Pure-mode network analyzer concept for on-wafer measurements of differential circuits at millimeter-wave frequencies

A measurement concept based on a two-port vector network analyzer has been developed, which enables pure-mode on-wafer measurements of differential circuits in the millimeter-wave frequency range. An error model for the measurement system is derived as required for future calibration algorithms. Based on WR15 waveguide components, together with 1.85-mm coaxial probes, a setup has been built and its amplitude and phase imbalances have been characterized in the frequency range from 50 to 65 GHz.