Note: Phase-locked loop with a voltage controlled oscillator based on a liquid crystal cell as variable capacitance

Copyright 2011 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Review of Scientific Instruments (2011), 82 (12). and may be found at http://dx.doi.org/10.1063/1.3666865A phase-locked loop is demonstrated using a twisted-nematic liquid crystal cell as a capacitance that can be varied as a function of applied voltage. The system is formed by a phase detector, a low-pass filter, as well as a voltage controlled oscillator including such variable capacitance. A theoretical study is proposed and experimentally validated. Capture and locked ranges of hundreds of kHz have been obtained for the configuration used in this circuit. An application as frequency demodulator using a practical implementation of this circuit has been demonstrated.This work was supported in part by the Spanish Ministry of Science and Technology (TEC2009-13991-C02-01) and the Comunidad de Madrid (FACTOTEM2-CM, REF.S2009/ESP-1781).Publicad