| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface acoustic wave filter device which has its band attenuation quantity improved without causing degradation of temperature characteristics nor an increase in element size. SOLUTION: On the surface of a piezoelectric substrate 31, 1st to 3rd directional couplers 32 to 34 which are 1/2 time as long as coupling length are arranged zigzag side by side in an ultrasonic-wave propagation direction so that nearly halves of the opposite sides of the directional couplers face each other in the direction parallel to the ultrasonic-wave propagation direction and nearly halves of the sides on the opposite sides from the mutually opposite sides of those directional couplers and two reflectors 36 and 37, 38 and 39, and 40 and 41 are arranged opposite each other; and an input-side interdigital electrode 35 is arranged opposite a nearly half of one side of the 1st directional coupler and an output-side interdigital electrode 42 is arranged opposite a nearly half of one side of the 3rd directional coupler 34.
|
