FREQUENCY MODULATED SIGNAL DEMODULATOR

PURPOSE:To provide modulation output convenient for a digital processing by defining pulse density modulation signals as demodulation output from frequency modulated input signals. CONSTITUTION:FM signals are inputted to one of the terminals of a frequency converter 13. The local oscillation signals of a frequency equal to the carrier wave frequency of the FM signals are supplied from a frequency modulation circuit 30 to the other terminal of the converter 13. Phase signals for which the input FM signals are converted into base band signals appear in the output of the converter 13 and are inputted to an integrator 11. When the output level of the integrator 11 reaches a level set in a comparator 22, the output is transmitted from the comparator 22. The output of the comparator 22 is inputted to a delay circuit 23 and after set delay time, the local oscillation frequency of the circuit 30 is substantially shifted. Thus, the output level of the integrator 11 is lowered and the output of the comparator 22 is transmitted only by the delay time and stopped. Thus, compression pulses are transmitted corresponding to the frequency displacement of the input signals and the FM signals are converted to the pulse density modulation(PDM) signals.