The use of punch-through diodes in self-oscillating mixers

Abstract

Several works on punch-through diodes have shown the capability of the device when used as a low-noise local oscillator or amplifier. Similar noise performances are thus expected in self-mixing systems. Some experimental and theoretical results concerning punch-through diodes used as self-oscillating X-band mixers are presented. The noise figure and conversion gain have been measured against bias current, self oscillator (LO) power level and input power, for IF frequencies ranging from 100 KHz to 100 MHz. A noise figure of 8.5 dB was obtained with N+P pi N+ diodes. An analytical treatment is given for frequency conversion effects in terms of a quasilinear network theory. Theoretical results on conversion gain are presented which indicate substantial qualitative agreement with experimental results.