A Low-Loss 74–110-GHz Faraday Polarization Rotator

We have developed a switchable Faraday polarization rotator for 74-110 GHz with a typical room-temperature insertion loss of 0.6 dB and a maximum of ~1.3 dB. The device uses a cylindrical ferrite rod in the mode with an axial magnetic field applied by a solenoid. The ports are square metallic waveguides transitioning to ceramic tapers, which then couple to the ferrite rod. The device is designed for use at a temperature of 20 K, where typical loss is <0.5 dB. The design rotation is about plusmn45deg the zero-bias value, but up to 90deg is possible. The switching time is <10 s.