Conceptual design of a compact four‐element UWB MIMO slot antenna array

Abstract

In this study, an effective methodology to design a compact four-element multiple-input-multiple-output (MIMO) antenna with high performance over ultra-wide bandwidth (BW) is presented and discussed. Taking the advantages of symmetry of most planar ultra-wideband (UWB) antennas, an asymmetric feeding scheme technique is utilised to chop a previously developed UWB slot antenna with overall dimensions of 30 mm × 30 mm into two halves to yield a more compact structure while retaining its overall frequency- and time-domain performances. Benefiting from orthogonal orientation, a compact UWB MIMO antenna system is arranged using four half-sized elements. The proposed MIMO antenna has an overall size of 40 mm × 40 mm and exhibits impedance BW from 2.94 to more than 14 GHz (10 dB return loss) with port isolation better than 17 dB over the entire operating band without using any decoupling structures. This is achieved via the inherent directional radiation properties of slot antenna elements and their asymmetrical placements. Envelope correlation coefficient is computed, and it is within the acceptable limit, which validates the design concept for building a compact MIMO antenna system with good performance.