A 2 × 2 Filtering subarray element antennas using all-resonator structures

This study presents two novel topologies of a 2 × 2 filtering antenna subarray based on all resonator structures. The coupling matrix theory is used to extract the interresonator coupling coefficients and quality factors. The matrix parameters give a controllable bandwidth to the filtering subarrays. Rectangular waveguide cavity resonators are utilised to implement the physical layouts of the topologies. They operate at a centre frequency of 10 GHz and have a fractional bandwidth of 10% with return loss of -20 dB. The first topology consists of seven resonators feeding from beneath, while the second topology consists of six resonators feeding from the side. Compared to previous 2 × 2 waveguide cavity-backed subarray antennas, the proposed 2 × 2 filtering subarrays have the advantage of having a larger bandwidth, flatter gain over the passband and larger roll-off of the gain at the band edges. Also, when providing the feed network, the all-resonator structure removes the need to place a bandpass filter after the antenna at the front end of a communication system. Fabrication and measurements have been performed by validating the designs. © 2021 The Authors. IET Microwaves, Antennas & Propagation published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.