Quasi optical circulator X-band scale model utilizing a circular polarization frequency selective surface

A prototype X-band scale model for a quasi optical 3-port circulator utilizing a double-layer circularly polarizing frequency selective surface is proposed. The operating principles and measured characteristics of the device are discussed. A prototype device operating at 9.9 GHz is built and validated experimentally. The port 1 to port 2 insertion loss of the circulator has been measured to be 2 dB while port 1 to port 3 isolation is 15 dB. It is demonstrated that port 1 to 3 isolation can be increased to 25 dB by embedding the circulator in a feed forward set up.