A Broadband Mutimode Antenna Based on the Theory of Characteristic Mode

This paper presents a four-port multimode antenna designed by the theory of characteristic mode. The antenna is fed by four SMA ports through a feeding network and works at a broadband of 3~6 GHz. Each port of the antenna excites one or more characteristic mode(s) which do not correlate with other ports, resulting in high port-to-port isolation over the operating band. To improve the port reflection, a capacitive mode is added and compensates the imaginary part of the port admittance. The fabricated antenna has been measured, which shows good agreement with simulation.