| 摘要 |
PURPOSE:To improve an intermodulation disturbance ratio as a variable attenuation circuit by giving a forward current of a certain value to a PIN diode to decrease the intermodulation distortion of the PIN diode in adjusting the attenuation to the maximum attenuation. CONSTITUTION:A balanced 2-wire transformer 10 and the PIN diode 14 are inserted in parallel between input/output terminals 1, 2 in terms of high frequency. Then the signal passing through the balanced 2-wire transformer 10 and a signal passing through the PIN diode 14 are in phase opposite to each other. Then a control voltage given to a control voltage input terminal 7 is changed to adjust the equivalent resistor of the PIN diode 14 thereby making the signal passing through the PIN diode 14 coincident with the signal level outputted from the transformer 10, then the maximum attenuation is obtained by a control voltage because of mutual cancellation.
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