An efficient dual frequency antenna feed

Terminals for weather satellite readout require a compact feed for small reflector antennas and operate at L-band (1670-1710 MHz) and S-band (2200-2300 MHz). Both bands require right hand circular polarization and L-band requires linear polarization as well. The analysis and measurement of a novel dual frequency antenna feed is described. Stacked microwave patches for operation at the two separated frequency bands are surrounded by a corrugated surface to improve illumination efficiency. The feed is configured for orthogonal linear polarization, has filtering and modest preamplification with amplitude and phase matched LNAs for each linearly polarized feed terminal, and uses a quadrature hybrid to combine the two outputs for circular polarization. Linear polarization is obtained by turning off one of the preamplifiers.