JP2001285001A - Manufacturing method for surface acoustic wave filter, surface acoustic wave filter, and communications equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To design a flexible surface acoustic wave filter on an NSPUDT substrate where the excitation of a surface acoustic wave becomes unidirectional because of the anisotropy of crystal. SOLUTION: This surface acoustic wave filter 105 has a piezoelectric substrate 101 having NSPUDT characteristics, and one transmission-side interdigital transducer(IDT) electrode 103, which is provided on the piezoelectric substrate and sends the surface acoustic wave and one reception-side IDT electrode 104, which receives the surface acoustic wave, and the directivity of the surface acoustic wave is set by setting the width of the electrode fingers of the transmission-side IDT electrode 103.

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 filter used for a high-frequency circuit in a wireless communication device and a communication device.

[0002]

2. Description of the Related Art In recent years, surface acoustic wave filters have been widely used as RF and IF stage filters in transmission / reception circuits of communication equipment. Particularly recently, La ₃ Ga ₅ SiO ₁₄ and La
_{3 Ga 5 .5 Nb 0.5 O 14} , La 3 Ta 0.5 Ga 5.5 O 14, Li
₂ B ₄ O ₇ Development of a surface acoustic wave filter using a piezoelectric substrate having a natural unidirectional (NSPUDT property), such as are becoming popular.

The NSPUDT characteristic means that a phase difference is generated between the excitation center and the reflection center only by periodically arranging the electrode fingers due to the anisotropy of the crystal of the substrate, and the surface acoustic wave from the IDT becomes unidirectional. It is a substrate. While referring to the drawings below,
An example of a conventional surface acoustic wave filter using a piezoelectric substrate having NSPUDT characteristics will be described.

FIG. 4 shows an NSP conventionally known in general.
The outline of a surface acoustic wave filter using a piezoelectric substrate having UDT characteristics is shown. Reference numeral 401 denotes a piezoelectric substrate having NSPUDT characteristics, and a surface acoustic wave is excited by forming an electrode pattern thereon. 403 is a transmitting side IDT electrode,
Reference numeral 04 denotes a receiving-side IDT electrode, and the IDT electrodes 403, 4
Reference numeral 04 denotes a transversal SAW filter 405 which is installed at a distance of SAW propagation distance W1.

The wavelength at the center frequency of the surface acoustic wave excited by the SAW filter 405 is defined as λ. Further, the transmitting side IDT electrode 403 and the receiving side IDT electrode 404
Are defined as + X direction, and the opposite direction is defined as -X direction. The transmitting-side IDT electrode 403 is a single IDT electrode in which positive and negative electrode fingers having a width of about λ / 4 are alternately arranged one by one with a center-to-center distance of each electrode being λ / 2.
The positive and negative electrode fingers of about λ / 8 width set the distance between the centers of the electrodes to λ.
/ 4 are double IDT electrodes alternately arranged two by two.

When a signal is applied to the transmitting IDT electrode 403, a surface acoustic wave is strongly excited in the + X direction due to the NSPUDT characteristic of the piezoelectric substrate 401.

[0007]

However, the above configuration has a problem that the target surface acoustic wave filter cannot be designed flexibly because the electrode finger of the transmitting IDT electrode has a width of about λ / 4. Was.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem of the conventional surface acoustic wave filter on a piezoelectric substrate having NSPUDT characteristics, and has as its object to increase the degree of freedom in designing a surface acoustic wave filter. I do.

[0009]

In order to achieve the above object, a first aspect of the present invention (corresponding to claim 1) is an NSPUD.
A step of providing at least one transmitting interdigital transducer (IDT) electrode for transmitting a surface acoustic wave and at least one receiving IDT electrode for receiving the surface acoustic wave on a piezoelectric substrate having T characteristics. A method for manufacturing a surface acoustic wave filter, comprising a step of setting the one-directional strength of the surface acoustic wave by controlling a width of an electrode finger of the transmitting-side IDT electrode. This is a method for manufacturing a surface acoustic wave filter.

Further, the second invention (corresponding to claim 2)
Is a step of controlling the thickness of the electrode finger of the transmission-side IDT electrode to set the strength of the surface acoustic wave in one direction.

Further, a third aspect of the present invention (corresponding to claim 3)
Is a surface acoustic wave filter manufactured by the method for manufacturing a surface acoustic wave filter according to the first or second aspect of the present invention,
At least a piezoelectric substrate having NSPUDT characteristics, a transmitting-side interdigital transducer (IDT) electrode for transmitting a surface acoustic wave, and a receiving-side IDT electrode for receiving the surface acoustic wave, provided on the piezoelectric substrate. It is a surface acoustic wave filter characterized by being provided one by one.

Further, the fourth invention (corresponding to claim 4)
The present invention is characterized in that at least two electrode fingers of the transmitting-side IDT electrode are provided within one wavelength of the surface acoustic wave.

Further, the fifth invention (corresponding to claim 5)
Wherein at least one electrode finger of the at least two transmitting-side IDT electrodes provided within one wavelength of the surface acoustic wave has a width different from other electrode fingers. This is the invention.

Further, a sixth aspect of the present invention (corresponding to claim 6)
The present invention is characterized in that the electrode fingers of the transmitting-side IDT electrode have respective widths set for each wavelength unit.

A seventh aspect of the present invention (corresponding to claim 7)
Indicates that the transmitting-side IDT electrode has the electrode finger having a period λ.
(Λ: one wavelength of the center frequency of the surface acoustic wave) has a positive electrode and a negative electrode, and the receiving-side IDT electrode has two electrode fingers each having a center-to-center distance of about λ / 4. Has a positive electrode and a negative electrode arranged at a period λ, and in the transmitting-side IDT electrode, an interval between the electrode finger of the positive electrode and the electrode finger of the negative electrode is about λ / 2. In the receiving IDT electrode, the interval between the pair of two electrode fingers of the positive electrode and the pair of two electrode fingers of the non-electrode is about λ.
/ 2, and the width of the electrode finger of the wave receiving side IDT electrode is substantially λ / 8.

An eighth aspect of the present invention (corresponding to claim 8)
Means that the width of the electrode finger of the transmitting side IDT electrode is substantially λ / 4
The present invention is characterized in that:

The ninth invention (corresponding to claim 9)
Means that the width of the electrode finger of the transmitting-side IDT electrode is substantially λ
/ 4 of the present invention.

A tenth aspect of the present invention (corresponding to claim 10) comprises a first filter track and a second filter track provided on the piezoelectric substrate in parallel with each other, and the first filter The track includes a first transmitting interdigital transducer (IDT) electrode for transmitting a surface acoustic wave, a first reflector for reflecting the surface acoustic wave, and the first IDT electrode and the first reflection. A first receiving-side IDT electrode that receives the surface acoustic wave and is disposed between the first and second filter tracks, and the second filter track includes a second transmitting side that transmits the surface acoustic wave. An interdigital transducer (IDT) electrode, a second reflector for reflecting the surface acoustic wave, and receiving the surface acoustic wave disposed between the second IDT electrode and the second reflector Second receiving wave An IDT electrode, a distance between the first transmitting-side IDT electrode and the first receiving-side IDT electrode, and a distance between the second transmitting-side IDT electrode and the second receiving-side IDT electrode. Are substantially the same, and the first
The difference between the distance between the receiving side IDT electrode and the first reflector and the distance between the second receiving side IDT electrode and the second reflector is (n + ／) λ ( λ: one wavelength of the center frequency of the surface acoustic wave, n: 0 or a positive integer), and the first transmitting IDT electrode and the second transmitting IDT electrode, or the first receiving. A surface acoustic wave filter in which one of the side IDT electrode and the second receiving side IDT electrode is electrically connected in the opposite phase, and the other is electrically connected in the same phase; As the first and second transmitting-side IDT electrodes, any of the seventh to ninth transmitting-side IDT electrodes of the present invention is used, and as the first and second receiving-side IDT electrodes, the seventh to ninth transmitting-side IDT electrodes are used. A ninth aspect of the present invention is the above-described present invention, characterized by using the wave-receiving-side IDT electrode of the present invention.

The eleventh aspect of the present invention (corresponding to claim 11) is a method according to claim 11, wherein the material of the piezoelectric substrate is an Euler angle (0 °,
The present invention is characterized in that La ₃ Ga ₅ SiO _{14 (} 140 °, 25 °) cut is used.

A twelfth aspect of the present invention (corresponding to claim 12) is a communication device comprising the surface acoustic wave filter according to any one of the third to ninth aspects of the present invention.

The surface acoustic wave filter on a piezoelectric substrate having NSPUDT characteristics according to the present invention as described above is characterized by setting the optimum electrode width and electrode thickness of the IDT electrode. In addition, it is possible to set the directionality of the surface acoustic wave excitation, thereby increasing the degree of freedom in designing the surface acoustic wave filter.

[0022]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described.

(Embodiment 1) FIG. 1 shows a configuration of a surface acoustic wave filter according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 101 denotes a piezoelectric substrate having NSPUDT characteristics,
Here, La ₃ Ga ₅ SiO ₁₄ cut at Euler angles (0 °, 140 °, 25 °) is used. By forming an electrode pattern on the piezoelectric substrate 101, a surface acoustic wave is excited. 103 is a transmitting side IDT electrode, 104 is a receiving side ID
It is a T electrode, and the IDT electrodes 103 and 104 are arranged at a SAW propagation distance W1 to form a transversal SAW filter 105.

The wavelength at the center frequency of the surface acoustic wave excited by the SAW filter 105 is λ. Further, the transmitting side IDT electrode 103 and the receiving side IDT electrode 104
Are defined as + X direction, and the opposite direction is defined as -X direction.

The transmitting-side IDT electrode 103 includes a positive electrode having an electrode finger formed at a period λ and a negative electrode having an electrode finger formed at a period λ and arranged at a distance of λ / 2 from the electrode finger of the positive electrode. And the width of one electrode finger is e.

The receiving-side IDT 104 has a width in the propagation direction of the surface acoustic wave of about λ / 8 and a center-to-center distance of about λ / 4.
A positive electrode formed by forming a pair of two electrode fingers with a period λ;
Similarly, a set of two electrode fingers having a width in the propagation direction of the surface acoustic wave of about λ / 8 and a center-to-center distance of about λ / 4 is formed with a period λ, and a set of electrode fingers adjacent to the positive electrode. And a negative electrode arranged at a distance of λ / 2.

FIG. 2 is a cross-sectional view of the transmitting IDT electrode 103. In FIG. 2, the same or corresponding parts as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will not be repeated. The electrodes 201 and 202 are adjacent electrode fingers in the transmitting-side IDT electrode 103. For these electrode fingers, the direction in which the electrode fingers 201 and 202 are arranged in the order is the + X direction, and the direction in which the electrode fingers 202 and 201 are arranged in the order is the -X direction.

The operation of the surface acoustic wave filter according to the present embodiment configured as described above will be described below.

When a signal is applied to the transmitting-side IDT electrode 103, the phase difference S between the excitation center and the reflection center of the electrode fingers 201 and 202 in the IDT electrode 103 is increased in the + X direction from the NSPUDT characteristics of the piezoelectric substrate 101. To occur. The center of excitation of the surface acoustic wave by the electrode finger 201 is 211 and the center of reflection is 221. The center of excitation of the surface acoustic wave by the electrode finger 202 is 212 and the center of reflection is 222.

In FIG. 2, a surface acoustic wave 231N is a surface acoustic wave excited at the excitation center 211 and traveling in the −X direction. The surface acoustic wave 231P is a surface acoustic wave excited at the excitation center 211 and traveling in the + X direction. The surface acoustic wave 231P is reflected at the reflection center 221 at the reflection phase G and proceeds in the −X direction. If this is a surface acoustic wave 231PN, the surface acoustic wave 231PN is combined with the surface acoustic wave 211N with a phase difference of 2S + G. (Synthesis result 1) Similarly, the surface acoustic waves 232N and 232P are
2 are surface acoustic waves excited in the −X direction and traveling in the + X direction, respectively. The surface acoustic wave 232N is reflected at the reflection center 22.
At 1, the light is reflected at the reflection phase G and proceeds in the + X direction. If this is a surface acoustic wave 232NP, the surface acoustic wave 232NP
Is the phase difference (λ / 2−S) × 2 +
It is synthesized with G. (Synthesis Result 2) From the synthesis results 1 and 2, directionality is generated in the excitation of the surface acoustic wave on the piezoelectric substrate 101. When the synthesis result 1 has an antiphase relationship, that is, 2S + G = ± λ / 2, and the synthesis result 2 has an inphase relationship, that is, 2S−G = 0, −λ, the surface acoustic wave is strong in the + X direction and the surface acoustic wave is strong. Excited. Conversely, when the synthesis result 1 has an in-phase relationship and the synthesis result 2 has an anti-phase relationship, the surface acoustic wave is strongly excited in the −X direction. However, since the reflection of the surface acoustic wave by the double IDT electrode is canceled out, the receiving-side IDT electrode 104 on the piezoelectric substrate 101 having the NSPUDT characteristic is bidirectional without excitation in the surface acoustic wave. Will have.

Here, the phase difference S between excitation and reflection can be determined by the width e of the electrode finger of the transmitting side IDT electrode 103 and the thickness t of the electrode finger. That is, the phase relationship at the time of combining the surface acoustic waves based on the combination results 1 and 2 can be set by e and t. Further, the amount of reflection of the reflected wave by each electrode changes depending on the width e of the electrode finger and the thickness t of the electrode finger. As a result, the directionality of the surface acoustic wave excitation can be set.

For example, if the synthesis result 1 is shifted to the opposite phase relationship and the synthesis result 2 is shifted to the same phase relationship by the width e of the electrode finger and the thickness t of the electrode finger of the transmitting-side IDT electrode 103, the surface acoustic wave is Strongly excited in + X direction, receiving side IDT electrode 1
At 04, surface acoustic waves can be strongly received. As a result, the output of the SAW filter 105 can be reduced. The above is the principle of the method for manufacturing a surface acoustic wave filter according to the present invention.

As described above, according to the surface acoustic wave filter of the present embodiment, by changing the values of the width e of the electrode finger and the thickness t of the electrode finger of the transmitting-side IDT electrode 103,
By strengthening that direction or deliberately weakening it,
The output of the SAW filter 105 can be set.
The degree of freedom in designing the AW filter can be increased.

Further, in the present embodiment, the transmitting side I
The width of the electrode finger of the DT electrode 103 has been described assuming that both the positive and negative electrode fingers are e. However, these may have different widths for each of the positive and negative electrode fingers. The width may be changed only on one side.

In this embodiment, the transmitting side ID
When the width e of the electrode finger is set for each of the electrodes constituting the T electrode 103 for each wavelength unit, the same effect can be obtained, and the degree of freedom in design can be further increased.

In this embodiment, the transmitting side ID
Although the T electrode 103 has been described as a single IDT electrode,
This is an IDT structure in which the direction of surface acoustic wave excitation has directivity on a piezoelectric substrate having NSPUDT characteristics, and the electrode finger corresponding to the phase difference between the excitation center and the reflection center of the surface acoustic wave and the distance between the electrode fingers. By setting the width e and the thickness t of the electrode finger, the same effect can be obtained.

In this embodiment, the receiving side ID
Although the T electrode 104 has been described as a double IDT electrode, a similar effect can be obtained with a bidirectional IDT structure in which no directionality appears in the excitation of surface acoustic waves on a piezoelectric substrate having NSPUDT characteristics. .

In the present embodiment, the receiving side ID
Although the T electrode 104 has been described as a double IDT electrode, the wave receiving side IDT electrode 104 may be a directional inversion electrode (RDT) having a reverse direction on a piezoelectric substrate having NSPUDT characteristics.

In this embodiment, the transmitting side ID
Although the T electrode 103 has unidirectionality due to the NSPUDT characteristic, and the receiving-side IDT electrode 104 has been described as a bidirectional electrode or a directional inversion electrode (RDT), the NSPUD
In the case where the + X direction and the −X direction of the piezoelectric substrate 101 having the T characteristic are used in reverse, the transmitting side IDT electrode 103 is connected to the bidirectional or directional inversion electrode (RDT) for the reverse direction,
The same effect can be obtained by designing the DT electrode 104 to have one-way characteristics based on the NSPUDT characteristic and setting the width e of the electrode finger and the thickness t of the electrode finger of the receiving IDT electrode.

In this embodiment, the transmitting side ID
The directional inversion electrode (RD) is connected to the T electrode or the receiving IDT electrode.
When T) is used, the same effect can be obtained by setting the width e ′ of the electrode finger and the thickness t ′ of the electrode finger.

In this embodiment, NSPUD
The piezoelectric substrate 101 having the T characteristic is placed at the Euler angle (0 °, 14 °).
0 °, 25 °) Cut La_ThreeGa_FiveSiO₁₄Described as
However, if the cut angle has NSPUDT characteristics,
La of cut angle_ThreeGa_FiveSiO ₁₄But it doesn't matter.

In this embodiment, NSPUD
The piezoelectric substrate 101 having the T characteristic is placed at the Euler angle (0 °, 14 °).
0 °, has been described as La ₃ Ga ₅ SiO ₁₄ of 25 °) cut, if the piezoelectric substrate having NSPUDT property, for example, _{La 3 Ga 5.5 Nb 0.5 O 1} 4, La 3 Ta 0.5 Ga 5.5 O
₁₄ , other piezoelectric materials such as Li ₂ B ₄ O ₇ can also be used.

By mounting the surface acoustic wave filter described in the present embodiment on a communication device, a communication device with higher performance can be realized.

(Embodiment 2) FIG. 3 shows a configuration of a surface acoustic wave filter according to Embodiment 2 of the present invention. In FIG. 3, the same or corresponding components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will not be repeated.

In FIG. 3, a first filter track 301 and a second filter track 3
02 are arranged in parallel, and the first filter track 301 is composed of the transmitting IDT electrode 103 and the receiving IDT electrode 1.
04 and a reflector 311. Similarly, the second filter track 302 includes a transmitting IDT electrode 303, a receiving IDT electrode 304, and a reflector 312. Transmitting side IDT electrode 30 of second filter track
3 is a transmitting side IDT electrode 103 of the first filter track.
IDT electrode equivalent to.

The receiving side I of the second filter track
The DT electrode 304 is a receiving side ID of the first filter track.
Although the IDT electrodes are equivalent to the T electrodes 104, the two receiving-side IDT electrodes 104 and 304 have an antiphase relationship as described later. First filter truck 30
1 transmission-side IDT electrode 103 and reception-side IDT electrode 104
And the distance W3 between the transmitting IDT electrode 303 and the receiving IDT electrode 304 of the second filter track 302.
Are equal and the receiving side ID of the first filter track 301
The distance W2 between the T electrode 104 and the reflector 311 is different from the distance W4 between the receiving IDT electrode 304 of the second filter track 302 and the reflector 312, and the difference is as follows, assuming that the wavelength of the surface acoustic wave is λ. nλ + λ / 4 (n: non-negative integer). Further, the receiving-side IDT electrodes 104 and 304 are electrically connected in opposite phases to each other to form balanced terminals.

In the present embodiment shown in FIG. 3, a propagation path of a surface acoustic wave is considered. The surface acoustic waves excited by the transmitting-side IDT electrodes 103 and 303 correspond to the receiving-side IDT electrode 1.
04 and 304 are reached.

However, this surface acoustic wave has an electrical phase difference of 180 ° between the receiving IDT electrode 104 of the first filter track 301 and the receiving IDT electrode 304 of the second filter track 302. Since they are present, they are not extracted as electrical signals. The surface acoustic waves that are excited by the transmitting-side IDT electrodes 103 and 303, pass through the receiving-side IDT electrodes 104 and 304, are reflected by the reflectors 311 and 312, and are received by the receiving-side IDT electrodes 104 and 304 are:
Receiving-side IDT electrode 10 of first filter track 301
4 and the IDT electrode 304 on the wave receiving side of the second filter track 302 have an electrical phase difference of 0 °, and can be extracted as an output signal.

The operation of the surface acoustic wave filter configured as described above will be described below.

Assuming that the electrode width of the transmitting-side IDT electrodes 103 and 303 is e and the electrode thickness is t, the values of the electrode finger width e and the electrode finger thickness t are set as described in the first embodiment. By doing so, it is possible to set the phase relationship when the surface acoustic waves are combined. Furthermore, the amount of reflection of the reflected wave by each electrode also changes due to a change in the value of the width e of the electrode finger and the thickness t of the electrode finger. As a result, the directionality of the surface acoustic wave excitation can be set artificially.

As described above, according to the SAW filter according to the present embodiment, the values of the electrode finger width e and the electrode finger thickness t of the transmitting-side IDT electrodes 103 and 303 are artificially set. The output of the surface acoustic wave filter can be set by strengthening the directionality of the surface acoustic wave or, on the contrary, intentionally weakening the direction, and the degree of freedom in designing the surface acoustic wave filter can be increased.

In this embodiment, the transmitting side ID
Although the T electrodes 103 and 303 have been described as single IDT electrodes, similar effects can be obtained with an IDT structure in which the direction of surface acoustic wave excitation appears on a piezoelectric substrate having NSPUDT characteristics.

In this embodiment, the transmitting side ID
T electrodes 103 and 303 are single IDTs with electrode finger width e
Although described as an electrode, an electrode having a width of λ / 4 can be used.

Further, in the present embodiment, the transmitting side I
In the description, the width of the electrode fingers of the DT electrodes 103 and 303 has been described assuming that both the positive and negative electrode fingers are e. However, these may have different widths for the positive and negative electrode fingers. Alternatively, only one of the widths may be changed.

In this embodiment, the transmitting side ID
By setting the electrode finger width e for each wavelength unit for the electrodes constituting the T electrodes 103 and 303, the same effect can be obtained and the degree of freedom in design can be further increased.

In the present embodiment, the receiving side ID
Although the T electrodes 104 and 304 have been described as double IDT electrodes, similar effects can be obtained with an IDT structure in which the direction of surface acoustic wave excitation does not appear on a piezoelectric substrate having NSPUDT characteristics.

In this embodiment, NSPUD
The piezoelectric substrate 101 having the T characteristic is placed at the Euler angle (0 °, 14 °).
0 °, 25 °) Cut La_ThreeGa_FiveSiO₁₄Described as
However, if the cut angle has NSPUDT characteristics,
La of cut angle_ThreeGa_FiveSiO ₁₄But it doesn't matter.

In this embodiment, NSPUD
The piezoelectric substrate 101 having the T characteristic is placed at the Euler angle (0 °, 14 °).
0 °, has been described as La ₃ Ga ₅ SiO ₁₄ of 25 °) cut, if the piezoelectric substrate having NSPUDT property, for example, _{La 3 Ga 5.5 Nb 0.5 O 1} 4, La 3 Ta 0.5 Ga 5.5 O
₁₄ , other piezoelectric materials such as Li ₂ B ₄ O ₇ can also be used.

Further, by mounting the surface acoustic wave filter described in the present embodiment on a communication device, a communication device with higher performance can be realized.

[0060]

As described above in detail, according to the present invention, it is possible to set the directionality of a surface acoustic wave, and to provide a method of manufacturing a surface acoustic wave filter and a surface acoustic wave with a high degree of design freedom. A filter can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a surface acoustic wave filter according to a first embodiment of the present invention.

FIG. 2 shows a transmitting side ID of the surface acoustic wave filter according to the present invention.
Cross section of T electrode

FIG. 3 is a diagram showing a configuration of a surface acoustic wave filter according to a second embodiment of the present invention;

FIG. 4 is a diagram showing an example of a configuration of a surface acoustic wave filter according to a conventional technique.

[Explanation of symbols]

 Reference Signs List 101 piezoelectric substrate having NSPUDT characteristics 103 transmitting-side IDT electrode 104 receiving-side IDT electrode 105 transversal-type SAW filter 201, 202 electrode finger in transmitting-side IDT electrode 103 211, 212 excitation center of surface acoustic wave 221, 222 Reflection center of surface acoustic wave 231N, 231P, 231PN Surface acoustic wave 232N, 232P, 232NP Surface acoustic wave 301 First filter track 302 Second filter track 303 Transmitting side IDT electrode 304 Receiving side IDT electrode 311, 312 Reflection Apparatus 401 Piezoelectric substrate having NSPUDT characteristics 403 Transmitting IDT electrode 404 Receiving IDT electrode 405 Transversal SAW filter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toru Yamada 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Terms (reference) 5J097 AA28 BB11 CC08 CC15 DD04 DD08 DD17 FF01 HB00

Claims (12)

[Claims] 1. A piezoelectric substrate having NSPUDT characteristics,
A method for manufacturing a surface acoustic wave filter comprising a step of providing at least one transmitting-side interdigital transducer (IDT) electrode for transmitting a surface acoustic wave and at least one receiving-side IDT electrode for receiving the surface acoustic wave. And a step of controlling the width of the electrode finger of the transmitting side IDT electrode to set the strength of the surface acoustic wave in one direction, the method for manufacturing a surface acoustic wave filter. . 2. The method according to claim 1, further comprising the step of controlling the thickness of the electrode finger of the transmission-side IDT electrode to set the strength of the surface acoustic wave in one direction. Method for manufacturing a surface acoustic wave filter. 3. A surface acoustic wave filter manufactured by the method for manufacturing a surface acoustic wave filter according to claim 1 or 2, wherein a piezoelectric substrate having NSPUDT characteristics and an elastic substrate provided on the piezoelectric substrate are provided. A surface acoustic wave filter comprising at least one transmitting-side interdigital transducer (IDT) electrode for transmitting a surface wave and at least one receiving-side IDT electrode for receiving the surface acoustic wave. 4. The surface acoustic wave filter according to claim 3, wherein at least two electrode fingers of the transmission-side IDT electrode are provided within one wavelength of the surface acoustic wave. . 5. The at least one electrode finger of the at least two transmitting-side IDT electrodes provided within one wavelength of the surface acoustic wave has a width different from other electrode fingers. The surface acoustic wave filter according to claim 4, wherein 6. The surface acoustic wave filter according to claim 3, wherein a width of each of the electrode fingers of the transmission-side IDT electrode is set for each wavelength unit. 7. The transmitting IDT electrode includes a positive electrode and a negative electrode in which the electrode fingers are arranged at a period λ (λ: one wavelength of the center frequency of the surface acoustic wave). The electrode has a positive electrode and a negative electrode in which a set of two electrode fingers having a center-to-center distance of about λ / 4 is arranged at a period of λ. In the transmitting-side IDT electrode, an electrode of the positive electrode The distance between the finger and the electrode finger of the negative electrode is about λ / 2, and in the reception-side IDT electrode, a set of two electrode fingers of the positive electrode and two electrodes of the non-electrode. The elasticity according to any one of claims 3 to 6, wherein an interval between the pair of fingers is about λ / 2, and a width of the electrode finger of the reception-side IDT electrode is substantially λ / 8. Surface wave filter. 8. The width of the electrode finger of the transmitting-side IDT electrode is:
The surface acoustic wave filter according to claim 7, wherein the filter has substantially λ / 4. 9. The surface acoustic wave filter according to claim 3, wherein the width of the electrode finger of the transmitting-side IDT electrode is substantially different from λ / 4. 10. A first filter track and a second filter track provided in parallel with each other on the piezoelectric substrate, wherein the first filter track transmits a first surface acoustic wave. Wave side interdigital transducer (ID
T) an electrode, a first reflector for reflecting the surface acoustic wave, and a first, disposed between the first IDT electrode and the first reflector, for receiving the surface acoustic wave. Receiving side I
A second transmission track interdigital transducer (ID) for transmitting a surface acoustic wave;
T) an electrode, a second reflector for reflecting the surface acoustic wave, and a second electrode for receiving the surface acoustic wave, disposed between the second IDT electrode and the second reflector. Receiving side I
A first transmitting-side IDT electrode and a first receiving-side IDT;
The distance between the electrodes and the distance between the second transmitting-side IDT electrode and the second receiving-side IDT electrode are substantially the same, and the first receiving-side IDT electrode and the first And the distance between the second receiving-side IDT electrode and the second reflector are (n + ／) λ (λ: one center frequency of the surface acoustic wave). Wavelength, n: 0 or a positive integer), wherein the first transmitting IDT electrode and the second transmitting IDT
An electrode or the first receiving-side IDT electrode and the second
One of the receiving-side IDT electrodes is electrically connected in the opposite phase, and the other is electrically connected in the same phase. The transmitting-side IDT electrode according to any one of claims 7 to 9 is used as the wave-side IDT electrode, and the transmitting-side IDT electrode according to any one of claims 7 to 9 is used as the first and second receiving-side IDT electrodes. A surface acoustic wave filter using a receiving IDT electrode. 11. The material of the piezoelectric substrate is a La ₃ Ga ₅ SiO cut at Euler angles (0 °, 140 °, 25 °).
_The surface acoustic wave filter according to any one of claims 3 to 10, wherein ₁₄ is used. 12. A communication device comprising the surface acoustic wave filter according to claim 3.