| 摘要 |
A transponder (10) that selectively provides both global and spot beam antenna coverage. The transponder (10) comprises a channel amplifier (12) and an antennafeed network (18) that includes coupler means (20) for coupling energy into a plurality of power distribution networks (21, 22) that feed a plurality of antenna radiating elements that form a beam that illumates the desired coverage area. A variable power divider (13) is coupled to the amplifier (12) that variably couples power along two channel output paths. Each output path includes a matched bandpass filter (14, 16) and the second output path includes a phase delay circuit (15). Selective control of the ratio of the power coupled to the respective output paths, and the phase delay provided by the phase delay circuit (15), provides for selective coupling of the total power provided by the channel amplifier (12) to either the full set (26), or a selected subset (25) of the antenna elements which generates global and spot beams, respectively. A more complex version is described which additionally incorporates an Nchannel multiplexer (30). The present invention may also be employed as an interface circuit that may be interposed between a transponder channel amplifier (12) and an antenna feed network (18) to retrofit existing transponders to provide for selectable beam coverage.
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