Compact wideband single-ended and differential microstrip-to-waveguide transitions at W-band

Two W-band inline transitions between microstrip line and rectangular waveguide are presented. They cover the single-ended and equivalent differential microstrip line case and result from a common design procedure. This is based on antipodal finlines and Vivaldi-like antennas on an ultrathin liquid crystal polymer substrate inserted in a WR10-waveguide. The designs are presented and the performance of the transitions is evaluated in simulation and measurements. The back-to-back measurement results show good agreement with simulation and exhibit less than 0.9 dB insertion loss and more than 12 dB return loss for the differential transition over the whole W-band.