A Dual-Port Single-Dipole MIMO Antenna Pair Based on Selective Modal Excitation for 5G Metal-Rimmed Terminals

Abstract

This study presents a dual-port single-dipole MIMO antenna pair, which is accomplished by selectively exciting the dominant dipole-type current mode and the second higher current mode of a single suspended metal strip. A magnetic coupling method based on a feeding loop is implemented at the current maximum portion of the dominant mode of the suspended metal strip, such that the suspended metal strip operates as a half-wavelength dipole radiator. An electrical coupling method based on a feeding capacitor, otherwise, excites the wavelength dipole mode of the suspended metal strip, and this higher mode resonance is further controlled by a tuning capacitor. In this way, the suspended metal strip involves a dual-port MIMO antenna pair, and both antennas operate as dipole-type radiators while having high port-to-port isolation because of the modal orthogonality. Therefore, the operation mechanism of the proposed technique is straightforward, and the implementation is simple, free of any additional decoupling components or a complex excitation network. This feature makes the proposed technique an attractive solution in metal-rimmed terminals for 5G applications, so 4× 4 MIMO antennas operating at the N78 band were constructed and verified in both simulation and measurement.