Experimental Evaluation of Noise Parameters in Gunn and Avalanche Oscillators

Equations are presented that express noise-to-carrier ratio and rms frequency deviation of a negative-resistance oscillator with a multiple-resonant circuit in terms of effective available noise power densities of both 1/f and white-noise sources, an effective saturation factor, and an appropriate Q/sub L/ of the oscillator. Experimental evaluation of the noise parameters in Gunn and avalanche oscillators by use of these equations is described. AM and FM noise measurements have been made on X-band Gunn oscillators and Si and GaAs avalanche oscillators for frequency off carriers extending from 1 kHz to 10 MHz. Both 1/f and white noise have been observed in these oscillators. The validity of the above equations has been verified for Gunn oscillators from the dependence of the noise spectra on Q/sub L/. For Gunn oscillators and Si and GaAs avalanche oscillators, the effective noise-temperature ratio for white noise, N/kT/sub 0/, has been found to be 23~29, 41~51, and 38~44 dB, and the effective saturation factor to be 2~2.9, 0.5~2.4, and 2, respectively. An increase of N/kT/sub 0/ with the RF voltage across the diode has been observed in Si avalanche oscillators. Parameters for 1/f noise have also been evaluated approximately.