| 摘要 |
PURPOSE:To extend the life of an electron beam tube, by controlling simultaneously the anode voltage of the electron beam tube and a heater voltage to eliminate the excess power of a transmission power amplifier and reducing the power consumption when the electron beam tube is operated with a power lower than the maximum output power. CONSTITUTION:The output power value of a power amplifier 3 using an electron beam tube is detected by a power detecting circuit 16, and the detected value is supplied to a voltage setting circuit 15. This detected value is compared with an indicated value from an output voltage setting circuit 14 in the voltage setting circuit 15; and if they are different from each other, a heater voltage controlling circuit 11 and an anode voltage controlling circuit 12 are operated. The heater voltage and the anode voltage are lowered to lower the output power of the electron beam tube if the detected value is larger than the indicated value, and the heater voltage and the anode voltage are raised to raise the output power if the detected value is smaller; and thus, these voltages are so controlled that the detected value coincides with the indicated value. |
