A Tunable Omnidirectional Circularly Polarized Antenna Based On VO2

In this paper, a tunable omnidirectional circularly polarized (CP) antenna based on the vanadium dioxide (VO₂) is proposed. The operating bandwidth of such an antenna can be controlled by changing the external temperature (T), which is achieved by the phase transition of VO₂. The proposed antenna is based on a loop antenna-dipole model, which includes a modified floor loaded with VO2 and metal (Cu) resonant units, 14 shorting vias, and a top patch with slits. The simulated results show that when T = 80 °C (State I), the 10-dB impedance bandwidth is 15.9% (2.09-2.45 GHz), and the 3-dB axial ratio (AR) bandwidth is 23.4% (2.04-2.58 GHz). When T = 50 °C (State II), the 10-dB impedance bandwidth is 6.5% (2.38-2.54 GHz), and the 3-dB AR bandwidth is 19.9% (2.39-2.92 GHz).