Novel $W$ -Band Millimeter-Wave Transition From Microstrip Line to Groove Gap Waveguide for MMIC Integration and Antenna Application

For monolithic microwave integrated circuit integration and antenna application, a novel W-band millimeter-wave transition from microstrip line to groove gap waveguide (GWG) is proposed in this communication. The transition is achieved by a modified planar triangular-microstrip patch resonator with an inner shorting via. To give a physical insight, E-field analysis is presented, and its working mechanism is similar to that of the passband filter based on coupled resonators. The proposed transition may contribute to a potential groove GWG application in the W-band radar and communication system. Finally, a back-to-back transition prototype is fabricated and assembled for measurement. To improve $S_{11}$ of the prototype, a modified CPW probe pad is applied. Moreover, the influences on $S_{11}$ and $S_{21}$ of the conductor losses are given. The measured results show that there is an excellent transition passband from 90 to 99.5 GHz, in which frequency band, $S_{11}$ is almost below −12 dB.