Use of Thermochromic Properties of VO₂ for Reconfigurable Frequency Selection

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.