公开(公告)号：EP1739830B1

公开(公告)日：2012-05-02

申请号：EP05728857.3

申请日：2005-04-04

申请人： MURATA MANUFACTURING CO., LTD.

发明人： SHIBAHARA, Teruhisa, c/o Murata Manufacturing Co., Ltd. ,  TANI, Masakazu, c/o Murata Manufacturing Co., Ltd. ,  SHIN, Yasuaki, c/o Murata Manufacturing Co., Ltd.

IPC分类号： H03H9/00 ,  H03H9/64 ,  H03H9/02

CPC分类号： H03H9/0222 ,  H03H9/0061 ,  H03H9/02952 ,  H03H9/14588 ,  H03H9/6469

摘要： On a piezoelectric substrate, there are formed a plurality of longitudinally-connected resonator type elastic wave filter elements, which are cascade-connected so as to constitute an elastic wave filter. By reducing the adverse affect of the parasitic capacitance coming into the cascade connection between the longitudinally-connected resonator type elastic wave filter elements, it is possible to improve the impedance matching at the cascade connection point and improve VSWR at the elastic wave filter I/O terminal. The elastic wave filter (350) includes a piezoelectric substrate (300) having a cascade connection of two longitudinally-connected resonator type elastic wave filters (306, 312), each connecting three IDT (302, 303, 304; 308, 309, 310) formed along the propagation direction of the elastic wave. At least in one of the longitudinally-connected resonator type elastic wave filters (306, 311), the IDT (302, 304; 308, 310) have an electrode finger pitch smaller than the electrode finger pitch of the other IDT (303; 309).