Design Procedure for 5G/IoT Multiple-Port Cavity-Backed Antennas

The design procedure of a multiple-port cavity-backed antenna is presented using characteristic modes analysis (CMA). This methodology ease the design process, starting from the modes of a squared ground plane with length a, and then analyzing how they change when the plane is reshaped into a (a-2b) x (a-2b) x b cavity. Characteristic modes analysis gives a visual insight establishing some constrains for setting the optimum height (b) of the cavity and the optimum feeding configuration of the ports. A complementary full-wave analysis is also introduced for obtaining additional information regarding the input impedance and isolation between the ports. A 2-port cavity-backed antenna with 4.1 GHz (2.9-7 GHz) impedance bandwidth and 15 dB isolation has been optimized with the proposed procedure.