Design of a broadband sub-harmonic mixer using planar Schottky diodes at 330 GHz

The design of a broadband fix-tuned 330 GHz sub-harmonic mixer is presented. The possibility to model accurately the hot electron noise of Schottky diodes using Agilent ADS software suite has been investigated. The circuit uses an anti-parallel pair of Schottky diodes fabricated by the University of Virginia and flip-chipped on a suspended microstrip filter. The circuit is mounted in a split-block that includes a Pickett feedhorn. At room temperature, the mixer performances were measured in the band 300-360 GHz with conversion losses of 6.5 dB and DSB noise temperature below 800 K with a local oscillator power ranging from 2.5 to 4 mW. Best performances were obtained at 330 GHz with a DSB mixer noise temperature of 650 K.