Mutual coupling and correlation of closely spaced patch antennas

It is commonly believed that orthogonal polarisations lead to negligible correlation. In this Letter, it is shown that for the closely spaced patch antennas, orthogonal polarisations alone do not ensure uncorrelation. The surface waves must be suppressed (in combination with orthogonal polarisation) to achieve uncorrelated antennas. This is validated by different realisations of closely spaced patch antennas. The final design with reduced mutual coupling and correlation has been fabricated and measured. Good agreements between measured and simulated results are observed.