Pattern diversity and defected ground structure for decoupling planar Yagi MIMO antenna

Abstract

In this paper, a novel decoupling technique both in pattern diversity (PD) and defected ground structure (DGS) is proposed for planar Yagi multiple-input multiple-output (MIMO) antenna arrays. The proposed planar Yagi antenna (PYA) is composed of two symmetrical printed dipoles and U-/V-shape directors. Based on the redirection effect of the directors, the desired pattern diversity and isolation improvement are achieved. DGS is added outside the excitation dipoles for closely packed elements, which achieves decoupling and better impedance matching. Through the whole frequency bandwidth (5.5–6.1 GHz), the mutual coupling between two-ports Yagi antenna elements is lower than −25 dB, and the stable gain is above 8 dBi with the variation of 1 dBi. Moreover, the validation of the proposed decoupling method is carried out on three and four-ports MIMO antenna arrays. By combining two kinds of directors and asymmetric DGS, the imbalance problem of the multi-port antennas is solved. The simulated and measured results validate the effectiveness of PD-DGS in MIMO directional antenna systems with high isolation and gain for 5.8 GHz WLAN application.