Interdigital transducer and elastic wave resonator
By using a specific apodization curve in the interdigital transducer electrode structure to block the propagation of transverse modes, the problem of increased ripple caused by transverse modes in the prior art is solved, thereby improving device performance and maintaining the quality factor.
Patent Information
- Application Number
- CN202411115982.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-14
- Publication Date
- 2026-03-03
Smart Images
Figure CN121602944A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of surface acoustic wave technology, and particularly relates to an interdigital transducer and an elastic wave resonator. Background Technology
[0002] Filters composed of elastic wave resonators possess advantages such as low insertion loss, high suppression, and small size, making them widely used in radio frequency filtering. In elastic wave devices excited by interdigital transducers, reflections of transversely propagating acoustic waves at the boundaries cause transverse modes to appear in the resonator. Elastic wave devices excited by interdigital transducers (IDTs) include various acoustic wave devices utilizing surface wave (SAW), Lamb waves, and higher-order SH modes. The presence of transverse modes leads to ripple in the in-band and near-passband of piezoelectric filters. These ripples increase device losses and degrade the performance of the resonator and filter. Therefore, suppressing transverse modes in elastic wave devices is a problem that needs to be solved. Summary of the Invention
[0003] This application aims to at least solve one of the technical problems existing in the prior art. To this end, this application proposes an interdigital transducer and an elastic wave resonator, which suppresses transverse modes by apodizing the edges of the interdigital transducer electrode structure without reducing the quality factor by apodizing the edges of the fingers.
[0004] In a first aspect, this application provides an interdigital transducer, comprising:
[0005] The interdigitated transducer electrode structure includes a first interdigitated electrode and a second interdigitated electrode arranged opposite to each other along a first direction, and a plurality of fingers in the first interdigitated electrode and the second interdigitated electrode are arranged alternately along a second direction, with the first direction and the second direction intersecting.
[0006] The edges of the fingers in the first interdigital electrode form a first curve, and the edges of the fingers in the second interdigital electrode form a second curve. The first and second curves are located on both sides of the centerline of the interdigital transducer structure, and the centerline is parallel to the second direction. Both the first and second curves satisfy the following apodization function:
[0007] y=(arccos(a / cos(x*arccos(a)*2)) / arccos(a)) / 2;
[0008] Where x is the normalized coordinate of the interdigital transducer structure in the second direction, with a value range of [-0.5, 0.5]; y is the normalized coordinate of the interdigital transducer structure in the first direction, with a value range of [0, 0.5]; and a is the weighting factor, with a value range of [0.01, 0.99].
[0009] The reflective grid strips are arranged along the second direction on both sides of the interdigital transducer structure.
[0010] According to the interdigital transducer of this application, by apodizing the edges of the interdigital transducer electrode structure and using a specific apodization curve, the propagation of the transverse mode is blocked, thereby suppressing the transverse mode without reducing the quality factor.
[0011] According to one embodiment of this application, the number of the first curve and the number of the second curve are both one, and they are connected on the center line.
[0012] According to one embodiment of this application, the x-axis coordinate range of the apodization function is normalized by the total length of the interdigital transducer structure in the second direction, and the y-axis coordinate range of the apodization function is normalized by the width of the interdigital transducer structure from the center line to one side in the first direction.
[0013] According to one embodiment of this application, there are multiple first curves, each arranged along a second direction and adjacent first curves are connected. There are multiple second curves, each arranged along a second direction and adjacent second curves are connected. The first curves and second curves that are opposite to each other along the first direction are connected on the center line.
[0014] According to one embodiment of this application, the x-axis coordinate range of the apodization function is normalized by the length L / M of the interdigital transducer structure in the second direction, and the y-axis coordinate range of the apodization function is normalized by the width of the interdigital transducer structure from the center line to one side in the first direction, where L is the total length of the interdigital transducer structure in the second direction, and M is the number of the first curve or the second curve.
[0015] According to one embodiment of this application, both the first curve and the second curve further satisfy the following random function:
[0016] y'=y±b*w;
[0017] Where y' is the corrected y value, b is a random number with a value range of (0, 0.1], and w is the total width of the aperture region in the first direction.
[0018] According to one embodiment of this application, the random number b in the random function takes values in the range of [0.04, 0.06].
[0019] According to one embodiment of this application, the weighting factor 'a' in the apodization function takes values ranging from [0.4, 0.6].
[0020] According to one embodiment of this application, the first interdigital electrode includes a first true finger and a first virtual finger, and the second interdigital electrode includes a second true finger and a second virtual finger. The first true finger and the second virtual finger are arranged opposite to each other along a first direction, and the second true finger and the first virtual finger are arranged opposite to each other along the first direction. The edge of the finger strip of the first true finger forms a first curve, and the edge of the finger strip of the second true finger forms a second curve.
[0021] Secondly, this application provides an elastic wave resonator, including a piezoelectric layer and an interdigital transducer formed on the piezoelectric layer according to the foregoing.
[0022] According to the elastic wave resonator of this application, by employing an interdigital transducer that effectively suppresses transverse modes, the in-band and passband ripple can be reduced, device losses can be avoided, and device performance can be improved.
[0023] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description
[0024] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:
[0025] Figure 1 This is one of the structural schematic diagrams of the interdigital transducer provided in the embodiments of this application;
[0026] Figure 2 This is one of the structural schematic diagrams of interdigital transducers in related technologies;
[0027] Figure 3 This is a contour diagram of the fundamental modes of a two-dimensional resonant cavity for an interdigital transducer;
[0028] Figure 4 This is a graph of the change function provided in the embodiments of this application;
[0029] Figure 5 This is a second schematic diagram of the structure of the interdigital transducer provided in the embodiments of this application;
[0030] Figure 6 This is the third schematic diagram of the interdigital transducer provided in the embodiments of this application;
[0031] Figure 7 This is the second schematic diagram of the structure of the interdigital transducer in the related technology;
[0032] Figure 8 It is one of the admittance performance curves of various interdigital transducers;
[0033] Figure 9 It is one of the real part admittance performance curves of various interdigital transducers;
[0034] Figure 10 It is one of the Bode-Q curves of various interdigital transducers;
[0035] Figure 11 This is the second of several admittance performance curves for interdigital transducers;
[0036] Figure 12 This is the second of several admittance real part performance curves for interdigital transducers;
[0037] Figure 13 This is the second Bode-Q curve of various interdigital transducers;
[0038] Figure 14 This is a schematic diagram of the structure of the elastic wave resonator provided in the embodiments of this application.
[0039] Figure label:
[0040] Interdigital transducer 10, interdigital transducer electrode structure 11, first interdigital electrode 111, second interdigital electrode 112, first reflective grating 12, second reflective grating 13, piezoelectric layer 20. Detailed Implementation
[0041] The embodiments of this application are described in detail below, examples of which are illustrated in the accompanying drawings. In the drawings, for clarity, the dimensions of layers, regions, elements, and their relative dimensions may be exaggerated. The same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.
[0042] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this disclosure, the first element, component, area, layer, or portion discussed below may be referred to as a second element, component, area, layer, or portion. And the discussion of a second element, component, area, layer, or portion does not imply that the first element, component, area, layer, or portion necessarily exists in this disclosure.
[0043] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0044] In related technologies, elastic wave resonators typically employ weighted curves, such as cosine function curves, at the finger tips of the interdigital transducer. Alternatively, a load can be applied to the finger tips of the interdigital transducer to suppress transverse modes. However, these methods have limited effectiveness in suppressing transverse modes, and in some applications, elastic wave resonators require higher transverse mode suppression capabilities.
[0045] The embodiments of this application provide an interdigital transducer and an elastic wave resonator. By apodizing the edges of the interdigital transducer electrode structure and using a specific apodization curve, the propagation of transverse modes is blocked, thereby suppressing transverse modes without reducing the quality factor.
[0046] Reference Figure 1 , Figure 1The structure of a first type of interdigital transducer is shown. One embodiment of this application proposes an interdigital transducer 10. In this embodiment, the interdigital transducer 10 includes an interdigital transducer electrode structure 11, a first reflective grating 12, and a second reflective grating 13. The interdigital transducer electrode structure 11 includes a first interdigital electrode 111 and a second interdigital electrode 112 arranged opposite each other along a first direction X. A plurality of fingers in the first interdigital electrode 111 and the second interdigital electrode 112 are arranged alternately along a second direction Y. The first direction X and the second direction Y intersect. The first reflective grating 12 and the second reflective grating 13 are arranged along the second direction Y on both sides of the interdigital transducer electrode structure 11.
[0047] In this design, the edge of the finger strip in the first interdigital electrode 111 forms a first curve, and the edge of the finger strip in the second interdigital electrode 112 forms a second curve. The first curve and the second curve are located on both sides of the center line cl of the interdigital transducer structure. The center line cl is parallel to the second direction Y. Both the first curve and the second curve satisfy the following apodization function:
[0048] y=(arccos(a / cos(x*arccos(a)*2)) / arccos(a)) / 2;
[0049] Where x is the normalized coordinate of the interdigital transducer electrode structure 11 in the second direction Y, and its value ranges from [-0.5, 0.5]; y is the normalized coordinate of the interdigital transducer electrode structure 11 in the first direction X, and its value ranges from [0, 0.5]; a is the weighting factor, and its value ranges from [0.01, 0.99].
[0050] Interdigital transducers can be used to form elastic wave resonators, and are formed above the piezoelectric layer. When an alternating electrical signal is applied to the interdigital transducer, a periodically distributed electric field is generated. Due to the inverse piezoelectric effect, corresponding elastic deformation is excited near the surface of the piezoelectric medium, causing vibration of solid particles and forming surface acoustic waves propagating along the substrate surface. The first reflective grating 12 and the second reflective grating 13 reflect the signal at the interdigital transducer electrode structure 11, forming a resonant cavity. This resonant cavity can limit the propagation range of the surface acoustic wave energy, concentrating it mainly in the region composed of the two reflective gratings.
[0051] Reference Figure 2 and Figure 3 , Figure 2 The structure of the interdigital transducer in the first related technology is shown. Figure 3 The contour lines of the fundamental modes of a two-dimensional resonant cavity are shown.
[0052] by Figure 2Taking the interdigital transducer 10 shown as an example, the horizontal axis x represents the normalized coordinate relative to the length L of the interdigital transducer electrode structure 11 in the second direction Y, and the vertical axis y represents the normalized coordinate relative to the maximum overlap length W of the interdigital electrodes in the first direction X. Based on the two-dimensional resonant cavity, when both sides are reflection boundaries, the following calculations are obtained: Figure 2 The contour lines shown are schematic diagrams.
[0053] In this embodiment, by means of Figure 3 The contour map shown is transformed using coordinates to obtain a series of function curves. The mathematical expressions for these functions are:
[0054] y=(arccos(a / cos(x*arccos(a)*2)) / arccos(a)) / 2;
[0055] Where x is the normalized coordinate of the interdigital transducer electrode structure 11 in the second direction Y, and its value ranges from [-0.5, 0.5]; y is the normalized coordinate of the interdigital transducer electrode structure 11 in the first direction X, and its value ranges from [0, 0.5]; a is the weighting factor, and its value ranges from [0.01, 0.99].
[0056] Reference Figure 4 , Figure 4 The function curve corresponding to the above mathematical expression is shown. Figure 4 In the function curve shown, the x-axis coordinate ranges from [-0.5, 0.5], and the y-axis coordinate ranges from [0, 0.5]. The larger the value of the weighting factor a, the smoother the weighted function will be. The edges of the finger strips in the first interdigital electrode 111 and the edges of the finger strips in the second interdigital electrode 112 are arranged according to the function curve corresponding to the above mathematical expression with a determined weighting factor a.
[0057] In some embodiments, the weighting factor 'a' in the apodization function takes values in the range of [0.4, 0.6].
[0058] It should be noted that the larger the value of the weighting factor 'a', the better the suppression effect on the transverse mode when the fingers in the interdigital transducer electrode structure 11 are arranged according to the corresponding function curve, but it may lead to a decrease in the quality factor Q. Therefore, to balance the two performance characteristics, a median weighting factor can be used. For example, the weighting factor 'a' can be equal to 0.4, 0.5, or 0.6, etc.
[0059] It should be noted that normalization refers to transforming the target length or target width of the interdigitated transducer electrode structure 11 in one direction using coordinates. Figure 1Taking the interdigital transducer 10 shown as an example, there is one first curve and one second curve. The total length L of the interdigital transducer electrode structure 11 in the second direction Y is normalized as the target length. That is, the midpoint of the total length L is taken as the origin, and the two ends are taken as -0.5 and 0.5 respectively. After normalization, a set of points with a value range of [-0.5, 0.5] is formed, which serves as the x-axis of the first curve and the second curve. The midpoint of the total width W of the interdigital transducer electrode structure 11 in the first direction X is taken as the origin, and both ends are taken as 0.5. The target width is normalized with W / 2. From the midpoint of the total width W, normalization is performed to both sides to form two set of points with a value range of [0, 0.5], which serve as the y-axis of the first curve and the second curve respectively.
[0060] In this example, the midpoint of the total width W of the interdigital transducer structure 11 in the first direction X is taken as the origin, so the first curve and the second curve are connected on the center line cl. Of course, the target length and / or target width can also be selected according to requirements. For example, a certain distance can be reserved on both sides of the interdigital transducer structure 11 in the second direction Y to prevent apodization, and / or they can not intersect on the center line in the first direction X.
[0061] In some embodiments, the first interdigital electrode 111 includes a first true finger and a first imaginary finger, and the second interdigital electrode 112 includes a second true finger and a second imaginary finger. The first true finger and the second imaginary finger are arranged opposite each other along a first direction X, and the second true finger and the first imaginary finger are arranged opposite each other along the first direction X. The edge of the finger strip of the first true finger forms a first curve, and the edge of the finger strip of the second true finger forms a second curve.
[0062] There are gaps between the first true finger and the second imaginary finger, as well as between the second true finger and the first imaginary finger, and the lengths of each gap in the first direction X are approximately equal. Therefore, when the edge of the first true finger forms a first curve, the edge of the second imaginary finger also forms a first curve; when the edge of the second true finger forms a second curve, the edge of the first imaginary finger also forms a second curve. The first curve and the second curve can be axially symmetrical about the center line c1.
[0063] According to the interdigital transducer 10 of this application, by apodizing the edges of the interdigital transducer electrode structure 11, a specific apodization curve is adopted to block the propagation of the transverse mode, thereby suppressing the transverse mode without reducing the quality factor.
[0064] Reference Figure 5 , Figure 5The structure of a second type of interdigital transducer is shown. In some embodiments, there are multiple first curves, each arranged along the second direction Y, and adjacent first curves are connected. There are also multiple second curves, each arranged along the second direction Y, and adjacent second curves are connected. The first and second curves opposite each other along the first direction X are connected on the center line.
[0065] In this embodiment, multiple first curves and second curves can be set. Multiple target lengths are formed by dividing the total length L in the second direction Y of the interdigital transducer structure 11. Each target length is normalized to form a set of points with values ranging from [-0.5, 0.5], which serve as the x-axis of each first curve and each second curve. The normalization of the y-axis of each first curve and each second curve can be referred to the foregoing. Therefore, the interdigital transducer structure 11 can be envelope-weighted using the aforementioned function curves, and the transverse mode can be suppressed as needed.
[0066] As an example, the x-axis coordinate range of the apodization function is normalized by the length L / M of the interdigital transducer electrode structure 11 in the second direction Y, and the y-axis coordinate range of the apodization function is normalized by the width of the interdigital transducer electrode structure 11 from the center line to one side in the first direction X, where L is the total length of the interdigital transducer electrode structure 11 in the second direction, and M is the number of the first curve or the second curve. Of course, a portion of the length of the interdigital transducer electrode structure 11 can be reserved without apodization.
[0067] Reference Figure 6 , Figure 6 The structure of a second type of interdigital transducer is shown. In some embodiments, both the first and second curves also satisfy the following random function:
[0068] y'=y±b*W;
[0069] Where y' is the corrected y value, b is a random number with a value range of (0, 0.1], and W is the total width of the aperture region in the first direction.
[0070] The apodization curve formed by the edge of the finger strip in the interdigital transducer electrode structure 11 can also be superimposed with a random function. For example, taking the apodization curve formed by the edge of the finger strip of the real finger as an example, under the superimposed random function, the length of the real finger can be randomly increased or decreased by a certain length (i.e., b*W), and the corresponding imaginary finger will be decreased or increased by a certain length (i.e., b*W), which does not exceed 10% of the total width W of the interdigital transducer electrode structure 11 in the first direction X.
[0071] As an example, in an apodization curve of an interdigital transducer electrode structure 11, one or more random numbers can be set. In this apodization curve, the random function can be superimposed only on a portion of the finger edges, or it can be superimposed on all the finger edges. When an interdigital transducer electrode structure 11 includes multiple first curves and multiple second curves, the random numbers among the first curves can be the same or different, and the random numbers among the second curves can be the same or different.
[0072] In some embodiments, the random number b in the random function takes values in the range of [0.04, 0.06].
[0073] It should be noted that superimposing a portion of the random function onto the apodization function can suppress spurious modes near the resonant point. However, this will slightly reduce the resonator's quality factor. To achieve a more balanced device performance, the random number can typically be set to an intermediate value. For example, the random number b could be 0.04, 0.05, or 0.06. Figure 6 In the structure shown, the degree of variation of the finger strip edge accounts for 5% of the total width W of the interdigital transducer structure 11.
[0074] Reference Figure 7 , Figure 7 The structure of the interdigital transducer in the second related technology is shown. Figure 1 The structure shown is an example of Embodiment 1. Figure 6 The structure shown is an example of Embodiment 2. Figure 2 The structure shown serves as a comparative example 1 and Figure 7 The structure shown is used as a comparative example 2 for performance comparison. Among them, Figure 7 In the structure shown, the edges of the interdigital transducer electrode structure 11 use a conventional cosine function curve.
[0075] Reference Figure 8 , Figure 9 and Figure 10 , Figure 8 The admittance performance curves of Example 1, Comparative Example 1, and Comparative Example 2 are shown. Figure 9 The admittance real part performance curves of Example 1, Comparative Example 1, and Comparative Example 2 are shown. Figure 10 The Bode-Q curves for the quality factors of Example 1, Comparative Example 1, and Comparative Example 2 are shown. The comparison between Example 1 and Comparative Example 1 demonstrates that Example 1 effectively reduces the intensity of the transverse modes of the elastic wave resonator. The comparison between Example 1 and Comparative Example 2 shows that Example 1 achieves a higher quality factor compared to the common cos-weighted method (Comparative Example 2).
[0076] Reference Figure 11 , Figure 12 and Figure 13 , Figure 11 The admittance performance curves between Embodiment 1 and Embodiment 2 are shown. Figure 12 The admittance real part performance curves for Embodiment 1 and Embodiment 2 are shown. Figure 13 The Bode-Q curves for the quality factor between Embodiment 1 and Embodiment 2 are shown. As can be seen from the figure, adding a random effect can suppress spurious modes near the resonant point, but it slightly reduces the resonator's quality factor.
[0077] Reference Figure 14 One embodiment of this application also provides an elastic wave resonator, including a piezoelectric layer 20 and an interdigital transducer 10 formed on the piezoelectric layer 20 according to the foregoing. The specific structure and principle of the interdigital transducer 10 can be referred to the foregoing embodiments, and will not be repeated here.
[0078] When the interdigital transducer 10 is excited by an alternating electrical signal, it generates a periodically distributed electric field. Due to the inverse piezoelectric effect, corresponding elastic deformation is excited near the surface of the piezoelectric layer 20, causing the piezoelectric layer 20 to vibrate and forming surface acoustic waves propagating along the surface. Elastic wave resonators can also be used to form filters, etc.
[0079] According to the elastic wave resonator of this application, by employing an interdigital transducer that effectively suppresses transverse modes, in-band and passband ripple can be reduced, device losses can be avoided, and device performance can be improved. The interdigital transducer 10 can also employ the technical solutions mentioned in the above embodiments, which also have the corresponding technical effects.
[0080] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application.
[0081] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.
Claims
1. An interdigital transducer, characterized in that, include: The interdigitated transducer structure includes a first interdigitated electrode and a second interdigitated electrode arranged opposite to each other along a first direction, and a plurality of fingers in the first interdigitated electrode and the second interdigitated electrode are arranged alternately along a second direction, wherein the first direction and the second direction intersect. The edges of the fingers in the first interdigital electrode form a first curve, and the edges of the fingers in the second interdigital electrode form a second curve. The first curve and the second curve are located on both sides of the center line of the interdigital transducer structure, and the center line is parallel to the second direction. Both the first curve and the second curve satisfy the following apodization function: y=(arccos(a / cos(x*arccos(a)*2)) / arccos(a)) / 2; Where x is the normalized coordinate of the interdigital transducer electrode structure in the second direction, with a value range of [-0.5, 0.5]; y is the normalized coordinate of the interdigital transducer electrode structure in the first direction, with a value range of [0, 0.5]; and a is a weighting factor, with a value range of [0.01, 0.99]. Reflective gratings are arranged along the second direction on both sides of the interdigital transducer structure.
2. The interdigital transducer according to claim 1, characterized in that, The number of the first curve and the number of the second curve are both one, and they are connected on the center line.
3. The interdigital transducer according to claim 2, characterized in that, The x-axis coordinate range of the apodization function is normalized by the total length of the interdigital transducer structure in the second direction, and the y-axis coordinate range of the apodization function is normalized by the width of the interdigital transducer structure from the center line to one side in the first direction.
4. The interdigital transducer according to claim 1, characterized in that, There are multiple first curves, each arranged along the second direction, and adjacent first curves are connected. There are multiple second curves, each arranged along the second direction, and adjacent second curves are connected. First curves and second curves that are opposite each other along the first direction are connected on the center line.
5. The interdigital transducer according to claim 4, characterized in that, The x-axis coordinate range of the apodization function is normalized by the length L / M of the interdigital transducer structure in the second direction, and the y-axis coordinate range of the apodization function is normalized by the width of the interdigital transducer structure from the center line to one side in the first direction, where L is the total length of the interdigital transducer structure in the second direction, and M is the number of the first curve or the second curve.
6. The interdigital transducer according to any one of claims 1-5, characterized in that, Both the first curve and the second curve also satisfy the following random function: y'=y±b*W; Where y' is the corrected y value, b is a random number with a value range of (0, 0.1], and w is the total width of the aperture region in the first direction.
7. The interdigital transducer according to claim 6, characterized in that, The random number b in the random function takes values in the range of [0.04, 0.06].
8. The interdigital transducer according to any one of claims 1-5, characterized in that, The weighting factor 'a' in the apodization function has a value range of [0.4, 0.6].
9. The interdigital transducer according to any one of claims 1-5, characterized in that, The first interdigital electrode includes a first true finger and a first virtual finger, and the second interdigital electrode includes a second true finger and a second virtual finger. The first true finger and the second virtual finger are arranged opposite to each other along the first direction, and the second true finger and the first virtual finger are arranged opposite to each other along the first direction. The edge of the finger strip of the first true finger forms the first curve, and the edge of the finger strip of the second true finger forms the second curve.
10. An elastic wave resonator, characterized in that, It includes a piezoelectric layer and an interdigital transducer formed on the piezoelectric layer according to any one of claims 1-9.