JP2003298383A - Surface acoustic wave element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave element as a langasite piezoelectric crystal substrate which facilitates the electrode design and improves its flexibility. <P>SOLUTION: The surface acoustic element includes a surface acoustic wave converter which has a positive electrode finger connected to a positive electrode and a negative electrode finger connected to a negative electrode formed on a surface of the langasite single crystal substrate 300. The surface acoustic wave converter has a transmission side converter 310 for generating an excitation wave and a receiving side converter 320 for receiving the excitation wave, and the respective electrodes are formed along the propagation direction of the surface acoustic wave so that natural directionality disappears. And W (tungsten) is used as the electrode material of the surface acoustic wave converter. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device used in mobile communication equipment and the like.

[0002]

2. Description of the Related Art In recent years, mobile communication devices such as mobile phones and mobile terminals have been dramatically spread, but filters used for these terminals are required to have characteristics such as low loss, wide band and small size. A transmission type surface acoustic wave (SAW) filter having a single-phase unidirectional converter has been put into practical use as a device that satisfies the characteristics of (1). In a single-phase unidirectional filter,
The phase difference between the excitation wave and the reflected wave becomes in-phase in the front (forward direction) and the two waves strengthen each other, and 2 in the opposite direction (reverse direction).
Since the two waves cancel each other, the surface acoustic wave is strongly excited only in the forward direction. As a result, the unidirectional direction of the transmitting electrode and the receiving electrode is made to face each other, and theoretically
It is possible to realize a low loss filter of dB or less.

As a method for realizing a one-way converter,
EWC-SPUDT and DART-SPUDT using an asymmetrical electrode structure have been devised. In addition to these filters that utilize the asymmetry of the electrode structure, a natural unidirectional filter (NSPUDT: N
atural Single Phase Unidirecitonal Transduce
There is something called r). The natural unidirectional filter realizes unidirectionality by utilizing the asymmetry of the substrate crystal. For this reason, a regular interdigital transducer (ID
T) structure, which has both electrode width and electrode spacing of λ /
Unidirectionality can be realized with a converter having a structure in which a plurality of positive and negative electrode fingers to be 4 are periodically and continuously arranged.

Even if a normal type IDT is formed on an ST-X crystal substrate to generate a surface acoustic wave, the wave propagates in both directions of the normal type IDT, and unidirectionality cannot be realized. In other words, natural unidirectionality means normal type IDT on the surface of the piezoelectric substrate.
It shows the characteristics of the substrate in which the surface acoustic waves are strongly excited in one direction when the is formed. In the surface acoustic wave converter using the natural unidirectional substrate, since the anisotropy of the substrate itself is used, it is not possible to face the forward direction of the transmitter side transducer and the receiver side transducer. It is impossible to fabricate a low-loss filter unless the transmitting and receiving electrodes can face each other unidirectionally.

As a means for solving this problem, an electrode structure for reversing the direction of natural unidirectionality by Takeuchi et al. Is disclosed in Japanese Patent Application Laid-Open No. 8-125484, which is arranged at a pitch of λ with a width of approximately λ / 8. A surface acoustic wave converter has been proposed which is composed of positive and negative electrode fingers and a floating electrode having an electrode width of 3 / 8λ, which is arranged between the electrode fingers at an edge distance of approximately λ / 8.

[0006]

The characteristics of the surface acoustic wave device depend on the characteristics of the piezoelectric crystal used as the substrate. It is important that the piezoelectric crystal has a large electromechanical coupling coefficient and good frequency-temperature characteristics. At present, langasite is attracting attention as a crystal that simultaneously satisfies these two characteristics. Eulerian angle display (φ, θ, ψ) -5 ° ≤ φ ≤ 5 °, 1
Langasite in the range of 35 ° ≦ θ ≦ 145 ° and 20 ° ≦ ψ ≦ 30 ° has an electromechanical coupling coefficient of 0.3% to 0.
4%, the frequency-temperature characteristic exhibits a second-order dependence, and the peak temperature exists near room temperature. Electromechanical coupling coefficient is ST
This crystal is about three times that of quartz, and its second-order temperature coefficient in frequency-temperature characteristics is twice as good as that of quartz, which is expected to be applied to a low-loss surface acoustic wave filter.

The Langasite single crystal within the above range in Euler angle display has NSPUDT characteristics, and in order to realize a low loss filter using this substrate, electrodes which are unidirectionally opposed to each other are used for transmitting and receiving electrodes. The structure must be constructed. Therefore, when a normal type IDT in which a plurality of positive and negative electrode fingers whose electrode width and electrode interval are both λ / 4 are periodically arranged is used for the transmitting electrode, the receiving electrode has unidirectionality. The inverted structure must be used. However, the electrode structure proposed by Takeuchi et al. Cannot meet the demand for low loss of the filter.

In general, Al is used as the material of the electrodes formed on the piezoelectric crystal substrate used for the surface acoustic wave device. In this case, as described above, when quartz is used as the piezoelectric crystal substrate, even if Al is used as the electrode material, the surface acoustic wave propagates in both directions of the surface acoustic wave converter. Is used as the piezoelectric crystal substrate and Al is used as the electrode material, a phase shift occurs between the excitation wave and the reflected wave, and unidirectionality occurs.

For this reason, natural unidirectionality (NSPUDT characteristic)
To use the Langasite having a as a piezoelectric crystal substrate and design the electrodes so that the direction of the propagation direction of the surface acoustic wave is opposed to the transmitting side and the receiving side on this electrocrystalline substrate,
The electrodes on the transmitting side and the electrodes on the receiving side need to have different structures. In this case, the structure of the inversion electrode that changes the directionality of the electrode from the natural unidirectional direction to the opposite direction becomes complicated, and SA
The design of the W filter is complicated. Further, there is a problem that the reflection coefficient of the electrode with respect to the elastic wave is small and the reversal of the directionality is insufficient.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a surface acoustic wave device using a langasite as a piezoelectric crystal substrate, which facilitates electrode design and improves the degree of freedom. And

[0011]

In order to achieve the above object, the invention according to claim 1 is connected to a positive electrode finger connected to a positive electrode formed on the surface of a Langasite single crystal substrate and a negative electrode. A surface acoustic wave device having a surface acoustic wave converter including a negative electrode finger, the surface acoustic wave converter including a transmitting side transducer that generates an exciting wave and a receiving side transducer that receives the exciting wave. And each electrode is formed along the propagation direction of the surface acoustic wave so that the natural unidirectionality disappears, and the electrode material of the surface acoustic wave converter is W. It is characterized by

The invention described in claim 2 is the same as claim 1.
In the surface acoustic wave device described in the paragraph (1), the transmitting side transducer includes a first positive electrode finger and a second positive electrode finger which are adjacent to each other in the positive electrode finger in the propagation direction of the surface acoustic wave. A first negative electrode finger adjacent to one side, and the positional relationship between the first and second positive electrode fingers and the first negative electrode finger and the width of each electrode finger are determined by the wavelength of the surface acoustic wave. When λ, the width W1 of the first positive electrode finger is 13λ / 48 ≦ W1 ≦ 16λ / 48,
The width W2 of the second positive electrode finger is W2 = λ / 8,
The width W3 of the negative electrode finger is W3 = λ / 8, and the gap d1 between the first positive electrode finger and the second positive electrode finger is 3λ / 4.
8 ≦ d1 ≦ 6λ / 48, the gap d2 between the second positive electrode finger and the first negative electrode finger is d2 = λ / 8, and the gap d3 between the first negative electrode finger and the next adjacent positive electrode finger. Is 14λ / 48 ≦ d3 ≦ 8λ
/ 48.

The invention described in claim 3 is the same as claim 1
Or the surface acoustic wave device according to any one of 2 above,
The receiving-side transducer includes fourth and fifth positive electrode fingers in a surface acoustic wave propagation direction, and a second negative electrode located between the fourth positive electrode finger and the fifth positive electrode finger. A finger, and the positional relationship between the fourth and fifth positive electrode fingers and the second negative electrode finger and the width of each electrode finger is such that the width W4 of the fourth positive electrode finger is 13λ / 4.
8 ≦ W4 ≦ 16λ / 48, the width W5 of the fifth positive electrode finger is W5 = λ / 8, and the width W6 of the second negative electrode finger is W6 = λ
/ 8, and the gap d4 between the fourth positive electrode finger and the second negative electrode finger is 3λ / 48 ≦ d4 ≦ 6λ / 48, and the second
Of the negative electrode finger and the fifth positive electrode finger of d5 = λ /
8. The gap d6 between the fifth positive electrode finger and the next adjacent positive electrode finger is 14λ / 48 ≦ d6 ≦ 8λ / 48.

The invention according to claim 4 is the same as claim 1
In the surface acoustic wave device according to any one of items 1 to 3, 0.03 <λ / H <0., Where H is a film thickness of an electrode in the surface acoustic wave converter and λ is a wavelength of the surface acoustic wave. 0
It is characterized by being 5.

The invention described in claim 5 is the same as claim 1.
The surface acoustic wave device according to any one of claims 1 to 4, wherein the transmitting side converter is a receiving side converter and the receiving side converter is a transmitting side converter.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. First, a so-called normal type electrode (normal type IDT), in which a plurality of positive and negative electrode fingers having an electrode width and an electrode interval of λ / 4 are periodically arranged, is formed on a Langasite piezoelectric substrate. The principle of having natural unidirectionality when driven by excitation will be described with reference to FIG.

FIG. 1 shows a schematic diagram of a normal type electrode. In the same figure, this normal type electrode is composed of a positive electrode 1 and a negative electrode 2, and a positive electrode finger 1A that constitutes the positive electrode 1 and a negative electrode 2 that constitutes the negative electrodes 2 arranged to the left and right of this positive electrode finger 1A. An electric field is generated between the electrode fingers 2A and 2B. At this time,
The excitation center of the surface acoustic wave generated on the Langasite piezoelectric substrate by being excited by this electric field is the positive electrode finger 1A.
Is almost the center A of.

Further, in this electrode structure, the electrode fingers of the electrode width λ / 4, which are periodically arranged, serve as the reflection source of the surface acoustic wave. Since the reflection is caused by the discontinuity of the acoustic impedance, the surface acoustic wave is reflected at the end of each electrode finger. In this way, the surface acoustic waves are reflected at two positions on both ends of the electrode finger, but it is considered that they are equivalently reflected at the center of the electrode finger, and there is no problem. At this time, the phase of the reflected wave changes. This amount of change depends on the type of piezoelectric substrate, its cut surface, the propagation direction of surface acoustic waves, and the electrode material and its thickness. For example, when ST-cut X-propagation quartz is used for the piezoelectric substrate and Al is used as the metal material, the phase of the reflected wave is delayed by 90 °, that is, the amount of phase change is 90 °.

On the other hand, as a piezoelectric crystal, the substrate orientation and the surface acoustic wave propagation direction are represented by Euler angles (φ, θ, ψ).
-5 ° ≦ φ ≦ 5 °, 135 ° ≦ θ ≦ 145
A normal type IDT using a Langasite single crystal in the range of °, 20 ° ≤ ψ ≤ 30 °, or a crystallographically equivalent orientation as the substrate and Al as the electrode material.
When the is formed, the phase change amount of the surface acoustic wave reflected by the electrode finger is −90 ° + 2α. When this 2α is considered to be the phase shift at the time of reflection, if the reflection center is defined as being displaced from the center of the electrode finger by the amount corresponding to this 2α, the shift δ of the reflection center is

[Equation 1] Becomes When δ is positive, the center of reflection is shifted to the right from the center of the electrode finger, and when δ is negative, the reflection center is shifted to the left.

When the deviation between the center of reflection and the center of the electrode finger is λ / 8, the wave excited by the positive electrode finger 1A and the reflection center B of the adjacent negative electrode finger 2A and the positive electrode finger 1A. Considering the phase at the point A of the wave reflected at the end C using FIG. 1,
The phase at the point A of the wave reflected on the path of A → B → A is

[Equation 2] And has the same phase as the excitation wave. On the other hand, A → C
→ The phase at the point A of the wave reflected on the path of A is

[Equation 3] And the opposite phase of the excitation wave. For this reason, the surface acoustic wave is strongly excited in the right direction in FIG. 1, and unidirectionality is realized.

From the above, as shown in FIG. 2, the distance between the excitation center and the reflection center is

[Equation 4] Then, it becomes possible to realize unidirectionality from the excitation center to the reflection center. That is, when a periodic electrode structure (IDT) capable of exciting surface acoustic waves is formed on an arbitrary crystal, whether or not the surface acoustic wave converter has one-sidedness is determined by the positions of the excitation center and the reflection center. If it can be identified, it can be determined. The positions of the excitation center and the reflection center are described by the mode coupling parameter when using the mode coupling theory.

The mode coupling parameters are self-coupling coefficient κ ₁₁ , intermode coupling coefficient κ ₁₂ , excitation coefficient ζ, and capacitance C.
Consists of. Here, the coupling coefficient between modes κ ₁₂ is

[Equation 5] The phase component of corresponds to the deviation of the reflection center from the reference surface, and the magnitude of the deviation is expressed by equation (1).

The excitation coefficient ζ is

[Equation 6] And from the reference plane

[Equation 7] However, it may be considered that the excitation center is located at a distance. Therefore, in order for the difference between the reflection center and the excitation center to satisfy Eq. (4), the difference between the phases of the coupling coefficient between modes and the excitation coefficient ζ is

[Equation 8] It would be good if there was a relationship.

However, it is difficult to design a SAW filter in consideration of the unidirectionality expressed by the value of α. In the present invention, the phase shift α of the reflected wave in the surface acoustic wave element is
However, by appropriately selecting the electrode material, the film thickness of the electrode, and the electrode pitch so that α = 0 °, the natural unidirectionality of the surface acoustic wave device using the langasite as the piezoelectric crystal substrate can be improved. Extinguish. As a result, in the surface acoustic wave device in which the Langasite is used as the piezoelectric crystal substrate and the normal type IDT is formed on the substrate, the propagation directions of the surface acoustic waves are bidirectional, so that the electrodes can be formed according to the required characteristics of the SAW device. It is not necessary to complicate the arrangement and shape of the electrodes, and the electrode design can be facilitated.

FIG. 3 is a characteristic diagram showing the result of simulating the relationship between H / λ and the phase shift α for a plurality of electrode materials in the surface acoustic wave device to which the present invention is applied. The simulation method will be described below.

From the upper and lower limit frequencies of the stop band of the grating reflector corresponding to the case where the electric terminals of the normal type IDT are short-circuited and opened, the potential standing wave distribution on the substrate surface, and the electrostatic capacitance Cs per pair of electrodes. Various constants in the mode coupling equation can be obtained. The hybrid finite element method was used to calculate all the quantities necessary for these calculations.

As shown in FIG. 3 by the above simulation, when Ta is used as the electrode material, H /
α = 0 ° near λ = 0.0375, and when H is used as an electrode material, α = 0 ° near H / λ = 0.0325, and a surface acoustic wave device using Langasite as a piezoelectric crystal substrate. The natural one-way nature of can be eliminated. Further, it is found that when Al is used as the electrode material, the phase shift does not converge, and the natural unidirectionality of the surface acoustic wave device using the langasite as the piezoelectric crystal substrate cannot be eliminated.

Therefore, when Ta is selected as the electrode material, in the range of 0.035 <H / λ <0.04,
When W is selected as the electrode material, 0.03
It is preferable to determine the arrangement of the electrodes within the range of <H / λ <0.05.

The surface acoustic wave device according to this embodiment is a surface acoustic wave conversion device including a positive electrode finger connected to a positive electrode formed on the surface of a Langasite single crystal substrate and a negative electrode finger connected to a negative electrode. A surface acoustic wave device having a container, wherein the surface acoustic wave converter is a transmitter transducer that generates an excitation wave,
The transducer is a receiving side transducer that receives this excitation wave, and each of the transducers has the electrodes formed along the propagation direction of the surface acoustic wave so that the natural unidirectionality disappears. It is characterized in that the electrode material of the converter is W.

The surface acoustic wave converter on the transmitting side used in the surface acoustic wave element according to the present embodiment is, as shown in FIG.
First and second positive electrode fingers 12 and 14 which are composed of a positive electrode 10 and a negative electrode 20 and which are adjacent to each other in the surface acoustic wave propagation direction;
It has a first negative electrode finger 22 adjacent to one side of the second positive electrode finger 14.

The first and second positive electrode fingers 12, 14 and the first
The positional relationship of the negative electrode finger 22 and the width of each electrode finger are such that the width W of the first positive electrode finger 12 is W, where λ is the wavelength of the surface acoustic wave.
1 is 13λ / 48 ≦ W1 ≦ 16λ / 48, the width W2 of the second positive electrode finger 14 is W2 = λ / 8, and the width W3 of the first negative electrode finger 22 is W3 = λ / 8. First positive electrode finger 12 and second
Of the positive electrode finger 14 of 3λ / 48 ≦ d1 ≦ 6
λ / 48, the space d2 between the second positive electrode finger 14 and the first negative electrode finger 22 is d2 = λ / 8, and the space d3 between the first negative electrode finger 22 and the next adjacent positive electrode finger 16 is d3. Is 14λ / 48 ≦ d3 ≦
It is 8λ / 48.

Further, as shown in FIG. 5, the receiving side surface acoustic wave converter used in the surface acoustic wave device according to the present embodiment is composed of a positive electrode 100 and a negative electrode 200, and the surface acoustic wave The fourth and fifth positive electrode fingers 102, 10 are arranged in the propagation direction.
4, the fourth positive electrode finger 102 and the fifth positive electrode finger 104
And a second negative electrode finger 202 located between and.

The positional relationship between the fourth and fifth positive electrode fingers 102 and 104 and the second negative electrode finger 202 and the width of each electrode finger is such that the width W4 of the fourth positive electrode finger 102 is 13λ / 48 ≦ W4. ≤16
λ / 48, the width W5 of the fifth positive electrode finger 104 is W5 = λ /
8. The width W6 of the second negative electrode finger 202 is W6 = λ / 8, and the gap d4 between the fourth positive electrode finger 102 and the second negative electrode finger 202 is 3λ / 48 ≦ d4 ≦ 6λ / 48, the gap d5 between the second negative electrode finger 202 and the fifth positive electrode finger 104 is d5 = λ
/ 8, positive electrode finger 1 adjacent to the fifth positive electrode finger 104 next
The gap d6 with 06 is 14λ / 48 ≦ d6 ≦ 8λ / 48.

Next, the structure of the transmission type surface acoustic wave filter manufactured by using the electrode structure of the surface acoustic wave converter used in the surface acoustic wave device according to the embodiment of the present invention shown in FIGS. 4 and 5 will be described. As shown in FIG. In the figure, on the Langasite single crystal substrate 300 along the propagation direction of the surface acoustic wave,
Normal type IDT as a transmitter converter (corresponding to transmitter electrode)
310 and a normal type IDT 320 as a receiving side converter (corresponding to a receiving electrode) are provided via a shield electrode 330. The shield electrode 330 has a function of reducing direct waves.

The normal type IDT 310 is composed of a positive electrode 312 and a negative electrode 314, each electrode width and electrode spacing are as shown in FIG. 4, and the electrode structure shown in FIG. 4 is periodically and continuously arranged. The unidirectionality is realized by utilizing the NSPUDT characteristic. Further, the IDT 320 as a receiving electrode is composed of a positive electrode 320 and a negative electrode 324, and the electrode width and the electrode interval are as shown in FIG.
The electrode structure shown in FIG. 5 is formed such that a plurality of electrode structures are periodically and continuously arranged, and unidirectionality is realized by utilizing NPUDT characteristics. In FIG. 6, a sound absorbing material is applied to the end portion of the Langasite substrate 300, and has a function of absorbing unnecessary surface acoustic waves.

FIG. 7 shows frequency characteristics of the transmission type surface acoustic wave filter having the above structure. As is apparent from FIG. 7, the transmission type surface acoustic wave filter manufactured by using tungsten (W) to which the present invention is applied as an electrode material has features of low insertion loss and wide pass band. There is. The transmitting side converter in the surface acoustic wave device shown in FIG. 4 may be used as the receiving side converter, and the receiving side converter in the surface acoustic wave device shown in FIG. 4 may be used as the transmitting side converter. Even with such a configuration, the same effect as that obtained by the above-described embodiment of the present invention can be obtained.

[0037]

As described above, according to the present invention, a surface acoustic wave device having a surface acoustic wave transducer formed of a positive electrode finger and a negative electrode finger formed on the surface of a Langasite single crystal substrate is provided. Therefore, in the surface acoustic wave converter using W as the electrode material, the electrodes are formed along the propagation direction of the surface acoustic wave so that the natural unidirectionality disappears.
It is possible to facilitate the electrode design and improve the degree of freedom in the surface acoustic wave device using the langasite as the piezoelectric crystal substrate.

[Brief description of drawings]

FIG. 1 is a plan view showing an electrode structure of a normal type IDT.

FIG. 2 is an explanatory view showing a positional relationship between an excitation center and a reflection center for realizing unidirectionality by the normal type IDT shown in FIG.

FIG. 3 is a characteristic diagram showing a result of simulating a relationship between H / λ and a phase shift α for a plurality of electrode materials in the surface acoustic wave device according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an electrode structure of a surface acoustic wave converter on the transmitting side used in the surface acoustic wave device according to the embodiment of the invention.

FIG. 5 is an explanatory diagram showing an electrode structure of a surface acoustic wave converter on the receiving side used in the surface acoustic wave device according to the embodiment of the invention.

FIG. 6 is an explanatory diagram showing a configuration of a transmission type surface acoustic wave filter manufactured by using an electrode structure of a surface acoustic wave converter used in the surface acoustic wave device according to the embodiment of the invention.

7 is a characteristic diagram showing frequency characteristics of the transmission type surface acoustic wave filter shown in FIG.

[Explanation of symbols]

1, 10, 100, 310, 322 ... Positive electrode 2, 20, 200, 314, 324 ... Negative electrode 1A, 12, 14, 16, 102, 104, 106 ... Positive electrode finger 2A, 2B, 22, 202 ... Negative Electrode finger 300 ... Langasite substrate 310 ... Transmitting side converter 320 ... Receiving side converter 330 ... Shield electrode 340 ... Sound absorbing material

Continued front page    (72) Inventor Satoshi Uda             Saitama Prefecture Chichibu City Yokose Town 2270 Yokoze             Ryo Materials Co., Ltd. Ceramics Factory Den             Child Device Development Center (72) Inventor Koji Hasegawa             Muroran Industry Co., Ltd. 27-1, Mizumoto-cho, Muroran-shi, Hokkaido             University of Electrical and Electronic Engineering F term (reference) 5J097 AA01 AA13 BB11 CC15 DD05                       DD14 DD18 DD28 FF01 FF03                       GG01 GG05 KK03 KK05

Claims (5)

[Claims] 1. A surface acoustic wave device having a surface acoustic wave converter including a positive electrode finger connected to a positive electrode formed on a surface of a Langasite single crystal substrate and a negative electrode finger connected to a negative electrode. The surface acoustic wave converter includes a transmitter transducer that generates an excitation wave and a receiver transducer that receives the excitation wave, and each transducer has a surface acoustic wave so that the natural unidirectionality disappears. The respective electrodes are formed along the propagation direction of
A surface acoustic wave device, wherein the electrode material of the surface acoustic wave converter is W. 2. The transmitter transducer is adjacent to first and second positive electrode fingers of the positive electrode finger which are adjacent to each other in the propagation direction of the surface acoustic wave and one side of the second positive electrode finger. A first negative electrode finger, the positional relationship between the first and second positive electrode fingers and the first negative electrode finger, and the width of each electrode finger, when the wavelength of the surface acoustic wave is λ. And the width W1 of the first positive electrode finger is 13λ / 48 ≦
W1 ≦ 16λ / 48, the width W2 of the second positive electrode finger is W
2 = λ / 8, the width W3 of the first negative electrode finger is W3 = λ /
8 and the gap d1 between the first positive electrode finger and the second positive electrode finger is 3λ / 48 ≦ d1 ≦ 6λ / 48, and the gap between the second positive electrode finger and the first negative electrode finger is The gap d2 is d2 = λ / 8, the first
The gap d3 between the negative electrode finger and the next adjacent positive electrode finger is 14
The surface acoustic wave device according to claim 1, wherein λ / 48 ≦ d3 ≦ 8λ / 48. 3. The transducer on the receiving side is located between the fourth and fifth positive electrode fingers in the propagation direction of the surface acoustic wave and between the fourth positive electrode finger and the fifth positive electrode finger. A second negative electrode finger, and the positional relationship between the fourth and fifth positive electrode fingers and the second negative electrode finger and the width of each electrode finger is the width W4 of the fourth positive electrode finger.
Is 13λ / 48 ≦ W4 ≦ 16λ / 48, the width W5 of the fifth positive electrode finger is W5 = λ / 8, and the width W of the second negative electrode finger is
6 is W6 = λ / 8, and the gap d4 between the fourth positive electrode finger and the second negative electrode finger is 3λ / 48 ≦ d4 ≦ 6λ / 4.
8. Gap d5 between the second negative electrode finger and the fifth positive electrode finger
Is d5 = λ / 8, and the gap d6 between the fifth positive electrode finger and the next adjacent positive electrode finger is 14λ / 48 ≦ d6 ≦ 8λ / 48. The surface acoustic wave device as described in 1. 4. When the film thickness of the electrode in the surface acoustic wave converter is H and the wavelength of the surface acoustic wave is λ, 0.03.
4. The surface acoustic wave device according to claim 1, wherein <λ / H <0.05. 5. The transmitting side converter is a receiving side converter,
The surface acoustic wave device according to claim 1, wherein the transducer on the receiving side is a transducer on the transmitting side.