30 GHZ IMAGE ENHANCED MIXER “FRONT-END” FOR SPACEBORNE LOW NOISE RECEIVER USAGE

Abstract

A Ka-band low noise “front-end” currently under development for ultimate spaceborne receiver deployment, consists of a 27.5-30 GHz image-enhanced mixer integrated with a 3.7-6.2 GHz FET low noise IF amplifier and driven by a self-contained 23.8 GHz phaselocked LO source. The image enhanced mixer, designed for 5 dB overall “front-end” SSB noise figure, utilizes a balanced pair of in-house high quality GaAs Schottky mixer diodes embedded in a composite waveguide/TEM “crossbar” balanced mixer structure possessing inherent mutual RF/LO isolation. The three stage FET IF amplifier, implemented in a single-ended microstrip configuration, has, in a preliminary breadboard, exhibited 24.5 ±0.5 dB gain and 1.5 to 2.4 dB noise figure over the 3.7-6.2 GHz band. The LO source, consisting of a C-band high power FET VCO, phase locked to an external 500 MHz crystal reference, and driving a C-to-K band varactor quadruplet, will provide up to 40 mW LO drive at 23.8 GHz.