BALANCE TYPE ELASTIC SURFACE WAVE FILTER

Title:

BALANCE TYPE ELASTIC SURFACE WAVE FILTER

Document Type and Number:

WIPO Patent Application WO/2006/043445

Kind Code:

A1

Abstract:

An elastic surface wave filter (1) of 5IDT type having a balance-unbalance conversion function and enabled to effectively suppress the occurrence of spuriousness near a transmission band. First to fifth IDTs (11 - 15) are arranged over a piezoelectric substrate (2) in a surface wave transmission direction. The second IDT (12) and the fourth IDT (14) have a phase difference of 180 degrees and are connected with an unbalance terminal. The third IDT has first and second division IDT portions (13a, 13b), of which the first IDT (11) and the first division IDT portion (13a) are connected with a first balance terminal (4) whereas the second division IDT portion (13b) and the fifth IDT (15) are connected with a second balance terminal (5). When the numbers of electrode fingers for determining the center frequencies of the first, third and fifth IDTs (11, 13, 15) are designated by N1, N3 and N5, respectively, they are set such that 1.55 ≤ N3/N1 ≤ 2.58, and such that N1 = N5.

Inventors:

TAKAMINE YUICHI (JP)

Application Number:

PCT/JP2005/018754

Publication Date:

April 27, 2006

Filing Date:

October 12, 2005

Export Citation:

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Assignee:

MURATA MANUFACTURING CO (JP)
TAKAMINE YUICHI (JP)

International Classes:

H03H9/64; H01L41/09; H01L41/18; H01L41/187; H01L41/22; H01L41/29; H03H9/145

Foreign References:

JP2004088551A	2004-03-18
JPH1197966A	1999-04-09
JP2003507917A	2003-02-25
JP2004096244A	2004-03-25
JP2004096244A	2004-03-25
US20040006615A1	2004-01-08

Other References: