Communications: radio wave antennas – Antennas – With polarization filter or converter
Reexamination Certificate
1993-02-04
2001-03-06
Issing, Gregory C. (Department: 3662)
Communications: radio wave antennas
Antennas
With polarization filter or converter
C343S7000MS, C342S361000
Reexamination Certificate
active
06198451
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a radar antenna feed arrangement and is particularly suited to radar operation at high frequencies above, say, 70~80 GHz. At such frequencies it is difficult to achieve an antenna feed which is at the same time efficient and inexpensive.
2. Description of Related Art
Microwave integrated circuits (MIC's) have been proposed for use in antenna feeds but have tended to introduce limitations in both physical arrangement and efficiency. Quasi-optic (or Gaussian optic) techniques have also been proposed but without achieving the desired level of efficiency and ease of manufacture.
SUMMARY OF THE INVENTION
According to the present invention, a radar antenna feed arrangement comprises an optical axis extending towards an antenna interface, a microwave integrated circuit extending parallel to the optical axis, the microwave integrated circuit comprising an array of conductive antenna patches and associated stripline circuitry, quasi-optical focusing means coupling the antenna patches and the antenna interface, and duplexing means for coupling common transmit and receive signal paths at the antenna interface to separate transmit and receive signal paths at the microwave integrated circuit.
The arrangement preferably comprises a parallel-conductor grid adapted to transmit or reflect a radar signal according to the relative orientation of the polarization plane of the radar signal and the grid conductors, the grid being disposed on and obliquely to the optical axis to reflect suitably polarized signals between the microwave integrated circuit and the antenna interface and thus separate either differently polarized receive signals or transmit and receive signal paths. There may be included two parallel-conductor grids arranged to reflect co-polar and cross-polar received signals to respective arrays of antenna patches, the arrays being oriented in alignment with the respective co-polar and cross-polar signals. The conductors of the grids, as projected on to a plane to which the optical axis is perpendicular, may be mutually displaced by 45°, and the arrangement further include means disposed between the two grids for rotating the polarization plane of an incident signal by 45°, the grid more remote from the antenna interface together with the means for rotation through 45° constituting the aforesaid duplexing means.
There may be included a third grid disposed on the optical axis remote from the antenna interface, the two grids providing separation of co-polar and cross-polar received signals and the third grid providing diversion of the transmit signal path to a transmitting antenna patch array, the three antenna patch arrays being co-planar and having orientations such that the cross-polar array is at 45° to each of the co-polar array and the transmitting array which are mutually 90° apart. Alternatively there may be a transmitting horn feed aligned with the optical axis and separated from the antenna interface by the two grids.
The antenna patch arrays are preferably mounted on a common substrate.
One of the patch arrays may constitute a transmitting and a receiving array and the duplexing means may be provided by the associated stripline circuitry.
In any arrangement as aforesaid, there may be included a quarter-wave plate interposed between the antenna interface and the nearest grid, the quarter-wave plate converting between linear polarization on the feed side of the quarter-wave plate and circular polarization on the antenna side.
REFERENCES:
patent: 2788440 (1957-04-01), Ramsay et al.
patent: 2814724 (1957-11-01), Culshaw
patent: 5034750 (1991-07-01), Cardiasmenos
patent: 2067843 (1981-07-01), None
Aylward Michael James
Rowatt Charles Anthony
Issing Gregory C.
Kirschstein et al.
Marconi Electronic Systems Limited
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