| 摘要 |
<p>A ladder circuit type SAW filter device (100) includes series arm resonators (211a,b) and parallel arm resonators (212a-c) that are defined by SAW resonators. Among the parallel arm resonators, a first parallel arm resonator (212a,c) that is connected to one of an input end (100A) and an output end (100B) and a second parallel arm resonator (212b) that is connected to a junction (X) between two series arm resonators (211a,b) have the relationship of Cp1 x 2 < Cp2, where Cp1 represents the capacitance of the first parallel arm resonator (212a,c) and Cp2 represents the capacitance of the second parallel arm resonator (212b). The inductance of an inductor (213b) that is connected to the second parallel arm resonator (212b) is equal to or less than the inductance of the inductor (213a,c) that is connected to the first parallel arm resonator (212a,c). The SAW filter device has superior steepness of filter characteristics in the lower range of a pass band and outstanding attenuation in a stop band. <IMAGE></p> |
