| 摘要 |
PURPOSE:To bring data fed to an input terminal of a demodulation circuit to a prescribed level by providing an amplifier circuit whose amplification factor is variable to the pre-stage of a band pass filter and using an output of the band pass filter to control the amplification factor of the amplifier circuit. CONSTITUTION:The amplifier circuit 4 whose amplification factor is variable is provided to the input side of the band pass filter 1. Then the data subjected to carrier modulation is amplified by the circuit 4 and the result is fed to an amplifier circuit 2 via the filter 1. The output of the circuit 2 is fed to a demodulation circuit 3 and also to a control circuit 5, where the level is detected. The amplification factor of the circuit 4 is controlled immediately based on the result of detection to control the output level of the circuit 2 to a predetermined constant level. |
