US5334981A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Airborne metal detecting radar
Assignee: Raytheon Co
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Filing: 1992-04-09
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Granted: 1994-08-02
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Expires: 2012-04-09
Abstract
Abstract Method and arrangement for an airborne radar system particularly adapted to detect large metal targets that are concealed from the air by camouflage or natural foliage. The arrangement includes an antenna that transmits a continuous wave electromagnetic signal having a selectable frequency that preferably has a wave length generally twice the length of an anticipated target and which is carried by a flying vehicle. The frequency of the transmitted signal is chosen to provide maximum penetration of the camouflage or natural foliage and maximum re-radiation from a metal target. Receivers connected to an in-line receiving antenna and to a crossed receiving antenna carried by a flying vehicle detect the radiation that is reflected from the terrain and a target with the same polarization as that transmitted. The co-linear antenna and receiver respond to the reflected radiation while the cross-polarized antenna does not detect this reflected radiation. However, a metal object on the ground re-radiates cross polarized electromagnetic waves in proportion to their angular orientation and lateral distance to the transmitting antenna so that a metal target is detected by observing the output differences for the two receivers.
Inventors
- 👤 Carter C. Smith
- 👤 John B. Gehman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 12:48
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/0209; G01S13/04; G01S7/00; G01S7/02; G01S7/024; G01S7/025; G01S7/41; G01S7/411
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
112 words
A radar system for detecting a metal target which may be camouflaged or concealed by natural foliage from an airborne flying vehicle and comprising: an antenna carried by a flying vehicle for transmitting an electromagnetic signal, first receiving antenna means carried by the flying vehicle for receiving the transmitted electromagnetic signal selected from the terrain and the target, second receiving antenna means carried by the flying vehicle and arranged orthogonally to the first antenna means for receiving the transmitted electromagnetic signal reflected from the target, and means coupled to the first and second receiving antenna means for processing the received signals to provide information as to the presence of a metal target.
Claim 2
Dependent Claim
112 words
A radar system for detecting a metal target which may be camouflaged or concealed by natural foliage from an airborne flying vehicle and comprising: an antenna carried by a flying vehicle for transmitting an electromagnetic signal, first receiving antenna means carried by the flying vehicle for receiving the transmitted electromagnetic signal selected from the terrain and the target, second receiving antenna means carried by the flying vehicle and arranged orthogonally to the first antenna means for receiving the transmitted electromagnetic signal reflected from the target, and means coupled to the first and second receiving antenna means for processing the received signals to provide information as to the presence of a metal target.
Claim 3
Dependent Claim
24 words
The radar system of claim 1 wherein the transmitting antenna is a trailing wire antenna which extends rearwardly from the flying vehicle during flight.
Claim 4
Dependent Claim
20 words
The radar system of claim 1 which further includes a continuous wave radio frequency oscillator coupled to the transmitting antenna.
Claim 5
Dependent Claim
36 words
The radar system of claim 3 wherein the oscillator comprises means for generating a signal having a frequency that penetrates foliage of the terrain and which interacts with a metal target to provide a reflected signal.
Claim 6
Dependent Claim
22 words
The radar system of claim 4 wherein the oscillator comprises means for generating a signal having a frequency range of 2-30 MHZ.
Claim 7
Dependent Claim
23 words
The radar system of claim 4 wherein the oscillator comprises means for generating a signal having a frequency range of approximately 7-8 MHZ.
Claim 8
Dependent Claim
27 words
The radar system of claim 1 wherein the first antenna means is carried by the flying vehicle in an orientation that is in-line with the transmitting antenna.
Claim 9
Dependent Claim
16 words
The radar system of claim 1 wherein the transmitting antenna is isolated from the flying vehicle.
Claim 10
Dependent Claim
16 words
The radar system of claim 1 wherein the first and second antenna means are dipole antennas.
Claim 11
Dependent Claim
49 words
The radar system of claim 1 wherein the antenna to transmit the electromagnetic signal is carried by a first flying vehicle and the first and second receiving antenna means and the signal processing means coupled to said first and second receiving means are carried by a second flying vehicle.
Claim 12
Independent Claim
104 words
A method to detect a metal target that is camouflaged or concealed by natural foliage which comprises the steps of: illuminating a metal target and surrounding terrain with an electromagnetic signal having a frequency in the band of 2 to 30 MHz and transmitted by an antenna carried by a flying vehicle, receiving the transmitted signal re-radiated from the metal target with an antenna also carried by the flying vehicle and oriented orthogonally to the in-line antenna, and processing the re-radiated signals received from the metal target and the terrain by the antennas to develop data indicative of the presence of a metal target.
Claim 13
Independent Claim
104 words
A method to detect a metal target that is camouflaged or concealed by natural foliage which comprises the steps of: illuminating a metal target and surrounding terrain with an electromagnetic signal having a frequency in the band of 2 to 30 MHz and transmitted by an antenna carried by a flying vehicle, receiving the transmitted signal re-radiated from the metal target with an antenna also carried by the flying vehicle and oriented orthogonally to the in-line antenna, and processing the re-radiated signals received from the metal target and the terrain by the antennas to develop data indicative of the presence of a metal target.
Claim 14
Dependent Claim
29 words
The method of claim 11 wherein step of illuminating includes the step of radiating an electromagnetic wave having a wave length of twice the length of the metal target.
Claim 15
Dependent Claim
37 words
The method of claim 11 wherein the processing step includes the step of detecting the signals re-radiated from the target from the clutter re-radiated from the target from the clutter re-radiated by the terrain surrounding the target.
Claim 16
Dependent Claim
33 words
The method of claim 13 wherein the processing step also includes detecting a metal target by observing the output difference from the detected signals re-radiated from the target and separated from the clutter.
Claim 17
Dependent Claim
40 words
The method of claim 11 wherein the step of illuminating includes the step of radiating an electromagnetic signal having a frequency that is operated over a predetermined range selected to maximize re-radiation from targets having a plurality of predetermined sizes.
Claim 18
Dependent Claim
31 words
The method of claim 11 wherein the step of illuminating includes the step of radiating an electromagnetic signal operable at predetermined frequencies within the predetermined range for selectable periods of time.
Claim 19
Dependent Claim
44 words
The method of claim 11 wherein the electromagnetic signal is transmitted from a first flying vehicle and the receiving step and the processing step are performed on a second flying vehicle that is flying in a predetermined orientation relative to the first flying vehicle.
Claim 20
Dependent Claim
26 words
The method of claim 11 wherein the frequency of the transmitted electromagnetic signal is chosen to maximize foliage penetration and the detection of large metal objects.
Claim 21
Independent Claim
105 words
A method to detect a metal target that is camouflaged or concealed by natural foliage which comprises the steps of: illuminating a metal target and surrounding terrain with an electromagnetic signal transmitted by a transmitting antenna carried by a flying vehicle, receiving the transmitted signal re-radiated from the metal target with a first antenna carried by the flying vehicle, and a second antenna carried by the flying vehicle and oriented orthogonally to the first antenna, and processing the re-radiated signals received from the metal target and the terrain by the first and second antennas to develop data indicative of the presence of a metal target.
Claim 22
Independent Claim
105 words
A method to detect a metal target that is camouflaged or concealed by natural foliage which comprises the steps of: illuminating a metal target and surrounding terrain with an electromagnetic signal transmitted by a transmitting antenna carried by a flying vehicle, receiving the transmitted signal re-radiated from the metal target with a first antenna carried by the flying vehicle, and a second antenna carried by the flying vehicle and oriented orthogonally to the first antenna, and processing the re-radiated signals received from the metal target and the terrain by the first and second antennas to develop data indicative of the presence of a metal target.
Claim 23
Dependent Claim
27 words
The method of claim 19, wherein the step of illuminating includes the step of radiating an electromagnetic signal having a frequency in the band of 2-30 MHz.
Claim 24
Dependent Claim
28 words
The method of claim 19, wherein the step of illuminating includes the step of radiating an electromagnetic signal having a wavelength twice that of an anticipated metal target.
Claim 25
Dependent Claim
29 words
The method of claim 19, wherein the step of illuminating includes the step of radiating an electromagnetic signal whose wavelength is intentionally varied with time over a predetermined range.
References Cited (Backward Citations)
US3614778A
Cited
US3500395A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-08-01 | 1998-01-31 | 1998-08-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-08-01 | 2002-01-31 | 2002-08-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-08-01 | 2006-01-31 | 2006-08-02 | $7700.00 | Window Closed / Lapsed |