| 摘要 |
<p>In the surface acoustic wave filter (Fig. 7 (8)), a longitudinally-coupled double-mode resonator filter (1) formed by arranging a plurality of inter-digital transducers (3,4) for exciting and receiving a surface acoustic wave adjacent each other in the direction of propagation of the surface acoustic wave is connected in series to a resonator (2) having one or a plurality of inter-digital transducers (13) for exciting and receiving a surface acoustic wave. A cutoff frequency on the high-frequency side of the pass band of the longitudinally-coupled double-mode resonator filter and the antiresonant frequency of the resonator are substantially equal. In the surface acoustic wave filter, the sharpness in the vicinity of the cutoff frequency on the high-frequency side of the pass band is high, sufficient attenuation can be obtained, and the input and output impedance matching state is good.</p> |
