Diversity optimization by axial rotation of helical antennas in a MIMO system

This paper describes a technique for optimizing the diversity of two same-sense, axial-mode helical antennas in a MIMO system. It is shown that for a fixed spatial separation, a mechanical rotation of one of the helical antennas about its longitudinal axis will always minimize the envelope correlation coefficient. The mutual coupling between the antennas can be reduced at the same time. The technique is verified by simulations and s-parameter measurements on 5.8 GHz helical antennas.