking the discrete sidelobe clutter returns detected by said detecting means from the output of said providing means, said blanking means being responsive to said detecting means to provide the target returns of the received signals; and means for determining the range of the target in response to said target returns provided by said blanking means.
Claim 18
Dependent Claim
44 words
The apparatus of claim 12 wherein said detecting means includes: means for folding the discrete sidelobe clutter returns detected by said detecting means into a predetermined range, such that said detecting means provides an ambiguous pulse repitition frequency discrete signal to said blanking means.
Claim 19
Dependent Claim
330 words
A pulse doppler radar receiver for detecting the range of a target from received signals which include target returns, main beam clutter returns, area sidelobe clutter returns and discrete sidelobe clutter returns, said receiver comprising: means for filtering the main beam clutter returns from said received signals; means for providing a threshold signal which varies in response to the area sidelobe clutter returns, said providing means being responsive to said filtering means to remove said area sidelobe clutter returns from said received signals; means for unfolding the output of said providing means over a predetermined range said unfolding means being responsive to the output of said providing means to provide an unambiguous range signal; first means for comparing the unambiguous range signal of said unfolding means to a sensitivity time control threshold signal, said comparing means being responsive to the unambiguous range signal and to the sensitivity time control threshold signal to detect target returns in the unambiguous range signal; first means for correlating the target returns and discrete sidelobe clutter returns of at least two unambiguous range signals in response to the output of said unfolding means; second means for correlating the target returns detected by said first comparing means in at least two unambiguous range signals in response to the output of said first comparing means; second means for comparing the correlations of said first and second correlating means, said second correlating means being responsive to the outputs of said first and second correlating means to detect discrete sidelobe clutter returns in the unambiguous range signals of said unfolding means; means for blanking the discrete sidelobe clutter returns detected by said second comparing means from the output of said providing means, said blanking means being response to said second comparing means and to the output of said providing means to provide the target returns of said received signals; and means for determining the range of the target in response to the target returns provided by said blanking means.
Claim 20
Dependent Claim
330 words
A pulse doppler radar receiver for detecting the range of a target from received signals which include target returns, main beam clutter returns, area sidelobe clutter returns and discrete sidelobe clutter returns, said receiver comprising: means for filtering the main beam clutter returns from said received signals; means for providing a threshold signal which varies in response to the area sidelobe clutter returns, said providing means being responsive to said filtering means to remove said area sidelobe clutter returns from said received signals; means for unfolding the output of said providing means over a predetermined range said unfolding means being responsive to the output of said providing means to provide an unambiguous range signal; first means for comparing the unambiguous range signal of said unfolding means to a sensitivity time control threshold signal, said comparing means being responsive to the unambiguous range signal and to the sensitivity time control threshold signal to detect target returns in the unambiguous range signal; first means for correlating the target returns and discrete sidelobe clutter returns of at least two unambiguous range signals in response to the output of said unfolding means; second means for correlating the target returns detected by said first comparing means in at least two unambiguous range signals in response to the output of said first comparing means; second means for comparing the correlations of said first and second correlating means, said second correlating means being responsive to the outputs of said first and second correlating means to detect discrete sidelobe clutter returns in the unambiguous range signals of said unfolding means; means for blanking the discrete sidelobe clutter returns detected by said second comparing means from the output of said providing means, said blanking means being response to said second comparing means and to the output of said providing means to provide the target returns of said received signals; and means for determining the range of the target in response to the target returns provided by said blanking means.
Claim 21
Dependent Claim
44 words
The apparatus of claim 14 wherein said second comparing means includes: means for folding the discrete sidelobe clutter returns detected by said second comparing means into a predetermined range, such that an ambiguous pulse repetition frequency discrete signal is provided to said blanking means.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-06-12 | 1981-12-12 | 1982-06-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-06-12 | 1985-12-12 | 1986-06-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-06-12 | 1989-12-12 | 1990-06-13 | $7700.00 | Window Closed / Lapsed |