Resonant-grid quasi-optical diplexers

Experimental results are reported concerning the transmission, reflection, and depolarization of metal grids that reflect an upper band, centered at 30 GHz, and transmit a lower band, centered at 20 GHz. With a single grid, the transmission loss is less than 0.1 dB, and the rejection exceeds 44 dB. Depolarization is measured under realistic conditions with direct dual-mode feed excitation. In a 10-percent band, depolarization is below 34 dB at all scanning angles for both the transmitted and reflected waves. Experiments with two parallel resonant grids are also reported.