US3742500A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Mti radar
Assignee: Raytheon Co
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Filing: 1970-08-24
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Granted: 1973-06-26
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Expires: 1990-08-24
Abstract
Abstract A radar system adapted to discriminate between signals from clutter and moving targets. The disclosed system includes at least one digital canceller and an associated digital correction circuit which together are operative to produce a digital signal indicative of the average Doppler frequency of all targets within a selected group of range cells. Such digital signal, in turn, is applied to a digital phase shifter in circuit with the output signal from a reference oscillator to shift the frequency of such output signal until the clutter rejection notch of the digital canceller is centered on the average Doppler frequency of the targets within the selected group of range cells.
Inventors
- 👤 N Freedman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 21:55
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/50; G01S13/52; G01S13/522; G01S13/524; G01S13/5244
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
341 words
In the receiver of an adaptive MTI radar system, such receiver including a coherent oscillator and a digital phase shifter in circuit to provide a local oscillator signal having its phase varying in accordance with the average Doppler velocity of targets illuminated by radio frequency energy during predetermined intervals of time, such local oscillator signal thereby becoming a reference signal coherent with echo signals from targets moving at velocities near the average Doppler velocity of all targets to permit such echo signals to be cancelled, improved control circuitry for such digital phase shifter comprising: a. quadrature phase detector means, responsive to a signal analogous to each echo signal on each one of the range sweeps and to the then existing reference signal out of the digital phase shifter, for producing a first group and a second group of video signals representative, respectively, of the magnitude and sense of the phase difference between each signal analogous to each echo signal and the then existing reference signal out of the digital phase shifter; b. digital signal processing means, responsive to the first group and to the second group of video signals out of the quadrature phase detector, for producing first and second digital error signals, the first digital error signals being indicative of the difference in phase between corresponding echo signals during successive intervals of time, and the second digital error signals being indicative of the sense of such difference; c. digital multiplier means for multiplying the first and the second digital error signals to produce a third group of digital signals, each digital signal in such third group being representative to the magnitude and sense of the phase difference between each signal analogous to each echo signal and the then existing reference signal out of the digital phase shifter; d. digital integrator means, responsive to the third group of digital signals, for producing a digital correction signal corresponding to the average of the third group of digital signals; and e. means for applying the digital correction signal to the digital phase shifter.
Claim 2
Dependent Claim
341 words
In the receiver of an adaptive MTI radar system, such receiver including a coherent oscillator and a digital phase shifter in circuit to provide a local oscillator signal having its phase varying in accordance with the average Doppler velocity of targets illuminated by radio frequency energy during predetermined intervals of time, such local oscillator signal thereby becoming a reference signal coherent with echo signals from targets moving at velocities near the average Doppler velocity of all targets to permit such echo signals to be cancelled, improved control circuitry for such digital phase shifter comprising: a. quadrature phase detector means, responsive to a signal analogous to each echo signal on each one of the range sweeps and to the then existing reference signal out of the digital phase shifter, for producing a first group and a second group of video signals representative, respectively, of the magnitude and sense of the phase difference between each signal analogous to each echo signal and the then existing reference signal out of the digital phase shifter; b. digital signal processing means, responsive to the first group and to the second group of video signals out of the quadrature phase detector, for producing first and second digital error signals, the first digital error signals being indicative of the difference in phase between corresponding echo signals during successive intervals of time, and the second digital error signals being indicative of the sense of such difference; c. digital multiplier means for multiplying the first and the second digital error signals to produce a third group of digital signals, each digital signal in such third group being representative to the magnitude and sense of the phase difference between each signal analogous to each echo signal and the then existing reference signal out of the digital phase shifter; d. digital integrator means, responsive to the third group of digital signals, for producing a digital correction signal corresponding to the average of the third group of digital signals; and e. means for applying the digital correction signal to the digital phase shifter.
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) | 1976-06-25 | 1976-12-25 | 1977-06-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-25 | 1980-12-25 | 1981-06-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-25 | 1984-12-25 | 1985-06-26 | $7700.00 | Window Closed / Lapsed |