Millimeter‐wave frequency reconfigurable antenna using simple VO ₂ ‐based paired metasurface

Abstract

In this article, a millimeter-wave frequency-reconfigurable metasurface antenna by electrically controlling vanadium dioxide (VO 2 ) is proposed and studied. As a phase change material, VO 2 is an insulator at room temperature but can turn into high conductivity metallic state when activated by continuous direct current (DC) voltage. By integrating the VO 2 film between two simple rectangle metasurface cells, a frequency-reconfigurable paired metasurface structure (FRPMS) is achieved. The FRPMS can be considered as one unit when VO 2 film is activated to metallic state while as two independent cells when VO 2 film is in insulating state. In this way, the FRPMS can operate, respectively at 28 and 38 GHz with independent tunability. Moreover, a coplanar and staggered DC bias circuit with little effect on radiation is designed to switch the operating modes of VO 2 easily. The antenna is fed by a stepped waveguide with ridges through a loop slot, which is suitable for dual-band feeding with large frequency ratio. One prototype is fabricated and measured for demonstration. When the VO 2 film is in metallic state, the measured working band covers from 28.5 to 29.6 GHz with the maximum gain of about 7.1 dBi. When cooled down to insulating state, the antenna can work in a higher band from 36.7 to 38.3 GHz with the maximum gain of about 7.9 dBi. Due to the advantages of simple structure, high gain and easy tuning, the antenna can be expected to use in mmW wireless communication.

A Reflective Metalens With Tunable Focal Length for Millimeter Waves

“…Such a buffer is composed of a bottom VO2 layer in contact with copper (with a thickness of h1 = 0.08 mm) separated from a top VO2 layer (with a thickness of h2 = 0.12 mm) by means of a high thermal and electrical insulating layer of Polyvinyl chloride (PVC) foam (see parameters value in Table I). Both VO2 layers are much thicker than the skin depth of VO2 in the millimeter wave in a range of 30 -300 GHz, which is in the interval 14.81-20.54 μm based on the resistivity data (2.6×10 -5 -5×10 -4 Ω m [42], [43]). The bottom and top VO2 layer temperatures are independently controlled by an electric current flowing either through the metal at the ground layer or through the thin ITO layer.…”

Wavefront Control of Millimeter Waves With a VO2-Based Reconfigurable Meta-Reflectarray

“…The structure switches the angle of the reflected wave when the operating temperature increases above the critical temperature of the VO 2 phase transition (T C = 68 • C). The substrate is made of copper (Cu), and the thickness of the VO 2 ''skin'' layer is 50 µm, larger than the penetration depth of the metallic state of VO 2 in the millimeter-wave range , which is about 15 µm based on the resistivity data (2.6 × 10 −5 -5 × 10 −4 .m [30], [31]). When VO 2 is in the insulator state, it has a relative permittivity of 9.…”