40 GHz parallel plate slot array fed by single-layer waveguide consisting of posts in a dielectric substrate

A parallel plate slot array is an attractive candidate for a high-efficiency and mass-producible planar antenna for millimeter-wave applications since the transmission loss in a parallel plate waveguide is generally small in comparison with other feed lines such as a microstrip or a suspended line. The radiating part has a simple structure that consists of slots etched on the upper plate. There are various ways to feed a plane TEM wave in a parallel plate. Feed structures using a horn or a parabolic reflector are simple but need relatively large areas. We introduce a novel single-layer structure of a feed waveguide. Densely arrayed posts equivalently compose the waveguide walls. We make many through-holes in a metal-grounded dielectric substrate and metalizing them as posts. The structure is advantageous for fabricating planar antennas for millimeter-wave applications with low costs. In this paper, we make a 40-GHz model of the parallel plate slot array with the feed waveguide. We have confirmed the uniform dividing of the feed waveguide in amplitude and phase at 40.2 GHz. An antenna gain of 30.6 dBi with 29% efficiency is obtained.