US3757326A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Low angle tracking system
Assignee: United States Department of the Navy
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Filing: 1971-12-21
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Granted: 1973-09-04
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Expires: 1991-12-21
Abstract
Abstract A radar array is aimed to receive a signal directly reflected from a target as well as an image signal reflected from the target and from the adjoining ground surface or sea surface. An ambiguity introduced in the direct signal by the image signal, is resolved by a system which includes independent steering means and beam forming networks to form sum and difference signals from the image and the direct signals. These signals are mixed by computer controlled mixing networks to provide modified sum and difference signals. When the antenna pointing angle coincides with the target elevation angle, the modified direct sum and difference signals are uncontaminated by the image signals and vice versa. A composite error signal is obtained from the modified signals whose polarity is an indication of the error of the pointing angle. This signal is used to drive the steering mechanism into alignment with the direct path where a zero or null error signal is produced corresponding to the correct elevation angle of the target.
Inventors
- 👤 W White
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 18:19
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/66; G01S13/68; G01S13/685
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
130 words
A low angle radar tracking system for individual angular steering alignment of a radar antenna with the correct target angle comprising; a first means including an antenna means steerable at an assumed direct target angle for receiving the target signals reflected through the direct and image paths and producing signals responsive to said received reflections; a second means connected to said antenna means and having a first output signal responsive to said assumed direct path signal and second output responsive to the assumed image path signal; third means connected to said second means for receiving said signals responsive to said direct and image signals to produce a D.C. voltage whose polarity is indicative of the angular displacement between the steered angle of said antenna means and the correct target angle.
Claim 2
Dependent Claim
130 words
A low angle radar tracking system for individual angular steering alignment of a radar antenna with the correct target angle comprising; a first means including an antenna means steerable at an assumed direct target angle for receiving the target signals reflected through the direct and image paths and producing signals responsive to said received reflections; a second means connected to said antenna means and having a first output signal responsive to said assumed direct path signal and second output responsive to the assumed image path signal; third means connected to said second means for receiving said signals responsive to said direct and image signals to produce a D.C. voltage whose polarity is indicative of the angular displacement between the steered angle of said antenna means and the correct target angle.
Claim 3
Dependent Claim
29 words
The system of claim 1 wherein: said third means includes means to compare and null said D.C. voltages when said antenna means is steered at the correct target angle.
Claim 4
Dependent Claim
107 words
The system of claim 2 wherein: said output signal responsive to the direct path signal is a direct sum signal and a direct difference signal; said output signals responsive to the image signal path being an image sum signal and an image difference signal; and said third means includes means to combine said image sum and said direct sum signals to form a modified image sum signal; means to combine said direct difference signal and said modified image sum signal to form a modified direct difference signal; and means to combine said direct image sum and said direct sum signal to form a modified direct sum signal.
Claim 5
Dependent Claim
80 words
The system of claim 3 wherein: said third means includes a phase detector; said means for forming said modified direct difference signal being connected to a first input of said phase detector; said means for forming a modified direct sum signal being connected to a second input of said phase detector; said phase detector having a voltage output whose polarity is indicative of the angular displacement between The steered direction of said antenna means and the correct target path angle.
Claim 6
Dependent Claim
67 words
The system of claim 3 wherein: said third means includes means connected to receive said image difference signal and said modified direct sum signal for forming a modified image difference signal; said third means includes means for comparing said modified image signals and modified direct signals for indicating the angular difference between the said steered angle of a said antenna means and said correct target path angle.
Claim 7
Dependent Claim
71 words
The system of claim 5 wherein said means for comparing includes: a plurality of phase detectors having inputs connected to receive said modified image difference signal, said modified image sum signal, said modified direct sum signal, and said modified direct difference signal; said phase detectors having a voltage output whose polarity is indicative of the angular difference between the steered direction of said antenna means and the correct target path angle.
Claim 8
Dependent Claim
101 words
The system of claim 6 wherein: said means for forming said modified direct sum signal includes an attenuator connected to receive said direct image sum signal for attenuating said image sum signal to an amplitude equal to the direct sum signal amplitude received at the said assumed image angle by an antenna steered at an assumed direct target angle; means connected to receive said attenuated signal and said direct sum signal for subtracting said attenuated signal from said direct sum signal to form said modified direct sum signal; said modified direct sum signal having a null at said steered image angle.
Claim 9
Dependent Claim
89 words
The system of claim 7 wherein: said means for forming said modified image sum signal includes an attenuator connected to receive said direct sum signal for attenuating said direct sum signal to be equal in amplitude to the direct image sum signal amplitude received at the assumed direct angle by an antenna steered at the assumed image angle and means connected to receive said attenuated direct sum signal and said image sum signal for subtracting said attenuated signal from said image signal to form said modified image sum signal.
Claim 10
Dependent Claim
105 words
The system of claim 8 wherein: said means for forming said modified direct difference signal includes an attenuator connected to receive said modified image sum signal; said attenuator attenuating the amplitude of said modified image sum signal to be equal to the direct difference signal amplitude received at the assumed image angle by said antenna steered in an assumed direct signal path angle; means connected to receive said attenuated signal and said direct difference signal for subtracting said attenuated signal from said direct difference signal to form said modified direct difference signal; said modified direct difference signal possessing nulls at said direct and image angles.
Claim 11
Dependent Claim
96 words
The system of claim 9 wherein: said means for forming said modified image difference signal includes an attenuator connected to receive said modified direct sum signal; said attenuator attenuating said modified direct sum signal amplitude to be equal in amplitude to the direct image difference signal received at the assumed direct signal path angle by an antenna aligned in the assumed image signal path angle; and means connected to receive said attenuated signal and said direct image difference signal to subtract said attenuated signal from said image difference signal to form said modified image difference signal.
Claim 12
Dependent Claim
61 words
The system of claim 10 wherein: said plurality of phase detectors includes a first and second phase detector; the inputs of said first detector being connected to receive said modified image difference signal and said modified image sum signal; the inputs of said second phase detector being connected to receive said modified direct sum signal and said modified direct difference signal.
Claim 13
Dependent Claim
104 words
The system of claim 11 wherein: said antenna is a multi-array antenna; Said second means includes a plurality of phase shifters, each of said phase shifters being connected to a respective element of said array and to a first beam forming network for forming the image sum and image difference signals; a second plurality of phase shifters, each said phase shifter connected to a respective element in said array and to a second beam forming network for forming the direct sum and difference signals; said phase shifters steering said antenna above and below the horizon in said assumed direct and image signal paths respectively.
Claim 14
Dependent Claim
89 words
The system of claim 12 comprising: a steering computer connected to receive the error signal output of said comparing means; said steering computer output being connected to said phase shifters and said attenuators; said steering computer resteering said array toward said true target angle and at a new assumed target angle in response to said error signal; said computer being programmed with the response pattern of said array and changing the attenuation levels of said attenuators to correspond to the response pattern at the said new assumed target angle.
Claim 15
Dependent Claim
89 words
The system of claim 4 wherein: said means for forming said modified image sum signal includes an attenuator connected to receive said direct sum signal for attenuating said direct sum signal to be equal in amplitude to the direct image sum signal received at the assumed direct angle by an antenna steered at the assumed image angle and means connected to receive said attenuated direct sum signal and said image sum signal for subtracting said attenuated signal from said image sum signal to form said modified image sum signal.
Claim 16
Dependent Claim
95 words
The system of claim 14 wherein: said means for forming said modified direct sum signal including an attenuator connected to receive said direct image sum signal for attenuating said image sum signal to an amplitude equal to the direct sum signal amplitude received at the assumed image angle by an antenna steered at an assumed direct target angle and means connected to receive said attenuated direct image sum signal for subtracting said attenuated direct image sum signal from said direct sum signal; said modified direct sum signal having a null at said steered image angle.
Claim 17
Dependent Claim
103 words
The system of claim 15 wherein: said means for forming said modified direct difference signal includes an attenuator connected to receive said modified image sum signal; said attenuator attenuating the amplitude of said modified image sum signal to be equal to the direct difference signal received at the assumed image angle by said antenna steered in the direct signal path angle and means connected to receive said attenuated and said direct difference signals to subtract said attenuated signal from said direct difference signal to form said modified direct difference signal; said modified direct difference signal possessing nulls at said direct and image angles.
Claim 18
Dependent Claim
79 words
The system of claim 16 including: a feed structure and means for directing said signals received by said antenna to said feed structure; said direct signal being focused at a first point on the feed structure and said image signal being focused by said first means at a second point on said feed structure, said second point being separated from said first point by a space functionally related to the angle between the direct signal path and the horizon.
Claim 19
Dependent Claim
27 words
The system of claim 17 including: means connected to said feed structure for selectively coupling said direct and said image signal focal areas to said third means.
Claim 20
Dependent Claim
110 words
The system of claim 18 wherein: said means for selectively connecting said image signal focal point to said third means includes a Butler matrix having its input connected to said feed structure and its output connected to a plurality of phase shifters; said third means including an image beam forming network having its input connected to said phase shifters; said Butler matrix, sAid phase shifters, and said image beam forming network cooperating to selectively connect the instantaneous assumed focal area of said image signal on said feed structure to said image beam forming network, as the image focal point changes in response to a changing steering angle or target angle.
Claim 21
Dependent Claim
67 words
The system of claim 19 wherein: said feed structure is an array of feed horns; said direct signal focal area being stationary; said horns being arranged in a line, with each horn sharing a common wall with an adjacent horn; and said instantaneous image focal area selected being functionally related to the quantity of phase shift between each of said phase shifters connected to said Butler matrix.
Claim 22
Dependent Claim
97 words
The system of claim 20 wherein: said horn array includes first, second, third, and fourth horns; said fourth horn being coupled to said beam forming network when said phae shift difference is zero; said adjacent areas of said third horn and said fourth horn being selected when said phase shift difference is 45*; said third horn being selected when said phase shift difference is 90*; said adjacent areas of said third horn and said second horn being selected when said phase shift difference is 135*; said second horn being selected when said phase shift difference is 180*.
Claim 23
Dependent Claim
85 words
The system of claim 21 comprising: a steering computer connected to receive the error signal output of said comparing means; said steering computer being connected to said phase detectors and said attenuators; said steering computer resteering said array at a new assumed direct angle and toward said true target angle in response to said error signal; said computer being programmed with the response pattern of said array and changing the attenuating levels of said attenuators responsive to said new steered angle, to said error signal.
Claim 24
Independent Claim
127 words
A system for separating and selectively connecting at direct and image path radar signals reflected from a target and received by an antenna comprising: antenna means for receiving said direct and image signals; a feed structure; a first means connected to said antenna means for steering said antenna means in the direction of said direct signal path and for directing said received signals to said feed structure; said direct signal being focused by said first means at a first area on the feed structure and said image signal being focused by said first means at a second area on said feed structure; said second area being separated from said first area by a space functionally related to the angle between the direct signal path and the horizon.
Claim 25
Independent Claim
127 words
A system for separating and selectively connecting at direct and image path radar signals reflected from a target and received by an antenna comprising: antenna means for receiving said direct and image signals; a feed structure; a first means connected to said antenna means for steering said antenna means in the direction of said direct signal path and for directing said received signals to said feed structure; said direct signal being focused by said first means at a first area on the feed structure and said image signal being focused by said first means at a second area on said feed structure; said second area being separated from said first area by a space functionally related to the angle between the direct signal path and the horizon.
Claim 26
Dependent Claim
36 words
The system of claim 23 including: means connected to said feed structure for selectively extracting said direct and said image signals from their respective focal areas and separately producing each said signal at a respective output.
Claim 27
Dependent Claim
106 words
The system of claim 24 wherein: said means for selectively extracting said image signal focal area includes a Butler matrix having its input connected to said feed structure, a plurality of phase shifters having their inputs connected to said Butler matrix, and an image beam forming network having its inputs connected to said phase shifter outputs; said Butler matrix, said phase shifters, and said image beam forming network cooperating to selectively connect the instantaneous focal area of said image signal on said feed structure to said image beam forming network as the image focal point changes in response to a changing steering angle or target angle.
Claim 28
Dependent Claim
67 words
The system of claim 25 wherein: said feed structure is an array of feed horns; said direct signal focal area being a stationary area on said horn array; said horns being arranged in a line with each horn having a common wall with an adjacent horn; and said image focal area selected being functionally related to the quantity of phase shift between each of said phase shifteRs.
Claim 29
Dependent Claim
123 words
The system of claim 26 wherein: said horn array includes a first, second, third, and fourth horns; said fourth horn being coupled to said image beam forming network when said phase shift difference is zero; said adjacent areas of said third horn and said fourth horn being coupled to said image beam forming network when said phase shift difference is 45*; said third horn being coupled to said image beam forming network when said phase shift difference is 90*; said adjacent area between said third horn and said second horn being coupled to said image beam forming network when said phase shift difference is 135*; said second horn being coupled to said image beam forming network when said phase shift difference is 180*.
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) | 1976-09-03 | 1977-03-05 | 1977-09-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-03 | 1981-03-05 | 1981-09-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-03 | 1985-03-05 | 1985-09-04 | $7700.00 | Window Closed / Lapsed |