Mutual Coupling Reduction in an Array of Patch Antennas Using CLL Metamaterial Superstrate for MIMO Applications

The capability of a magnetodielectric superstrate to suppress the surface wave propagation is investigated. It is shown that the capacitively loaded loop (CLL) metamaterial (MTM) superstrate exhibits a high degree of surface wave attenuation. One of the important applications of such structure is to reduce the mutual coupling between the microstrip patch elements in array antennas. The results of numerical simulations show a significant reduction in the mutual coupling between the antenna elements. To verify and confirm the simulation results, a prototype of the CLL-MTM superstrate incorporating an array of rectangular patch antennas are fabricated and tested. The proposed two-element array antenna has a dimension of approximately 1.6λ × 0.9λ × 0.16λ while achieving a gain and an efficiency of 8.2 dB and 97%, respectively. Measurement shows the mutual coupling reduction of over 55 dB. The CLL-MTM superstrate provides the gain and efficiency almost the same of unloaded array antennas with 0.1 dB and 2% changes, respectively.