A Wideband Sectoral Quasi-Yagi MIMO Antenna System With Multibeam Elements

A novel printed Quasi-Yagi based multiple-input-multiple-output (MIMO) antenna system is proposed in a triangular configuration targeting sectors of 120°. A novel and simple proof of concept for splitting the single main endfire directional beam of a typical Yagi-Uda antenna into multiple beams is proposed by carefully exciting the 3.5 λ_g resonance mode of the loop antenna. It has been shown that by proper excitation of the loop resonance modes, multiple beams can be achieved from a single Yagi element to suit the application of interest. The proposed MIMO antenna system has a measured impedance bandwidth of 16.2% targeting the 5.8 WLAN band. The board diameter of the antenna system is only 120 mm, making it suitable for small size wireless access points. A high front-to-back ratio (FBR) of 14 dB and a gain of around 6 dBi is achieved by carefully optimizing the multiple parasitic director elements in the location of the maximum energy densities. The proposed MIMO antenna system has high port isolation of 28 dB, very low held envelope correlation coefficient value of 0.012, and high total radiation efficiency of greater than 90% in the band of operation.