Certain peculiarities of the noise characteristics of Gunn diodes

The spectral density of the noise power of a Gunn diode was determined as a function of applied bias voltage for various frequencies, i.e., 12.2, 14.2, and 16.6 GHz. A qualitative analysis of the experimental results shows that the avalanche-transit time effect is present in the cathodic static domain of a Gunn diode. The results obtained make it possible to choose an optimal operational mode for a noisy diode with a cathodic static domain, assuring a constant level of noise in a wide range of frequencies. For the diode investigated here, a bias voltage of 16 to 17.5 V assures a noise level of 38 dB with an accuracy of + or - 2 dB in the 12-16.5 GHz range.