Ladder filter and duplexer
Abstract:
A ladder filter includes a piezoelectric substrate, an insulating film on the piezoelectric substrate, first and second electrodes provided on the piezoelectric substrate and including a pair of busbars and plurality of electrode fingers, a first line electrode at least a portion of which is defined by the busbar at one side of the first electrode, a second line electrode at least a portion of which is defined by the busbar at one side of the second electrode, and a third line electrode laminated on the second line electrode. The first line electrode and the second line electrode are electrically connected to different electric potentials. The first line electrode is separated from the second line electrode by a predetermined distance. At least a portion of the third line electrode is overlapped with at least a portion of the first line electrode with the insulating film interposed therebetween in a laminating direction.
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