Compact split-ring resonator-loaded multiple-input–multiple-output antenna with electrically small elements and reduced mutual coupling

The authors present a compact four-element multiple-input-multiple-output antenna with the potential to operate in WiMAX frequency bands, with its elements being not only closely spaced but also electrically small. Split-ring resonators or metal stipes are utilised to achieve both goals, that is element miniaturisation and reduction of mutual coupling. The design process is systematic, as it deals with both issues quite separately. Very low values of the envelope correlation coefficient and overall good performance are obtained, without compromising planarity and simplicity.