| 摘要 |
A 5-IDT longitudinally coupled resonator-type SAW filter has a balanced-to-unbalanced conversion function. In areas where first to fifth IDTs are adjacent to each other, each IDT includes a narrow-pitched electrode finger portion. The IDTs are configured such that one condition selected from among conditions (1) to (3) and one condition selected from among conditions (4) to (6) are satisfied when the numbers and pitches of electrode fingers in the narrow-pitched portions of the first to fifth IDTs are denoted by N 1 and P 1 , N 2 a and P 2 a, N 2 b and P 2 b, N 3 and P 3 , N 4 a and P 4 a, N 4 b and P 4 b, and N 5 and P 5 , respectively: Conditions (1): When N 1 =N 3 =N 5 , 0.992<=P 1 /P 3<= 1.008 and P 1= P 5 (2): When N 1= N 5< N 3 , 0.9<=P 1 /P 3 <1 and P 1= P 5 (3): When N 3< N 1= N 5 , 1 <P 1 /P 3 <=1.1 and P 1= P 5 (4): When N 2 a=N 2 b=N 4 a=N 4 b, 0.991<=P 2a/P 2 b<=1.009 and P 2 a/P 2 b=P 4 b/P 4 a (5): When N 2 a=N 4 b>N 2 b=N 4 a, 1<P 2a/P 2 b<=1.1 and P 2 a/P 2 b=P 4 b/P 4 a (6): When N 2 a=N 4 b<N 2 b=N 4 a, 0.9<=P 2a/P 2 b<1 and P 2 a/P 2 b=P 4 b/P 4 a When Conditions (1) and (4) are selected, Condition (7): N 1<> N 2 a or P 1<> P 2 a is satisfied.
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