FREQUENCY DEMODULATOR HAVING FUNCTION OF AUTOMATICALLY ADJUSTING RESONANT FREQUENCY AND PHASE SHIFTER EMBEDDED IN INTEGRATED CIRCUIT

摘要

PURPOSE: A frequency demodulator having a function of automatically adjusting a resonant frequency and phase shifter embedded in an integrated circuit is provided to automatically compensate a deviation of the resonant frequency due to an element Deterioration and an exterior temperature change. CONSTITUTION: A phase shifter(44) inputs a message signal frequency modulated via a communication channel from an exterior transmission side. The phase shifter(44) shifts the phase in proportion to an instant frequency of the inputted signal in reference to an internal resonant frequency and changes the resonant frequency according to the a predetermined control voltage. A phase comparer(42) compares the phase of the shifted signal and the phase of the message signal and outputs the result. A low pass filter(46) filters a low part of the signal from the phase comparer(42) and restores the original message signal. A switch(SW40) switches in response to a switching control signal and applies a direct current of the restored message signal as the control voltage.