| 摘要 |
PROBLEM TO BE SOLVED: To provide a transmission power control circuit capable of keeping transmission power constant over a wide transmission power setup range while maintaining high efficiency of an amplifier, linearity between output levels is enhanced, and preventing a control loop from becoming unstable. SOLUTION: A transmission power amplifier is divided into pre-amplifiers 1, 2 and a final-stage power amplifier 4, a directional coupler 3 and a detector 5 are provided before the power amplifier 4, and a feed voltage is applied from a variable power source 6 to the power amplifier 4. At the same time, the feed voltage is added to a detection voltage by adder circuits 7a, 7b, a differential between an added output and a reference voltage is outputted by an operational amplifier 8, and a variable resistance attenuator 1 that is input of the pre-amplifiers, is controlled. Efficiency is improved by controlling the feed voltage of the power amplifier 4, linearity of output levels due to gain variation in that case is enhanced, and the control loop is prevented from becoming unstable. COPYRIGHT: (C)2008,JPO&INPIT
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