| 摘要 |
This invention provides a duplexer that makes it possible to improve isolation characteristics in the passband of a transmission filter and increase out-of-band attenuation near the passband of a reception filter. Said duplexer (1) comprises a transmission filter (5), said transmission filter (5) having a ladder-like circuit architecture, and a reception filter (6). The reception filter (6) comprises a series trap element (7), said series trap element (7) being connected to an antenna terminal (2), and a longitudinally-coupled-resonator-type surface-acoustic-wave filter (8). A coupling capacitance (11) is connected between a parallel-arm-resonator (P1, P2)-side terminal of an inductance (L1) in the transmission filter (5) and a wire (12) that connects the series trap element (7) to the longitudinally-coupled-resonator-type surface-acoustic-wave filter (8) in the reception filter (6). |
