| 摘要 |
PURPOSE:To reduce a response time of level control. CONSTITUTION:A subtractor circuit 3 calculates a difference between a reference level and a level of a burst signal detected by a level detection circuit 2 and inputted to a demodulator 1 and outputs a signal C2. A filter circuit 4 eliminates an undesired harmonic component from the signal C2 and outputs a control signal C3. A reception discrimination circuit 8 receives a signal C4 representing the detection of the burst signal and a unique word detection signal C6, decides the time when the burst signal is surely received, and outputs a signal C7. An average value arithmetic operation circuit 11 calculates a mean value between a maximum and a minimum value of the control signal C3 and outputs a mean value signal C8. Upon the receipt of the signal C7, a changeover circuit 12 selects the control signal C3 and the circuit 12 selects the mean value signal C8 when the signal C7 is not received, and outputs the selected signal to a variable attenuator 13 as a control signal C9. The variable attenuator 13 changes the attenuation of the burst signal Si depending on the control signal C9. |
