| 摘要 |
An adjustable resonator filter ( 200 ), the operating band of which can be shifted by a one-time adjustment. The natural frequency of each resonator ( 210, 220 ) is affected, in addition to the basic tuning arrangement, by an adjustment circuit (ACI), which includes a fixed tuning element ( 280 ) in the resonator cavity and an adjusting part ( 290 ) outside the cavity. The tuning element has an electromagnetic coupling to the basic structure of the resonator. The adjustment circuit is functionally a short transmission line, which is "seen" by the resonator as a reactance of a certain value. By changing the electric length of the transmission line, the value of the reactance and the electric length and natural frequency of the whole resonator are changed. The change is implemented in the adjustment part by means of switches or a movable dielectric piece. In the resonator filter each resonator has a similar adjustment circuit, and the adjustment circuits have common control (CNT) for shifting the band of the filter. When the subband division is in use, the filters need not be separately adjusted for each subband in connection with the manufacture. No moving parts are required inside the filter housing.
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