A quasi-optical isolator

A nonferrite X-band quasi-optical isolator is presented. The isolator consists of six cascaded printed gratings loaded with lumped elements and exhibits less than 2-dB insertion loss. The isolator is designed for protection and stabilization of quasi-optical amplifiers. A linearly polarized output wave from a quasi-optical amplifier becomes circularly polarized in the isolator, which in this case serves as a linear-to-circular polarization converter as well. Isolation of 9 and 19 dB was measured for the co- and cross-polarized waves, respectively.