Neutralization-line-based decoupling for miniaturized MIMO antenna array

In this paper, a miniaturized multiple-input, and multiple-output (MIMO) antenna array is proposed based on quarter-mode substrate-integrated waveguide. The decoupling structure of composite neutralization lines (NLs) is used to improve the isolation of the MIMO antenna array. Each NL comprises a simple metal strip attached to each of the two antenna radiators to create an extra coupling path that opposes the primitive antenna coupling to reduce mutual coupling. Eventually, the 2 x 2 MIMO antenna array is fabricated and implemented to verify the design. The measured impedance bandwidth of S-11 less than -10 dB ranges from 3.48 to 3.52 GHz, and the peak gain of the element is 4.87 dBi, the mutual coupling levels between the orthogonal and the parallel antenna elements are -19.2, -22.6, and -17.9 dB, respectively, making it a suitable candidate for MIMO systems.