On the Design of Four-Element Pattern Diversity MIMO Antennas for Mutual Coupling Reduction

We revisit the design procedure of printed four element pattern diversity antennas, starting from the concept of printed dipoles on dielectric substrates arranged in a rotationally symmetric configuration. We systematically modify this basic dipole-based configuration to realize electrical miniaturization, wideband performance and sectorial beam-forming. Especially, we show that by utilizing stub-like structures analogous to neutralization lines, the port-to-port mutual coupling can be significantly reduced in the working band, without gain-reduction or pattern distortion.