| 摘要 |
PURPOSE:To eliminate erroneous action in loop response and phase jumping due to noise, etc. by setting the maximum delay amount of the group delay characteristic of a PLL for demodulation to a specific value. CONSTITUTION:The titled demodulator 15 is constituted of the PLL consisting of a phase detector 9, a VCO 11, and a loop filter 10. By setting the characteristic of this filter 10 at the center frequency of an FM audio signal, and selecting the open-loop characteristic so as to satisfy a necessary condition, the maximum delay amount of the group delay characteristic of the PLL can be set at a specific value, and the loop response characteristic can be set within one period of the carrier frequency of an FM signal. As a result, an erroneous action in loop response and a phase jumping due to noise, etc. can be eliminated, hence the extent of occurrence of distortion due to detection can be reduced. |
