| 摘要 |
PURPOSE:To enable circuit integration of detection circuit, by making unnecessary the reed filter, by forming the reference signal, detecting the phase difference with the control signal and discriminating the control channel signal. CONSTITUTION:The control channel signal consists of the control signal and the control sub-carrier signal. The control signal is introduced from the AM detector 2 as the detection output, and the control sub-carrier signal is made for waveform processing at the wave shape circuit 11, frequency division 12 is made to a given frequency, and both are fed to the phase comparator 13. The output of the comparator 13 is inputted to LPF 14, it is converted into potential difference and inputted to the voltage comparator 15, and the first and second control signals are detected with the difference of voltages. The comparator 13 detects the phase difference between the reference signal in frequency division 12 and the first and second control signals, and it is introduced as the error voltage via LPF 14. The signal selection circuit B selects and drives the stereo broadcast, double audio broadcast and monaural broadcast based on the control signal detected with the detection circuit A, through the buffer circuits 16, 17. |
