Doppler-shift radar transceiver for traffic monitoring system
First Claim
1. A traffic monitoring system for monitoring speeds of moving vehicles, said traffic monitoring system comprising:
- a Doppler radar transceiver; and
a digital computer connected to said Doppler radar transceiver for processing a Doppler signal from said Doppler radar transceiver to determine speeds of said vehicles monitored by said Doppler radar transceiver;
wherein said Doppler radar transceiver includes a pyramidal horn antenna having a rectangular aperture and a dielectric lens mounted at said rectangular aperture.
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Abstract
A Doppler radar transceiver in a traffic monitoring system includes a pyramidal horn antenna having a rectangular aperture and a dielectric lens mounted at the rectangular aperture. Preferably the pyramidal horn antenna is corrugated and the rectangular aperture has a breadth at least twice its width in order to provide a fan-shaped radar beam most effective for detecting moving vehicles in a stream of traffic. To reduce standing waves in the horn antenna that would otherwise cause nulls that would intermittently interfere with detection of a Doppler signal, the dielectric lens has impedance matching means for matching impedance of the dielectric lens to impedance of free space to reduce standing waves in said horn antenna. Suitable impedance matching means include a quarter-wave transformer or a tapered transformer structure at the interfaces between the dielectric body of the lens and the free-space region inside the horn and outside of the horn. In a preferred embodiment, the front surface of said dielectric lens is flat and the back surface of said dielectric lens is parabolic, and the impedance matching means defines a series of quarter-wavelength deep grooves on both the front and back surfaces of the lens, and the grooves are concentric in a circular pattern about an axis of the lens. This construction facilitates the fabrication of the grooves when the lens faces are formed by turning operations performed by a lathe.
39 Citations
20 Claims
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1. A traffic monitoring system for monitoring speeds of moving vehicles, said traffic monitoring system comprising:
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a Doppler radar transceiver; and
a digital computer connected to said Doppler radar transceiver for processing a Doppler signal from said Doppler radar transceiver to determine speeds of said vehicles monitored by said Doppler radar transceiver;
wherein said Doppler radar transceiver includes a pyramidal horn antenna having a rectangular aperture and a dielectric lens mounted at said rectangular aperture. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 14, 15, 16, 18, 19, 20)
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13. A traffic monitoring system for monitoring speeds of moving vehicles, said traffic monitoring system comprising:
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a Doppler radar transceiver; and
a digital computer connected to said Doppler radar transceiver for processing a Doppler signal from said Doppler radar transceiver to determine speeds of said vehicles monitored by said Doppler radar transceiver;
wherein said Doppler radar transceiver includes a horn antenna having an aperture and a dielectric lens mounted at said aperture, and said dielectric lens has impedance matching means for matching impedance of said dielectric lens to impedance of free space to reduce standing waves in said horn antenna.
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17. A traffic monitoring system for monitoring speeds of moving vehicles, said traffic monitoring system comprising:
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a Doppler radar transceiver; and
a digital computer connected to said Doppler radar transceiver for processing a Doppler signal from said Doppler radar transceiver to determine speeds of said vehicles monitored by said Doppler radar transceiver;
wherein said Doppler radar transceiver includes a corrugated pyramidal horn antenna having a rectangular aperture and a dielectric lens mounted in said rectangular aperture, said rectangular aperture has a width and a breadth, said breadth is at least twice said width, and said dielectric lens has a front surface and a back surface, and said front surface and said back surface have indentations for matching impedance of said dielectric lens to impedance of free space to reduce standing waves in said corrugated pyramidal horn antenna.
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Specification