Tunable waveguide‐to‐microstrip transition for W‐band antenna

At millimetre‐wave frequencies, the discrepancy between simulation and measurement comes from the relative permittivity tolerance and fabrication tolerance. This discrepancy can mainly cause resonant frequency shift. A tunable waveguide‐to‐microstrip transition for the W‐band antenna is proposed to overcome this discrepancy. A typical transition consists of a microstrip probe on a substrate and a waveguide back short in a fixed structure. The tunability has been designed by making a movable back short through WR‐10 waveguide. This design can change the back‐short distance mechanically to tune resonant frequency. The tunability of this design has been verified with a W‐band substrate integrated waveguide (SIW) slot array radar antenna.