Frequency reconfigurable absorber using a uniform vanadium dioxide film-based substrate thickness modulator

Abstract Vanadium dioxide (VO 2 ) is a phase change material that manifests as a reversible insulator-to-metal transition (IMT). Significant changes in the electrical and optical properties of VO 2 during the phase transition have prompted substantial interest in switchable and reconfigurable microwave devices. Since reflection/transmission of electromagnetic waves through a VO 2 film can be controlled by modulating its electrical properties thermally, it can potentially be used to regulate the RF signal propagation path by modulating the effective substrate thickness. As a proof of concept, we design and experimentally demonstrate a Salisbury screen-based reconfigurable absorber using a uniform VO 2 film-based substrate thickness modulator. The proposed absorber operates partially in the C and X-bands (5.4–9.3 GHz) with the secondary absorption band at 19.83–23.5 GHz in the insulating state of VO 2 . In the metallic state, the operating band shifts to 11.89–20.15 GHz (Ku- and partially K-bands). The absorber also shows a wide range of reflection magnitude tuning in the operating band due to the change in the electrical properties of VO 2 during IMT. We also present a transmission line-based equivalent circuit model to validate the measurement results and to understand the temperature-dependent performance of the absorber. Uniform VO 2 film-based thermally actuated substrate thickness modulator offers a low-cost and easier integration method for system miniaturization by enabling multi-band functionality.