| 摘要 |
<p>A cascaded longitudinally coupled resonator-type surface acoustic wave filter device including an inter-stage capacitor is miniaturized. A first and a second longitudinally coupled resonator-type surface acoustic wave filter (3 and 4) are disposed on a piezoelectric substrate (2). One end of a first IDT (3a) arranged at the middle of the first longitudinally coupled resonator-type surface acoustic wave filter is connected to a first unbalanced terminal (5), and one end of a first IDT (4a) arranged at the middle of the second longitudinally coupled resonator-type surface acoustic wave filter is connected to a second unbalanced terminal (6). Signal terminals of second IDTs (3b and 4b) of the first and the second longitudinally coupled resonator-type surface acoustic wave filter (3 and 4) are connected to each other with a first signal line (9). Third IDTs (3c and 4c) are connected to each other with a second signal line (10). A capacitor (11) is connected between the first and the second signal line (9 and 10).</p> |
