Large-signal noise, frequency conversion and parametric instabilities in impatt diode networks

IMPATT diodes exhibit a number of unique nonlinear effects when strongly driven as an amplifier or self-excited oscillator. The avalanche zone behaves as a highly nonlinear inductor, causing parametric effects such as frequency conversion with gain and spurious oscillations in some network configurations. At high drive levels, noise output is enhanced and the spectral distribution is affected by intermodulation. These effects have been studied theoretically using the Read diode model. Using a perturbation technique, equations are derived for the multiple-frequency responses to an applied small signal in the presence of a large signal excitation at another frequency. The equations have also been analyzed for stability against spurious "parametric" oscillations. Theoretical expressions have also been obtained for noise generation at high signal levels and for the noise spectral distribution as affected by intermodulation. Computed curves have been derived for a number of these effects.