| 摘要 |
PURPOSE:To obtain stable control by preventing deterioration in system noise temperature in an optical transmitter so as to prevent chattering of a step attenuator used to eliminate restriction on a reception system dynamic range. CONSTITUTION:Optical transmitters 4, 5 sending a signal for an IF band are provided to the receiver and a step attenuator 3 is connected to a pre-stage of the optical transmitter 4 and the step attenuator 3 is switched by a switching control signal obtained by comparing an AGC voltage corresponding to an input signal level with a reference voltage at a comparator 8, and two different voltages are set for reference voltages of the comparator 8 and a hysteresis is provided to the comparison output to prevent chattering with respect to an input signal in the vicinity of the control level. |
