DICHROIC DESIGN FOR THE ORBITING VLBI EARTH STATION ANTENNA

In the paper the design and performance of a single screen frequency s elective surface (FSS) with gridded square loop patch element are desc ribed for diplexing the X- and Ku-band signals in an orbiting very lon g baseline interferometer (OVLBI) earth station reflector antenna syst em. The FSS grids were designed using an analysis code incorporating t he accurate integral equation technique. The effects of the dielectric substrate and superstrate are accurately evaluated by this technique. Excellent agreement is obtained between the predicted and measured re sults. This validates the FSS design using the gridded square loop ele ment. If the grid is sandwiched between two 0.889 mm thick Teflon slab s, the resonant frequency drift is noticeably reduced as the incident angle steered from normal to 40-degrees.