| 摘要 |
PROBLEM TO BE SOLVED: To planarize the passing band of a filter constituted by cascading two primary-tertiary longitudinally coupled double-mode SAW filters, and to set the voltage standing wave ratio(VSWR) to less than 2. SOLUTION: The filter is constituted, by longitudinally cascading two primary-tertiary longitudinally coupled double-mode SAW filters, composed of three IDT electrodes with electrode finger pitch L1. The pitch of the center IDT electrode of one double-mode SAW filter is set to L2, electrode fingers are removed symmetrically from both sides of the IDT electrode, and the removed electrode fingers are connected to facing IDT electrodes to form dummy electrodes with pitch L2, which is made larger than L1.
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