US 2002/0163403 A1Published application

Surface acoustic wave filter device

AssigneeMurata Manufacturing Co., Ltd.

InventorsYoichi Sawada, Yuichi Takamine

Life of this patent

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Abstract

A surface acoustic wave filter device, having a balanced-to-unbalanced conversion function, in which input/output impedances are different and in which the in-band degree of balance is satisfactory, is obtained. The surface acoustic wave filter device has a balanced-to-unbalanced conversion function, in which the spacing of input/output IDTs of a second surface acoustic wave filter element is larger by approximately half the wavelength of the surface-acoustic wave than that of a first surface acoustic wave filter element so that the phase is inverted, wherein the total of the electrostatic capacitance values of a plurality of IDTs of the second surface acoustic wave filter element is larger than the total of the electrostatic capacitance values of a plurality of IDTs of the first surface acoustic wave filter element.

Claims19

Dependent claims

A surface acoustic wave filter device comprising:

a piezoelectric substrate;
a first surface acoustic wave filter element having a plurality of IDTs arranged along a propagation direction of a surface acoustic wave on the piezoelectric substrate and having first and second terminals;
and
a second surface acoustic wave filter element having a plurality of IDTs including input/output IDTS arranged along the propagation direction of a surface acoustic wave on the piezoelectric substrate, the spacing between the input/output IDTs being greater than that of the first surface acoustic wave filter element by approximately half the wavelength of the surface acoustic wave, and having first and second terminals;
the first terminals of the first and second surface acoustic wave filter elements being commonly connected to an unbalanced terminal, and the second terminals of the first and second surface acoustic wave filter elements being connected to a balanced terminal;
wherein the total of the electrostatic capacitance values of the plurality of IDTs of the second surface acoustic wave filter element is greater than the total of the electrostatic capacitance values of the plurality of IDTs of the first surface acoustic wave filter element.

3 more elements

A surface acoustic wave filter device comprising:

a piezoelectric substrate;
a first surface acoustic wave filter element having a plurality of IDTs arranged along a propagation direction of a surface acoustic wave on the piezoelectric substrate and having first and second terminals;
and
a second surface acoustic wave filter element having a plurality of IDTs including input/output IDTs provided along the propagation direction of a surface acoustic wave on the piezoelectric substrate, the spacing between input/output IDTs being larger than that of the first surface acoustic wave filter element by approximately half the wavelength of the surface-acoustic wave, and having first and second terminals;
the first terminals of the first and second surface acoustic wave filter elements being commonly connected to an unbalanced terminal, and the second terminals of the first and second surface acoustic wave filter elements being connected to a balanced terminal;
wherein in at least one of the first and second surface acoustic wave filter elements, at least one IDT-to-IDT spacing is different from the other IDT-to-IDT spacings by an integer multiple of the wavelength of the surface-acoustic wave.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/087,800Filed 5 Mar 2002
Priority: JP 2001-08513823 Mar 2001
Published: 7 Nov 2002
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

H03H 9/6436
Coupled resonator filters: having one acoustic track only
H03H 9/0071
Being electrically parallel: the balanced terminals being on the same side of the tracks
H03H 9/0085
Using surface acoustic wave devices: having four acoustic tracks
H03H 9/14582
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