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Surface acoustic wave device

A surface elastic wave and substrate technology, applied in the direction of electrical components, impedance networks, etc., can solve the problems of SAW speed increase, frequency temperature coefficient increase and decrease, etc., and achieve the effect of large electrical mechanical coupling coefficient and small SAW speed

Inactive Publication Date: 2002-07-10
TDK CORPARATION
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0010] However, in conventionally known substrates having unidirectional characteristics, the SAW speed becomes large, and the electromechanical coupling coefficient k 2 become smaller, the frequency temperature coefficient becomes larger, etc.

Method used

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Examples

Experimental program
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Effect test

no. 1 example

[0054] In the first embodiment, a cut substrate 1 of (0°, 140°, 23°) represented by Euler angles included in the first region is prepared to fabricate a surface acoustic wave filter. In this filter, the number of pairs of interdigitated electrodes 2 is 100 pairs, the opening length (the length of the intersecting portion) is 80λ (λ is the wavelength of the surface acoustic wave), and as the film thickness h of the electrode and the wavelength of the surface acoustic wave The normalized film thickness h / λ of the λ ratio is 0.02.

[0055] Figure 4 It is the relationship between the normalized frequency and the conversion loss, which is the frequency characteristic of the above-mentioned filter obtained in the calculation. exist Figure 4 In , the solid line indicates the characteristics in the forward direction, and the dashed line indicates the characteristics in the reverse direction. as from Figure 4 As can be seen, there is a large difference in the conversion loss bet...

no. 2 example

[0059] In the second embodiment, using the cut substrate 1 represented by Euler angles (0°, 140°, 23°) contained in the first region, the Figure 5 The measurement device including the surface acoustic wave filter is shown, and the transmission characteristics of the device are measured. Figure 5 The shown measurement device includes: a transmitting electrode 2A provided on a substrate 1 as an interdigital electrode, and two receiving electrodes 2B arranged on both sides of the transmitting electrode 2A in the propagation direction of a surface acoustic wave.

[0060] exist Figure 5 In the measurement device shown, the electrode period (λ) is 30 μm, the number of pairs of transmitting electrodes 2A is 100.5 pairs, the opening length (the length of the intersection portion) is 30λ, and the number of pairs of receiving electrodes 2B is 20.5 pairs. In this example, a measurement device with a normalized film thickness h / λ of 0.01 and a measurement device with a normalized film...

no. 3 example

[0063] In the third embodiment, using the cut substrate 1 represented by Euler angles (0°, 140°, 25°) included in the first area, a Figure 5 The measurement device including the surface acoustic wave filter is shown, and the transmission characteristics of the device are measured. Other conditions of the measurement device are the same as those of the second example.

[0064] Figure 8 It shows the results of measuring the transmission characteristics of a measurement device with a normalized film thickness h / λ of 0.01, that is, the relationship between frequency and insertion loss. and, Figure 9 It shows the results of measuring the relationship between frequency and insertion loss, which is the transmission characteristic of a measurement device whose normalized film thickness h / λ is 0.02. exist Figure 8 and Figure 9 In , the solid line indicates the characteristics in the forward direction, and the dashed line indicates the characteristics in the reverse direction....

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Abstract

The invention is to realize a surface acoustic wave device that attains a wide band and a small size, and lowers a loss by utilizing the natural single-phase unidirectional transducer characteristics. The surface acoustic wave device comprises a piezoelectric substrate (1) and a pair of interdigitated electrodes (2) provided on one main surface of the piezoelectric substrate 1. As the material of the piezoelectric substrate (1), a single crystal is used that belongs to the point group 32, has the Ca3Ga2Ge4O14 type crystalline structure, comprises La, Ta, Ga and O as main components, and is represented by a chemical formula La3Ta0.5Ga5.5O14. When the cut angle of the substrate (1) and the propagation direction are represented by Eulerian angles (phi, theta, psi), phi, theta and psi are in a first region where phi is from -50 DEG C to 5 DEG C, theta is from 135 DEG C to 155 DEG C, and psi is from 15 DEG C to 40 DEG C, or in a second region where phi is from 10 DEG C to 20 DEG C, theta is from 140 DEG C to 157 DEG , and psi is from 30 DEG C to 60 DEG C.

Description

technical field [0001] The present invention relates to a surface acoustic wave device having inherent characteristics of a single-phase unidirectional transducer (Natural Single-Phase Unidirectional Transducer). Background technique [0002] In recent years, mobile communication terminals such as mobile phones have spread rapidly. Such a terminal device is particularly desired to be small and light because of its portability. In order to realize the miniaturization and weight reduction of the terminal, electronic components used therein are required to be small and lightweight. Therefore, surface acoustic wave devices, which are advantageous for size and weight reduction, that is, surface acoustic wave filters, are often used in the high frequency section and the intermediate frequency section of terminal equipment. In the surface acoustic wave device, interdigitated electrodes for exciting, receiving, reflecting or transmitting surface acoustic waves are formed on a piez...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03H9/02H03H9/145H03H9/25
CPCH03H9/14505H03H9/02543H03H9/0259
Inventor 竹内正男井上宪司佐藤胜男
Owner TDK CORPARATION
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