Patent ID: 7796710

Claim:
A digital demodulator to demodulate a frequency signal modulated by phase shift keying and having a specific carrier frequency, the digital demodulator comprising: an input port to which an input signal is supplied; a resonator having a resonance frequency same as a carrier frequency to store a charge corresponding to a digital signal modulated by phase shift keying and including a high-frequency component; an input switch connected between an input node of the resonator and the input port to allow electrical disconnection between the input signal and the resonator; a capacitor to store the charge including the high-frequency component from the resonator; an amplifier including an input node and an output node between which the capacitor is connected to convert a stored charge of the capacitor into a voltage signal; a plurality of switches connected between the resonator and the amplifier to switch between a sampling mode for accumulating the charge in the resonator and a readout mode for transferring the charge of the resonator to the capacitor; and a controller to output a control signal for switching between the sampling mode and the readout mode at different timings to the input switch and the switches and to output the voltage signal corresponding to the stored charge of the capacitor from the output node of the amplifier in the readout mode.