Dichroic design for the orbiting VLBI earth station antenna

The design and performance of a single screen frequency selective surface (FSS) with gridded square loop patch element are described for diplexing the Xand Ku-band signals in an orbiting very long baseline interferometer (OVLBI) earth station reflector antenna system. The FSS grids were designed using an analysis code incorporating the 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 results. This validates the FSS design using the gridded square loop element. If the grid is sandwiched between two 0.889 mm thick Teflon slabs, the resonant frequency drift is noticeably reduced as the incident angle steered from normal to 40°