| 摘要 |
PROBLEM TO BE SOLVED: To make the filter small-sized by cascading two couples of laterally coupled dual-mode piezoelectric filters, composed of IDT electrodes and reflectors, in the center area of a piezoelectric substrate and connecting the bus bar of the IDT electrode close to an end part of the piezoelectric substrate to a pad in the center area by a lead wire extending around a reflector. SOLUTION: On the piezoelectric substrate 1, 1st and 2nd IDT electrodes 2 and 3 are arranged closely in parallel to each other and at both end parts of the IDT electrodes 2 and 3, reflectors 4 and 5 are arranged to constitute a 1st laterally coupled dual-mode filter. At a position where acoustic coupling with the 1st laterally coupled dual-mode filter is avoided, a 2nd laterally coupled dual-mode filter is formed which consists of IDT electrodes 8 and 9 and reflectors 10 and 11. The IDT electrodes 3 and 8 are connected in the center area with a lead electrode 7 to obtain a two-stage cascaded dual-mode filter. The bus bars of the IDT electrodes 2 and 9 are connected to bonding pads 6-1 and 12-1 in the center area by lead wires L1 and L2 extending around the reflectors 4 and 11.
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