Design of a tunable omnidirectional circularly polarized antenna based on VO2

In this article, a VO2-based tunable omnidirectional circularly polarized (CP) antenna is designed. The proposed antenna combines copper and metamaterial VO2. By utilizing the characteristics of insulator-metal phase transition of VO2, we can change the length of the resonant branches to achieve tunable working bandwidth. The proposed antenna is composed of a modified floor loaded with VO2 and copper resonant branches, a top patch with slits, and 14 shorting vias connecting the top path and bottom floor. Different from the traditional electric controlled antennas, antennas based on metamaterial VO2 do not need to design complicated circuit structures and can be easily tailored by the external temperature (T). The simulated results illustrate that when T >= 68 degrees C (state I), the proposed antenna has a 10-dB impedance bandwidth of 15.9% (2.09-2.45 GHz), and a 3-dB axial ratio (AR) bandwidth of 23.4% (2.04-2.58 GHz). When T < 68 degrees C (state II), it has a bandwidth of 6.5% (2.38-2.54 GHz) with S-11 below -10 dB, and a bandwidth of 19.9% (2.39-2.92 GHz) with AR below 3 dB.