Elastic wave filter device

Active Publication Date: 2011-06-30
MURATA MFG CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0027]According to various preferred embodiments of the present invention, in the 5-IDT longitudinally coupled resonator type elastic wave filter device including first to fifth IDT electrodes, since the total number of electrode fingers Nx is preferably different from the total number of electrode fingers Ny, the steepness of the filter characteristics in the low frequency range of the passband is effectively increased.
[0028]In addition, since the average period of electrode fingers in the narrow-pitch electrode finger portion in an area including the larger total number of electrode fingers Nx and Ny is preferably greater than that in an area including the smaller total numbers of

Problems solved by technology

Accordingly, it is difficult to further increase the steepness of the filter characteristic by increasing the Q value of the elastic wave resonator.
However, in such a structure, the steepness of the filter characteristic cannot be sufficiently increased.
As noted above, the surface acoustic wave filter device described in Japanese Unexamined Patent Application Publication No. 4-54011 is limited i

Method used

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Example

[0060]Preferred embodiments of the present invention are described below with reference to the drawings.

First Preferred Embodiment

[0061]FIG. 1 is a schematic plan view of an elastic wave filter device according to a first preferred embodiment of the present invention. According to the first preferred embodiment, an elastic wave filter device 1 includes a piezoelectric substrate 2. As shown in FIG. 1, an electrode structure is provided on the piezoelectric substrate 2. In this manner, a surface acoustic wave filter device having a balanced-unbalanced conversion function is provided.

[0062]The elastic wave filter device 1 according to the first preferred embodiment can preferably be used as a receiving filter of the UMTS-Band 2 of a cell phone, for example. The transmitting frequency of the UMTS-Band 2 ranges from about 1.850 GHz to about 1.910 GHz, while the receiving frequency of the UMTS-Band 2 ranges from about 1.930 GHz to about 1.990 GHz.

[0063]The elastic wave filter device 1 prefer

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Abstract

A 5-IDT longitudinally coupled resonator type elastic wave filter device includes a narrow-pitch electrode finger portion arranged to increase the steepness of the filter characteristic includes first to fifth IDTs. When the total number of electrode fingers in a first area and a fourth area is Nx and the total number of electrode fingers in a second area and a third area is Ny, an average period of electrode fingers in one of the areas including larger total numbers of the electrode fingers Nx and Ny is greater than that in the area including smaller total numbers of the electrode fingers Nx and Ny. Among the first IDT electrode, the third IDT electrode, and the fifth IDT electrode, the period of electrode fingers in a portion other than the narrow-pitch electrode finger portion of the IDT electrode in the area including the larger numbers of electrode fingers is less than the period of electrode fingers in a portion other than the narrow-pitch electrode finger portion of the IDT electrode in the area including the smaller numbers of electrode fingers.

Description

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Claims

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Application Information

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Owner MURATA MFG CO LTD
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