| 摘要 |
PURPOSE:To control a 2-input control variable attenuator with one input control voltage by controlling a reception signal to be a prescribed level with two control signals to a prescribed relation in response to an amplitude frequency characteristic of the reception signal. CONSTITUTION:An electric signal converted by an APD 11 is inputted to a variable attenuator (ATT) 14 via a preamplifier 13. The ATT 14 uses control voltages V1, V2 to adjust the attenuation of an electric signal and to smooth the amplitude frequency characteristic and outputs the result to an FDM output terminal 16 and an amplitude detection circuit 17 via a main amplifier 15. In order to control the gain of the ATT 14, the circuit 17 outputs a control voltage V1 to the ATT 14 and an inverting amplifier 18 based on a peak value of a signal output. The amplifier 18 compares the input control voltage V1 with a bias VB to output a prescribed control voltage V2 to the ATT 14. Since the receiver is subjected to automatic gain control by two kinds of the gain control by a current multiple factor of the APD 11 and the ATT 14, the output level at the terminal 16 is made stable. |
