US Patent No. 9,190,980

ELASTIC WAVE FILTER


Patent No. 9,190,980
Issue Date November 17, 2015
Title Elastic Wave Filter
Inventorship Tadaaki Tsuda, Sayama (JP)
Assignee Nihon Dempa Kogyo Co., Ltd., Tokyo (JP)

Claim of US Patent No. 9,190,980

1. An elastic wave filter comprising:
a first filter part and a second filter part each having tapered IDT electrodes including a plurality of electrode fingers
and a pair of busbars which are disposed as an input-side electrode and an output-side electrode on a piezoelectric substrate
so as to be apart from each other in a propagation direction of an elastic wave;

wherein the input-side electrode of the first filter part and the input-side electrode of the second filter part are arranged
in a direction perpendicular to the propagation direction of the elastic wave, and the output-side electrode of the first
filter part and the output-side electrode of the second filter part are arranged in the direction perpendicular to the propagation
direction of the elastic wave;

wherein, when the first filter part is placed at a lower side and the second filter part is placed at an upper side of the
first filter part, an upper busbar of the pair of busbars is positioned at the upper side in each of the first filter part
and second filter part and a lower busbar of the pair of busbars is positioned at the lower side for both the first filter
part and the second filter part, and the input-side electrode and the output-side electrode of the first filter part are structured
by the plurality of electrode fingers such that a cycle unit ? becomes smaller toward the upper busbar from the lower busbar,
and the input-side electrode and the output-side electrode of the second filter part are structured by the plurality of electrode
fingers such that the cycle unit ? becomes larger toward the upper busbar from the lower busbar;

wherein a distance between the pair of busbars of the first filter part and a distance between the pair of busbars of the
second filter part are the same;

wherein said cycle unit ? becomes smaller towards the upper busbar of said first filter part in a same relationship as said
cycle unit ? becomes larger toward the upper busbar for said second filter part for any position along the plurality of electrode
fingers of the first filter part and a corresponding position along the second filter part;

wherein the upper busbar in the input-side electrode of the first filter part and the lower busbar in the input-side electrode
of the second filter part are electrically connected to each other;

wherein the upper busbar in the output-side electrode of the first filter part and the lower busbar in the output-side electrode
of the second filter part are electrically connected to each other;

wherein one of the lower busbar in the input-side electrode of the first filter part and the upper busbar in the input-side
electrode of the second filter part connected to one a first input port and a first ground port, and another of the lower
busbar in the input-side electrode of the first filter part and the upper busbar in the input-side electrode of the second
filter part is connected to another of the first input port and the first ground port; and

wherein one of the lower busbar in the output-side electrode of the first filter part and the upper busbar in the output-side
electrode of the second filter part is connected to one a second output port and a second ground port, and another of the
lower busbar in the output-side electrode of the first filter part and the upper busbar in the output-side electrode of the
second filter part is connected to another of the second output port and the second ground port.