US3720941A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic monopulse clutter cancellation circuit
Assignee: General Electric Co
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Filing: 1970-04-13
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Granted: 1973-03-13
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Expires: 1990-04-13
Abstract
Abstract Clutter cancellation is provided in a monopulse radar system by placing a null in the angle response of the radar on the clutter. This is achieved by cross-cancellation of signals as received at two antennas oriented to provide vertically displaced response patterns, the null thus provided being maintained centered on the clutter by operation of control means which adjust the phase and amplitude of one or both of the signals prior to their crosscancellation. The signal phase and amplitude adjustment means may take any of several different forms but in each case they form part of closed loop controls which optimize the cancellation of clutter returns from received signals while preserving target returns.
Inventors
- 👤 M Ares
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 11:22
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/06; G01S13/42; G01S13/44; G01S13/449; G01S13/50; G01S13/52
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
154 words
In a monopulse radar system, a clutter cancellation circuit comprising in combination: a. means for deriving first and second signals respectively indicative of first and second reception lobe responses of a monopulse antenna; b. first and second channels respectively coupled to said first and second signals; c. signal combining means for algebraically combining the signals in said first and second channels, for providing a difference signal indicative of the algebraic difference of the signals in the said first and second channels, whereby a clutter cancelled output is provided when the phase and amplitude differences between the signals in said first and second channels are nulled; d. phase shifting means connected in series in said first channel for nulling the phase difference of the signals in said first and second channels; and e. amplitude adjusting means connected in said first channel for nulling the amplitude difference between the signals in said first and second channels.
Claim 2
Dependent Claim
154 words
In a monopulse radar system, a clutter cancellation circuit comprising in combination: a. means for deriving first and second signals respectively indicative of first and second reception lobe responses of a monopulse antenna; b. first and second channels respectively coupled to said first and second signals; c. signal combining means for algebraically combining the signals in said first and second channels, for providing a difference signal indicative of the algebraic difference of the signals in the said first and second channels, whereby a clutter cancelled output is provided when the phase and amplitude differences between the signals in said first and second channels are nulled; d. phase shifting means connected in series in said first channel for nulling the phase difference of the signals in said first and second channels; and e. amplitude adjusting means connected in said first channel for nulling the amplitude difference between the signals in said first and second channels.
Claim 3
Dependent Claim
154 words
In a monopulse radar system, a clutter cancellation circuit comprising in combination: a. means for deriving first and second signals respectively indicative of first and second reception lobe responses of a monopulse antenna; b. first and second channels respectively coupled to said first and second signals; c. signal combining means for algebraically combining the signals in said first and second channels, for providing a difference signal indicative of the algebraic difference of the signals in the said first and second channels, whereby a clutter cancelled output is provided when the phase and amplitude differences between the signals in said first and second channels are nulled; d. phase shifting means connected in series in said first channel for nulling the phase difference of the signals in said first and second channels; and e. amplitude adjusting means connected in said first channel for nulling the amplitude difference between the signals in said first and second channels.
Claim 4
Dependent Claim
154 words
In a monopulse radar system, a clutter cancellation circuit comprising in combination: a. means for deriving first and second signals respectively indicative of first and second reception lobe responses of a monopulse antenna; b. first and second channels respectively coupled to said first and second signals; c. signal combining means for algebraically combining the signals in said first and second channels, for providing a difference signal indicative of the algebraic difference of the signals in the said first and second channels, whereby a clutter cancelled output is provided when the phase and amplitude differences between the signals in said first and second channels are nulled; d. phase shifting means connected in series in said first channel for nulling the phase difference of the signals in said first and second channels; and e. amplitude adjusting means connected in said first channel for nulling the amplitude difference between the signals in said first and second channels.
Claim 5
Dependent Claim
51 words
In a monopulse radar system according to claim 1 and including a monopulse antenna having first and second poRts in which said means for deriving said first and second signals comprises direct coupling means for coupling said first and second channels respectively to first and second ports of the monopulse antenna.
Claim 6
Dependent Claim
88 words
A monopulse radar system according to claim 1 and including a monopulse antenna unit having first and second ports respectively providing signals indicative of the sum and of the difference of first and second lobe responses of a monopulse antenna in which said means for deriving said first and second signals comprises a magic tee having first and second input terminals for respective coupling to the first and second ports of the monopulse antenna unit and third and fourth terminals respectively coupled to said first and second channels.
Claim 7
Dependent Claim
68 words
A clutter cancellation circuit according to claim 1 in which said signal combining means comprises a hybrid circuit having first and second terminals connected to receive signals from said first and second channels respectively, and third and fourth terminals, said third terminal providing a sum signal indicative of the algebraic sum of the signals in said first and second channels, and said fourth terminal providing the difference signal.
Claim 8
Dependent Claim
97 words
A clutter cancellation circuit according to claim 4 in which said phase shifting means comprises a variable phase shifter and further comprising a phase sensitive detector having a first input terminal connected to receive the difference signal from said hybrid circuit shifted by 90*, and a second input terminal connected to receive the sum signal from said hybrid circuit and an output terminal connected to regulate the magnitude of phase shift produced by said variable phase shifter, whereby a closed loop is formed to null the phase error between the signals in said first and second channels.
Claim 9
Dependent Claim
71 words
A monopulse clutter cancellation circuit according to claim 5 further comprising a second phase sensitive detector having first and second inputs connected to receive said sum and difference signals respectively from said hybrid circuit and an output terminal connected to regulate the level of output of said amplitude control, whereby a closed loop is formed to null the error between the amplitudes of the signals in said first and second channels.
Claim 10
Dependent Claim
60 words
A monopulse clutter cancellation circuit according to claim 6 in which said first and second channels include intermediate frequency stages and further comprising first and second amplitude detectors coupled respectively to the sum and difference signal outputs of said hybrid circuit and means coupling the output of said first amplitude detector to said intermediate frequency stages to control their gain.
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) | 1976-03-12 | 1976-09-11 | 1977-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-12 | 1980-09-11 | 1981-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-12 | 1984-09-11 | 1985-03-13 | $7700.00 | Window Closed / Lapsed |