Communications: radio wave antennas – Antennas – Wave guide type
Patent
1993-10-13
1995-10-31
Hajec, Donald T.
Communications: radio wave antennas
Antennas
Wave guide type
343776, 343772, H01Q 1300
Patent
active
054634075
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates generally to antenna feeds and more particularly to feed structures for receiving orthogonal linearly polarized microwave signals.
BACKGROUND OF THE INVENTION
Microwave signals are broadcast from communication satellites in various frequency bands (e.g. C band and Ku band) to be received in television receive only (TVRO) systems. Each microwave signal is typically linearly polarized in one of two possible orientations whose electric field vectors are orthogonal to one another. Adjacent television channel signals are typically orthogonal to one another to enhance channel isolation. Orthogonal linearly polarized signals may be received by rotatable receiving systems configured for repeated alignment with the signal polarization or in fixed receiving systems designed to remain in a fixed orientation after an initial alignment. Fixed systems have become increasingly attractive as more satellites, and hence their orthogonal signals, are maintained in absolute geophysical alignment.
U.S. patents of interest in reception of orthogonal linearly polarized signals include U.S. Pat. Nos. 2,825,032; 3,358,287; 3,388,399; 3,389,394; 3,458,862; 3,573,838; 3,668,567; 3,698,000; 3,864,687; 4,041,499; 4,117,423; 4,414,516; 4,528,528; 4,544,900; 4,554,553; 4,595,890; 4,672,388; 4,679,009; 4,707,702; 4,755,828; 4,758,841; 4,862,187; 4,890,118; 4,903,037; 4,951,010; 4,996,535; 5,043,683; 5,066,958 and 5,107,274. Apparatus intended for reception of orthogonal linearly polarized signals are supplied by SPC Electronics under the designations of models DPS-710 Series and DPS-710R Series and by Pro Brand International under the designation of Aspen Eagle LNBF 1000.
SUMMARY OF THE INVENTION
The present invention is directed to feed structures for receiving orthogonal linearly polarized microwave signals.
Structures in accordance with the invention include a feed horn defining a microwave cavity with first and second probes projecting into the cavity in respective alignment with the electric field vectors of the orthogonal signals. To reduce signal coupling between the probes, an isolation member extends from the cavity back wall and is preferably centered on the cavity axis.
In a preferred embodiment, the isolation member defines a plurality of radial arms, one of which is preferably arranged to lie in the cavity quadrant bounded by the probes.
In a preferred embodiment, the probes project through the cavity side wall for direct external delivery of the received signals to amplifier circuitry adjacent the side wall.
In another preferred embodiment, the probes project through the cavity back wall for direct external delivery of the received signals to amplifier circuitry adjacent the back wall. In this embodiment each of the probes preferably terminates in the cavity in a substantially axially and longitudinally extending receive portion. Transmission members preferably at least partially surround each probe to enhance signal transmission therealong.
In accordance with a feature of the invention, each probe, after passing through the cavity wall, terminates in a launch portion where its associated signal is available. This direct path facilitates realization, in external receiver circuits, of a high signal to noise ratio.
Feed structures in accordance with the invention are particularly suited for realization in simple one piece castings and for installation as part of a fixed satellite receiving system.
The invention is extended to more than one frequency band by repeating the feed structures coaxially with dimensional scaling appropriate to each frequency band.
The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a top plan view of a feed assembly incorporating a preferred dual mode feed structure embodiment in accordance with the present invention;
FIG. 2 is a botto
REFERENCES:
patent: 5216432 (1993-06-01), West
patent: 5331332 (1994-07-01), West et al.
Gabrelian Edward E.
West Laurice J.
California Amplifier, Inc.
Freilich Arthur
Hajec Donald T.
Le Hoang-anh
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