Patent ID: 9294071
Filing Date: 2016-03-22
CPC Classification: H01P,H03H,H04B

Claim Text:
1. An antenna duplexer comprising: a first ladder-type acoustic wave filter connected between an antenna terminal and an input terminal and having a first passband in a first frequency band; and a second ladder-type acoustic wave filter connected between the antenna terminal and an output terminal, the second ladder-type acoustic wave filter having a second passband in a second frequency band higher than the first frequency band, the first and second frequency bands being non-overlapping, the second ladder-type acoustic wave filter including a plurality of series-arm resonators connected in series along a signal path between the antenna terminal and the output terminal, and a plurality of parallel-arm resonators connected between the signal path and a ground, the plurality of parallel-arm resonators including a first parallel-arm resonator and at least one other parallel-arm resonator connected at a position closer to the antenna terminal than the first parallel-arm resonator, the first parallel-arm resonator having an interdigital transducer (IDT) electrode that includes a pair of busbars and a plurality of electrode fingers that extend from the pair of busbars and that interdigitate with each other, the IDT electrode including a constant pitch section in which certain ones of the plurality of electrode fingers are arranged at a substantially constant first pitch, and at least one narrow pitch section in which certain other ones of the plurality of electrode fingers are arranged at a varying pitch that varies between the substantially constant first pitch and a minimum pitch that is narrower than the substantially constant first pitch, the constant pitch section including a first region and a second region, and the at least one narrow pitch second being disposed between the first and second regions of the constant pitch section.