| 摘要 |
PROBLEM TO BE SOLVED: To obtain a passband filter which is excellent in low loss and withstand power and also can secure attenuation quantity in a frequency band which is higher than the center frequency. SOLUTION: A plurality of cylindrical hollow resonators 2 of a TE012 mode, in which high Q0 can be expected in a resonance mode are used, and selection is made so that spurious signals due to high-order and lower-order modes cannot fall in a use band as the positions of connection holes 5 between these resonators. For this reason, the positions of the holes 5 are made to be located, at least either about 1/4 or 3/4 length from the end face of the cylindrical hollow resonators, i.e., where electric fields concentrate. The higher-order mode can be reduced, high attenuation quantity can be secured, the number of connection holed where electric fields concentrate is also increased, a load supplying to the connection holes can be reduced, and high withstand power performance can be obtained consequently by especially making four connection holes in all, while the positions of the connection holes are made as two places of about 1/4 and 3/4 lengths.
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