Noise at large RF amplitudes in IMPATT oscillators ?

The non-stationary noise generator of a large-signal IMPATT oscillator is studied. It is shown that only the zeroth-order term of the series expansion of the autocorrelation for the noise voltage is of importance for the oscillator noise spectrum. The zeroth-order term is determined by an integral of the square of the Green's function for the total voltage from a generation of a pair of carriers weighted by the mean generation rate

A PIN diode model with a fixed rectangular voltage is studied numerically. The short-circuit noise current is shown to be inversely proportional to the reverse saturation current,J_s. The possibility of improving the noise properties by increasing J_s is discussed.