Controlling coupling between two transmitting antennas for MIMO handset applications

We introduce a method to control mutual coupling and correlation between two transmitting antennas for multi-antenna applications in the handset. The method is based on controlling the forward and the back-scattering currents at the antenna ports taking each antenna´s driving point impedance into account. We achieve this using a six-section connection circuit that is placed between the multi-antenna system ports and the rest of the transceivers. The method is presented through application to a printed two-monopole antenna example and is implemented in a number of ways showing the technique´s flexibility. An improvement in the mutual coupling ranging between 4-10 dB was achieved. The technique is general and does not require the MIMO problem to be symmetric, i.e., it can be implemented to MIMO systems with different antenna types.