Frequency-scanning grating-reflector antenna for multibeam satellite communications

The analysis and design of a circularly polarized frequency-scanning grating-reflector antenna is presented. The antenna is intended for a multibeam satellite communication system, covering 3.1° north-south and 7.2° east-west with 25 spot beams. Frequency scanning is used for the north-south coverage, while the east-west coverage is obtained by the use of a cluster feed. The grating reflector consists of a planar frequency-scanned reflection grating with a quasi-periodic lattice geometry. The frequency-scanned grating reflects the incident field into a diffracted field composed of the first-order diffracted grating lobe. A focus-feed position for the diffracted field is obtained by a proper design of the quasi-periodic lattice geometry. Design principles for the planar grating-reflector antenna are presented together with an analysis method for predicting copolar and cross-polar radiation patterns. The analysis method is verified by experimental results