Image-frequency effects in a microwave crystal mixer

An investigation of the properties of an image-reflection microwave mixer is described. Experimental results are presented which show an improvement in conversion loss and noise figure over the image-absorption mixer. In general, the optimum image termination is an open circuit. The output of the mixer at image frequency is investigated and the condition for zero image output is established. It is shown that image output is strongly dependent on i.f. load. When operated in the region of low image output the mixer is insensitive to image termination, and the increase in noise factor is small. Measurements show that reciprocity holds for the CV2154 mixer. In general, good agreement is obtained between theoretical and experimental results.