Tunable substrate integrated waveguide bandpass filter using liquid crystal material

A microwave tunable substrate integrated waveguide bandpass filter using nematic liquid crystals is researched in this paper combined with the complementary split-ring resonators. The nematic liquid crystal is used to control the corresponding working frequency, with its permittivity changing caused by deflection angle of the liquid crystal molecules. And its deflection angle changing is controlled by the bias voltage. The simulation results show that the permittivity of liquid crystal changes from 2.79 to 3.56 to make the passband frequency achieve 490 MHz frequency offset.