Microstrip Antenna Array Fed by a Low-Loss Gap-Waveguide Feed Network

Abstract

A Ku-band quasi-planar microstrip antenna array fed by a gap-waveguide feed network is demonstrated. The upper microstrip substrate is not in electric contact with the lower feed network, which relaxes the fabrication process considerably. The 64-element array consists of 16 2-by-2 subarrays arranged to form an 8-by-8 configuration of array elements. To ensure minimum feed losses, the subarrays are excited by a corporate feed network composed of groove-gap-waveguide components. The first part of the feed network consists of the ground plane of the antenna array which also plays the role of the upper plate of the waveguide network. The second part is an artificial magnetic conductor (AMC) structure realized within the lower plate of the waveguide feed network via milling. In this communication, the AMC structure is made of a bed-of-nails. Array elements are rectangular patches showing 8.85 dBi gain each at the center frequency. The maximum measured gain of the antenna array is 26.18 dBi, which is equivalent to 57.81% aperture efficiency.