Circularly Polarized Reconfigurable MIMO Antenna for WLAN Applications

This paper presents a simple design of a two-element antenna with circularly polarized (CP) reconfigurability for multiple-input multiple-output wireless local-area network (WLAN) applications. A MIMO element consists of a reconfigurable feeding network, a CP source, and a 2 × 2 unit-cell metasurface (MS). By controlling the ON/OFF state of PIN diodes, the proposed MIMO system can operate in either right-hand CP (RHCP) or left-hand CP (LHCP) for all ports, or either RHCP or LHCP for each port. For all operating modes, the proposed antenna exhibits good performance with a matching performance of less than -10 dB, an axial ratio of lower than 3 dB, as well as an inter-port isolation of better than 24 dB at 2.45 GHz. Additionally, the MIMO diversity performance is also satisfied by the proposed antenna. Compared to related works, the proposed antenna has advantages of high gain and compact size, as well as a simple switching mechanism with a small number of PIN diodes.