Circularly Polarized MIMO Antenna Utilizing Parasitic Elements for Simultaneous Improvements in Isolation, Bandwidth and Gain

Abstract A circularly polarized (CP) multiple-input multiple-output (MIMO) antenna with wideband operation and high isolation characteristics is presented. The proposed antenna is first designed with two diagonal slotted square patches and then, four parasitic elements are utilized to significantly improve the antenna performances. Notably, besides enhancing the operating bandwidth and the gain radiation, the parasitic elements also contribute to reduce the mutual coupling between the MIMO elements. The measurements demonstrate that the proposed two-element MIMO antenna with edge-to-edge spacing of 0.09λo and profile of 0.05λo at the center operating frequency has operating bandwidth of 12.8% (5.1–5.8 GHz) and high isolation of better than 22 dB. The antenna also achieves high gain of better than 7.5 dBic and good diversity performances. Compared to other CP MIMO antennas reported in literature, our design possesses several exclusive features including wideband operation, high gain, very small edge-to-edge element spacing as well as low-profile configuration.