Mutual Coupling Reduction for Dual-Band MIMO Antenna via Artificial Transmission Line

Abstract

A dual-band decoupling strategy via artificial transmission line (TL) for closely spaced two-element multiple-input multiple-output (MIMO) antenna is proposed, which consists of two composite right-/left- handed TLs for dual-band phase shifting and a cross-shaped TL for suscep- tance elimination to counteract the real and imaginary part of the mutual coupling coefficient S21 at dual frequency bands, respectively. The decou- pling principle and detailed design process of the dual-band decoupling scheme are presented. To validate the dual-band decoupling technique, a closely spaced dual-band MIMO antenna for 5G (sub-6G frequency band) utilization is designed, fabricated, and tested. The experimental results agree well with the simulation ones. A dual-band of 3.40 GHz-3.59 GHz and 4.79 GHz-4.99 GHz (S11&S22 < -10 dB, S12&S21 < -20 dB) has been achieved, and the mutual coupling coefficient S21 is significantly re- duced 21 dB and 16.1 dB at 3.5 GHz and 4.9 GHz, respectively. In addition, the proposed dual-band decoupling scheme is antenna independent, and it is very suitable for other tightly coupled dual-band MIMO antennas.