| 摘要 |
PURPOSE:To enable to identify a stereo broadcast and a duplex audio signal only with an electronic circuit, by processing an output mixing a signal dividing the carrier of a control signal with an original AM signal by a low pass filter and a phase comparator. CONSTITUTION:A composite signal input is given to a selection amplifier 1 and only the AM signal in a given frequency being the identification signal is amplified. This amplified signal is branched into two: one is inputted to a frequency mixer 7, as it is and another is inputted to the frequency mixer 7 via a limiter 5 and a frequency-divider 6. The output of the mixer 7 is applied to the 1st low pass filter 8 to pick up the component difference between the signal frequency-divided with the 1st low pass filter 8 and the AM signal. After giving the output to the 2nd low pass filter 9, the phase of both the low pass filters 8, 9 is compared at a phase comparator 10. Thus, identification is made between stereo and duplex audio broadcast through the output state of the phase comparator 10. |
