| 摘要 |
<p>The present invention increases the abruptness of filter characteristics, without increasing the size of an elastic wave filter and while suppressing increases in insertion loss in normal bandwidths. The elastic wave filter (1) comprises first and second signal terminals (12, 13a, 13b), a longitudinally-coupled resonator-type elastic wave filter unit (20) connected between the first signal terminal (12) and the second signal terminals (13a, 13b), and elastic wave resonators (30a, 30b). The elastic wave resonators (30a, 30b) are connected between a ground potential and connection points between the longitudinally-coupled resonator-type elastic wave filter unit (20) and the signal terminals (13a, 13b). The elastic wave resonators (30a, 30b) have piezoelectric substrates (10) and IDT electrodes (31a, 31b) formed on top of the piezoelectric substrates (10). The IDT electrodes (31a, 31b) are apodization weighted.</p> |
