Controlling coupling between two transmitting antennas for MIMO handset applications

Abstract

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.