Quasi-optical diplexer using two-Fabry-Perot resonators

A Fabry-Perot resonator, originally used in the optical region, is adapted to the millimeter-wavelength region. A circular polarizer, developed using an effective anisotropic material, is combined with a polarization splitter, and an FP resonator is placed normal to the Gauss beam. The behavior of the Gauss beam incident on the diplexer is studied theoretically, and the results are used to develop the design method for a quasi-optical diplexer. A test, performed in the 100 GHz range, gives proof of the diplexer's low-loss characteristics (a diplexing loss of 0.5 dB and a transmission loss of 0.3 dB). These values are comparable to those of the conventional waveguide diplexers; it is assumed, however, that the performance of the diplexer would surpass that of the conventional ones at higher frequencies.