| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a ladder filter, a duplexer and a module that implement high suppression over a wide band. <P>SOLUTION: The ladder filter, duplexer and module include: series resonators S11-Sx connected in series between an antenna terminal Ant and a transmission terminal Tx; parallel resonators P1-P3 connected in parallel with the series resonators S11-Sx; and an inductor Ls connected in parallel with the series resonator Sx. The series resonator Sx and the inductor Ls generate a first attenuation pole B1 at a frequency within or below a passband generated by the series resonators S11-Sx and the parallel resonators P1-P3, and generate a second attenuation pole B2 at a frequency above the passband. The first attenuation pole B1 is located at a frequency equal to or higher than the resonance frequency of the parallel resonator that has the highest resonance frequency of the parallel resonators P1-P3 and equal to or lower than a high frequency end of the passband. <P>COPYRIGHT: (C)2013,JPO&INPIT |
