Electrically tunable liquid crystal coplanar waveguide stepped-impedance resonator

A tunable stepped-impedance resonator using liquid crystal is demonstrated. Two resonant frequencies at 3.367 and 7.198 GHz are realized and can be continuously tuned by external applied voltages. Continuous tunable ranges of 52 and 210 MHz have been achieved at a particularly low driving voltage of 14 V, which shows good agreement with the simulation results. The voltage-induced hysteresis phenomenon is also investigated. This device also has a low insertion loss of −2.9 and −4 dB for the two resonant frequencies and the return losses are less than −21.5 dB. This work provides a new protocol to realize a tunable frequency for communication systems.