General-purpose fifth-harmonic waveguide mixer for 500-700 GHz

This paper presents the design of a wideband fah-harmonic waveguide mixer. The mixer uses two single planar Schottky diode chips in a balanced-mixer-type configuration It is designed to operate at 500-700 GHz radio frequency (RF) range applying an Id' Gum oscillator as the local oscillator (LO) source at 100-140 GHz. A novel transition structure is wed in the LO waveguide. The mixer block is compact comprising an integrated diagonal horn antenna, two 40-pun-thicqku artz circuits, and a coaxial connector. For effortless we in a submillimetre-wave antenna measurement set-up the mixer does not comprise any tnners. Mixer circuits were designed for wide-band operation and were not optimised for a certain frequency. The conversion lass is close to 27 dB at 650 GHz with an LO power of 10 dBm at 130 GHz. The mixer is currently being used for phase-locking of a submillimetre-wave backward wave oscillator in a hologram-based compact antenna test range.