| 摘要 |
PROBLEM TO BE SOLVED: To improve the detection precision of an ADC-less type digital FM detection circuit. SOLUTION: An FM modulation signal is converted into a pulse signal in which a time domain including a zero cross point is made to be an H-level. A cycle counter circuit 11 utilizes the pulse signal to detect the interval of zero cross points of the FM modulation signal. An interpolation circuit 12 performs linear interpolation on count values representing zero cross point intervals sequentially obtained by the cycle counter circuit 11. A correction circuit 13 calculates a phase difference equivalent time from the linearly interpolated count values and further compensates for the non-linearity of the phase difference equivalent time with respect to a frequency shift amount in frequency modulation. A digital filter 14 filters the output of the correction circuit 13. COPYRIGHT: (C)2008,JPO&INPIT
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