Broadband polarisation reconfigurable antenna based on crossed dipole and parasitic elements for LTE/sub-6 GHz 5G and WLAN applications

Broadband polarisation reconfigurable antenna based on crossed dipole and parasitic elements is proposed in this study, which can switch among three polarisation modes, i.e. linear polarisation, left-hand circular polarisation and right-hand circular polarisation. The proposed antenna consists of two crossed dipoles fed by a 3/4 square ring, two microstrip feeding elements etched at the centre of the upper and lower sides of the dielectric substrate, and three sets of microstrip parasitic elements helping broaden the axial-ratio (AR) bandwidth. Four PIN diodes are embedded between each crossed dipole and the microstrip feeding element, which enable the polarisation reconfigurability. The working principle of polarisation reconfigurability is analysed in detail. The measured results show that the proposed antenna has a -10 dB overlapped impedance bandwidth of 63.5% (2.04-3.94 GHz) and the 3 dB overlapped AR bandwidth is about 54.5% (2.4-4.2 GHz), resulting in a wide overall bandwidth of 48.6% (2.40-3.94 GHz). Besides, the measured peak gain of this antenna reaches up to 8.5 dBi. The proposed antenna can be a good candidate for 2.45 GHz WiFi, LTE 4G, and sub-6 GHz 5G applications.