| 摘要 |
PROBLEM TO BE SOLVED: To provide a variable attenuator that requires no phase adjustment device for compensating phase fluctuations and has a small passing phase fluctuation with a small size at a low cost. SOLUTION: The variable attenuator provided with 1st and 2nd FETs (variable resistive elements) 2a, 2b and 3, is provided with a ROM 6 that stores data acquired in advance showing a relation between control voltages Vg1, Vg2 applied to the 1st and 2nd FETs (variable resistive elements) 2a, 2b and 3 and a pass attenuation characteristic and a pass phase characteristic of the variable attenuator, a calculation circuit 5 that obtains a desired pass attenuation amount on the basis of the data recorded in the ROM 6 to obtain a control voltage application condition minimizing fluctuations in the pass phase, amount and digital/analog converter circuits 7a, 7b that apply the control voltages to the 1st and 2nd FETs (variable resistive elements) 2a, 2b and 3 on the basis of the obtained control voltage application condition.
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