RF-Impedance Determination of MM-Wave Waveguide Mixer Mounts

When making low noise millimeter wave mixers, knowledge of the RF-circuit is of great importance. The measurement of circuit properties is difficult due to lack of the sophisticated instruments available at lower frequencies. In this paper a method of determining the RF-impedance using simple reflectometer techniques and variation of the DC diode parameters is presented. The measured data are compared with a theoretical circuit model. The data can be conveniently illustrated in an impedance diagram together with the diode impedance. From knowledge of the RF-impedance one can predict and analyse many important properties of the mixers.