| 摘要 |
PROBLEM TO BE SOLVED: To provide a structure, in which an amplitude balancing degree and a phase balancing degree are improved in a transverse coupling resonator type surface acoustic wave filter, having balance-to-unbalance transforming function. SOLUTION: The longitudinal coupling resonator type surface acoustic wave filter 200 comprises first to third IDTs 201 to 203 with the number of electrode fingers of its central second IDT 202 being even, and polarities of the electrode fingers 201 and 203a adjacent to the IDT 202 are inverted to those of the left and first and right third IDTs 201 and 203 to have the balance-to-unbalance transforming function.
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