Thermally Tunable Frequency‐Selective Surface Based on VO2 Thin Film

An approach to a design of tunable frequency‐selective surfaces (FSSs) for radio frequency (RF) domain based on vanadium dioxide (VO2) thin films is proposed. As an example, a thermally tunable annular slot FSS with integrated VO2 switchable elements for C‐band of the RF domain is described. Switching is based on abrupt change of conductivity of the VO2 film, initiated by heating from room temperature to a temperature of the metal–insulator phase transition of 44 °C. A tuning mechanism of the FSS allows continuous change of frequency response from room temperature state, where the FSS acts as a band‐pass filter, to high‐temperature state, where the FSS works as a reflector. In the process of tuning, a reflection coefficient at a central frequency of the filter can be increased from −26.4 dB up to −2.2 dB. The proposed approach can be used for the design of tunable FSS for applications that allow thermal control of the frequency response. Vanadium dioxide film is used as active element in a band‐pass filter, based on a frequency‐selective surface. Frequency response of the filter can be tuned using heating: at 25 °C filter is “open” and has reflection of −26.4 dB at center frequency of 8 GHz; at 80 °C filter is “closed” and has reflection of −2 dB in 2–18 GHz.