A calibrated tuner for millimeter device evaluation

A description is given of a tuner which is a mechanically tuned, calibrated two-port impedance transformer which operates over the 33-50 GHz (WR22) waveguide band. With the input waveguide port terminated in a matched load, almost any desired impedance can be obtained at the output, open-microstrip port. This variation is obtained by setting two mechanical waveguide shorts to positions specified by a computer program. The author summarizes the analysis of the tuner and touches on an application of the tuner for determining the noise parameters of a chip (high-electromobility) transistor. This tuner is believed to provide the most accurate measurement of minimum noise temperature of a chip transistor at 43 GHz currently available, and is possibly the only component available for determining all four noise parameters.<>