| 摘要 |
PURPOSE:To protect a large electric power transmitter, used at a satellite communication ground station, etc., from being overexcited, by providing an open-loop- level controlling system consisting of a signal branching circuit, signal level detector, control circuit, and variable attenuator. CONSTITUTION:Output signal (b) is branched 6 and a signal whose level has been detected 8 is fed back to variable attenuator 1 via control circuit. Input signal (a), after attenuated at 1 and amplified at 3, is branched at 5 and its signal level is detected at 7 to send the detection signal to control circuit 9. This circuit 9, when the level of the input detection signal is less than a certain criterion level, judges that no signal arrives, thereby setting the attenuation of attenuator 2 properly. When the level of the detection signal increases above the criterion level, the attenuation of attenuator 2 is varied in a prescribed time, equivalent to the time width of overexcitement occurring when open-loop-level controlling system 11 is not in operation, so that the overexcitement is cancelled from the proper value to a minimum proper value in the stationary operation state. |
