A Self-Decoupling Method for MIMO Antenna Array Using Characteristic Mode of Ground Plane

A self-decoupling method for the multiinput multioutput (MIMO) antenna array is investigated. This method is based on the specific characteristic mode (CM) of the ground plane, which features two or multiple parallel null-field regions. By using one antenna element to excite such a mode on the ground plane while placing the other one/ones in a way that their feed points are located in the null-field region, very high isolation between antenna elements can be obtained naturally. To validate the feasibility of this decoupling method, a
$1\times $
2 microstrip patch antenna (MPA) array is simulated, fabricated, and measured. It has been shown that a maximum isolation level of 57 dB is achieved without any extra decoupling structure. Moreover, this self-decoupling method shows strong universality and extensibility, and it applies to different types of antenna arrays and multielement arrays.