Patent US3775768A successfully refreshed from Google Patents.
US3775768A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Adaptive mti clutter filter
Assignee: Westinghouse Electric Corp
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Filing: 1971-12-06
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Granted: 1973-11-27
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Expires: 1991-12-06
Abstract
Abstract A system for enhancing AMTI radar target velocity (Doppler) visibility in reduced clutter to noise environment by utilizing MTI filters selectively coupled into the system whose rejection characteristic is chosen as a function of clutter amplitude level as well as bandwidth whereby excessive signal rejection is not introduced with consequent target invisibility.
Inventors
- 👤 H Lisle
- 👤 R Hughes
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 11:31
CPC Classifications
G; G01; G01S; G01S7/00; G01S7/02; G01S7/36; G01S13/00; G01S13/02; G01S13/50; G01S13/52; G01S13/522; G01S13/524; G01S13/5244
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
215 words
In a pulse Doppler radar including a transmitter and receiver station wherein the transmitter section is triggered by a train of constant PRF pulses for a predetermined time period defined as the radar look time and wherein the receiver portion detects and digitally processes radar return signals which include a clutter frequency spectrum, the improvement comprising: MTI digital filter circuit means having an externally controlled filter characteristic coupled to said receiver section and being responsive to the clutter frequency spectrum to selectively attenuate said spectrum in relation to other radar return signals; clutter spectrum determining circuit means coupled to said receiver section and providing a digital output signal which is a function of both clutter amplitude and bandwidth; digital storage means having data stored therein comprising a plurality of threshold values corresponding to a respective plurality of predetermined digital clutter filter characteristics; and digital logic circuit means coupled between said clutter spectrum determining circuit means and said storage means, being operable to compare the digital output signal from said clutter spectrum determining circuit means with said threshold values in said digital storage means and gating out a predetermined enabling signal to said MTI filter circuit means when a predetermined comparison is made, causing said digital filter circuit means to provide a predetermined clutter filter characteristic.
Claim 2
Dependent Claim
215 words
In a pulse Doppler radar including a transmitter and receiver station wherein the transmitter section is triggered by a train of constant PRF pulses for a predetermined time period defined as the radar look time and wherein the receiver portion detects and digitally processes radar return signals which include a clutter frequency spectrum, the improvement comprising: MTI digital filter circuit means having an externally controlled filter characteristic coupled to said receiver section and being responsive to the clutter frequency spectrum to selectively attenuate said spectrum in relation to other radar return signals; clutter spectrum determining circuit means coupled to said receiver section and providing a digital output signal which is a function of both clutter amplitude and bandwidth; digital storage means having data stored therein comprising a plurality of threshold values corresponding to a respective plurality of predetermined digital clutter filter characteristics; and digital logic circuit means coupled between said clutter spectrum determining circuit means and said storage means, being operable to compare the digital output signal from said clutter spectrum determining circuit means with said threshold values in said digital storage means and gating out a predetermined enabling signal to said MTI filter circuit means when a predetermined comparison is made, causing said digital filter circuit means to provide a predetermined clutter filter characteristic.
Claim 3
Dependent Claim
17 words
The invention as defined by claim 1 wherein said clutter filter characteristic comprises a notch filter characteristic.
Claim 4
Dependent Claim
170 words
The invention as defined by claim 1 wherein said clutter spectrum determining circuit means comprises: envelope detector means in said receiver section; first circuit means coupled to said envelope detector means, said first circuit means being operable to integrate a predetermined number of radar return signal samples during said radar look time and providing a signal therefrom which is a function of the means amplitude of the clutter spectrum; second circuit means providing a digital signal which is a function of the clutter spectrum bandwidth; third circuit means coupled to said first and second circuit means, combining the signals provided thereby and coupling a digital output signal therefrom to said logic circuit means which is a function of both clutter amplitude and bandwidth; and fourth circuit means included in said MTI filter circuit means coupled to said logic circuit means and being responsive to said digital output signal therefrom and controlling the filter frequency rejection characteristic of said filter circuit means as a function of the clutter amplitude and bandwidth.
Claim 5
Dependent Claim
34 words
The invention as defined by claim 3 wherein said envelope detector means comprises a signal summer which is responsive to the absolute values of inphase and quadrature components of the detected radar return signals.
Claim 6
Dependent Claim
125 words
The invention as defined by claim 3 wherein said first circuit means comprises: an integrator circuit coupled to said envelope detector means; a coincidence circuit having a pair of inputs and one output including circuit means coupling one input to said integrator circuit; a clutter gate circuit responsive to the radar return signals coupled to the other input of said coincident circuit; a signal accumulator and dump circuit coupled to the output of said coincident circuit; a look sequencer, operated by said transmitter portion, to determine the radar look time and having an output circuit coupled to said dump circuit for dumping said signal samples at the end of said radar look time; and circuit means coupling said dump circuit to said third circuit means.
Claim 7
Dependent Claim
17 words
The invention as defined by claim 3 wherein said third circuit means comprises a digital signal multiplier.
Claim 8
Dependent Claim
18 words
The invention as defined by claim 3 wherein Said second circuit means comprises an analog to digital converter.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-11-26 | 1977-05-28 | 1977-11-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-26 | 1981-05-28 | 1981-11-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-26 | 1985-05-28 | 1985-11-27 | $7700.00 | Window Closed / Lapsed |