Wideband PCB-Based Planar Array Antenna With High Aperture Efficiency Based on Substrate Integrated Gap Waveguide

This communication addresses the cost challenges with implementing high-gain antennas in the millimeter-wave band. The designed antenna exhibits a favorable broadband of 32.9% and achieves an aperture efficiency of up to 79.5%. This proposed array is constructed from five stacked layers of printed circuit boards (PCBs), with four layers composed of FR-4 boards. The idea of air filling is widely used in this design to mitigate high dielectric loss of FR-4 boards. The array adopts a sandwich construction approach to realize air-filled high-efficiency radiation cavities, with the radiation elements sandwiched by the feeding structure. The feeding structure utilizes a hybrid network that combines a substrate integrated gap waveguide (SIGW) and microstrip (MS) lines. The air-filled SIGW (AF-SIGW) is improved to minimize dielectric loss, and the MS lines are terminated with loads to broaden the bandwidth. Particularly, to the best of authors' knowledge, this is the first reported instance of AF-SIGW utilization for planar array design in the available literature. A prototype of an <tex-math notation="LaTeX">8 × 8 </tex-math> array is implemented and tested, showing a good agreement between simulations and measurements.