| 摘要 |
PROBLEM TO BE SOLVED: To provide a balanced type surface acoustic wave device with high quality that acts as a balanced type device and has an excellent filter characteristics. SOLUTION: The surface acoustic wave device S1 is characterized in such configuration that resonator type electrode patterns 15, 15' consisting of 3 or more IDT electrodes arranged in parallel along the propagation direction of a surface acoustic wave are placed in plural stages on a piezoelectric substrate 18, one of the 1st stage and the final stage of the resonator type electrode patterns is used for a balanced input section or an unbalanced input section, and the other is use for an unbalanced output section or a balanced output section, and resonator type electrode pattern used for the unbalanced input section or the unbalanced output section is formed by placing IDT electrodes to both sides of a 1st center part IDT electrode for inter- stage connection for the resonator type electrode patterns in a way of having the same phase, and the resonator type electrode pattern used for the balanced input section or the balanced output section is formed by placing IDT electrodes to both sides of a 2nd center part IDT electrode for inter-stage connection consisting of a couple of interdigital electrodes whose numbers are equal to each other in a way of having the opposite phase.
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