Function Reconfigurable RF Microstrip Filter Based on VO2 Phase Transition

The function reconfigurable radio frequency (RF) microstrip filter based on vanadium dioxide (VO
2
) phase transition is realized by cascading the low-pass unit and the high-pass unit, wherein two units are respectively composed of defective ground structure (DSG) units and MIM (Metal-Insulator-Metal) capacitors loaded by λ/4 transmission-line elements. The function reconfigurability of the device is achieved by local sputtering of metal-insulator transition material VO
2
film in the low-pass unit and high-pass unit. The filter has four functions: low pass, high pass, band pass and all pass. For low-pass mode, the cut-off frequency is 3.8 GHz. The cut-off frequency corresponding to the high-pass mode is 1.5 GHz, and in-band loss is less than 1.5 dB. For band-pass mode, the center frequency is 2.65 GHz, and the fractional bandwidth is 86.8% (1.5 GHz – 3.8 GHz), and the minimum insertion loss in band is 1.2 dB. The minimum insertion loss in all-pass mode is 1 dB.