| 摘要 |
PURPOSE:To prevent the bit accuracy from being degraded by adopting the system that the automatic gain control is applied at a base band and the result is fed back to the pass band so as to attain high speed and stable operation. CONSTITUTION:A reception signal is divided into two; one is inputted to a main reception circuit 50 via a multiplier 33 and the other is inputted to an automatic gain control loop after the band is decreased into the base band by a demodulator 20 and a low pass filter 21. In giving a gain to the reception signal in the automatic gain control loop by a multiplier 22, the power is averaged by a mean power calculator 51, the mean power and a reference are subject to subtraction by a subtractor 25, the difference is integrated by an integration circuit 52, the result is inputted to a limiter 29 and the output of the limiter 29 is used as a new gain and given to the multiplier 22, then the output of the mean power calculator 51 is a constant level. The output of the limiter 29 obtained in this case is used as a new gain and inputted to a multiplier 33, then the input level of the main reception circuit 50 is made nearly constant.
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