Doppler radar velocity measurement horn
First Claim
1. Apparatus for use in a doppler radar velocity measurement system, comprisingmeans including a rectangular waveguide for generating an RF wave in said rectangular waveguide, said RF wave having a frequency in the range of 24 GHz,waveguide transformer means for providing a smooth RF transition between said rectangular waveguide and a circular waveguide,a circular pyramidal horn antenna having a flared section with a mouth and a throat, said horn also including a circular waveguide section formed at the throat of said flared section, said circular waveguide being coupled to said waveguide transformer for receiving said RF wave from said waveguide transformer and being dimensioned so that said RF wave can propogate in only the TE11 mode, mode generator means disposed at the junction of said circular waveguide and the throat of said flared section for generating a TM11 mode RF wave, said flared section guiding both RF wave modes from said mode generator means into free space, wherein said flared section has an interior mouth diameter of about 4.4 inches and a flare angle of about 39°
- so that the length of said flared section is only about 5.3 inches, anda dielectric lens positioned across the mouth of said flared section, said RF lens being spaced axially from the mouth of said horn so as to reduce the standing wave ratio in said horn, and having a focal length corresponding approximately to its axial spacing from the phase center of said horn antenna.
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Accused Products
Abstract
Doppler radar apparatus for use in a velocity measuring system for farm tractors and the like. The apparatus includes a dual mode conical horn having a flare angle substantially in excess of 12.5°, and a dielectric lens formed of a glass filled polymer. The doppler output signal provided by the RF transceiver associated with the dual mode horn is high pass filtered to remove low frequency signals therefrom. The horn is mounted in such a way that it is isolated from mechanical vibrations which would induce doppler signal frequencies in excess of the cutoff frequency of the high pass filter. Moreover, the horn assembly (which is aluminum) and a steel housing assembly are coupled together in such a way that thermal expansion and contraction will not loosen the friction fit between the two assemblies. The two assemblies are held together by a single, large diameter annular locking ring.
264 Citations
29 Claims
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1. Apparatus for use in a doppler radar velocity measurement system, comprising
means including a rectangular waveguide for generating an RF wave in said rectangular waveguide, said RF wave having a frequency in the range of 24 GHz, waveguide transformer means for providing a smooth RF transition between said rectangular waveguide and a circular waveguide, a circular pyramidal horn antenna having a flared section with a mouth and a throat, said horn also including a circular waveguide section formed at the throat of said flared section, said circular waveguide being coupled to said waveguide transformer for receiving said RF wave from said waveguide transformer and being dimensioned so that said RF wave can propogate in only the TE11 mode, mode generator means disposed at the junction of said circular waveguide and the throat of said flared section for generating a TM11 mode RF wave, said flared section guiding both RF wave modes from said mode generator means into free space, wherein said flared section has an interior mouth diameter of about 4.4 inches and a flare angle of about 39° - so that the length of said flared section is only about 5.3 inches, and
a dielectric lens positioned across the mouth of said flared section, said RF lens being spaced axially from the mouth of said horn so as to reduce the standing wave ratio in said horn, and having a focal length corresponding approximately to its axial spacing from the phase center of said horn antenna.
- so that the length of said flared section is only about 5.3 inches, and
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2. Apparatus for use in a doppler radar velocity measurement system, comprising
a microwave horn assembly for receiving and transmitting an RF electromagnetic wave, said assembly providing an electrical doppler signal having a frequency equal to the difference between the frequencies of said transmitted and received waves, electronic filter means responsive to said doppler signal provided by said microwave horn assembly for high pass filtering said signal to provide an output signal that includes only frequencies above a predetermined cutoff frequency, and means for resiliently mounting said microwave horn assembly on a vehicle, said resilient mounting means having spring rate and damping characteristics such that said microwave horn assembly is isolated from low level vibrations having frequencies which would produce doppler signals with frequencies greater than the cutoff frequency of the high pass filter means, whereby erroneous doppler signals produced by horn vibrations are effectively eliminated.
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11. Apparatus for use in a doppler velocity measurement system, comprising
a microwave horn assembly for transmitting and receiving an RF electromagnetic wave and providing a doppler signal having a frequency related to the velocity of the vehicle to which the system is attached, and a housing assembly for housing said horn assembly, said housing assembly being formed of a structural material having a coefficient of thermal expansion which is different than the coefficient of thermal expansion of the material of which said horn assembly is formed, said housing assembly having interior surfaces which abut matching exterior surfaces of said microwave horn assembly, wherein the planes of said surfaces are all selected to be parallel to the direction of movement of the material underlying said surfaces due to thermal expansion or contraction, whereby unequal thermal expansion or contraction of said materials of which said assemblies are formed causes said abutting surfaces to move parallel to one another rather than normal to one another.
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17. Apparatus for use in a doppler radar velocity measurement system, comprising:
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means for generating a dual mode RF electromagnetic wave and for guiding said wave to a horn; a conical horn having a small diameter end and a large diameter end and being coupled adjacent its smaller diameter end to said generating means for transmitting said dual mode RF wave into free space, said horn having a flare angle substnatially in excess of 12.5°
;lens means covering the large diameter end of said horn, said lens means having a focal length substantially equal to the distance from the phase center of said horn to said lens; said generating means including microwave transceiver means for generating said RF wave and for receiving said RF wave back again after reflection from an obstacle, said transceiver means providing a doppler signal having a frequency equal to the frequncey difference between said generated and received RF waves; high pass filter means for filtering said doppler signal to eliminate all frequencies in said doppler signal below a selected cutoff frequency; and resilient means for mounting said generating means, horn and lens means on a vehicle, said resilient means having characteristics selected such that said generating means is isolated from low level vibrations having frequencies which would produce doppler signal frequencies in excess of the cutoff frequency of said high pass filter means. - View Dependent Claims (18, 19, 20, 21)
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22. Apparatus for use in a doppler radar velocity measurement system, comprising:
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means for generating a dual mode RF electromagnetic wave and for guiding said wave to a horn; a conical horn having a small diameter end and a large diameter end and being coupled adjacent its smaller diameter end to said generating means for transmitting said dual mode RF wave into free space, said horn having a flare angle substantially in excess of 12.5°
, said horn and generating means are part of a microwave horn assembly;lens means covering the large diameter end of said horn, said lens means having a focal length substantially equal to the distance from the phase center of said horn to said lens; and a housing for said horn assembly, said housing being fabricated of a material having a coefficient of thermal expansion different from the coefficient of thermal expansion of a material of which said horn assembly is formed, said housing having interior surfaces which abut corresponding exterior surfaces of said horn assembly, said abutting interior and exterior surfaces being aligned at angles to a central longitudinal axis of the horn assembly selected so that expansion and contraction of the materials caused by temperature variation will produce movement of said abutting surfaces parallel to one another rather than normal to one another. - View Dependent Claims (23, 24, 25, 26)
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27. Apparatus for use in a doppler radar velocity measurement system, comprising:
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means for generating an RF electromagnetic wave having a frequency of at least 24 GHz and for guiding said wave to a horn; a horn coupled to said generating means for transmitting said RF wave into free space; a dielectric lens covering the mouth of said horn, said lens being formed of a glass filled polymer material; and said means for generating an RF electromagnetic wave comprises means for generating a wave in the dominant TE11 mode and wherein said horn includes means responsive to said TE11 mode RF wave for producing a TM11 mode RF wave therefrom, whereby the generated RF wave propagates through said horn in both the dominant TE11 and the higher order TM11 modes.
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28. Apparatus for use in a doppler radar velocity measurement system, comprising:
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means for generating an RF electromagnetic wave and for guiding said wave to a horn; a horn coupled to said generating means for transmitting said RF wave into free space; a dielectric lens covering the mouth of said horn, said lens being formed of a glass filled polymer material; said generating means comprises microwave transceiver means for generating said RF wave and for receiving said RF wave back again after reflection from an obstacle, said transceiver means providing a doppler signal having a frequency equal to the frequency difference between said generated and received RF waves; high pass filter means for filtering said doppler signal to eliminate all frequencies therein below a selected cutoff frequency; and resilient means for mounting said generating means, horn and lens means on a vehicle, said resilient means having characteristics selected such that said generating means is isolated from low level vibrations having frequencies which would produce doppler signal frequencies in excess of the cutoff frequency of said high pass filter means.
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29. Apparatus for use in a doppler radar velocity meansurement system, comprising:
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means for generating an RF electromagnetic wave and for guiding said wave to a horn; a horn coupled to said generating means for transmitting said RF wave into free space, said horn and said generating means are part of a microwave horn assembly; a dielectric lens covering the mouth of said horn, said lens being formed of a glass filled polymer material; and a housing for said microwave horn assembly, said housing being fabricated of a material having a coefficient of thermal expansion different from the coefficient of thermal expansion of a material of which said microwave horn assembly is formed, said housing having interior surfaces which abut matching exterior surfaces of said horn assembly, said abutting interior and exterior surfaces being aligned at an angle to a central longitudinal axis of the horn assembly selected so that expansion and contraction of the materials which is caused by temperature variations will produce movement of said abutting surfaces parallel to one another rather than normal to one another.
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Specification