Metamaterials Applied to ESPAR Antenna for Mutual Coupling Reduction

Phased array smart antennas are becoming the primary choice for wireless communication solutions. Along with the increased usage of this technology, the problems related to mutual electromagnetic coupling between elements become evident. On arrays consisting of only one active element and multiple parasite elements (which steer the radiation pattern), as is the case of the electronically steerable passive array radiator (ESPAR) antenna, it is desirable to have maximum mutual coupling between each parasite element and the active one. However, the mutual coupling between parasite elements decreases the overall efficiency of the adaptive algorithm used to optimize the radiating pattern of the array. This letter explores the use of metamaterial as a near-field electromagnetic insulator. A novel ESPAR antenna structure, composed by metamaterial between parasite elements, has been proposed. The metamaterial structure transforms the conventional behavior of electromagnetic waves. The wave-metamaterial interaction behaves as a high-impedance area, which attenuates electromagnetic waves that move across it. The results show an effective minimization of the mutual coupling between the passive elements, with no significant impact to the mutual coupling between the active element and each passive one.