| 摘要 |
PURPOSE:To prevent the deterioration of a closed gain due to a delay of a power amplifier or the like by obtaining a complex number amplitude mean value of an output of an orthogonal demodulator outputting the 1st and 2nd base band signals to the 1st and 2nd subtractors respectively and deciding the pahse change of a phase shifter so as to attain the obtained value to a desired value. CONSTITUTION:The orthogonal demodulator 135 uses an output of a sinusoidal wave generator 131 through a phase shifter 132 to demodulate an output of an attenuator 145 to obtain the 1st and 2nd base band signals. The base band signal is inputted respectively to subtractors 110 and 115. For example, an output of the orthogonal demodulator is inputted to sample circuits 510, 520 and an amplitude calculation circuit 150 is sampled by the leading of a pulse inputted from a terminal 503. Then the result is squared by square circuits 530, 540 and added by an adder 550. A control circuit compares the output of the amplitude calculation circuit 150 with a desired output to output a control signal to decide the phase change of the phase shifter 132. As a result, the designed closed gain is always obtained.
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