Tunable liquid-crystal millimeter-wave bandpass filter using periodical structure

For the first time, a tunable liquid crystal (LC) bandpass filter using a microstrip periodical structure for applications at millimeter-waves is presented. In the LC default state, it operates at 49 GHz with about 20% fractional bandwidth (9 GHz). The filter tunability range is 3.2 GHz over bias voltages 0 to 10 V and its insertion loss is about 4.7 dB. Dimensions of the filter can be scaled to increase its operating frequency to 77 GHz and hence, is a promising component for 60 GHz systems.