Note: Phase-locked loop with a voltage controlled oscillator based on a liquid crystal cell as variable capacitance.
A 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.
Departamento de Tecnología Electrónica, Universidad Carlos III, Avenida de la Universidad 30, Leganés E28911, Madrid, Spain. cmarcos@ing.uc3m.es
Carlos
C
Marcos
José M
JM
Sánchez-Pena
Juan C
JC
Torres
Isabel
I
Pérez
Virginia
V
Urruchi