| 摘要 |
Comprising one or more resonant cavities in which are produced two resonant modes at two different frequencies f1 and f2, both modes having essentially the same field distributions but rotated 90 .degree. with respect to each other. Each cavity comprises a tuning element (TS a) for tuning the resonant frequency f1 of the first mode along a first axis, a tuning element (TS b) for tuning the resonant frequency f2 of the second mode along a second axis perpendicular to the first, input coupling means (IC) and output coupling means (OC) for injecting into and extracting from the cavity, respectively, a radiofrequency signal along axes not parallel to those of resonance. Filter tuning is done by using only two tuning elements, which means that the filter cost is lower and the tuning time is reduced.
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