Isolation Enhancement in Closely Packed Wideband Antennas Using Metasurface

A planar anisotropic metasurface superstrate structure for isolation enhancement of two closely packed antennas is proposed in this paper. The spacing of the initial antennas is only 0.12 lambda(0) at 3.55 GHz (lambda(0) is the wavelength at the center frequency). The metasurface structure is consists of periodic rectangular-loop unit resonators, which are printed on the one side of 1.5 mm thick FR-4 substrate in E -plane. By placing the decoupling structure beside the initial antennas instead of putting it in the middle of the antennas, it can reject coupling wave propagation and improve isolation of two ports of the antenna further. The simulated results show that the proposed metasurface structure is able to achieve port isolation improvement at least 19.7dB and at most 31.9dB with in the operation band from 3.3 to 3.8 GHz. More importantly, the antenna still keeps good performance with S< -10 dB and has tendency to broaden bandwidth, while the metasurface superstrate structure is loaded.