W-Band High-Gain TE$_{220}$-Mode Slot Antenna Array With Gap Waveguide Feeding Network

In this letter, a high-order-mode substrate integrated cavity (SIC) excited 2 ×2-slot antenna subarray for wideband and high-gain W-band array application is presented. This antenna subarray is designed by using two low-cost double-side printed circuit broads (PCBs). The transmission loss caused by divider can be reduced by using the high-order-mode substrate integrated cavity to excite the slot antenna subarray. Furthermore, such use reduces processing difficulty and fabrication cost. The bandwidth and gain of the proposed antenna are also improved. To validate our design, an 8 ×8 antenna array with 4 ×4 SIC subarrays has been fabricated and measured. To reduce the loss further, the microstrip-based ridge gap waveguide (GWG) technology is applied to feed the SIC subarrays. Furthermore, for measurement purposes, a wideband transition structure between rectangular waveguide (RWG) and GWG is designed. Measured results show that an 8 ×8 slot array with the transition achieves a maximum boresight gain of 25.3 dBi and an impedance matching bandwidth of 82-102 GHz with a boresight gain above 24.5 dBi. In addition, the measured aperture efficiency is 64%.