Circuit Loss Characterisation with an IMPATT Diode

A convenient technique is described to measure the internal circuit loss, the load conductance and equivalent circuit susceptances of an IMPATT oscillator. The diode is biased just below its breakdown voltage and is used as a resonant reflection absorber. From these frequency dependent characteristics we are able to separate the load and internal circuit loss conductances providing that the circuit is singly resonant. The experimental technique does not require any mechanical disturbance of the diode in contrast to many network analyser techniques. It also allows a rapid and simple confirmation that the circuit is singly resonant.