| 摘要 |
PROBLEM TO BE SOLVED: To provide a longitudinally coupled multiple mode surface acoustic wave filter whose pass band is wide, and insertion loss in the pass band is small. SOLUTION: In a longitudinally coupled multiple mode surface acoustic wave apparatus, a plurality of interdigital electrodes are closely arranged on a piezoelectric substrate along the propagation direction of an exciting surface acoustic wave, and reflectors are arranged on both sides of this row of interdigital electrodes. A dummy electrode finger is formed between each electrode finger of an interdigital electrode and a bus bar, and an acoustic velocity in each reflector corresponding to the dummy electrode finger of the interdigital electrode and the air gap between the electrode finger and the dummy electrode finger, is made slower than the acoustic velocity of a uniform metallized region, so as to suppress unnecessary radiation of the surface acoustic wave at the reflectors. COPYRIGHT: (C)2006,JPO&NCIPI
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