A Low-Profile, Closely-Spaced 1 ×4 MIMO Array with Low Mutual Coupling

A single-layered, 1×4 linear array antenna, consisting of closely-spaced microstrip patches, is presented and investigated in this paper. The mutual coupling is reduced by utilizing a decoupling structure integrated within the array to generate a 180-degree phase reversal with the interfering signal. Compared to conventional probe-fed coupled arrays, the proposed antenna design realized a significant improvement in isolation levels between the elements, increasing from ∼4 dB to over 19 dB. More importantly, the proposed linear array is compact with a center-to-center element spacing of ∼0.26λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> and an edge-to-edge spacing of only about 0.016λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf>.