| 摘要 |
PROBLEM TO BE SOLVED: To set a fixed rate of the prescribed threshold against the level of a changed signal by controlling the relative value between the level of a detected received signal and the prescribed threshold set to a multi-valued comparator. SOLUTION: A threshold setting circuit 11 operates via a timing circuit 12 of a microcomputer, etc., to set the thresholds for a quadruple comparator 8 and an NRZ comparator 9 and also inputs the threshold of the comparator 9 to a local oscillator 10 to output a signal for the feedback control of the intermediate frequency, i.e., for the AFC. Then the circuit 11 detects both maximum and minimum output value of an LPF 7 and outputs the thresholds of both comparators 8 and 9 and the AFC voltage based on the output voltage of the LPF 7. Thus, each threshold can be set at a fixed rate even against the change of the output signal level of the LPF 7. |
