| 摘要 |
PROBLEM TO BE SOLVED: To provide a high frequency transmitter compatible with multi-channels requiring prescribed output power that is provided with a function that allows output power correction to follow a frequency of the output power with respect to a varied output from a local oscillator by adding a simple circuit to the high frequency transmitter. SOLUTION: The automatic power control circuit is provided with a power amplifier, a variable attenuator provided to its pre-stage, a detector that detects an output power of the power amplifier, an adder that superimposes a detected voltage or the like onto an output power correction voltage, and a differential amplifier that receives an output of the adder and an output power control reference voltage to amplify a difference voltage of them. A correction voltage variable circuit processes a frequency control voltage branched from a frequency control voltage that is applied to a local oscillator of a PLL circuit and in correlative relation to the frequency of the output power from the power amplifier into the output power correction voltage, the adder sums the output power correction voltage and the detected voltage, the differential amplifier receives the output of the adder and the output power control reference voltage, and the output of the differential amplifier is given to the variable attenuator to exclude a frequency deviation in the output power. |
