A W-band wafer probe

A W-band (75-110 GHz) wafer probe was successfully designed and built. The probe uses a ridge-trough waveguide as a transition from a rectangular waveguide input to the coplanar waveguide (CPW) used on the probe board output. Typical insertion loss and return loss figures were 3.5 dB and better than 13 dB, respectively. Losses were minimized in the CPW probe board by attention to conductor loss and taper design; in addition, the transition from rectangular waveguide to ridge-trough waveguide led to an insertion loss less than 1 dB. A crosstalk figure of better than -43 dB was achieved, which is important for accurate calibrations. These performance specifications allowed measured data to be corrected by a VNA for some W-band HEMT (high electron mobility transistor) devices.<>