| 摘要 |
<p>Disclosed is a tunable filter that has an excellent frequency-temperature characteristic, that is formed using a surface acoustic wave resonator with an increased electromechanical coupling coefficient, and that enables an improved temperature characteristic and frequency characteristic. The tunable filter (1) is equipped with a circuit structure whereby variable condensers are connected to surface acoustic wave resonators (S1, S2), (P1-P3), said surface acoustic wave resonators having a piezoelectric substrate (11) comprised of LiTaO3 or LiNbO3, an IDT electrode (12) which is formed of an electrode material filled into a concave part (11b) on the top face (11a) of said piezoelectric substrate; and an SiO2 film (15) which is provided to cover said piezoelectric substrate.</p> |
