| 摘要 |
PROBLEM TO BE SOLVED: To provide a voltage-controlled filter by which signals of frequencies away from the passing central frequency by certain frequencies can be attenuated without changing the attenuation characteristics in the proximity of the passband. SOLUTION: A pair of microstrip lines MLS1 and MLS2 constitute a coupler. Varactor diodes X1 and X2 change their capacity according to a control voltage V1 and control the passing central frequency by controlling the coupling amount of the coupler. Band-stop adjusting parts 11 and 12 have varactor diodes X3 and X4 respectively and attenuate signals of frequencies corresponding to control voltages V2 and V3 applied to the varactor diodes X3 and X4. The band-stop adjusting parts 11 and 12 do not change the coupling amount of the coupler even when the band-stop frequency is changed by changing the control voltage V2 and do not change attenuation characteristics in the proximity of the pass frequency band. COPYRIGHT: (C)2008,JPO&INPIT
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