Complementary pattern method to reduce mutual coupling in metamaterial antennas

A complementary pattern (CP) for multiple antennas in order to reduce mutual coupling between antenna elements is proposed and investigated. The proposed CP is comprised of meandered transmission lines between antennas on FR4 (ε_r=4.6) substrate. The multiple antennas are a printed embedded type based on composite right/left handed (CRLH) metamaterial transmission lines. In order to validate the CP effects, simulation and measurement results for both the with-CP case and the without-CP case in metamaterial antennas are compared. The CP is presented as an equivalent circuit. Through parametric studies, the optimal dimension of CP is determined. The return loss, isolation, radiation patterns of each plane, measured peak gain and current distributions are provided. By calculating the envelope correlation coefficient between two antennas, the authors also demonstrate the effect of the CP in a metamaterial antenna. The total PCB size is 21.5=50=mm² with 1 mm thickness, and the antenna space is 21.5 10 mm². The resonant frequency with good isolation value is 3.3 GHz. Since the metamaterial antenna and CP consist of transmission lines, the proposed structures are compatible with other radio frequency (RF) devices.