Use of Thermochromic Properties of VO2 for Reconfigurable Frequency Selection

Abstract

The thermochromic nature of vanadium dioxide (VO2) has facilitated many promising applications for reconfigurable frequency selectivity. The phase-changing property of VO2 was used to realise a reconfigurable frequency-selective surface (FSS) capable of manipulating electromagnetic waves for different functionalities. Diffractive optical elements (DOE) are used for diffracting laser beams to form conductive FSS images on the VO2 wafer for frequency selectivity. The dipoles on the VO2 wafer generate a stop band response of 12 dB and 10 dB for unit cells of the single dipole and double dipole at 3.5 GHz, respectively. A 10 GHz FSS array is projected by DOE on the 2-inch VO2 wafer with a filtering effect of 13 dB at 9.5–10.5 GHz. This solution is used to design a radar cross-section (RCS) modification FSS with reflected waves of about 20 dB higher reflectivity in the backscattering direction than in the specular direction.

Modeling Phase Changing Property of VO2 for Reconfigurable Microwave Frequency Selection Applications via Time-Resolved Microwave Conductivity

“…The use of TRMC method as demonstrated in the study highlights the importance of understanding the material properties of VO2 and similar materials for these applications such as chalcogenide glasses (GST) [26], liquid crystals [27], and graphene [28], [29] which exhibit unique electrical and thermal properties that can be used in FSS applications. It is important to note that while these materials may possess comparable attributes to VO2, VO2 has a distinct advantage due to its lower transition temperature, making it more suitable for specific applications [30].…”

“…One of the primary applications of VO2-based FSS is in RF and microwave communication systems, where the FSS can be used as a dynamically reconfigurable filter [25], [30]. The FSS can switch between multiple states to selectively pass or block different frequency bands, making it ideal for use in advanced communication systems that require bandwidthefficient signal processing and frequency management.…”

“…Another application of VO2-based FSS is in the field of smart antenna technology, where the FSS can be used to control the directivity of the antenna. The reconfigurable properties of the VO2-based FSS make it ideal for use in smart antenna systems that require the ability to adapt to changing environments, such as those encountered in mobile communication systems [30]. In addition to communication systems, VO2-based FSS can also be used in sensing applications, such as in the design of reconfigurable microwave sensors [31]- [33].…”

“…The VO2-based FSS in [30] works by utilizing the reversible metal-insulator transition of VO2 thin films. When an incident electromagnetic (EM) wave impinges on the FSS, the wave interacts with the VO2 layer, causing a change in its conductivity.…”

“…In this paper, we report a TRMC study used for FSS applications on VO2 compounds at 30 GHz. In these applications, the VO2 layer is quickly and readily altered between its high and low conductivity states using external switching mechanisms like holographic storage [35] or lasers for optically imprinting reconfigurable patterns [30]. Due to the VO2-based FSS's ability to dynamically adjust to variations in the incident wave's frequency, the transmission response is extremely adaptable and customizable.…”