| 摘要 |
PROBLEM TO BE SOLVED: To provide an attenuator which can increase its maximum attenuation without increasing its insertion loss by controlling the voltage or current applied to every high frequency variable resistance element for controlling the internal resistance of the resistance element and then controlling the attenuation of signals passing through a signal line. SOLUTION: An attenuator 21 includes an attenuation circuit 27 having a 5th PIN diode 39 which is added to aα-shaped circuit 26 having the 1st-4th PIN diodes 22-25. In such a constitution, the control voltage Vc to be applied to the diodes 22-25 and 39 is continuously controlled when the DC bias voltage of a constant level is applied to these diodes from a bias power unit 35. Thus, the internal resistance of each of diodes 22-25 and 39 is continuously controlled. As a result, the high frequency input signals of the microwaves, etc. which are inputted to the input terminal of a signal line 28 are continuously attenuated and outputted from the output terminal of the line 28. In such a way, the flat frequency characteristics of attenuation is enhanced.
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