Neutralization‐line‐based decoupling for miniaturized MIMO antenna array

Abstract 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 × 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.