| 摘要 |
PROBLEM TO BE SOLVED: To reduce electrode finger resistance and to satisfy the prescribed terminal condition of a request while the low insertion loss of an RF filter is maintained by setting the line occupation rate of a plurality of IDT electrodes arranged on a piezoelectric substrate to be larger than that of reflectors. SOLUTION: A resonator-type SAW filter is a cascade-connected duplex mode SAW filter where IDT electrodes 2 and 3 are closely arranged on the principal face of a piezoelectric substrate 1 along the transmission direction of a surface wave, and grating reflectors 4a and 4b are arranged on both sides. The IDT electrodes 2 and 3 are constituted of a pair of comb-type electrodes having a plurality of electrode fingers which are mutually inserted one another. One comb-type electrode in each IDT electrode 2 and 3 is connected to input/ output terminals IN and OUT and other comb-type electrode is grounded. The line occupation rateηr of the IDT electrodes 2 and 3 is made larger than that of the grating reflectors 4a and 4b.
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