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US3603992A
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Dual harmonic frequency synthetic aperture radar
Assignee: United States Department of the Air Force
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Filing: 1969-11-13
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Granted: 1971-09-07
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Expires: 1989-11-13
Abstract
Abstract A dual harmonic frequency synthetic aperture radar system in which synthetic aperture processing is used to achieve high angular resolution for two radars which operate at two or more harmonically related frequencies. These frequencies are related by the factor N. The processing is done so as to preserve the phase of the target return. After the synthetic aperture processing is completed, the phase angles are available at the two frequencies. The lower frequency phase angle is multiplied by N and compared with the phase angle at the upper frequency to obtain phase signature data on the target.
Inventors
- 👤 William B Goggins Jr
- 👤 John K Schindler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 03:01
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/88; G01S13/89; G01S13/90; G01S13/9021; G01S13/9029; G01S13/9004; G01S7/00; G01S7/02; G01S7/41; G01S7/414
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
350 words
A dual harmonic frequency synthetic aperture radar comprising first means to generate a stabilized continuous wave signal at a predetermined frequency to provide a first signal, first means to frequency multiply said continuous wave signal by a factor N to provide a second signal, means to pulse said first and second signals, first and second moving airborne antenna means receiving said first and second signals, respectively, for direction toward a target of interest, first and second means to receive return signals from said target of interest resulting from the first and second pulsed signals, respectively, being directed toward said target of interest, first, second, third, and fourth mixers, first and second 90* phase shifters receiving as inputs said first signal and said second signal, respectively, said first mixer receiving simultaneously the output signal from said first receiving means and said first signal, said second mixer receiving simultaneously the outputs from said first receiving means and said first 90* phase shifter, said third mixer receiving simultaneously the output signal from said second receiving means and said second signal, said fourth mixer receiving simultaneously the outputs of said second receiving means and said second 90* phase shifter, first, second, third and fourth sample and hold circuits receiving the outputs of said first, second, third and fourth mixers, respectively, first and second reference function generators, each having predetermined output being a linear frequency modulated reference signal, first, second, third and fourth multipliers, said first multiplier receiving simultaneously the outputs from said first sample and hold circuit and said first reference function generator, said second multiplier receiving simultaneously the outputs from said second sample and hold circuit and said first reference generator, said third multiplier receiving simultaneously the outputs from said third sample and hold circuit and said second reference function generator, said fourth multiplier receiving simultaneously the outputs from said fourth sample and hold circuit and said second reference function generator, first, second, third and fourth low pass filters passing the outputs of said first, second, third and fourth multipliers, respectively, to provide amplitude and phase signals representative of said target of interest.
Claim 2
Dependent Claim
350 words
A dual harmonic frequency synthetic aperture radar comprising first means to generate a stabilized continuous wave signal at a predetermined frequency to provide a first signal, first means to frequency multiply said continuous wave signal by a factor N to provide a second signal, means to pulse said first and second signals, first and second moving airborne antenna means receiving said first and second signals, respectively, for direction toward a target of interest, first and second means to receive return signals from said target of interest resulting from the first and second pulsed signals, respectively, being directed toward said target of interest, first, second, third, and fourth mixers, first and second 90* phase shifters receiving as inputs said first signal and said second signal, respectively, said first mixer receiving simultaneously the output signal from said first receiving means and said first signal, said second mixer receiving simultaneously the outputs from said first receiving means and said first 90* phase shifter, said third mixer receiving simultaneously the output signal from said second receiving means and said second signal, said fourth mixer receiving simultaneously the outputs of said second receiving means and said second 90* phase shifter, first, second, third and fourth sample and hold circuits receiving the outputs of said first, second, third and fourth mixers, respectively, first and second reference function generators, each having predetermined output being a linear frequency modulated reference signal, first, second, third and fourth multipliers, said first multiplier receiving simultaneously the outputs from said first sample and hold circuit and said first reference function generator, said second multiplier receiving simultaneously the outputs from said second sample and hold circuit and said first reference generator, said third multiplier receiving simultaneously the outputs from said third sample and hold circuit and said second reference function generator, said fourth multiplier receiving simultaneously the outputs from said fourth sample and hold circuit and said second reference function generator, first, second, third and fourth low pass filters passing the outputs of said first, second, third and fourth multipliers, respectively, to provide amplitude and phase signals representative of said target of interest.
Claim 3
Dependent Claim
261 words
A dual harmonic frequency synthetic aperture radar as described in claim 1 further including fifth, sixth, seventh and eighth multipliers, second means to generate a predetermined stabilized continuous wave signal to provide a third signal, third and fourth 90* phase shifters, means to scale a signal by a factor N, said fifth multiplier receiving simultaneously the output signal from said first low pass filter and said third signal by way of said scaling means, said sixth multiplier receiving simultaneously the output of said second low pass filter and said third signal by way of said scaling means and said third 90* phase shifter, said seventh multiplier receiving simultaneously the output of said third low pass filter and said third signal by way of said fourth 90* phase shifter, said eighth multiplier receiving simultaneously the output of said fourth low pass filter and said third signal, first and second summers, said first summer adding the outputs of said fifth and sixth multipliers to provide a first resultant signal, said second summer adding the outputs of said seventh and eighth multipliers to provide a second resultant signal, first and second linear detectors receiving said first and second resultant signals to provide outputs representative of the magnitudes of the two received return signals, second means to frequency multiply by a factor N, said second frequency multiplier receiving the output of said second Summer, and phase detector receiving the output signal from said second frequency multiplier and said first resultant signal, said phase detector providing an output phase signal characteristic of said target of interest.
Claim 4
Dependent Claim
30 words
A dual harmonic frequency synthetic aperture radar as described in claim 2 further including display means receiving the output signals from said first and second linear detector and phase detector.
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) | 1974-09-06 | 1975-03-08 | 1975-09-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-06 | 1979-03-08 | 1979-09-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-06 | 1983-03-08 | 1983-09-07 | $7700.00 | Window Closed / Lapsed |