| 摘要 |
<p>PURPOSE:To prevent the abnormal operation of a second power amplifier tube by providing a directional coupler, a detector and a level comparator between a first power amplifier tube and the second power tube and monitoring the exciting driving power level of the second power amplifier tube. CONSTITUTION:A directional coupler 8, a detector 9, a level comparator 10 and an AND circuit 1 are provided between first and second power amplifier tubes 2 and 3, respectively. Part of the output power of the first power amplifier tube 2 is inputted to the detector 9 via the directional coupler 8 to detect transmitting waves. The output of the detector 9 is compared with a reference level in the level comparator 10 and, when the output of the detector 9 is decreased below the reference level, the comparator 10 is operated to emit an alarm signal. When the alarm signal is emitted, a trigger signal from a trigger pulse generator 7 is stopped by the AND circuit 11 and the operation of a second high voltage pulse modulator 6 is stopped. Thus, the second power amplifier tube 3 is prevented from being operated in an unstable region.</p> |
