| 摘要 |
<P>PROBLEM TO BE SOLVED: To enlarge attenuation amounts at low-frequency and high-frequency sides rather than a pass frequency band while suppressing a loss within the pass frequency band. <P>SOLUTION: Two longitudinal coupling resonator type filter parts 1, 2 are provided on a piezoelectric substrate 20 in series to each other, a ladder-type filter part 3 obtained by connecting one-port resonators 30 in series and in parallel is interposed between these filter parts 1, 2, and an input port 15 and an output port 16 are connected to each of the filter parts 1, 2, respectively. When a capacitance value of a serial resonator 4 in the ladder-type filter part 3 is defined as Cs and a capacitance value of a parallel resonator 5 is defined as Cp, Cs/Cp is reduced, thereby enlarging a high-frequency side attenuation amount rather than a pass frequency band. <P>COPYRIGHT: (C)2012,JPO&INPIT |
