Doppler radar velocity measurement apparatus

• US 4,788,553 A
• Filed: 11/12/1986
• Issued: 11/29/1988
• Est. Priority Date: 04/06/1983
• Status: Expired due to Fees

• Current Assignee: TRW Inc. (Northrop Grumman Corporation)
• Original Assignee: TRW Inc. (Northrop Grumman Corporation)
• Inventors: Phillips, Oliver A.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): LE, HOANGANH T
• Application Number:
  US06/929,748
• Time in Patent Office: 748 Days
• Field of Search: 343/786, 343/753, 343/754, 343/912, 343/713
• US Class Current: 343/786
• CPC Class Codes: G01S 13/60 wherein the transmitter and receiver are mounted on the moving object, e.g. for determining ground speed, drift angle, ground track G01S13/64 takes precedence
• CPC Class Codes: H01Q 19/08 for modifying the radiation pattern of a radiating horn in which it is located corrugated horns H01Q13/0208; producing a circular polarisation H01Q13/0241

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.

Claims

1. Apparatus for use in a doppler radar velocity measurement system, comprising

means for generating an RF electromagnetic wave in the dominant TE₁₁ mode 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, said horn including means responsive to said RE₁₁ mode RF wave for producing a higher order TM₁₁ mode RF wave therefrom, both said TE₁₁ mode RF wave and said TM₁₁ mode RF wave propagating through said horn, the resultant RF wave being transmitted into free space, said horn having a flare angle substantially in excess of 12.5°

, and

lens means covering the large diameter end of said horn for focusing said RF wave passing therethrough, said lens means having a focal length substantially equal to the distance from the phase center of said horn to said lens means.

2. Apparatus as set forth in claim 1, wherein said flare angle is in excess of 25°

.

3. Apparatus as set forth in claim 1, wherein said lens means is formed of a glass filled polymer.

4. Apparatus as set forth in claim 1, wherein said lens means is formed of 40% glass filled polyester.

5. Apparatus as set forth in claim 1, wherein said TE₁₁ mode RF wave has a frequency in the range of 24 GHz, and wherein said horn has length of about 5.3 inches and an interior diameter at its large diameter end of about 4.4 inches.

6. Apparatus for use in a doppler radar velocity measurement system, comprising

means for generating an RF electromagnetic wave having a frequency of approximately 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, and

a dielectric lens covering the mouth of said horn for focusing said RF wave passing therethrough, said lens being formed of a glass filled polymer material.

7. Apparatus as set forth in claim 6, wherein said lens is formed of 40% glass filled polyester.

8. Apparatus as set forth in claim 6, wherein said horn has a circular cross section and a flare angle which is substantially greater than 12.5°

.