| 摘要 |
<p>A surface acoustic wave filter device in which sharpness of filter characteristics can be enhanced and pass bandwidth can be enlarged. In the surface acoustic wave filter device (1), longitudinal coupling resonator type first surface acoustic wave filter portion (10) and second surface acoustic wave filter portion (20) are cascaded, a signal flowing through a first signal line (6) connecting both second IDTs (12, 22) electrically has a phase shifted by 180° from that of a signal flowing through a second signal line (7) connecting both third IDTs (13, 23), a surface acoustic wave resonator (31) is connected between the first and second signal lines (6, 7), and the resonance point of the surface acoustic wave resonator (31) is arranged in an attenuation region in the vicinity of the low band side end of pass band of the filter or the antiresonance point is arranged in an attenuation region in the vicinity of the high band side end of pass band of the filter.</p> |
