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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 HEll 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 Index Terms--Faraday rotator, ferrite devices, ferrite switch, millimeter wave.

A new focal plane array for 85-115 GHz is described in this paper. This array has 16 pixels, and uses InP monolithic-microwave integrated-circuit preamplifiers with 40-dB gain, followed by a wide-band subharmonic mixer to convert to a 5-20-GHz intermediate-frequency band. A low-loss isolator is used to achieve an excellent input match. Square corrugated feed horns are used for efficient filling of the focal plane. Critical components are operated at a temperature of 20 K. Noise temperature varies from 50 to 130 K, including all pixels across the full band.