| 摘要 |
PURPOSE:To simplify a circuit constitution, to facilitate a circuit integration and to eliminate the secular change of the characteristic by switching the output of a digital BPF and a digital LPF so as to extract a stereo demodulation signal. CONSTITUTION:A pilot signal is extracted from an input multiplex signal by a digital BPF2 and fed to a digital differentiation device 3 and a delay 4. Each output is inputted to the EX-OR gate 6a of a gate circuit 6. On the other hand, a digital LPF5 extracts a composite signal from an input signal and gives the signal to the AND gates 6b, 6c of the circuit 6. The output of the gate 6a and a NOT gate 6d in the circuit 6 has the double frequency of that of the pilot signal and their polarity is opposite to each other. When the signal of the gate 6a is at logic 1, the output of the LPF5 is obtained from the gate 6b and when the signal of the gate 6d is logic 1, the output of the LPF5 is obtained from the gate 6c. Thus, the stereo demodulation signal is outputted.
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