JPH05291869A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To obtain the surface acoustic wave device with a structure able to suppress effectively spurious radiation resulting from the high order mode utilizing an SH type surface acoustic wave having a structure in which the static capacitance is reduced by dividing one side of interdigital electrodes. CONSTITUTION:An interdigital transducer is configured by forming an interdigital electrode 13 and 2-division type interdigital electrodes divided into 1st and 2nd interdigital electrodes 14,15 are formed on a piezoelectric substrate 12 so as to arrange plural vibration sources whose vibration source number is (a) at both sides of a zero vibration source along the propagation direction of a surface acoustic wave and the surface acoustic wave device is a surface acoustic wave device 11 in which a pair number N of the electrode fingers of the interdigital transducer is selected in a range of 8.5-45 and the surface acoustic wave of SH type is utilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an end surface reflection type surface wave device using SH type surface waves, and more particularly to a surface wave device having an improved interdigital transducer structure.

[0002]

2. Description of the Related Art BGS waves, Love waves, etc. are known as SH type surface waves whose displacement is mainly in the direction perpendicular to the surface wave propagation direction. An end surface reflection type surface acoustic wave resonator utilizing BGS waves has been conventionally known. As shown in a plan view in FIG. 2, an end surface reflection type surface acoustic wave resonator 1 utilizing a BGS wave is a pair of comb-teeth electrodes having a plurality of electrode fingers 3a and 4a which are interleaved on a piezoelectric substrate 2. 3,4
And has a structure in which an interdigital transducer is formed. In this surface wave resonator 1, the excited surface wave is completely reflected between the opposite end surfaces 2a and 2b of the piezoelectric substrate 2. The surface wave resonator 1 using the edge reflection type BGS wave can provide a resonator that can be used in a high frequency region that cannot be obtained by the surface wave resonator using Rayleigh waves.

By the way, as surface acoustic wave resonators utilizing SH waves such as BGS waves, LiNbO ₃ and LiTaO are available.
It has been reported that a piezoelectric substrate made of a material such as ₃ and Pb (Ti _1-x Zr _x ) O ₃ is used. In consideration of cost and electromechanical coupling coefficient, these piezoelectric substrate materials have Pb (Ti) compared to LiNbO ₃ and LiTaO _3.
It is preferable to use a piezoelectric ceramic such as _1-x Zr _x ) O ₃ or lead titanate.

[0004]

However, Pb
Since (Ti _1-x Zr _x ) O ₃ has a large relative permittivity ε,
When the surface acoustic wave device is formed by forming the normal type interdigital transducer, there is a problem that the capacitance C of the surface acoustic wave device becomes so large that it cannot be actually used, and it is required to reduce the capacitance. In order to reduce the capacitance in the surface acoustic wave resonator 1, it is conceivable to reduce the cross width of the interdigital transducers or reduce the number of pairs of the electrode fingers 2a and 3a, but these methods reduce the capacitance. There was a limit to what I could do.

On the other hand, it is also possible to divide one of the comb-teeth electrodes forming the interdigital transducer into a plurality of comb-teeth electrodes, and electrically connect the divided electrodes in series to reduce the capacitance. .. For example,
When one of the comb-teeth electrodes is divided into two, the capacitance of the surface acoustic wave device is greatly reduced to 1/4. However, when one of the comb-teeth electrodes is simply divided into a plurality of comb-teeth electrodes, as shown in FIG. 3, when the number of electrode finger pairs is N, 2N ± n in terms of impedance-frequency characteristics.
There is a problem that spurious vibration (disturbance of the waveform shown by arrow A in FIG. 3) due to a higher-order mode occurs at a position (n is an even number).

Accordingly, an object of the present invention is to provide a surface acoustic wave device utilizing an SH type surface wave having a structure in which one of the interdigital transducers of an interdigital transducer is divided into a plurality of parts to reduce the capacitance, and the surface acoustic wave device is set to a higher mode. It is an object of the present invention to provide a surface acoustic wave device having a configuration capable of effectively suppressing spurious vibrations caused by it.

[0007]

Each of the inventions described in claims 1 to 4 of the present application is an end-face reflection type surface acoustic wave device using an SH type surface wave, comprising a piezoelectric substrate and a piezoelectric substrate. And an interdigital transducer including a pair of interdigital electrodes having a plurality of electrode fingers that are interleaved with each other. In the invention according to claim 1, in the surface wave propagation direction, with the zero epicenter as the center,
So that multiple epicenters with epicenter number a are placed on both sides of it,
One interdigital electrode of the interdigital transducer is divided into first and second interdigital electrodes that are not connected to each other, and the number N of electrode fingers of the interdigital transducer is 8.5 or more and 45 or less. It is considered to be the range.

According to the second aspect of the invention, in the surface wave propagation direction, a plurality of epicenters of the epicenter number a are arranged on both sides of the epicenter * to which a voltage twice that of the remaining epicenter is applied. As described above, one interdigital electrode of the interdigital transducer is divided into first and second interdigital electrodes that are not connected to each other, and the number N of electrode fingers of the interdigital transducer is 7.
It is in the range of 5 or more and 45 or less.

According to the third aspect of the present invention, in the surface wave propagation direction, a plurality of hypocenters b are centered, and zero hypocenters are sandwiched on both sides of the hypocenters so that the hypocenters b are arranged. One interdigital electrode of the interdigital transducer is divided into first to third interdigital electrodes that are not connected to each other, and the number N of electrode fingers of the interdigital transducer is 7.0 or more and 60 or less. It is considered to be a range.

Further, in the invention described in claim 4, in the surface wave propagating direction, a plurality of hypocenters of the epicenter number b is centered, and a double voltage is applied to both sides of each of the hypocenters of the epicenter number b. One of the interdigital transducers of the interdigital transducer is divided into three so as to have first to third comb-teeth electrodes which are not connected to each other so that epicenters of epicenter number b are arranged across the * The number N of pairs of electrode fingers of the interdigital transducer is 7.0 or more and 60 or less.

[0011]

The present inventors have proposed a surface acoustic wave device utilizing the SH type surface acoustic wave, in which one of the comb tooth electrodes constituting the interdigital transducer is provided with a plurality of comb tooth electrodes. As a result of investigating to suppress the spurious vibration due to the higher-order mode in the structure formed by dividing the comb-teeth electrode, the method of dividing the comb-teeth electrode was devised, and the logarithm of the electrode fingers was changed according to the division method. It has been found that the above-mentioned problems can be achieved by selecting in a specific range. That is, as is apparent from the examples described below, in the invention according to claim 1, one of the comb-teeth electrodes is divided into two, and a structure in which an equal number of seismic sources are arranged on both sides of the zero seismic source is provided. In that case, the logarithm N of the electrode fingers of the interdigital transducer is 8.5 or more,
By setting it to 45 or less, it is possible to suppress spurious vibrations due to the higher-order modes by 24 dB or more.

Further, as in the invention described in claim 2, one of the comb-teeth electrodes is divided into two, and the center of the epicenter * to which a voltage twice that of the remaining epicenter is applied is the center of the epicenter a. In the structure where the epicenter is arranged, the spurious vibration due to the higher-order mode is set to 24 d by setting the number N of electrode fingers of the interdigital transducer to be 7.5 or more and 45 or less.
B or more can be suppressed.

Further, as in the invention described in claim 3,
In the structure in which one of the comb-shaped electrodes is divided into three parts, the epicenters are arranged along the surface wave propagation direction with a hypocenter of the number b of hypocenters-zero epicenter-a hypocenter of the epicenter b, a zero epicenter, and a plurality of epicenters of the epicenter b. In this case, by setting the number of pairs of electrode fingers of the interdigital transducer to be 7.0 or more and 60 or less, it is possible to suppress spurious vibrations caused by the higher-order mode by 24 dB or more.

According to the invention as set forth in claim 4, in a structure in which one of the comb-teeth electrodes is divided into three, the epicenters are arranged along the surface wave propagation direction, and a plurality of epicenters of the epicenter number b-the epicenter number. A hypothesis to which a voltage twice that of each epicenter of b is applied * -Multiple hypocenters of epicenter b-episodes * -When multiple epicenters of epicenter b are used, the logarithm of the electrode fingers of the interdigital transducer is 7 If it is 0.0 or more and 60 or less, it is possible to suppress spurious vibrations caused by the higher-order modes by 24 dB or more.

That is, according to the first to fourth aspects of the invention, in one of the interdigital transducers, one of the comb-teeth electrodes is divided into two or three, and the number of electrode finger pairs depends on the arrangement of the epicenter. If N is selected in the above specific range, spurious vibrations due to higher-order modes can be suppressed by 24 dB or more, and one interdigital electrode of the interdigital transducer is divided into a plurality of interdigital electrodes as described above. Therefore, the capacity of the surface acoustic wave device is effectively reduced. Therefore, it is possible to provide a surface acoustic wave device that can be used in a high frequency band by using a piezoelectric ceramic such as lead zirconate titanate-based ceramics, which is advantageous in terms of electromechanical coupling coefficient and cost.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1A and 1B are a plan view and a cross-sectional view showing an embodiment of a surface acoustic wave device according to the invention described in claim 1. The surface acoustic wave device 11 has a structure in which comb electrodes 13 to 15 are formed on a rectangular piezoelectric substrate 12. The comb electrode 13 has a plurality of electrode fingers 13a,
It is formed in a region extending from the end faces 12a to 12b of the piezoelectric substrate 12. On the other hand, the comb-teeth electrodes 14 and 15 correspond to the first and second comb-teeth electrodes of the present invention, and each of the plurality of electrode fingers 14 interposes with the electrode finger 13a of the comb-teeth electrode 13.
a and 15a. Each of the electrode fingers 13a to 15a of the comb-teeth electrodes 13 to 15 except that the electrode fingers at both ends of the comb-teeth electrode 13 have a width of λ / 8 when the wavelength of the surface wave is λ. , The widths of the remaining electrode fingers are all λ / 4, and the width of the gap between the plurality of electrode fingers is also λ / 4.
It is said that.

In the surface acoustic wave device 11 of the first embodiment, as shown in FIG.
Since the electrode fingers 13a ₁ and 13a _{2 of the} book are arranged adjacent to each other, as shown in FIG. 4, when the comb electrode 13 is virtually set to the ground potential and an AC voltage is applied between the comb electrodes 14 and 15. , The location of the source of the excited surface wave is as follows. That is, when the total number of electrode fingers of the comb-teeth electrodes 14 and 15 is n ₁ (n ₁ is an even number because the electrodes 14 and 15 are symmetrical), along the surface wave propagation direction (n ₁
/ 2-1 Number of epicenter) - it becomes (number of source of n ₁ / 2-1) that is disposed - (zero epicenter). That is, when the number of epicenters (n ₁ / 2-1) in the portion where the comb-teeth electrodes 14 and 15 are formed is a, along the surface wave propagation direction (the number of epicenters of a) − (zero epicenter) )-(A number of epicenters) will be placed.

In the first embodiment, in the surface acoustic wave device 11 having a structure in which a plurality of epicenters are arranged as described above, the number N of electrode fingers of the interdigital transducer is 8.5.
As described above, the range is selected to be 45 or less, and as a result, the spurious vibration due to the higher order mode is suppressed as described above. This will be described with reference to FIGS. In the surface acoustic wave device 11 shown in FIG. 1, the attenuation amount in the case where the logarithm of the electrode fingers of the interdigital transducer is N = 4.5-the frequency curve is shown in FIG. 5 and the attenuation amount in the case of N = 15.5- The frequency curve is shown in FIG.

As is apparent from FIG. 5, the number of pairs of electrode fingers =
In the case of 4.5, 2N ± determined by the length of the piezoelectric substrate 12.
At the frequency position of n (n is an even number) higher-order mode, the attenuation pole is
Do not match. For example, the frequency position of 2N-2 in FIG.
Between the virtual straight line and the attenuation-frequency curve
Make sure that the attenuation pole is located on the high frequency range side of the intersection B.
I understand. In other words, in the 2N-2 high-order mode
Since the amount of attenuation is as small as 20 dB or less,
Do you know that the resonance of the cord appears as spurious vibration?
It Similarly, in other high-order modes of 2 ± n, points
B₁, B₂, B₃, B _Four, B_FiveBut the frequency deviated from the attenuation pole
It is located at several positions, so the attenuation is 20 dB or less.
I understand that it is small.

On the other hand, as is clear from FIG.
In the case of the logarithm of electrode fingers N = 15.5, the point C where the virtual straight line extending upward from the frequency position of 2N−2 and the attenuation-frequency curve intersect is located near the attenuation pole. .. Therefore, the attenuation amount at the frequency position of 2N-2 is 2
It turns out that it is as large as 9 dB or more. Similarly, also at the frequency positions of other higher-order modes, it is understood that the attenuation amount is as large as 29 dB or more, as is clear from the points C _{1 to} C ₅ .
As described above, it is understood that the spurious vibration caused by the higher order mode of the surface wave can be suppressed by changing the logarithm N of the electrode fingers of the interdigital transducer. Therefore, the inventors of the present invention set the logarithm N of the electrode fingers to 4.5.
From 1 to 15.5, the amount of attenuation at the frequency position of the resonance points of the higher order modes of 2N ± 2, 2N ± 4 and 2N ± 6 was measured. The results are shown in Table 1 and FIG. 7.

[0021]

[Table 1]

As is clear from Table 1 and FIG. 7, in the surface wave device having the two-division type interdigital transducer having the arrangement of the number of sources a-zero source-the number of sources a,
It was found that when the logarithm N of the electrode fingers was changed from 7.5 to 8.5, the amount of attenuation at the frequency position of 2N ± 2 at which the largest spurious vibration was generated became large and exceeded 25 dB. Therefore, in the invention described in claim 1, it is understood that the number N of pairs of electrode fingers needs to be 8.5 or more.

It should be noted that as the number N of electrode fingers increases, spurious vibrations due to higher-order modes can be suppressed, but when N = 45 is exceeded, the capacitance increases and a two-division comb electrode is provided. The capacity reduction effect of the interdigital transducer is lost. Therefore,
In the invention according to claim 1, the logarithm N of the electrode fingers is 8.5 to
It is necessary to select in the range of 45, and it is possible to effectively suppress spurious vibrations caused by higher-order modes while reducing the capacity.

Second Embodiment FIG. 8 is a plan view showing a surface acoustic wave device according to a second embodiment of the invention. The surface acoustic wave device 21 has a structure in which comb-teeth electrodes 23, 24, 25 are formed on a rectangular piezoelectric substrate 22. A plurality of electrode fingers 23a of the comb electrode 23
And the plurality of electrode fingers 24a and 25a of the first and second comb-teeth electrodes 24 and 25, which are formed by dividing the comb-teeth electrode to be interleaved with the comb-teeth electrode 23, are arranged so as to be alternately interleaved. ing. Then, in the second embodiment, the electrode fingers 24a ₁ located at the end of the comb electrode 25 side of the electrode fingers 24a of the comb-shaped electrodes 24, comb-shaped electrodes of the comb electrode 25 24
The electrode finger 25a ₁ located at the end on the side is adjacently arranged with a gap of 4 / λ.

Therefore, in the surface acoustic wave device 21 of the second embodiment,
Is a comb-teeth electrode 23 and first and second comb-teeth electrodes 24,
When the number of hypocenters composed of 25 and is respectively a,
A number of source-electrode fingers 24a along the surface wave propagation direction
₁And electrode finger 25a₁The number of seismic sources * -a composed of
The source will be deployed. The epicenter * is the electrode finger 24a ₁
And electrode finger 25a₁Since it is composed of and,
Voltages of different polarities were applied between the comb electrodes 24, 25
In this case, a hypocenter with twice the voltage applied to the remaining hypocenters
Becomes In the surface acoustic wave device 21 of the second embodiment,
The logarithm N of all electrode fingers of the digital converter is
As in the case of the first embodiment, the range of 4.5 to 15.5
2 is the frequency position where spurious is generated by changing
Attenuation at N ± n (n is an even number) high-order mode resonance point
The quantity was measured. The results are shown in Table 2 and FIG.

[0026]

[Table 2]

As is clear from Table 2 and FIG. 9, in the surface acoustic wave device 21 of the second embodiment, the number of pairs of electrode fingers N = 7.5.
From the above, it can be seen that the amount of attenuation sharply increases and exceeds 25 dB at 2N ± 2 and 2N ± 4. Therefore, in the surface acoustic wave device 21 in which the epicenters of epicenter number-a epicenter * -episodes of epicenter number a are arranged along the surface wave propagation direction, it is necessary to set the logarithm N of the electrode fingers to 7.5 or more. .. On the other hand, as in the case of the first embodiment, when the number of pairs of electrode fingers exceeds 45, the capacitance of the surface acoustic wave device 21 increases and the capacitance reducing effect of forming the split-type comb-teeth electrode is impaired. Therefore, claim 2
In the invention described in (3), it is necessary that the number N of pairs of electrode fingers is in the range of 7.5 to 45.

Third Embodiment FIG. 10 is a schematic plan view for explaining the structure of the interdigital transducer in the surface acoustic wave device 31 of the third embodiment of the invention. In the surface acoustic wave device 31 of the present embodiment, the interdigital transducers are formed by forming the comb-teeth electrodes 33 to 36 on a rectangular piezoelectric substrate (not shown). Comb tooth electrode 33
The plurality of electrode fingers 33 a of the first to third comb-teeth electrodes 3
It is arranged so as to be interleaved with the plurality of electrode fingers 34a, 35a, 36a of 4 to 36. In addition, the comb electrode 33
The electrode fingers 33a ₁ and 33a _{2 on} both ends of the electrode have a width of 8 / λ, where λ is the wavelength of the surface wave, and the remaining electrode fingers have a width of 4 / λ. The width of the gap between all the electrode fingers is 4 / λ. Further, since the end face reflection type surface acoustic wave device is used, the electrode fingers 33a at both ends are
₁ , 33a ₂ are formed along the edge of the piezoelectric substrate.

In the third embodiment, the number of seismic sources composed of the first to third comb-teeth electrodes 34 to 36 and the comb-teeth electrode 33 is equal, and the number of seismic centers is b. .. In addition, an electrode finger 33a ₃ and an epicenter composed of the comb-teeth electrode 33 and the first comb-teeth electrode 34 and an epicenter composed of the comb-teeth electrode 33 and the second comb-teeth electrode 35 are provided. A zero epicenter composed of 33a ₄ and 33a ₄ is arranged. Similarly, the electrode fingers 33a ₅ , 33 are also provided between the comb electrodes 35, 36.
The zero epicenter composed of a ₆ is located. Therefore, along the surface wave propagation direction, the epicenter of the epicenter number of b-zero epicenter-b
The number of hypocenters of the number of hypocenters-the zero number of hypocenters-the number of hypocenters of b will be allocated. Also in the surface acoustic wave device 31, since the other comb tooth electrode to be interleaved with the comb tooth electrode 33 as described above is divided into the first to third comb tooth electrodes 34 to 36, the capacitance of the surface acoustic wave device is increased. Is effectively reduced. And
In the surface acoustic wave device 31, the number N of pairs of electrode fingers was changed in the range of 4 to 11.5 to measure the attenuation amount at the frequency position of the resonance point of the higher mode of 2N ± n (n is an even number). The results are shown in Table 3 and FIG.

[0030]

[Table 3]

As is clear from Table 3 and FIG. 11, by setting the logarithm N of the electrode fingers to be 7.0 or more, the spurious vibration appearing at the frequency position of 2N ± 2 which is the largest spurious vibration is suppressed by 24 dB or more. You know you will get. Therefore, in the third embodiment, the logarithm N of the electrode fingers is set to 7.0.
It is necessary to do the above. On the other hand, in the surface acoustic wave device 31, when the number N of pairs of electrode fingers exceeds 60, the capacitance becomes large, and the capacitance reduction effect using the three-division comb electrode is impaired. Therefore, in the invention described in claim 3, it is necessary to set the logarithm N of the electrode fingers in the range of 7.0 to 60.

Fourth Embodiment FIG. 12 is a schematic plan view showing the structure of the interdigital transducer of the surface acoustic wave device 41 of the fourth embodiment of the invention. A comb-shaped electrode 43 and first to third comb-shaped electrodes 44 are formed on a rectangular piezoelectric substrate (not shown).
To 46 are formed. The plurality of electrode fingers 43a of the comb-teeth electrode 43 are arranged so as to be interleaved with the plurality of electrode fingers 44a-46a of the comb-teeth electrodes 44-46, respectively. In the surface acoustic wave device 41 of the fourth embodiment, the electrode finger 44a ₁ at the inner end of the first comb tooth electrode 44 and the second
The electrode fingers 45a ₁ at the ends of the comb-teeth electrode 45 on the first comb-teeth electrode 44 side are arranged adjacent to each other with a gap of 4 / λ. Similarly, the electrode finger 45a ₂ arranged at the end of the second comb-teeth electrode 45 on the side of the third comb-teeth electrode 46 and the electrode finger 46a ₁ at the inner end of the third comb-teeth electrode 46 are 4 They are arranged with a gap having a width of / λ.

Therefore, at the epicenter between the electrode fingers 44a ₁ and 45a _{1 and} between the electrode fingers 45a ₂ and 46a ₁ , twice the voltage is applied as compared with the epicenter composed of the remaining electrode fingers. Between the electrode fingers 44a ₁ and 45a ₁ and 45a
_The epicenter composed of ₂ and 46a ₁ is the epicenter *
Each of the third comb-teeth electrodes 44 to 46 is a comb-teeth electrode 4
Assuming that 3 and the number of hypocenters b are configured, in the surface acoustic wave device 41 of the present embodiment, the number of hypocenters of the number of hypocenters b—the hypocenter of the number of hypocenters of b—the epicenter of the surface wave device 41 in the propagation direction of the surface wave. * -B epicenters are allocated. In the surface acoustic wave device 41 of the fourth embodiment, the number N of pairs of electrode fingers was changed in the range of 4 to 11.5, and the attenuation amount at the frequency position of the resonance point of 2N ± n (n is an even number) was measured. .. The results are shown in Table 4 and FIG.

[0034]

[Table 4]

As is clear from Table 4 and FIG. 13, it is understood that the attenuation amount at the frequency position of 2N ± 2, which is the largest spurious vibration, exceeds 24 dB when the number of pairs of electrode fingers N = 7.0 or more. On the other hand, also in the fourth embodiment, when the number N of pairs of electrode fingers exceeds 60, the capacity increases, and one of the comb-teeth electrodes becomes the first to third comb-teeth electrodes 34.
The capacity reduction effect due to the division into ~ 36 is impaired. Therefore, it can be seen that the number N of pairs of electrode fingers needs to be in the range of 7.0 to 60.

[Brief description of drawings]

1A and 1B are a plan view and a cross-sectional view taken along the line BB, respectively, for explaining a surface acoustic wave device according to an embodiment of the present invention.

FIG. 2 is a plan view for explaining a conventional surface acoustic wave device.

FIG. 3 is a diagram showing impedance-frequency characteristics in a conventional surface acoustic wave device.

FIG. 4 is a schematic plan view for explaining an interdigital transducer in the surface acoustic wave device according to the first embodiment.

FIG. 5 is a diagram showing attenuation-frequency characteristics when the number of pairs of electrode fingers N = 4.5.

FIG. 6 is a diagram showing attenuation-frequency characteristics when the number of pairs of electrode fingers N = 15.5.

FIG. 7 is a diagram showing a change in attenuation amount when the number N of electrode fingers is changed in the first embodiment.

FIG. 8 is a plan view for explaining a surface acoustic wave device according to a second embodiment.

FIG. 9 is a diagram showing changes in the amount of attenuation when the number N of electrode fingers is changed in the second embodiment.

FIG. 10 is a diagram showing a structure of an interdigital transducer of a surface acoustic wave device according to a third embodiment.

FIG. 11 is a diagram showing changes in the attenuation amount when the number of pairs of electrode fingers is changed in the third embodiment.

FIG. 12 is a schematic plan view showing the structure of an interdigital transducer in a surface acoustic wave device according to a fourth embodiment.

FIG. 13 is a diagram showing changes in the amount of attenuation when the number N of electrode fingers is changed in the fourth embodiment.

[Explanation of symbols]

 11 ... Surface wave device 12 ... Piezoelectric substrate 12a, 12b ... End surface 13 ... Comb-tooth electrode 14 ... First comb-tooth electrode 15 ... Second comb-tooth electrode

Claims (4)

[Claims] 1. An end surface reflection type surface acoustic wave device using SH type surface waves, comprising: a piezoelectric substrate; and a pair of electrode fingers formed on the piezoelectric substrate and interposing each other. An interdigital transducer formed of a comb electrode, wherein one of the interdigital transducers of the interdigital transducer is arranged so that a plurality of hypocenters a having a hypocenter a are arranged on both sides of the zero epicenter in the surface wave propagation direction. But,
A surface which is divided into first and second comb-teeth electrodes which are not connected to each other, and in which the number N of pairs of electrode fingers of the interdigital transducer is in the range of 8.5 or more and 45 or less. Wave device. 2. An end surface reflection type surface acoustic wave device using an SH type surface wave, comprising: a piezoelectric substrate; and a pair of electrode fingers formed on the piezoelectric substrate, the electrode fingers interposing each other. It has an interdigital transducer consisting of a comb-teeth electrode, and in the surface wave propagation direction, a plurality of epicenters a with a hypocenter number a are arranged on both sides of the epicenter * to which a voltage twice that of the remaining epicenter is applied. Thus, one interdigital electrode of the interdigital transducer is divided into first and second interdigital electrodes that are not connected to each other, and the number N of electrode fingers of the interdigital transducer is 7.5. The surface acoustic wave device is in the range of 45 or less. 3. An end surface reflection type surface acoustic wave device using an SH type surface wave, comprising a piezoelectric substrate and a pair of electrode fingers formed on the piezoelectric substrate and interleaved with each other. It is equipped with an interdigital transducer consisting of a comb tooth electrode, and in the surface wave propagation direction, a plurality of epicenters b are arranged with a zero epicenter on either side of the epicenters b of the epicenter b. In addition, one of the comb-teeth electrodes of the interdigital transducer is divided into three so as to have first to third comb-teeth electrodes that are not connected to each other, and the number N of electrode fingers of the interdigital transducer is N. A surface acoustic wave device characterized by being in a range of 7.0 to 60. 4. An end surface reflection type surface acoustic wave device using an SH type surface wave, comprising: a piezoelectric substrate; and a pair of electrode fingers formed on the piezoelectric substrate, the electrode fingers interposing each other. An interdigital transducer consisting of a comb-teeth electrode is provided, and in the surface wave propagation direction, a hypocenter * is applied to both sides of which there are twice the voltage of each hypocenter with the hypocenter b as the center. One of the interdigital transducers of the interdigital transducer is divided so as to have first to third comb electrodes that are not connected to each other so that a plurality of hypocenters b having the number of epicenters are arranged between them. And the number N of electrode fingers of the interdigital transducer
Is in the range of 7.0 or more and 60 or less, a surface acoustic wave device.