| 摘要 |
PROBLEM TO BE SOLVED: To reduce a phase change and occurrence of distortion caused by control of an attenuation quantity in a microwave variable attenuator using a field effect transistor (FET). SOLUTION: This device is provided with an FET 1 connected to connect a drain D to a microwave signal line 3, to connect a source S to the ground and to apply a control voltage to a gate G and a short stab 2 connected to regard the FET 1 as the same phase in the view from pure resistance or 50Ω. Then, the short stab 2 is connected through a capacitor 6 to the ground, the control voltage for controlling the attenuation quantity is applied from a terminal 5 to the gate G, and a voltage is applied from a terminal 4 to the drain D. Besides, reflection characteristics can be improved by combination with a 3 dB coupler.
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