FM noise measurement of w-band impatt diodes with a quasi-optical direct detection system

A simple and accurate method for determining the FM noise of negative-resistance regenerative oscillators in the microwave region is the so-called direct detection system, where the FM-AM noise conversion is achieved with a discriminator, usually a high Q-factor cavity. With increasing oscillator frequency (above 30 GHz), however, it becomes increasingly difficult to obtain reliable discriminators with high Q-factors. This difficulty can be overcome by applying high-quality quasi-optical resonators for the FM-AM noise conversion.