US3778827A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Short range monopulse marine search radar for small object detection
Assignee: Litton Marine Systems Inc
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Filing: 1972-01-27
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Granted: 1973-12-11
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Expires: 1992-01-27
Abstract
Abstract The subject invention comprises a short range monopulse marine search radar for detecting small targets such as channel markers in the water. The radar has its antenna directed so that its monopulse null intersects the surface of the water at an initial minimum range proximate the radar over which sea clutter is below the boresight line. This initial range is investigated by very narrow transmitted rf pulses to determine the presence of targets therein. The antenna is subsequently controlled in elevation by a signal coupled through a balanced modulator to the antenna so that the intersection of the monopulse null and the water surface is positioned at successive increased ranges which are investigated by the very narrow transmitted pulses. At each successive range, the geometry provided by the position of the radar antenna and the position of the monopulse null-water surface interface is such that sea clutter is below the boresight line and each successive range segment is increased exponentially by a range gate. When the range gate and the elevation monopulse both interpret the same time as corresponding to the time interval between the firing of the transmitter and the time corresponding to the range to the surface of the water, aboveboresight targets in the range segment preceding this interface are interpreted as being other than sea clutter and are displayed on a display device.
Inventors
- 👤 H Strenglein
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 05:36
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/66; G01S13/70; G01S13/02; G01S13/06; G01S13/08; G01S13/10; G01S13/18; G01S13/42; G01S13/44; G01S13/4445
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
373 words
A monopulse short-range marine radar for detecting and determining the range to small targets projecting above a water surface comprising transmitter means for providing very narrow pulses of electromagnetic energy, antenna means having one or more pairs of horns, a monopulse null and a bore sight line, said antenna means being coupled to said transmitter means for radiating said very narrow pulses and receiving very narrow return pulses of electromagnetic energy, receiver means coupled to said antenna means for providing sum and difference output signals proportional to the sum and difference of the electromagnetic energy received at said horns, balanced modulator means coupled to said receiver means and responsive to said sum and difference output signals for producing a modified difference signal by coupling a limited amount of said sum output signal to said difference output signal, phase sensitive demodulator means responsive to said sum and modified difference output signals for providing elevation difference video output signals, threshold means coupled to said demodulator means for providing an output signal when said demodulator means produces a difference video signal having an amplitude less than a preset threshold value, trigger pulse means coupled to said transmitter means for producing timing pulses which control the occurrence of said very narrow transmitter pulses, gating pulse means coupled to said demodulator means and said trigger pulse means for providing pulses which produce control signals proportional to sampled values of said difference video output signals, servo control loop means coupled to said modulator means and said antenna means for directing said antenna toward said water surface whereby the position of the monopulse null-water surface interface is time coincident with said occurrence of said sampling pulses as indicated by said demodulator means producing a difference video signal having an amplitude less than said preset threshold value, display means, logic means coupled to said threshold means, said demodulator means, said gating means, and said display means for allowing difference video signals from said demodulator means which occur prior to said sampling pulses to be coupled to said display means thereby producing a visual indication of the presEnce and the range to small targets which project about said water surface and said bore sight line as provided by said difference video signals.
Claim 2
Dependent Claim
373 words
A monopulse short-range marine radar for detecting and determining the range to small targets projecting above a water surface comprising transmitter means for providing very narrow pulses of electromagnetic energy, antenna means having one or more pairs of horns, a monopulse null and a bore sight line, said antenna means being coupled to said transmitter means for radiating said very narrow pulses and receiving very narrow return pulses of electromagnetic energy, receiver means coupled to said antenna means for providing sum and difference output signals proportional to the sum and difference of the electromagnetic energy received at said horns, balanced modulator means coupled to said receiver means and responsive to said sum and difference output signals for producing a modified difference signal by coupling a limited amount of said sum output signal to said difference output signal, phase sensitive demodulator means responsive to said sum and modified difference output signals for providing elevation difference video output signals, threshold means coupled to said demodulator means for providing an output signal when said demodulator means produces a difference video signal having an amplitude less than a preset threshold value, trigger pulse means coupled to said transmitter means for producing timing pulses which control the occurrence of said very narrow transmitter pulses, gating pulse means coupled to said demodulator means and said trigger pulse means for providing pulses which produce control signals proportional to sampled values of said difference video output signals, servo control loop means coupled to said modulator means and said antenna means for directing said antenna toward said water surface whereby the position of the monopulse null-water surface interface is time coincident with said occurrence of said sampling pulses as indicated by said demodulator means producing a difference video signal having an amplitude less than said preset threshold value, display means, logic means coupled to said threshold means, said demodulator means, said gating means, and said display means for allowing difference video signals from said demodulator means which occur prior to said sampling pulses to be coupled to said display means thereby producing a visual indication of the presEnce and the range to small targets which project about said water surface and said bore sight line as provided by said difference video signals.
Claim 3
Dependent Claim
35 words
A monopulse short-range marine radar as described in claim 1 in which said transmitter means includes means for providing pulses of electromagnetic energy having a pulse width in the range of 10 to 20 nanoseconds.
Claim 4
Dependent Claim
74 words
A monopulse short-range marine radar as described in claim 1 in which said phase sensitive demodulator means includes means for providing a positive output signal when the received electromagnetic energy above the boresight line within a pulse width exceeds the electromagnetic energy below the boresight line and for providing a negative output signal when the received electromagnetic energy below the boresight line within a pulse width exceeds the electromagnetic energy above the boresight line.
Claim 5
Dependent Claim
22 words
A monopulse short-range marine radar as described in claim 1 in which said phase sensitive demodulator means includes a phase sensitive detector.
Claim 6
Dependent Claim
47 words
A monopulse short-range marine radar as described in claim 1 in which said gating pulse means includes means for providing a range gate pulse and adjacent sampling pulses which sample the difference video output signals received from the interface between said monopulse null and said water surface.
Claim 7
Dependent Claim
51 words
A monopulse short-range marine radar as described in claim 5 in which said gating pulse means includes pulse generator means for providing a range gate pulse which has its duration increased exponentially and produces first and second adjacent sampling pulses which occur immediately following the termination of said range gate pulse.
Claim 8
Dependent Claim
59 words
A monopulse short-range marine radar as described in claim 6 in which said trigger pulse means further includes a circuit comprising the serial combination of a differentiator, a delay circuit and a PRF pulser, said combination being responsive to said second of said adjacent sampling pulses and produces output PRF pulses which initiate each timing cycle of said radar.
Claim 9
Dependent Claim
40 words
A monopulse short-range marine radar as described in claim 5 in which said gating pulse means which includes an integrator, a counter, a digital to analog network, and a plurality of parallel connected voltage dividers, voltage comparators, and bistable multivibrators.
Claim 10
Dependent Claim
31 words
A monopulse short-range marine radar as described in claim 1 in which said servo control loop means includes means for converting electrical input signals into mechanical output displacements of said antenna.
Claim 11
Dependent Claim
21 words
A monopulse short-range marine radar as described in claim 1 in which said balanced modulator means includes an electronically variable attenuator.
Claim 12
Dependent Claim
22 words
A monopulse short-range marine radar as described in claim 1 in which said logic circuit means includes a three input AND gate.
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) | 1976-12-10 | 1977-06-11 | 1977-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-10 | 1981-06-11 | 1981-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-10 | 1985-06-11 | 1985-12-11 | $7700.00 | Window Closed / Lapsed |