| 摘要 |
<p>A duplexer (D1) includes a piezoelectric substrate (S), a transmitting filter (F1), and a receiving filter (F2). The transmitting filter (F1) includes a ladder filter having a first resonator group (T1,T2,T3,T4,T6,T8) which has one or more resonators in one or more series arms and one or more resonators (T3,T5,T7) in one or more parallel arms. The receiving filter (F2) has a passband higher than that of the transmitting filter (F1), and includes a second resonator group (R2,R4,R6,R8) which has one or more resonators (R1,R3,R5,R7,R9) in one or more series arms and one or more resonators in one or more parallel arms. A node (N1) connects both the transmitting filter (F1) and the receiving filter (F2). The receive-side closest resonator (R1) closest to the node (N1) in the parallel arm is closer to the node than a resonator which is closest to the node (N1) in the series arm (R2), and a resonance frequency of the receive-side closest resonator (R1) is lower than the passband of the transmission filter (F1).
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