Millimeter-Wave Frequency-Reconfigurable Metasurface Antenna Based on Vanadium Dioxide Films

A novel frequency-reconfigurable method using vanadium dioxide (VO
₂
) is proposed. VO
₂
is one kind of phase change material (PCM) which can be electrically switched between the states of insulator and metal. By integrating the VO
₂
film into a uniplanar compact photonic-bandgap (UC-PBG) structure, a frequency-reconfigurable metasurface (FRMS) structure with frequency ratio of 1.78 is constructed accordingly. Moreover, the active VO
₂
-based FRMS is used as radiation element to design a high-gain millimeter-wave frequency-reconfigurable metasurface antenna (FRMSA), which is excited by a stepped waveguide through two slots of different lengths. In order to electrically activate the VO
₂
films of the antenna, a simple dc bias co-planarly localized with the FRMS is well designed. Benefiting from the convenient connection of the UC-PBG, only simple connection with two sides of the antenna is required for the dc bias, thus causing little impact on radiation due to far from the radiation region. One prototype is fabricated and measured for demonstration. When the VO
₂
film is activated to insulating state, the measured results show that the proposed FRMSA can operate in 23.25-24.3 GHz with the maximum gain of ~8.7 dBi, while it can work in 37-39.8 GHz with a peak gain of ~7.6 dBi when driven to metallic state. The ratio of two frequencies is about 1:1.61. Compared with other reported VO
₂
-based antennas, the proposed antenna exhibits a larger frequency ratio and higher gain in millimeter-wave bands.