A Novel 183GHz Subharmonic Schottky Diode Mixer

Abstract

The technique of microwave . limb sounding -from space represents a very powerful tool for determining the atmospheric processes involved in ozone depletion, the greenhouse effect, acid rain, etc.. Unfortunately, the technology involved in producing millimetric and submillimetric devices is highly complex, and miniature. The power levels and environmental conditions existing aboard spacecraft in present 'use, 5 differ from those required by the low noise heterodyne receivers employed by the Radio Astronomy community. Therefore, great effort has been spent in the design of radiometers with limited power and weight requirements, so that they can withstand the rigours of launch and operation in space. This thesis describes the design and construction of a subharmonically pumped, double diode mixer which is now used in an airborne atmospheric radiometer. The mixer power requirement and rugged nature make it an ideal option for space operation. The assembly of the millimetric circuit required the development, of novel techniques which enabled the incorporation of discrete circuit elements onto a single quartz substrate. This allowed the physical testing of the millimetric circuit independently of the RF block. A detailed investigation into the `whiskering' technique was carried out. It was thus possible to pinpoint errors that had previously occurred in assembly and which had resulted in the failure of a space flight device. With the adoption of quantified procedures, devices constructed using the `whiskering' technique were shown to be considerably more resilient than had previously been thought. The performance of the mixer is comparable with other designs using Schottky diodes at room temperature (-1200K DSB) and the local oscillator power requirement is easily met with a single solid state source. A simple theoretical analysis using the Seigel and Kerr program was undertaken in conjunction with RF measurements performed on a 65X scale model to determine steps required for further improvement.