| 摘要 |
PROBLEM TO BE SOLVED: To facilitate manufacture, to store a coupling capacitor mounted outside in one package, to realize high attenuation by four poles and to set the ability of a filter to be high by providing multiple electrodes with one package through the use of two two-pole crystal oscillation pieces in a crystal filter. SOLUTION: A crystal filter mounts a ceramic package (a) with a step and two crystal oscillation pieces (b) in the package (a) and mounts a coupling capacitor or an inductor on the mounting face and the back of the crystal oscillation piece (b). Namely, two crystal oscillation pieces (b) where the electrodes (d) of two poles are formed are fixed to the ceramic package (a) by conduction adhesive (c), and a four-pole crystal filter is formed. The coupling capacitor (e) is connected/fixed in the ceramic package (a) by conduction adhesive (c) or solder, it is sealed by resin, is interrupted from outdoor air and it is air-tightly sealed with a cap (g).
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