To provide a filter device having less variations in passage loss of a signal.
The filter device includes a metallic frame body 24 including: resonant elements 23 provided in a hollow casing 22 and having an opening 24a at the lower part of the casing 22; and a metallic lid 25 attached to the opening 24a. An end of the casing 22 which is of the opening 24a side is connected to the lid 25 via a solder 28, the resonant elements 23 each have a metallic pipe, a coarse surface portion 31b provided on at least the lower end of the pipe, and a plated layer made of copper or silver and formed on the entire surface of the pipe including the coarse surface portion 31b, and the plated layer is bonded to the inner surface of the casing 22 via the solder 28 in at least the coarse surface portion 31b. With this configuration, since the small amount of solder 28 can bond the resonant elements 23 and the solder 28 hardly causes a solder pool at the bonding portion to stabilize the shape, and variations of Q value can be made to be small.
| JPH09252206 | DIELECTRIC FILTER |
| JP3088992 | RECTANGULAR WAVEGUIDE RESONATOR BAND-PASS FILTER |
| WO/2005/091427 | FILTER |
YAMADA TAKASHI
NANBA HIDEKI
NAKAMURA TOSHIAKI
Daisuke Nagano
Kentaro Fujii
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