| 摘要 |
PURPOSE:To produce an accurate digital data by applying an output of a detecting means extracting an envelope component of an input data and an output of a circuit converting the former output into a DC voltage to a level comparator so as to change over a feedback loop characteristic by the output of the level comparator. CONSTITUTION:An envelope signal outputted from a detecting circuit 19 is applied to one input terminal of the level comparator 20 as it is. This signal is divided by a voltage dividing and integration circuit 21 and integrated and converted into a DC voltage as shown in a dotted chain line and applied to the other input terminal of the comparator 20. The comparator 20 outputs an L level when the level at a point A is higher than the level at a point B and outputs an H level when lower. When a rapid level fluctuation is caused in an RF signal 11 and an output level of the detecting circuit 19 is lower than an output level of the voltage dividing integration circuit 21, the comparator outputs the H level. The H level signal is applied to a base of a transistor(TR)Q2 via a resistor R8 so as to conduct the TRQ2. Then, the resistance value of an R3 of an inverse amplifier circuit 18 is lowered and the gain is varied. Thus, the DC level of the RF signal is changed and the digital data always accurate is produced. |
