US3896440A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Retrodirective passive beacon for simulating a moving target
Assignee: Westinghouse Electric Corp
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Filing: 1971-11-26
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Granted: 1975-07-22
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Expires: 1991-11-26
Abstract
Abstract There is disclosed a retrodirective passive beacon for use with MTI radar (moving-target-indicator radar) for mapping in heavy clutter or foliage and the like. The signal which this beacon reflects back to the radar simulates a signal from a target moving at a high speed and is readily distinguishable from the clutter or wind-blown foliage in which the beacon is placed. This beacon includes a generally spherical body of dielectric material permeable to the electromagnetic radiation transmitted by the radar. This body may be a helisphere or a Luneburg lens or a reflecting hemisphere for vertical radiation. Where the body is a helisphere electrical conductors are spaced along the surface of the body at distances less than one-half wavelength of the radiation, each at an angle of about 45* to the diametral plane of the body along the transmitted beam from the radar or to the so-called plane of omnidirectional coverage of the body. In the case of a Luneburg lens or a reflecting hemisphere the conductors may be in the plane of polarization of the radiation of the radar. Diodes are connected in the conductors at spacings along the conductors of less than one-half wavelength of the radiation. The diodes are rendered alternately conducting and non-conducting at about the range-gating repetition frequency of the radar. When the diodes are conducting, the conductors reflect the incident radiation and when the diodes are non-conducting the incident radiation is transmitted thru the body. The retrodirective reflector apparatus also includes a reflector spaced from the conductors about one-quarter wavelength of the radiation which reflects the radiation transmitted by the body. This latter reflected radiation is displaced in phase by about one-half wavelength of the radiation transmitted by the radar with respect to the radiation directly reflected by the conductors. The pairs of reflected signals thus reflected to the radar give the effect of a target moving at a very high speed. The beacon also includes a helisphere reflector or a Luneburg shpere for focussing the radiation from the radar on the conductors of the above-described reflector.
Inventors
- 👤 Myron S Wheeler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 06:14
CPC Classifications
H; H01; H01Q; H01Q15/00; H01Q15/23; G; G01; G01S; G01S7/00; G01S7/02; G01S7/40; G01S7/4052; G01S7/4082; G01S7/4095; H01Q15/14; H01Q15/22; H01Q3/00; H01Q3/44; H01Q3/46
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
116 words
A reflector for electromagnetic radiation including an array of conductors of said radiation spaced along a surface by a distance less than one-half wavelength of said radiation, diodes interposed in said conductors at intervals less than one-half wavelength of said radiation, means connected to said diodes for rendering said diodes alternately conducting and non-conducting, said conductors directly reflecting said radiation when said diodes are conducting and transmitting said radiation when said diodes are non-conducting, and means for reflecting the transmitted radiation, said directly reflected radiation and said reflected transmitted radiation being projected in a common beam in which said reflected transmitted radiation and said directly reflected radiation are displaced in phase with reference to each other.
Claim 2
Dependent Claim
116 words
A reflector for electromagnetic radiation including an array of conductors of said radiation spaced along a surface by a distance less than one-half wavelength of said radiation, diodes interposed in said conductors at intervals less than one-half wavelength of said radiation, means connected to said diodes for rendering said diodes alternately conducting and non-conducting, said conductors directly reflecting said radiation when said diodes are conducting and transmitting said radiation when said diodes are non-conducting, and means for reflecting the transmitted radiation, said directly reflected radiation and said reflected transmitted radiation being projected in a common beam in which said reflected transmitted radiation and said directly reflected radiation are displaced in phase with reference to each other.
Claim 3
Dependent Claim
36 words
The reflector of claim 1 wherein the means for reflecting is displaced from the conductors a distance of about one-fourth wavelength of the radiation so that the phase displacement is about one-half wavelength of said radiation.
Claim 4
Dependent Claim
115 words
The apparatus of claim 1 including a dielectric body in the form of a shell of a dielectric material permeable to said radiation of generally spherical contour and having an axis generally perpendicular to the direction of the radiation said axis being perpendicular to a diametral plane through said shell, an electrical conductor wound spirally about said shell with a first portion of each turn along the outer surface of said shell at an angle of about 45* to said plane and a second return portion of each turn along the inner surface of said shell, the diodes being interposed in the first portion of each turn and being connected in series in the conductor.
Claim 5
Dependent Claim
19 words
The apparatus of claim 3 including means connected to the conductor for rendering the diodes alternately conducting and non-conducting.
Claim 6
Dependent Claim
59 words
The apparatus of claim 4 wherein the means connected to the conductor for rendering the diodes alternately conducting and non-conducting is a substantially square-wave generator for impressing a periodic square-wave potential on the conductor, the diodes being conducting during a portion of the period of said potential and being non-conducting during another portion of the period of said potential.
Claim 7
Dependent Claim
42 words
The apparatus of claim 5 wherein the radiation is in the form of periodic pulses of short duration compared to the period between pulses, the periodicity of said pulses being different by a small magnitude from the period of the periodic potential.
Claim 8
Dependent Claim
227 words
Signalling apparatus including an MTI radar for transmitting electromagnetic radiation and receiving and processing the resulting electromagnetic radiation reflected by targets, a helisphere reflector including a generalLy spherical body of dielectric material disposed with its diametral plane generally parallel to the transmitted radiation, electrical conductors along the outer surface of said body generally at about 45* to said diametral plane and spaced less than one-half wavelength of said radiation, a second generally spherical body of dielectric material within said helisphere reflects with its diametral plane generally parallel to the diametral plane of the helisphere reflector and having a diameter such that radiation converged inwardly by said helisphere reflector is focussed on the surface of said second body electrical conductors on the surface said second body generally parallel to the conductors on said helisphere reflectors and spaced less than a half wavelength of said radiation, means connected to the conductors on said second body for rendering said last-named conductors directly reflective of said radiation during first intervals and non-reflective of said radiation during intervening intervals, said body transmitting said radiation during said intervening intervals, and means within said body for reflecting the radiation transmitted during said intervening intervals in a common beam with said radiation reflected during said first intervals, whereby said radar receives and processes a signal having the appearance of being reflected from a moving target.
Claim 9
Dependent Claim
227 words
Signalling apparatus including an MTI radar for transmitting electromagnetic radiation and receiving and processing the resulting electromagnetic radiation reflected by targets, a helisphere reflector including a generalLy spherical body of dielectric material disposed with its diametral plane generally parallel to the transmitted radiation, electrical conductors along the outer surface of said body generally at about 45* to said diametral plane and spaced less than one-half wavelength of said radiation, a second generally spherical body of dielectric material within said helisphere reflects with its diametral plane generally parallel to the diametral plane of the helisphere reflector and having a diameter such that radiation converged inwardly by said helisphere reflector is focussed on the surface of said second body electrical conductors on the surface said second body generally parallel to the conductors on said helisphere reflectors and spaced less than a half wavelength of said radiation, means connected to the conductors on said second body for rendering said last-named conductors directly reflective of said radiation during first intervals and non-reflective of said radiation during intervening intervals, said body transmitting said radiation during said intervening intervals, and means within said body for reflecting the radiation transmitted during said intervening intervals in a common beam with said radiation reflected during said first intervals, whereby said radar receives and processes a signal having the appearance of being reflected from a moving target.
Claim 10
Dependent Claim
168 words
Signalling apparatus including an MTI radar having means for transmitting a beam of electromagnetic radiation and means for receiving and processing the resulting radiation reflected from a target, a reflector for the transmitted radiation including a body of dielectric material, permeable to said radiation, having generally spherical form and having a diametral plane, said body being disposed with said plane generally parallel to said beam, electrical conductors on said body spaced less than one-half wavelength along said body, means for rendering said conductors electrically conducting during predetermined first intervals and electrically non-conducting during intervening second intervals, means focussing said transmitted radiation on certain of said conductors, said focussed radiation being reflected from said certain conductors, during said first intervals and being transmitted through said body during said second intervals, and means spaced from said conductors for reflecting the radiation transmitted through said body in a common reflected beam with the radiation reflected by said certain conductors, said common beam being directed to the receiving means of said radar.
Claim 11
Dependent Claim
168 words
Signalling apparatus including an MTI radar having means for transmitting a beam of electromagnetic radiation and means for receiving and processing the resulting radiation reflected from a target, a reflector for the transmitted radiation including a body of dielectric material, permeable to said radiation, having generally spherical form and having a diametral plane, said body being disposed with said plane generally parallel to said beam, electrical conductors on said body spaced less than one-half wavelength along said body, means for rendering said conductors electrically conducting during predetermined first intervals and electrically non-conducting during intervening second intervals, means focussing said transmitted radiation on certain of said conductors, said focussed radiation being reflected from said certain conductors, during said first intervals and being transmitted through said body during said second intervals, and means spaced from said conductors for reflecting the radiation transmitted through said body in a common reflected beam with the radiation reflected by said certain conductors, said common beam being directed to the receiving means of said radar.
Claim 12
Dependent Claim
21 words
The apparatus of claim 8 wherein the focussing means is a helisphere reflector in whose focal surface the conductors are disposed.
Claim 13
Dependent Claim
20 words
The apparatus of claim 8 wherein the focussing means is a Luneburg sphere adjacent whose surface the conductors are disposed.
Claim 14
Dependent Claim
21 words
The apparatus of claim 8 wherein the spaced reflecting means is spaced about one-fourth wavelength of the radiation from the conductors.
Claim 15
Dependent Claim
48 words
The apparatus of claim 8 wherein the means for rendering the conductors electrically conducting and non-conducting includes diodes interposed along said conductors at distances less than one-half wavelength of the radiation and said means also includes switching means for alternating switching said diodes between conducting and non-conducting conditions.
Claim 16
Dependent Claim
69 words
The apparatus of claim 8 wherein each conductor is an array of waveguides, the cross-sectional length of each waveguide being equal to about one-half the wavelength of the radiation and the depth of each waveguide being equal to about one-fourth the wavelength of the radiation, each waveguide being shunted at its outer rim by a diode which is switched on and off respectively during the first and second intervals.
Claim 17
Dependent Claim
216 words
Signalling apparatus for communicating with an overhead MTI radar having means for transmitting a beam of electromagnetic radiation and receiving means for receiving and processing the resulting radiation reflected from a target, the said apparaTus including a bowl-shaped body of dielectric material having a focal surface therein disposed to receive the said transmitted radiation, said body as so disposed extending about a vertical plane, first electrical conductors spaced along said body at an angle of about 45* to said plane, the spacing between said conductors being less than one-half wavelength of said radiation, a second body of dielectric material having a surface generally the same as said focal surface of said first body, said second body being disposed with its said surface generally coincident with the said focal surface of said first body, second electrical conductors spaced along said surface of said second body generally parallel to the said first electrical conductors spaced along said first body, the spacing between said second conductors being less than one-half wavelength of said radiation, means for rendering said second conductors alternately reflective and not reflective to said radiation, whereby said radiation is alternately reflected from and transmitted by said second body, and radiation reflecting means spaced from said second conductors for reflecting the radiation transmitted by said second body.
Claim 18
Dependent Claim
216 words
Signalling apparatus for communicating with an overhead MTI radar having means for transmitting a beam of electromagnetic radiation and receiving means for receiving and processing the resulting radiation reflected from a target, the said apparaTus including a bowl-shaped body of dielectric material having a focal surface therein disposed to receive the said transmitted radiation, said body as so disposed extending about a vertical plane, first electrical conductors spaced along said body at an angle of about 45* to said plane, the spacing between said conductors being less than one-half wavelength of said radiation, a second body of dielectric material having a surface generally the same as said focal surface of said first body, said second body being disposed with its said surface generally coincident with the said focal surface of said first body, second electrical conductors spaced along said surface of said second body generally parallel to the said first electrical conductors spaced along said first body, the spacing between said second conductors being less than one-half wavelength of said radiation, means for rendering said second conductors alternately reflective and not reflective to said radiation, whereby said radiation is alternately reflected from and transmitted by said second body, and radiation reflecting means spaced from said second conductors for reflecting the radiation transmitted by said second body.
Claim 19
Dependent Claim
50 words
The apparatus of claim 13 wherein the first and second bodies are in the form of generally hemispherical shells, the second conductors being spaced along a region of said second body of about half the diameter of the region of said first body along which the first conductors are spaced.
Claim 20
Dependent Claim
30 words
The apparatus of claim 13 wherein the radiation reflecting means is spaced about one-quarter wavelength of the radiation from the second conductors on the direction away from the first body.
Claim 21
Dependent Claim
126 words
A beacon for use with an MTI radar having means for transmitting electromagnetic radiation and receiving means for receiving and processing resulting radiation reflected from targets, said beacon including a generally spherical body of dielectric material having a plurality of conductors thereon, said conductors being spaced by less than a half wavelength of said radiation and being at an angle of 45* to the plane of omnidirectional coverage of said body, diodes interposed in said conductors at distances less than one-half wavelength of said radiation, means for focussing radiation on certain of said conductors, means connected to said conductors for rendering said diodes alternately conducting and non-conducting, and means for reflecting the focussed radiation transmitted through said body during the intervals when said diodes are non-conducting.
Claim 22
Dependent Claim
126 words
A beacon for use with an MTI radar having means for transmitting electromagnetic radiation and receiving means for receiving and processing resulting radiation reflected from targets, said beacon including a generally spherical body of dielectric material having a plurality of conductors thereon, said conductors being spaced by less than a half wavelength of said radiation and being at an angle of 45* to the plane of omnidirectional coverage of said body, diodes interposed in said conductors at distances less than one-half wavelength of said radiation, means for focussing radiation on certain of said conductors, means connected to said conductors for rendering said diodes alternately conducting and non-conducting, and means for reflecting the focussed radiation transmitted through said body during the intervals when said diodes are non-conducting.
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) | 1978-07-21 | 1979-01-20 | 1979-07-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-07-21 | 1983-01-20 | 1983-07-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-07-21 | 1987-01-20 | 1987-07-22 | $7700.00 | Window Closed / Lapsed |