| 摘要 |
A resonant surface acoustic wave filter device comprises an inter-digital transducer that has a first electrode area that excites a surface acoustic wave and a second electrode area that excites a surface acoustic wave of inverted phase with respect to that excited in the first electrode area, and grating reflectors. By selecting appropriately a ratio of numbers of electrode pairs and a pitch of electrodes of the first area and the second area, band pass characteristics and impedance characteristics of the filter devices can be controlled.
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