Novel CMA Scheme to Design Self-Decoupled MIMO Dipole Pair for Base-Station Applications

This article presents a novel method to design multiple-input–multiple-output (MIMO) antennas based on characteristic mode analysis (CMA), which is different from using individual excitation of each characteristic mode for high isolation. The CMA is performed to design a pair of symmetric slots on two connected dipole antennas (an MIMO dipole pair), so that two desired characteristic modes can be generated at the same frequency, one of which is in common mode and the other in differential mode. Hence, when one antenna element is excited, the two characteristic modes combine and cancel each other at the other antenna element, leading to high port isolation. The designed dipole pair is applied for use in 2G/3G/4G MIMO base-station arrays. The simulation and measurement results show that the antenna achieves a wide impedance bandwidth of 1.7–2.7 GHz (45.5%), low coupling below −20 dB, low cross-polarization below −20 dB, high efficiencies over 85%, and stable radiation patterns within the entire band. The results verified the advances of the proposed decoupling method, i.e., simplicity, effectiveness, wide bandwidth, good radiation, and so on.