JPH09130194A - Surface acoustic wave reflection and surface acoustic wave resonator using the reflector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave reflector which operates with a higher harmonic of a high order by dividing every electrode finger into steps in number equal to a desired number of orders of reflection and connecting together these divided steps in the propagation direction of a surface acoustic wave with each specific space secured among them. SOLUTION: If M=5 is satisfied, an electrode finger of a surface acoustic wave reflector having line width 1/4λ0 against a basic wave of wavelength λ0 is divided into 5 steps in response to 5, the desired number of order of higher harmonics to be reflected. These divided steps are respectively connected together with each space D=λ0 secured among them. When an SAW is made incident on the electrode finger of step 1 from the left side, the SAW is partly reflected at a boundary 2a set between an electrode part and a non-electrode part. The SAW that passed through the boundary 2a is partly reflected again at the next boundary 2b. The reflected waves of both boundaries can be expressed in a reflected wave W1 at a reflecting point set at the center of the electrode finger. Thus the reflected waves produced between steps 2 to 5 are added together at a reference point in the same phase. As a result, a 5th-order higher harmonic is intensively reflected.

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 reflector for reflecting surface acoustic waves (hereinafter referred to as SAW), and particularly to a surface acoustic wave intended for operation at higher harmonics of a fundamental wave. The present invention relates to a wave reflector and a surface acoustic wave resonator using the surface acoustic wave reflector.

[0002]

2. Description of the Related Art A conventional surface acoustic wave reflector has a line width of 1 / 4λ ₀ with respect to a fundamental wave of wavelength λ ₀ on a piezoelectric substrate.
A large number of / 4λ ₀ are arranged in parallel, and the surface acoustic waves are reflected at the boundary between the portion with electrodes and the portion without electrodes.

[0003]

However, no such surface acoustic wave reflector has been proposed so far for the purpose of operating at higher harmonics of the fundamental wave. Further, two surface acoustic wave reflectors may be arranged at intervals and one or two surface acoustic wave converters may be arranged between them to form a surface acoustic wave resonator. No surface acoustic wave resonator has been proposed for the purpose of operating harmonics.

On the other hand, a delay linear oscillator in which a surface acoustic wave converter for transmission and a surface acoustic wave converter for reception are provided, and one of the electrode terminals is connected via an amplifier, causes a harmonic operation. However, since such a delay linear oscillator is generally inferior to the resonator type in terms of stability, oscillation performance, etc., a surface acoustic wave resonator for the purpose of operating harmonics of the resonator type is proposed. Realization was desired.

The present invention has been made in view of the above problems, and an object thereof is to provide a surface acoustic wave reflector intended for operation at higher harmonics. Another object of the present invention is to provide a surface acoustic wave resonator for operating at higher harmonics by using the surface acoustic wave reflector.

[0006]

To achieve SUMMARY OF to the above objects, a first aspect of the present invention, the electrode fingers having a line width of 1 / 4.lamda ₀ with respect to the fundamental wave of wavelength lambda ₀ on a piezoelectric substrate 1/4 λ ₀
A plurality of surface acoustic wave reflectors are arranged in parallel at intervals of, and reflect the surface acoustic wave of the M-th harmonic of the fundamental wave at the boundary between the portion with electrodes and the portion without electrodes. Is divided into M steps equal to the order M of the harmonic to be reflected, and each step is shifted in the propagation direction of the surface acoustic wave by λ ₀ / M or λ ₀ / 2M and connected.

The principle of the present invention will be described with reference to FIG. Figure 1 shows the case of M = 5, the electrode fingers of the surface acoustic wave reflectors line width of 1 / 4.lamda ₀ with respect to the fundamental wave of wavelength lambda _0, depending on the order 5 of the harmonic to be reflected divided into five steps Te connects the respective D = lambda _0/5 only staggered. When the SAW is incident on the electrode finger in step 1 from the left side, a part of the SAW is reflected at the boundary 2a between the portion with the electrode and the portion without the electrode. SA that passed the boundary 2a
Part of W is also reflected again at the next boundary 2b. The reflected wave by these two boundaries can be represented by one reflected wave from the reflection point placed at the center of the electrode finger, and the reflection coefficient r is then given by the following equation.

[0008]

(Equation 1)

Here, Γ is a coefficient representing the SAW reflection caused by the difference in the speed of SAW propagating in a portion with and without an electrode, the acoustic impedance of the portion with the electrode is Zm, and the impedance of the portion without the electrode is Zg. And when

[0010]

(Equation 2) Is defined by Lm represents the line width of the electrode finger. Assuming that the center of the electrode finger in step 1 is zero as the reference point in the x direction, the reflected wave W ₁ reflected by the electrode finger in step ₁ is x
At the point of = 0, it is given by the following equation.

[0011]

(Equation 3)

Where A (f ₅ ) is the frequency f _{5 of the fifth} harmonic.
Represents the amplitude of the SAW at. Similarly, step 2
Reflected wave W ₂ that is reflected by the electrode fingers of the fifth-order wave number k ₅ harmonics is _{k 5 = 5 · 2π / λ} 0, also shift the electrode fingers of the step 2 only lambda _0/5 from the reference point Since it is located at the right position, it is expressed as follows.

[0013]

(Equation 4)

This reflected wave W ₂ is added in the same phase as W ₁ at the reference point, and the reflected waves from step 3 to step 5 are also added in the same phase in the same way, so that the surface acoustic wave reflection of this structure is eventually reflected. The fifth harmonic will be strongly reflected in the container. Next, considering the case of the fundamental wave, first, the reflected wave W ₁ of the electrode finger in step ₁ is expressed by the following equation.

[0015]

(Equation 5)

Here, A (f ₀ ) represents the SAW amplitude at the frequency f ₀ of the fundamental wave. From the above equation, the phase angle of the reflected wave from the electrode finger in step 1 at x = 0 is ∠0 °.
Similarly, the reflected wave W ₂ of the electrode finger in step ₂ is expressed by the following equation.

[0017]

(Equation 6)

Therefore, the phase angle of the reflected wave from the electrode finger in step 2 at x = 0 is ∠-144 °. Less than,
The reflected waves from step 3 to step 5 are expressed as follows.

[0019]

(Equation 7) Therefore, the phase angle of the reflected wave at x = 0 is ∠-288 °.

[0020]

(Equation 8) Therefore, the phase angle of the reflected wave at x = 0 is ∠-72 °.

[0021]

(Equation 9) Therefore, the phase angle of the reflected wave at x = 0 is ∠−216 °.

When these are vector-displayed on the complex plane, they can be expressed as shown in FIG. At the reference point of step 1, as a result of vector-wise addition of these five waves, the amplitude becomes zero as a whole, and the fundamental wave is not reflected. Similarly, for the harmonic components other than the 5th harmonic, the waves reflected from the electrode fingers in each step do not reinforce each other in the same phase at the reference point, and as a result, in the configuration of FIG. Only the second harmonic will be reflected efficiently.

Similarly, the shift amount of each step is D = λ
_{Even with 0} / 2M, it is possible to efficiently reflect only the Mth harmonic. This case is shown in FIG. In Figure 3 the amount of shifting this is set to D = λ _0/10. At this time, first
The reflected wave in step 1 is the same as in Fig. 1,

[0024]

(Equation 10) It is. Next, the reflected wave in step 2

[0025]

[Equation 11]

Then, they are added in the same phase at the reference point of x = 0. Similarly, the reflected waves from step 3 to step 5 are added in the same phase at x = 0, and as a result, the 5th harmonic is efficiently reflected. Next, considering the fundamental wave, the reflected wave from step 1 is the same as in FIG.

[0027]

(Equation 12) And the phase angle is ∠0 °. Next, the reflected wave from step 2 is

[0028]

(Equation 13)

And the phase angle is ∠-72 °. Similarly, the phase angle of the reflected wave from step 3 is ∠-144 °,
The phase angle of the reflected wave from step 4 is ∠-216 °, and the phase angle of the reflected wave from step 5 is ∠-288 °.
When the vector is displayed like, the addition result is zero and the fundamental wave is not reflected. According to the second aspect of the present invention, a large number of electrode fingers having a line width of 1 / 4λ ₀ with respect to the fundamental wave of wavelength λ ₀ are arranged in parallel at an interval of 1 / 4λ ₀ on the piezoelectric substrate to form the electrodes. Two surface acoustic wave reflectors that reflect the surface acoustic wave of the Mth harmonic of the fundamental wave are arranged at intervals at the boundary between the portion and the portion having no electrode, and a pair of electrode terminals are provided on the piezoelectric substrate. And a plurality of electrode fingers extending in a finger shape from the pair of electrode terminals, the electrode fingers having a period equal to the wavelength λ _{0 of the} fundamental wave. In the surface acoustic wave resonator arranged between the chambers, the surface acoustic wave reflector according to claim 1 is used as one of the two surface acoustic wave reflectors.

By using the surface acoustic wave reflector according to the first aspect, it is possible to obtain a surface acoustic wave resonator that operates efficiently only with harmonics to be excited and is excellent in stability and oscillation performance. According to the invention of claim 3, the wavelength λ ₀ is formed on the piezoelectric substrate.
Electrode finger with a line width of 1/4 λ ₀ is 1 /
A large number of surface acoustic wave reflectors that are arranged in parallel at intervals of 4λ ₀ and that reflect the surface acoustic wave of the Mth harmonic of the fundamental wave at the boundary between the part with electrodes and the part without electrodes are spaced apart. And a pair of electrode terminals and a plurality of electrode fingers extending in a finger shape extending from the pair of electrode terminals are formed on the piezoelectric substrate, and the period of the electrode fingers is the wavelength λ _{0 of the} fundamental wave. In the surface acoustic wave resonator having two surface acoustic wave converters for input and output arranged between the two surface acoustic wave reflectors, one of the two surface acoustic wave reflectors is provided. The surface acoustic wave reflector according to claim 1 is used.

By using the surface acoustic wave reflector according to the first aspect, it is possible to obtain a surface acoustic wave resonator that operates efficiently only with the harmonic wave to be excited and is excellent in stability and oscillation performance. According to the invention described in claim 4, in the surface acoustic wave resonator according to claim 2, each electrode finger of the surface acoustic wave converter is divided into M steps equal to the order M of the harmonic to be excited, It is characterized in that each step is connected while being shifted by λ ₀ / M in the propagation direction of the surface acoustic wave.

If the surface acoustic wave converter is divided into M steps, the M-th order harmonics are efficiently excited. Therefore, in combination with the surface acoustic wave reflector divided into M steps, A surface acoustic wave resonator that operates efficiently only with harmonics to be excited and is excellent in stability and oscillation performance can be obtained. According to a fifth aspect of the present invention, in the surface acoustic wave resonator according to the third aspect, each electrode finger of one of the two surface acoustic wave converters is equal to the harmonic order M to be excited. Divided into M steps,
It is characterized in that each step is connected while being shifted by λ ₀ / M in the propagation direction of the surface acoustic wave.

When the surface acoustic wave converter is divided into M steps, the M-th order harmonics are efficiently excited. Therefore, in combination with the surface acoustic wave reflector divided into M steps, Further, it is possible to obtain a surface acoustic wave resonator that operates efficiently only with harmonics to be excited and is excellent in stability and oscillation performance. According to a sixth aspect of the present invention, in the surface acoustic wave resonator according to the first aspect, each electrode finger of the surface acoustic wave converter is a split electrode finger separated into two parallel electrode pieces. To do.

The same can be applied to a so-called split electrode finger converter.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a surface acoustic wave reflector 10 of the present invention.
Is a large number of electrode fingers 2 made of a material such as aluminum or gold for the wavelength λ _{0 of the} fundamental wave on the surface of the single crystal piezoelectric substrate 1.
, ... are arranged in parallel for each 1 / 2λ ₀ , and the line width and space width of the electrode fingers 2 are both 1 / 4λ ₀ .

FIG. 1 shows, as an example, the case of constructing a reflector based on the fifth harmonic, in which each electrode finger of the surface acoustic wave reflector 10 is divided into five steps, and each of them is arranged in the SAW propagation direction. D = λ _0/5 by shifting and are connected. With such a configuration, the fifth harmonic can be efficiently reflected and the other waves can be suppressed as described above.

FIG. 3 shows another embodiment. In FIG.
Is the shift amount of each step D = λ ₀/ 10
The configuration is the same as that of FIG. 1 except for the points. In this example,
Since it requires only a small amount of displacement, it is easy to manufacture.
It has the advantage of Even with such a deviation amount,
As mentioned above, the 5th harmonic is reflected efficiently and other waves are reflected.
Can be suppressed.

FIG. 4 shows an example in which a surface acoustic wave resonator is constructed by using the surface acoustic wave reflector 10 of FIG. 1, and two surface acoustic wave reflectors 10 and 12 are arranged at intervals. Between the reflectors 10 and 12, an interdigitated finger type surface acoustic wave converter 1 for transmitting SAW (hereinafter, simply referred to as transmitting IDT).
1)) and a crossed finger type surface acoustic wave converter 2 for output for receiving SAW (hereinafter simply referred to as receiving IDT2), a two-terminal pair type surface acoustic wave resonator is shown. There is.

Each of the transmitting IDT 1 and the receiving IDT 2 has a pair of electrode terminals 3, 3 made of a material such as aluminum or gold and a pair of electrode terminals 3, on the surface of the single crystal piezoelectric substrate 1.
A plurality of electrode fingers 4, 4, ... Each transmitting IDT1 and receiving I
The electrode width Lm and the space width Lg of DT2 are defined by the following equations in order to efficiently excite the harmonics to be excited.

[0040]

[Equation 14]

Is prepared with η selected based on FIG. 10 showing the excitation efficiency of each harmonic. This example is a configuration example of a crossed finger type surface acoustic wave transducer (hereinafter, simply referred to as IDT) of single electrode fingers that excites harmonics of order M = 5, and is configured around η = 0.5. is, the line width and the space width of the electrode fingers 4 are both a lambda _0/4. One of the surface acoustic wave reflectors 10 and 12 is the surface acoustic wave reflector 10 shown in FIG. 1, and the other is a regular reflector having a plurality of electrode fingers 6 which are not divided into steps. It is 12.

When a voltage is applied between the electrode terminals 3 and 3 of the transmitting IDT 1, the fundamental wave excited on the piezoelectric substrate 1 by the transmitting IDT 1 and each harmonic including the fifth harmonic wave generate two surface acoustic waves. Although the reflection is repeated between the reflectors 10 and 12, the surface acoustic wave reflector 10 efficiently reflects the fifth harmonic and the other waves including the fundamental wave are not efficiently reflected. Only the fifth harmonic is efficiently received, and the electric signal is taken out from the electrode terminals 3 and 3 of the receiving IDT 2.

FIG. 5 shows another embodiment. In this embodiment, one input / output cross-finger type surface acoustic wave converter 3 (hereinafter, simply referred to as “I”) is provided between the two surface acoustic wave reflectors 10 and 12.
1 shows a one-terminal pair type surface acoustic wave resonator in which DT3) is arranged. The structure of the IDT3 is the transmission IDT of FIG.
1 or the same as the IDT2 for reception.

Also in this structure, each harmonic wave including the fundamental wave and the fifth harmonic wave excited on the piezoelectric substrate 1 by the IDT 3 is repeatedly reflected between the two surface acoustic wave reflectors 10 and 12. However, since the surface acoustic wave reflector 10 efficiently reflects the fifth harmonic wave and the other waves including the fundamental wave are not efficiently reflected, only the fifth harmonic wave is efficiently oscillated.

FIG. 6 shows another embodiment. This form example is an example in which the transmitting IDT 4 and the receiving IDT 5 of the split electrode finger are used for the transmitting and receiving IDTs of the single electrode finger used in the surface acoustic wave converter shown in FIG. That is, each of the electrode fingers 5, 5, ... That extend in a finger shape intersecting at a period λ ₀ from the pair of electrode terminals 3, 3 of the transmitting IDT 4 and the receiving IDT 5 has two parallel electrodes. It is separated into pieces 5a, 5a. Also, in the illustrated example,
The line width and space width of the electrode pieces 5a are both a λ _0/8, the metallization ratio eta is a eta = 0.5.

The electrode finger of one of the surface acoustic wave reflectors 10 and 12 arranged on both sides of the transmitting IDT 4 and the receiving IDT 5 is divided into three steps, and each step is divided into SAW propagation directions. It is connected shifted by D = λ _0/3 in. FIG. 11 shows the excitation efficiency of the harmonics excited by the IDT of the split electrode finger. For example, when trying to excite harmonics of order M = 3, in the IDT of a single electrode finger as shown in FIG.
Can't excite second harmonic. On the other hand, as shown in FIG. 11, in the IDT of the split electrode finger, the third harmonic can be excited near η = 0.5.

In this way, by selecting the IDT of the single electrode finger or the split electrode finger according to the order M to be excited, the ID near η = 0.5 which is suitable for manufacturing is obtained.
In addition, the number of steps of the surface acoustic wave reflector 10 is set to M, and each step is shifted by D = λ ₀ / M for connection, thereby aiming at operation at a harmonic of an arbitrary order. It can be a surface acoustic wave resonator.

FIG. 7 shows another embodiment. In the form example of FIG. 4, the two transmission / reception IDTs (transmission IDT1 and reception IDT2) are configured by the normal form IDT, but in this example, the electrode finger 7 of one of the IDTs (transmission IDT6) is reflector and according to the order 5 of the harmonic to be excited in the same manner divided into five steps, further D = lambda _0/5 by SAW
Step electrode finger-shaped IDTs connected with staggered in the propagation direction
It consists of. In such an IDT, since the fifth harmonic is efficiently excited, the surface acoustic wave reflector 10 and the surface acoustic wave reflector 10 operate efficiently only at the harmonic to be excited, and the elastic surface having excellent stability and oscillation performance. It can be a wave resonator.

Further, in the embodiment shown in FIG. 5, the IDT 3 is composed of a normal form IDT, but like the reflector, the IDT is divided into 5 steps according to the order 5 of the harmonic to be excited, and the SAW propagation is further performed. It may be constituted by the step electrode finger type IDT that is connected shifted by lambda _0/5 in the direction. In such an IDT, the 5th harmonic is efficiently excited, so that the surface acoustic wave resonator that operates efficiently only with the harmonic to be excited can be combined with the surface acoustic wave reflector 10.

FIG. 8 shows another embodiment. In the present embodiment, in a resonator filter composed of two resonators 20 and 21, one reflector of each resonator is provided as shown in FIG.
The surface acoustic wave reflector 10 shown in is used.
That is, the resonator 20 is composed of the input crossed finger type surface acoustic wave converter 7 (hereinafter simply referred to as the input IDT 7), the surface acoustic wave reflector 10 and the in-line coupler 14, and the resonator 21 is Crossed finger type surface acoustic wave converter 8 for output (hereinafter,
The output IDT 8), the surface acoustic wave reflector 10 and the in-line coupler 14. The in-line coupler 14 is common, and by adjusting the number of electrodes of the in-line coupler 14 to a specific number, a part of the SAW that is repeatedly reflected by the resonator 20 passes through the in-line coupler 14 and the surface acoustic wave reflection of the resonator 21 is performed. Reflection is repeated between the resonator 10 and the in-line coupler 14, and this SAW is reflected by the resonator 2
By detecting with the output IDT 8 of No. 1, the filter is a filter that can obtain a frequency characteristic in which the frequency characteristics of the resonator 20 and the resonator 21 are combined.

Since the surface acoustic wave reflector 10 efficiently reflects only the fifth harmonic, the resonator 20 efficiently resonates the fifth harmonic, and the resonance of other harmonics including the fundamental wave is suppressed. It A part of the higher harmonic wave resonating in the resonator 20 passes through the in-line coupler 14, and the fifth harmonic wave resonates efficiently again in the resonator 21. FIG. 9 shows another form example. The present embodiment is an example in which the present invention is applied to an oblique electrode reflector in which a large number of electrode fingers obliquely inclined with respect to the SAW propagation direction are arranged in parallel.

In this example as well, for the fundamental wave of wavelength λ ₀ , S
A large number of electrode fingers 2 ′ having a line width of ¼λ ₀ as viewed from the AW propagation direction (SAW incident direction, x direction in the figure) are arranged in parallel at intervals of ¼λ ₀ . Further, each electrode finger 2 ′ is divided into five steps, and each step is λ ₀ / in the SAW propagation direction (SAW incident direction, x direction in the figure).
They are connected by shifting by 5. With this configuration, at the observation point, the combined sum of the fundamental waves reflected at each step becomes zero, and the fundamental waves are suppressed, while all the fifth harmonics are added in phase and strengthen each other.

[0053]

As described above, according to the present invention, the effects listed below can be obtained. (1) In a surface acoustic wave reflector in which a large number of electrode fingers having a line width of 1 / 4λ ₀ are arranged in parallel at an interval of 1 / 4λ ₀ , the desired harmonic wave is efficiently reflected and includes the fundamental wave. It is possible to obtain a reflector in which the reflection of higher harmonics is suppressed. (2) By forming a surface acoustic wave resonator using the surface acoustic wave reflector described above, a resonator type resonator that operates efficiently only with the harmonic wave to be used can be obtained. (3) Compared to the conventional delay linear resonator, by adopting a resonator type, it is possible to obtain a resonator excellent in stability, oscillation performance, etc., which were problems in delay linear. (4) Single electrode metallization ratio η =
Even with harmonics of orders that cannot be excited near 0.5, a step electrode finger reflector can be obtained near η = 0.5 by using the split electrode. (5) By using harmonics, it is possible to obtain a resonator operating at a higher frequency with the electrode line width and space width of the resonator using the conventional fundamental wave without using a special process technology.

[Brief description of the drawings]

FIG. 1 is a plan view showing a surface acoustic wave reflector of the present invention.

FIG. 2 is a diagram showing the operation of the fundamental wave of FIG. 1 as a vector on a complex plane.

FIG. 3 is a plan view showing another surface acoustic wave reflector of the present invention.

FIG. 4 is a plan view showing an example in which a surface acoustic wave resonator is configured using the surface acoustic wave reflector shown in FIG.

5 is a plan view showing an example in which a surface acoustic wave resonator is configured using the surface acoustic wave reflector shown in FIG.

FIG. 6 is a plan view showing an example in which a surface acoustic wave resonator is configured using the surface acoustic wave reflector shown in FIG.

7 is a plan view showing an example in which a surface acoustic wave resonator is configured using the surface acoustic wave reflector shown in FIG.

8 is a plan view showing a resonator filter formed of a surface acoustic wave resonator using the surface acoustic wave reflector shown in FIG. 1. FIG.

FIG. 9 is a plan view showing a configuration example of another surface acoustic wave reflector.

FIG. 10 is a diagram showing a relative amplitude intensity with respect to a metallization ratio η of a harmonic wave excited by a single electrode finger.

FIG. 11 is a diagram showing a relative amplitude intensity with respect to a metallization ratio η of a harmonic wave excited by a split electrode finger.

[Explanation of symbols]

 1 Piezoelectric substrate 2 Electrode finger 3 Electrode terminal 4, 5, 7 Electrode finger 5a Electrode piece

Claims (6)

[Claims] 1. A electrode fingers having a line width of 1 / 4.lamda ₀ with respect to the fundamental wave of wavelength lambda ₀ on the piezoelectric substrate is a large number arranged at intervals of 1 / 4.lamda _0, portion of the electrode and the electrode A surface acoustic wave reflector that reflects the surface acoustic wave of the M-th harmonic of the fundamental wave at the boundary with a portion without a mark, wherein each electrode finger is divided into M steps equal to the order M of the harmonic to be reflected. A surface acoustic wave reflector, which is divided and connected by shifting each step by λ ₀ / M or λ ₀ / 2M in the surface acoustic wave propagation direction. Wherein the electrode fingers having a line width of 1 / 4.lamda ₀ with respect to the fundamental wave of wavelength lambda ₀ on the piezoelectric substrate is a large number arranged at intervals of 1 / 4λ _0, portion of the electrode and the electrode Reflects the M-th order surface acoustic wave of the fundamental wave at the boundary with the part without
Two surface acoustic wave reflectors are arranged at intervals, and a pair of electrode terminals and a plurality of electrode fingers extending in a finger shape extending from the pair of electrode terminals are formed on the piezoelectric substrate. A surface acoustic wave resonator in which a surface acoustic wave converter having a period equal to the wavelength λ _{0 of the} fundamental wave is arranged between the two surface acoustic wave reflectors, wherein one of the two surface acoustic wave reflectors is used. Claim 1 on one side
A surface acoustic wave resonator characterized by using the surface acoustic wave reflector as described above. 3. A plurality of electrode fingers having a line width of ¼λ ₀ with respect to a fundamental wave of wavelength λ ₀ are arranged in parallel on a piezoelectric substrate at intervals of ¼λ ₀ , and a portion having an electrode and an electrode. Two surface acoustic wave reflectors that reflect the surface acoustic wave of the Mth harmonic of the fundamental wave are arranged at intervals at the boundary with the non-exposed portion, and a pair of electrode terminals and the pair of surface acoustic waves are provided on the piezoelectric substrate. A plurality of electrode fingers extending in an interdigitated finger shape from the electrode terminals of the input terminal and the electrode fingers having a cycle of the fundamental wave wavelength λ _0.
A surface acoustic wave resonator comprising two surface acoustic wave converters arranged between the two surface acoustic wave reflectors, wherein one of the two surface acoustic wave reflectors is provided.
A surface acoustic wave resonator characterized by using the surface acoustic wave reflector as described above. 4. Each electrode finger of the surface acoustic wave converter is divided into M steps equal to the order M of the harmonic to be excited, and each step is λ ₀ / in the propagation direction of the surface acoustic wave.
The surface acoustic wave resonator according to claim 2, wherein the surface acoustic wave resonators are connected while being shifted by M. 5. Each electrode finger of one of the two surface acoustic wave converters is divided into M steps equal to the order M of the harmonic to be excited, and each step is divided into surface acoustic wave steps. The surface acoustic wave resonator according to claim 3, wherein the surface acoustic wave resonators are connected while being shifted by λ ₀ / M in the propagation direction. 6. Each of the electrode fingers of the surface acoustic wave transducer has two electrodes.
6. The surface acoustic wave resonator according to claim 2, wherein the surface acoustic wave resonator is a split electrode finger separated into parallel electrode pieces.