A Satellite System with Limited-Scan Spot Beams

A satellite system with several independent spot beams is considered, wherein each spot beam can be scanned over a limited portion of some large service region. The spectral band is totally reused in each spot beam, thereby providing high system capacity. Such a system combines the high antenna gain advantages of a fixed beam system while providing access to the satellite from any point within the overall service region. Moreover, the transmission resources of the satellite can be dynamically allocated to match time-varying changes of the possibly nonuniform terrestrial traffic patterns. The limited-scan antenna forms multiple spot beams, each of which scans only in one dimension; by alternating polarizations among scan strips, high isolation between beams is guaranteed. We show that nearly equal volumes of traffic can be served by each limited scan beam by proper orientation of the scan regions, and complete interconnectivity among all points in all scan regions is achieved easily. A practical antenna design to implement this concept is presented.