| 摘要 |
PURPOSE:To decrease the circuit scale by using an AGC amplifier and applying gain control by an equalized output of base band normally and with an output of the IF band at a fault. CONSTITUTION:A reception signal of the IF band is inputted to a synchronous detector 13 via a variable gain amplifier 12, detected synchronously and waveform distortion is equalized by a transversal equalizer 23. An error signal is identified from an output of the equalizer 23 by identifiers 51, 52 and the signal is inputted to a tap coefficient control circuit 54. The circuit 54 controls each coefficient other than the main tap of the equalizer 23 and transmits a control signal to a base band AGC circuit 55. The circuit 55 forms a control signal of the amplifier 12 by the identification signal and the error signal from the identifier 52. The gain to the amplifier 12 is controlled by the AGC control signal from the circuit 55 normally. When the error rate of the identifier 51 is high, an identification error alarm unit 56 raises an alarm, which changes over a switch 58 via a switch 59 and the control signal of an AGC control circuit 11 obtained from the output of the amplifier 12 controls the gain of the amplifier 12 to obtain a stable operation. |
