Microwave tunable split ring resonator bandpass filter using nematic liquid crystal materials

In order to improve frequency selectivity of microwave devices and raise the frequency spectrum efficiency effectively, a new kind of microwave continuously tunable Split Ring Resonator (SRR) band-pass filter, using the field-induced nematic liquid crystal, is presented in this paper. Based on the fundamental theory of the electro-optic effect of liquid crystal, applying the bias voltage on liquid crystal can change its permittivity to mainly realize passband frequency shift at microwave band. The frequency characteristics of the filter are analysed. The proposed parameter extraction on the base of the frequency characteristics can easily analyze distributing parameter circuit about this liquid crystal filter. The simulation results shows that this liquid crystal tuning filter achieves 750 MHz offset obviously. Compared with the other tuning techniques, the liquid crystal tuning technology has many advantages, such as continuously tuning, miniaturization, low tuning voltage, etc. Thus, it shows great potentials for modern communication applications.