Noise in Gunn oscillators

We estimate the ultimate noise of Gunn oscillators in the absence of 1/fnoise. The basic noise source considered is thermal or Johnson noise augmented by intervalley noise of carriers hopping between the high and low mobility bands. For example, for Qext= 10²and Pout=10^-1W we estimate δfrms≈ 1-2 Hz, and AM noise relative to the carrier of -156 dD, both measured in 1-kHz bandwidths.