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(11) | EP 0 786 826 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Intermodulation scattering communications apparatus |
| (57) Multiple beam, multi-frequency communication apparatus (10) that provides for significant
intermodulation scattering improvements for multiple beam, multi-frequency communications
systems implemented using directly radiating active phased array (15), or multi-feed
reflector systems fed from composite, multiple shared transmit amplifiers (13). The
multiple bearn, multi-frequency communications apparatus (10) comprises a defocused
antenna array (15) having a plurality of antenna elements (15a) and a plurality of
feeds (15b). A hybrid amplifier structure (18) is coupled to the feeds (15b) of the
defocused antenna array (15) and shares the plurality of transmit amplifiers (13)
among the feeds (15b) of the antenna array (15). Assignment apparatus (20) is coupled
to the hybrid amplifier structure (18) for assigning particular transmit amplifier
(13) to be contributors to particular beams (16) radiated by the antenna array (15)
in response to a desired beam profile (11). Improvements result from judicially combining
the effects of the shared transmit amplifiers (13) (that carry all the signals in
the frequency reuse system), with phasing effects inherent in rhe multiple beam radiating
structure in order to realize the desired zonal frequency reuse pattem 21. An optimal
assignment algorithm implemented in the assignment apparatus (20) results in a uniform
distribution of power over the transmit amplifiers (13), resulting in corresponding
improvements in system performance in the far field. |