Circularly polarized MIMO patch antenna with high isolation and wideband characteristics for WLAN applications

This paper presents a two-element multiple-input multiple-output (MIMO) antenna with circular polarization diversity. The primary radiating elements are two conventional truncated corner microstrip patches. To enhance the antenna's bandwidth, gain, and port isolation, multiple parasitic elements are employed and they are positioned in different layer with the radiating patches. For further isolation improvement, a method of using defected ground structure is employed. The measured results demonstrate that the proposed antenna possesses wideband operation of 9.3% (5.1-5.6 GHz) with the gain of better than 8.0 dBi. Regarding the MIMO performances, the antenna obtains high isolation, which is from 30 to 63 dB. Besides, the MIMO parameters such as envelope correlation coefficient and diversity gain are found to be good in the scale of diversity standards. Compared to other related works, the proposed design has the best operating BW with 40-dB isolation and stable gain while keeping small element spacing.