Noise figure and conversion loss of self-excited Gunn-diode mixers

Gunn-effect oscillators, used as self-excited mixers in X band/v.h.f. band convertors, are investigated. Noise figure and conversion loss are measured. It is shown that both fairly high oscillator Q factor and proper matching of the input signal to the Gunn diode leads to mixers comparable in performance with usual microwave mixers. Because of the negative differential resistance of Gunn diodes, conversion gain is easily realisable.