A demodulator for processing a PWM (pulse width modulation) signal
includes a variable capacitor, a charging unit, a discharging unit, and a
tuner. The charging and discharging units charge or discharge the
variable capacitor depending on the PWM signal. The tuner determines a
capacitance of the variable capacitor and a discharge current of the
discharging unit for proper operation of the demodulator in various RF
environments.