Elastic wave resonator, ladder filter and duplexer
AssigneeMurata Manufacturing Co., Ltd.
InventorToshiaki TAKATA
Life of this patent
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Abstract
An acoustic wave resonator that is excellent in terms of return loss characteristics at the resonant and anti-resonant frequencies and that is capable of effectively reducing loss includes an IDT electrode in which a plurality of first electrode fingers and a plurality of second dummy electrode fingers are connected to a first common electrode, a plurality of second electrode fingers and a plurality of first dummy electrode fingers are connected to a second common electrode. Apodization weighting is applied in the acoustic wave propagation direction. The metallization ratio of a non-crossing region is relatively high compared with the metallization ratio of a crossing region in the acoustic wave propagation direction.
Claims11
An elastic wave resonator comprising:
- a piezoelectric substrate;
- and
- an IDT electrode located on the piezoelectric substrate;
- wherein
- the IDT electrode includes:
- first and second common electrodes arranged so as to be separated from each other on the piezoelectric substrate;
- a plurality of first electrode fingers each including a first end connected to the first common electrode and a second end extending toward the second common electrode;
- a plurality of second electrode fingers each including a first end connected to the second common electrode and a second end thereof extending toward the first common electrode;
- a plurality of first dummy electrode fingers each including a first end connected to the second common electrode, and a second end extending toward the first common electrode and being arranged with a gap interposed between itself and a leading end of one of the plurality of first electrode fingers;
- a plurality of second dummy electrode fingers each including a first end being connected to the first common electrode, and a second end being arranged on a side of the second common electrode and being arranged with a gap interposed between itself and a leading end of one of the plurality of second electrode fingers;
- wherein
- a crossing region is defined by a portion in which the first and second electrode fingers overlap one another in an elastic wave propagation direction, and a portion in which the first and second dummy electrode fingers are located is a non-crossing region;
- the IDT electrode is apodization weighted so that a crossing width of the first and second electrode fingers changes in the elastic wave propagation direction, there being at least two points of change in the apodization weighting at which the crossing width changes from increasing to decreasing;
- and
- a metallization ratio that is a ratio of an area of electrode portions including the first and second finger electrodes or the first and second dummy electrode fingers to an entire area of a region in which the electrode portions are provided, is relatively high in at least a portion of the non-crossing region compared with that in the crossing region.
Dependencies are inferred from the claim text.