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Composite multi-beam and shaped beam antenna system
| Details |
Inventors: Hwang, Yeongming; Jakstys, Vito J.;
Assignee: Space Systems/Loral, Inc. (Palo Alto, CA)
Primary Examiner: Hajec; Donald T.
Assistant Examiner: Ho; Tan
Attorney, Agent or Firm: Perman & Green
A composite antenna for use in satellite communication provides both the functions of multiple beams and a shaped beam radiated from a single radiating aperture. The radiating aperture may employ a mirror or a lens. Transmitted radiation from an array of radiators is coupled via a subreflector to the main reflector or lens which constitutes the radiating aperture of the antenna system. During reception of radiant-energy signals, signals received by the main reflector or lens are coupled via a separate subreflector to a separate array of receiving radiators operated at a frequency band different from that of the transmit array. The two subreflectors are combined into a single subreflector assembly employing a metallic concave reflector covered by a layer or coating of frequency selective optical material which allows for propagation of radiation at one frequency to the metal reflector while reflecting radiation in the other frequency band from a surface of the coating. Separate beamformers are employed for receiving and transmitting radiant-energy signals, the beamformers combining signals of clusters of radiators to provide for multiple beams wherein each of a plurality of the beams is formed by a cluster of radiators. Additional connection is provided via diplexers to the beamformers to select radiators to be employed for generation of shaped beams for both reception and transmission. The reflecting surfaces have diameters much larger than the diameters of the radiators to provide for individual beams from each of the radiators. |
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DETAILED DESCRIPTION FIG.
1 shows a satellite 30 stationary in a geosynchronous orbit 32 above the earth 34.
The satellite 30 carries electronics communication equipment 36 connecting with an antenna system 38 which serves, in accordance with the invention, for receiving uplink signals transmitted from stations on the earth, and for transmitting downlink signals to receiving stations on the earth.
Communication with a region of the earth, such as a subject 40 portrayed as a land mass, requires illumination of the subject by means of a shaped-beam with a footprint having the general configuration of the subject 40 or, alternatively, by means of a set of multiple beams which are excited sequentially for successive illumination of various portions of the subject 40 wherein each of the multiple beams has a footprint covering a portion of the subject.
By way of example, FIG.
1 shows a plurality of beams 42 of a set of multiple beams wherein one of the beams 42A (indicated in dot-dash lines) has a footprint 44 which covers a portion of the subject 40.
Other footprints, 44A-C provide coverage of other portions of the subject 40.
The footprints 44-44C overlap in their coverage at their respective interfaces with each other.
Each of the footprints 44-44C is associated with a specific beam 42 such as, for example, a beam 42B illuminating the region of the footprint 44A.
FIG.
2 shows construction of the antenna system 38 wherein, in accordance with the invention, the antenna system 38 is capable of transmitting and receiving radiant energy signals concurrently in separate frequency bands, one frequency band being employed for reception and the other frequency band being employed for transmission and, wherein, in each of the frequency bands, the antenna system 38 is capable of providing either a shaped-beam illumination of the subject 40 (FIG.
1) or multiple beam illumination of the subject 40.
The antenna system 38 comprises two optical elements of which a first element is a subreflector assembly 46 and the second optical element may be either a mirror 48, as shown in FIG
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Radio 
