Polarization-Reconfigurable Compact Wideband Slot Antenna by Using Liquid Metal

In this letter, a compact, low-profile, and wideband slot antenna with polarization reconfigurability is presented by using liquid metal (LM). A small rectangular ring placed below the microstrip line of a symmetric coplanar waveguide (CPW) is used for bandwidth enhancement. Three horizontal currents performed by LM injection are inserted for wide circular polarized excitation. The channel realized by three-dimensional printed technique is loaded on the antenna to provide reconfiguration conditions. By injecting the LM into the left or right channels, the radiation of right-hand circular polarization or left-hand circular polarization is achieved. While when the two channels are empty or both LM injections, the linear polarization (LP) radiations at two operating frequency bands are obtained. A prototype was fabricated and measured. Measurements show that the proposed antenna exhibits a wide impedance bandwidth (IBW) of 67% and an overlapped axial ratio bandwidth of 39.2% for the CP modes. While in the LP states, the overall reconfigurable IBW is 39.7%. Besides, the size of the antenna is 0.30 λ ₀ × 0.32 λ ₀ × 0.03 λ ₀ , which is quite compact and low-profile.