Systematic Design of an Ultra-Wideband Six-Port Multi-Mode Antenna Element Using Symmetry Properties of Characteristic Modes

A design of an ultra-wideband six-port multi-mode antenna element intended for use in a massive MIMO array is presented. By leveraging symmetry properties of characteristic modes, six uncorrelated antenna ports can be defined on a square plate while offering wideband potential with minimum dimensions. Excitation slots are introduced and systematically optimized based on symmetry considerations in such a way that an inherent impedance match is realized for all six ports. In order to cover the desired ultra-wide bandwidth from 6 GHz to 8.5 GHz, the excitation slots are stepped in width and the feed network is adjusted accordingly, achieving the design goals.