Wang Ziyang, Zhao Luyu, Cai Yuanming, Zheng Shufeng, Yin Yingzeng
Xidian University, National Key Laboratory of Antennas and Microwave Technology, Xi'an, 710071, People's Republic of China.
Sci Rep. 2018 Feb 16;8(1):3152. doi: 10.1038/s41598-018-21619-z.
In this paper, a method to reduce the inevitable mutual coupling between antennas in an extremely closely spaced two-element MIMO antenna array is proposed. A suspended meta-surface composed periodic square split ring resonators (SRRs) is placed above the antenna array for decoupling. The meta-surface is equivalent to a negative permeability medium, along which wave propagation is rejected. By properly designing the rejection frequency band of the SRR unit, the mutual coupling between the antenna elements in the MIMO antenna system can be significantly reduced. Two prototypes of microstrip antenna arrays at 5.8 GHz band with and without the metasurface have been fabricated and measured. The matching bandwidths of antennas with reflection coefficient smaller than -15 dB for the arrays without and with the metasurface are 360 MHz and 900 MHz respectively. Using the meta-surface, the isolation between elements is increased from around 8 dB to more than 27 dB within the band of interest. Meanwhile, the total efficiency and peak gain of each element, the envelope correlation coefficient (ECC) between the two elements are also improved by considerable amounts. All the results demonstrate that the proposed method is very efficient for enhancing the performance of MIMO antenna arrays.
本文提出了一种在极紧密间距的二元MIMO天线阵列中降低天线间不可避免的互耦的方法。将由周期性方形开口环谐振器（SRR）组成的悬浮超表面置于天线阵列上方以实现去耦。该超表面等效于一种负磁导率介质，沿其方向波传播被抑制。通过合理设计SRR单元的抑制频段，可显著降低MIMO天线系统中天线单元间的互耦。制作并测量了5.8 GHz频段有和没有超表面的两种微带天线阵列原型。对于没有超表面的阵列，反射系数小于 -15 dB时天线的匹配带宽为360 MHz，有超表面的阵列则为900 MHz。使用超表面后，在感兴趣频段内，单元间的隔离度从约8 dB提高到超过27 dB。同时，每个单元的总效率和峰值增益、两个单元间的包络相关系数（ECC）也有显著改善。所有结果表明，所提方法对于提升MIMO天线阵列的性能非常有效。
