| 摘要 |
PROBLEM TO BE SOLVED: To provide a sound multiplex demodulation circuit capable of making the output from a CUE signal processing circuit more stable. SOLUTION: The circuit has a first band-pass filter 31 for extracting a control channel signal from a sound multiplex signal; an AM demodulating circuit 32 for performing AM demodulation for the channel signal outputted from the filter 31 and taking out a CUE signal; a comparator 34 for converting the CUE signal into a rectangular wave on the basis of an output signal from the circuit 32; and a control channel signal determining circuit 35 provided with determining sections 41, 44 for determining whether the CUE signal is a stereo mode or a bilingual mode on the basis of the CUE signal pulse output from the comparator 34 and the previously set reference frequency, and control sections 47, 48 for changing the frequency of the reference frequency on the basis of the change of the output signals of the determining sections 41, 44. COPYRIGHT: (C)2006,JPO&NCIPI
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