| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface acoustic wave filter device having a balanced- unbalanced input-output function in which the level of spurious waves outside the passing band is improved, and communication equipment. SOLUTION: Four vertically coupled resonator surface acoustic wave filter elements 101 to 104 provided with three comb-shaped electrode parts 121, 122 and 123, or 121, 128 and 123 provided along the propagation direction of a surface acoustic wave, and respective reflectors 124 and 125, or 126 and 127 sandwiching the respective comb-shaped electrodes 121 to 123 are provided on a piezoelectric board so as to have a balanced-unbalanced input-output function. The respective reflectors 124 and 125, and the respective reflectors 126 and 17 are provided so that at least one among the number of electric fingers, pitch, duty and film thickness can be different from each other.
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