Application of Metamaterial Wall for Mutual Coupling Mitigation of a Dual Differential Fed 2x2 Patch Array Antenna

An effective technique for mutual coupling mitigation in a 2 x 2 dual differential fed patch antenna array (DDFPAA) is presented. Metamaterial walls are placed between the radiating elements of an array in the two orthogonal planes of the antenna to reduce mutual coupling in both planes. The wall comprises a double-layer array of split ring resonators (SRR) to suppress coupling through space wave effects. The radiating elements are microstrip patches that are differentially fed to achieve polarization diversity. The impact of interelement mutual coupling on functionalities, mechanism, and mode of operation of the array antenna are discussed in conjunction with the SRR metamaterial wall. A composite antenna array is implemented and computationally validated with an overall footprint of 1.24 lambda x1.24 lambda at the resonant frequency of 9.37 GHz. A fabricated array prototype with a patch edge-to-edge distance of 0.18 lambda has a measured mutual coupling reduction of more than 15 dB and 5 dB in E- and H-planes, respectively, within the operating frequency band. The proposed antenna has a measured 10dB impedance bandwidth of 9.27-9.45 GHz, a broadside measured peak gain of 11.4 dBi, and multiple polarizations of CP and/or LP.