Design of a tunable omnidirectional circularly polarized antenna based on VO ₂

Abstract

In this article, a VO 2 -based tunable omnidirectional circularly polarized (CP) antenna is designed. The proposed antenna combines copper and metamaterial VO 2 . By utilizing the characteristics of insulator-metal phase transition of VO 2 , 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 VO 2 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 VO 2 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 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 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. K E Y W O R D S omnidirectional circular polarization, phase transition, tunable antenna, VO 2

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