Balanced monolithic mixer for use at 44 GHz

Abstract

Receiver front ends for satellite applications require low noise devices that have been space qualified to withstand shock and vibration during launch and to operate reliably for many years with continuous LO power and cyclic temperature changes as the satellite passes in and out of earth's shadow. Whisker-contacted Schottky barrier diodes that were hermetically sealed in copper-ceramic packages were developed for the Lincoln Experimental Satellites LES-8 and LES-9 [1], Pairs of these diodes were mounted in a two-diode balanced waveguide mixer. Although these diodes have operated flawlessly in space for over nine years, difficult and time-consuming manufacturing procedures were required to provide this level of reliability. This is because the device essentially used a mechanical pressure contact between an etched gold-plated tungsten whisker and a 3-μm diameter Schottky barrier metallization. As device diameters were reduced to submicrometer dimensions in order to provide low capacitance for operation into the submillimeter region, the difficulties of whisker contacting and reliability of the resulting contact under shock and vibration were of even greater concern.