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Surfac acoustic wave device and communication device comprising same

A surface acoustic wave and resonator technology, applied in piezoelectric devices/electrostrictive devices, electrical components, impedance networks, etc., can solve problems such as balance deterioration

Inactive Publication Date: 2003-08-06
MURATA MFG CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0012] However, in the above structure, since the phase of the resonator filter 110 is 180° different from that of the resonator filter 100, the signal terminal and the ground of the electrode fingers in the IDT 111 at the center of the resonator filter 110 are For the resonator type filter 100 reversed, therefore, it includes the situation that the number of signal terminals and grounding of the resonator type filter 100 and the resonator type filter 110 are different and the signal terminal and grounding in the boundary between IDT and IDT Factors that deteriorate the balance, such as the case where an unnecessary electric field is generated by paralleling
As a countermeasure to improve the balance, there is still a method of grounding the electrode finger of the signal terminal, but there is a problem in the balance

Method used

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  • Surfac acoustic wave device and communication device comprising same
  • Surfac acoustic wave device and communication device comprising same
  • Surfac acoustic wave device and communication device comprising same

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no. 1 approach

[0033] Based on Figure 1 to Figure 7A description of the first embodiment of the present invention follows. A surface acoustic wave device (SAW device) having an unbalanced-balanced conversion function according to this embodiment is shown in FIG. . These resonator filters 1, 2 have substantially equal passbands. In addition, these resonator filters 1 and 2 are provided on a piezoelectric substrate (not shown). The above-mentioned piezoelectric substrate is composed of lithium tantalate, lithium niobate, and the like.

[0034] In the resonator filter 1 described above, the IDT 11 is at the center, and the IDTs 12 and 13 are arranged on the left and right (right and left along the surface acoustic wave propagation direction) thereof. These IDTs 11 , 12 , 13 have reflectors 14 , 14 sandwiched from left and right (right and left along the surface acoustic wave propagation direction), respectively.

[0035] The above-mentioned resonator filter 2 has IDT21 as the center, and ...

no. 2 approach

[0054] Based on Figure 8 to Figure 10 A description of other embodiments of the present invention follows. In addition, for the convenience of description, the components having the same function as those shown in the above-mentioned first embodiment are assigned the same symbols, and the description thereof will be omitted.

[0055] In this embodiment, in the substantially same design as the surface acoustic wave device of the first embodiment, a notch wave including a resonator 31a connected to the unbalanced signal terminal 7 side and reflectors 32 and 32 sandwiching it The resonator 3 is changed to a trap resonator 3a including a resonator 31a and reflectors 32a and 32a sandwiching it. The resonator 31 and the resonator 31a have different crossing widths. In this way, in order to study the balance by the cross widths of the trap resonators 3 a and 4 , a specific example will be described. Table 3 shows design parameters in the above-mentioned surface acoustic wave devi...

no. 3 approach

[0061] based on Figure 14 to Figure 21 A description of other embodiments of the present invention follows.

[0062] A surface acoustic wave device (SAW device) having an unbalanced-balanced conversion function according to this embodiment is as follows: Figure 14 As shown, in LiTaO propagated by 40±5°YcutX 3 The formed piezoelectric substrate (not shown) is provided with longitudinally coupled resonator-type surface acoustic wave filters (surface acoustic wave elements) 501 and 502 formed by A1 electrodes, and has an impedance of 50Ω at the unbalanced signal end and an impedance of the balanced signal end. It is a 150Ω balanced-unbalanced signal conversion function. Furthermore, surface acoustic wave resonators (resonators) 503 and 504 are connected in series between the unbalanced signal terminal 515 and each of the longitudinally coupled resonator-type surface acoustic wave filters 501 and 502 .

[0063] The longitudinally coupled resonator type surface acoustic wave f...

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Abstract

A surface acoustic wave device has an unbalanced-to-balanced conversion function, which is capable of improving balanced characteristics, includes a first resonator filter and a second resonator filter, having a plurality of interdigital transducers disposed along the propagation direction of a surface acoustic wave. The surface acoustic wave device has an unbalanced-to-balanced conversion function as a result of the phase of the second resonator filter being reversed by 180 DEG with respect to that of the first resonator filter. The surface acoustic wave device further includes a first resonator connected in series to an unbalanced signal terminal side of the first resonator filter, and a second resonator connected in series to an unbalanced signal terminal side of the second resonator filter. The first resonator and the second resonator have different design parameters.

Description

technical field [0001] The present invention relates to a surface acoustic wave device used in a delay line, a filter, etc., and a communication device including the surface acoustic wave device. Background technique [0002] In recent years, electronic components have been required to be multifunctional due to miniaturization and weight reduction of electronic equipment. Against such a background, a surface acoustic wave filter (hereinafter referred to as a SAW filter) as a surface acoustic wave device used in a communication device such as a mobile phone is also required to have an unbalanced-balanced conversion function, In order to achieve direct connection with ICs that operate on balanced inputs, research has also become active. [0003] In particular, in a SAW device having an unbalanced-to-balanced conversion function composed of a resonator-type filter, the amplitude difference and phase difference on the balanced side become important characteristics (hereinafter ...

Claims

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Application Information

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IPC IPC(8): H03H9/64H01L41/08H03H9/145H03H9/25
CPCH03H9/0071H03H9/14582H03H9/25
Inventor 柴田治高峰裕一
Owner MURATA MFG CO LTD
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