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This letter presents an efficient technique to reduce the mutual coupling between two 5.2-GHz probe-fed patch antennas in an array format. Two different designs of folded split-ring resonators (FSRRs), composed of single and double rows, etched into the ground plane are proposed for more reduction of the mutual coupling and spacing between antennas. Parametric studies show that by carefully adjusting the basic design parameters, and so equivalent capacitance and inductance of the FSRRs, a reduction of more than 30 dB in the mutual coupling between two antennas with a very close distance of about 0.039 λ0 (edge-to-edge distance) and 0.27 λ0 (center-to-center distance) can be obtained. Measured S21 of the array in the first and second designs of the FSRRs are about -56 and -45 dB, respectively. The features including very small occupied area, high performance, and noncomplex structure make the proposed FSRRs more useful for various related applications.