SURFACE ACOUSTIC WAVE FILTER, BALANCED FILTER, AND COMMUNICATION DEVICE

摘要

PROBLEM TO BE SOLVED: To solve the problem that a longitudinal mode type surface acoustic wave filter which has an unbalanced type terminal and a balanced type terminal deteriorates in degree of balance. SOLUTION: On a piezoelectric substrate 101, the longitudinal mode type surface acoustic wave filter is formed which comprises a 1st IDT electrode 102, 2nd and 3rd IDT electrodes 103 and 104, and 1st and 2nd reflector electrodes 105 and 106. An upper electrode 102a of the 1st IDT electrode 102 is connected to one side 107 of the balanced type terminal and a lower electrode 102b of the 1st IDT electrode 102 is connected to the other side 108 of the balanced type terminal. Further, an upper electrode 103a of the 2nd IDT electrode 103 is connected to the unbalanced type terminal 109 and a lower electrode 103b is grounded. A lower electrode 104b of the 3rd IDT electrode 104 is connected to the balanced type terminal 109 and an upper electrode 103a is grounded. COPYRIGHT: (C)2003,JPO