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EP0058032A2
Expired / Lapsed
EP
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Radar arrangements
Assignee: RACAL-MESL Ltd
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Filing: 1982-02-01
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Granted: —
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Expires: 2002-02-01
Abstract
Abstract A portable security unit operating by radar has an antenna (20) mounted at a predetermined distance above the ground which emits an FM CW signal having a carrier frequency in the range 1-2 GHz for example. Reflections from moving targets are sensed and processed with a signal at the transmitted frequency to obtain the second harmonic of the modulation frequency from which in turn the Doppler frequency component is extracted and its amplitude, which varies with range as a second order Bessel function, is measured. The second order Bessel component has a low amplitude for targets near to the unit, thereby minimising false alarms from birds and the like. The amplitude of this component is also attenuated beyond a predetermined distance from the unit and this, in conjunction with attenuation caused by interference between direct and reflected transmitted waves which is arranged to occur beyond the same distance, prevents unwanted echoes from targets outside the desired range of the unit.
Inventors
- 👤 Thomas George Thorne
- 👤 Louise Ireland Ruffe
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 15:02
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/50; G01S13/52; G01S13/56; G01S13/06; G01S13/08; G01S13/32; G01S13/36; G01S7/00; G01S7/003; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2491
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
82 words
A portable intruder detection unit (5) for detecting by radar, targets within a predetermined area extending at least partially around the unit, comprising a base (6) carrying transmitting and receiving antenna means (20), a power supply, means for energising the antenna means (20) for emitting a frequency-modulated carrier wave, and means (32 to 46) for sensing a Doppler-shifted component in a signal produced by a signal reflected from a moving target within the predetermined area and received by the antenna means (20).
Claim 2
Dependent Claim
82 words
A portable intruder detection unit (5) for detecting by radar, targets within a predetermined area extending at least partially around the unit, comprising a base (6) carrying transmitting and receiving antenna means (20), a power supply, means for energising the antenna means (20) for emitting a frequency-modulated carrier wave, and means (32 to 46) for sensing a Doppler-shifted component in a signal produced by a signal reflected from a moving target within the predetermined area and received by the antenna means (20).
Claim 3
Dependent Claim
15 words
A unit according to claim 1, characterised in that the power supply is battery operated.
Claim 4
Dependent Claim
28 words
A unit according to claim 1 or to claim 2, characterised by means responsive to the sensed Doppler-shifted component to transmit a warning signal to a distant location.
Claim 5
Dependent Claim
19 words
A unit according to claim 3, characterised by a-radio link for transmitting said warning signal to said distant location.
Claim 6
Dependent Claim
215 words
A portable radar arrangement comprising a base (6), transmitting antenna means (20) mounted on the base (6) so as to be at a predetermined height above the ground when the base (6) is standing on the ground, means (22) for energising the.antenna means (20) with a carrier frequency-modulated at a predetermined frequency, receiving antenna means (20) mounted on the base (6) so as to receive reflected signals from targets, signal processing means (32) responsive to the reflected signals to produce a processed signal dependent on reflected signals differing in frequency from the transmitted signals, the said processed signal including a series of harmonics of the modulating frequency each modulated by a Doppler-frequency component having an amplitude dependent on a Bessel function term of respective order, means (36) for selecting a predetermined one of the said harmonics, means (38) for extracting the Doppler-frequency component therefrom, and means (46) for sensing the amplitude of the extracted components; the selected harmonic being such that its amplitude is reduced by the respective Bessel function for targets adjacent the transmitting antenna means (20); and the said predetermined height of the transmitting antenna means (20) being such that direct and ground reflected waves originating from the transmitting antenna means (20) are subject to mutual interference at distances beyond said predetermined distance.
Claim 7
Dependent Claim
215 words
A portable radar arrangement comprising a base (6), transmitting antenna means (20) mounted on the base (6) so as to be at a predetermined height above the ground when the base (6) is standing on the ground, means (22) for energising the.antenna means (20) with a carrier frequency-modulated at a predetermined frequency, receiving antenna means (20) mounted on the base (6) so as to receive reflected signals from targets, signal processing means (32) responsive to the reflected signals to produce a processed signal dependent on reflected signals differing in frequency from the transmitted signals, the said processed signal including a series of harmonics of the modulating frequency each modulated by a Doppler-frequency component having an amplitude dependent on a Bessel function term of respective order, means (36) for selecting a predetermined one of the said harmonics, means (38) for extracting the Doppler-frequency component therefrom, and means (46) for sensing the amplitude of the extracted components; the selected harmonic being such that its amplitude is reduced by the respective Bessel function for targets adjacent the transmitting antenna means (20); and the said predetermined height of the transmitting antenna means (20) being such that direct and ground reflected waves originating from the transmitting antenna means (20) are subject to mutual interference at distances beyond said predetermined distance.
Claim 8
Dependent Claim
36 words
An arrangement according to claim 5, characterised in that the transmitting and receiving antenna means (20) are the same and the signal processing means is connected to respond to the reflected signals via a circulator (30).
References Cited (Backward Citations)
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