Surface acoustic wave device and radio frequency front-end module

Abstract

The utility model discloses a surface acoustic wave device and a radio frequency front-end module. The surface acoustic wave device comprises a piezoelectric substrate and an interdigital transducer. The interdigital transducer comprises a first bus bar, a second bus bar and an electrode finger, in the extending direction of the electrode fingers, an overlapping area is formed between the first bus bar and the second bus bar, a first area is formed between the overlapping area and the first bus bar, a second area is formed between the overlapping area and the second bus bar, and the first area and the second area are adjacent to the two ends of the overlapping area respectively; wherein the critical positions of the overlapping area and the first area and the second area respectively form a first curve and a second curve, and the edges, deviating from the overlapping area, of the first area and the second area respectively form a third curve and a fourth curve; the difference between the maximum length and the minimum length of the first region in the extending direction of the electrode fingers is smaller than or equal to 3 lambda. The utility model aims to solve the problem of unstable quality factor of the surface acoustic wave device in the prior art.

Description

Technical Field

[0001] The present application relates to the field of radio frequency filtering technology, and in particular to a surface acoustic wave device and a radio frequency front-end module. Background Art

[0002] A surface acoustic wave (SAW) device, such as a surface acoustic wave resonator, converts electrical signals into acoustic signals or vice versa. However, a SAW resonator typically includes a piezoelectric substrate and an interdigital transducer (IDT). The IDT is formed on the piezoelectric substrate and can be used to convert electrical signals into acoustic signals or vice versa.

[0003] Currently, the development of radio frequency technology has placed higher requirements on the performance of surface acoustic wave devices. Therefore, how to improve the performance of surface acoustic wave devices, especially the quality factor (Bode Q) of surface acoustic wave devices, has become an urgent problem to be solved. Utility Model Content

[0004] The present application provides a surface acoustic wave device and a radio frequency front-end module, which solve the problem of unstable quality factor (Q value) of the surface acoustic wave device in the related art.

[0005] In a first aspect, the present application provides a surface acoustic wave device, comprising a piezoelectric substrate and an interdigital transducer disposed on a surface of the piezoelectric substrate, wherein the interdigital transducer comprises a first bus bar and a second bus bar disposed opposite to each other and electrode fingers;

[0006] The electrode fingers are arranged between the first bus bar and the second bus bar, and the electrode fingers include a plurality of first electrode fingers and a plurality of second electrode fingers, one end of the first electrode finger is electrically connected to the first bus bar, and the other end of the first electrode finger is spaced from the second bus bar, and one end of the second electrode finger is electrically connected to the second bus bar, and the other end of the second electrode finger is spaced from the first bus bar, and the plurality of first electrode fingers and the plurality of second electrode fingers are alternately arranged in sequence; in the extension direction of the electrode fingers, there is an overlapping area between the first bus bar and the second bus bar, and the overlapping area is an area where the first electrode fingers and the second electrode fingers overlap with each other, a first area is included between the overlapping area and the first bus bar, and a second area is included between the overlapping area and the second bus bar, and the first area and the second area are respectively adjacent to two ends of the overlapping area;

[0007] In which, the critical positions of the overlapping area and the first area and the second area form a first curve and a second curve respectively, the edges of the first area and the second area away from the overlapping area respectively form a third curve and a fourth curve, the first curve and the second curve are symmetrically distributed with the center line as the symmetry axis, the third curve and the fourth curve are symmetrically distributed with the center line of the interdigital transducer as the symmetry axis, the center line is perpendicular to the extension direction of the electrode finger, and the difference between the maximum length and the minimum length of the first area along the extension direction of the electrode finger is less than or equal to 3λ, where λ is the wavelength of the sound wave.

[0008] In a second aspect, the present application also provides a radio frequency front-end module, comprising the surface acoustic wave device as described above.

[0009] The surface acoustic wave device provided by the present application includes a piezoelectric substrate and an interdigital transducer arranged on the surface of the piezoelectric substrate, the interdigital transducer includes a first bus bar and a second bus bar and electrode fingers arranged relatively to each other; the electrode fingers include a plurality of first electrode fingers and a plurality of second electrode fingers, and in the extension direction of the electrode fingers, there is an overlapping area between the first bus bar and the second bus bar, the overlapping area and the first bus bar include a first area, and the overlapping area and the second bus bar include a second area, and the first area and the second area are respectively adjacent to the two ends of the overlapping area; wherein, the critical positions of the overlapping area and the first area and the second area form a first curve and a second curve respectively, and the edges of the first area and the second area away from the overlapping area respectively form a third curve and a fourth curve respectively, the first curve and the second curve are symmetrically distributed with the midline as the symmetry axis, the third curve and the fourth curve are symmetrically distributed with the midline of the interdigital transducer as the symmetry axis, and the difference between the maximum length and the minimum length of the first area along the extension direction of the electrode fingers is less than or equal to 3λ. By varying the aperture length of the electrode fingers, the interdigital transducer can present apodized first and second regions at both ends of the overlapping region. Furthermore, the difference between the maximum and minimum lengths of the first region along the extension direction of the electrode fingers is controlled to be less than or equal to 3λ. This allows the equivalent area of the main-mode energy concentration region (i.e., the overlapping region) to be approximately equal to the area of the overlapping region before apodization, thereby simplifying the structural design of the surface acoustic wave device. Furthermore, the Q value can be modulated by the main-mode energy concentration region, thereby improving Q value fluctuations between the resonance point and the antiresonance point and enhancing the Q value stability of the surface acoustic wave device. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0011] FIG1( a ) is a schematic diagram of a top view of a surface acoustic wave device provided by the related art;

[0012] FIG1( b ) is a schematic top view of another surface acoustic wave device provided by the related art;

[0013] Figure 2 1 is a schematic top view of a surface acoustic wave device provided in an embodiment of the present application;

[0014] Figure 3 is a schematic top view of another surface acoustic wave device provided in an embodiment of the present application;

[0015] Figure 4 1 is a schematic diagram of a top view of an interdigital transducer provided in an embodiment of the present application;

[0016] Figure 5 is a schematic top view of another surface acoustic wave device provided in an embodiment of the present application;

[0017] Figure 6 1 is a schematic diagram of a top view of another interdigital transducer provided in an embodiment of the present application;

[0018] Figure 7 1 is a schematic diagram of a top view of another interdigital transducer provided in an embodiment of the present application;

[0019] Figure 8 is a schematic top view of another surface acoustic wave device provided in an embodiment of the present application;

[0020] Figure 9 is a schematic top view of another surface acoustic wave device provided in an embodiment of the present application;

[0021] Figure 10 1 is a schematic diagram of a top view of another interdigital transducer provided in an embodiment of the present application;

[0022] Figure 11 is a schematic top view of another surface acoustic wave device provided in an embodiment of the present application;

[0023] Figure 12 1 is a schematic diagram comparing the Q value change curves of the surface acoustic wave device provided in Example 1 and Comparative Example 1 provided in the embodiments of the present application;

[0024] Figure 13 3 is a schematic diagram comparing the Q value change curves of the surface acoustic wave device provided in Example 2 and Comparative Example 1 provided in the embodiments of the present application. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0026] The flowcharts shown in the accompanying drawings are for illustrative purposes only and do not necessarily include all contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may be decomposed, combined, or partially merged, so the actual execution order may vary depending on the actual situation.

[0027] It should be understood that the terms used in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0028] It will also be understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0029] The following describes some embodiments of the present application in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0030] The following briefly describes the implementation method in the related art.

[0031] 1(a) and 1(b), the surface acoustic wave device 100 includes a piezoelectric substrate 10 and an IDT 20 disposed on the surface of the piezoelectric substrate 10. The IDT 20 includes a first bus bar 21 and a second bus bar 22 disposed opposite to each other. An electrode finger 23 is disposed between the first bus bar 21 and the second bus bar 22. The electrode finger 23 includes a plurality of first electrode fingers 231 and a plurality of second electrode fingers 232. One end of the first electrode finger 231 is electrically connected to the first bus bar 21, and the other end of the first electrode finger 231 is spaced apart from the second bus bar 22. One end of the second electrode finger 232 is electrically connected to the second bus bar 22, and the other end of the second electrode finger 232 is spaced apart from the first bus bar 21. Multiple first electrode fingers 231 and multiple second electrode fingers 232 are arranged alternately and spaced apart in sequence; in the extension direction of the electrode finger 23, there is an overlapping area A between the first bus bar 21 and the second bus bar 22, and the overlapping area A and the first bus bar 21 include a first area B1, and the overlapping area A and the second bus bar 22 include a second area B2, and the first area B1 and the second area B2 are respectively adjacent to the two ends of the overlapping area A.

[0032] As shown in Figure 1(a) and Figure 1(b), the critical positions of the overlapping area A and the first area B1 and the second area B2 form a first straight line and a second straight line respectively, and the first area B1 and the second area B2 each form a third straight line and a fourth straight line respectively away from the edge of the overlapping area A; the first straight line, the second straight line, the third straight line and the fourth straight line are all arranged in parallel.

[0033] However, since the first straight line, the second straight line, the third straight line and the fourth straight line are not apodized and are arranged in parallel, such an arrangement may cause the Q value of the surface acoustic wave device 100 to fluctuate more drastically, thereby affecting the Q value stability of the surface acoustic wave device 100.

[0034] To this end, the present application provides a surface acoustic wave device and a radio frequency front-end module, wherein the surface acoustic wave device includes a piezoelectric substrate and an interdigital transducer arranged on the surface of the piezoelectric substrate, the interdigital transducer includes a first bus bar and a second bus bar and electrode fingers arranged opposite to each other; the electrode fingers include a plurality of first electrode fingers and a plurality of second electrode fingers, and in the extension direction of the electrode fingers, there is an overlapping area between the first bus bar and the second bus bar, the overlapping area and the first bus bar include a first area, and the overlapping area and the second bus bar include a second area, and the first area and the second area are respectively adjacent to the two ends of the overlapping area; wherein, the critical positions of the overlapping area and the first area and the second area form a first curve and a second curve respectively, and the edges of the first area and the second area away from the overlapping area respectively form a third curve and a fourth curve respectively, the first curve and the second curve are symmetrically distributed with the midline as the symmetry axis, the third curve and the fourth curve are symmetrically distributed with the midline of the interdigital transducer as the symmetry axis, and the difference between the maximum length and the minimum length of the first area along the extension direction of the electrode fingers is less than or equal to 3λ. By varying the aperture length of the electrode fingers, the IDT can exhibit apodized first and second regions at both ends of the overlap region A. By controlling the difference between the maximum and minimum lengths of the first region along the electrode finger extension direction to be less than or equal to 3λ, the equivalent area of the main mode energy concentration region (i.e., the overlap region) can be made approximately equal to the area of the overlap region before apodization. This simplifies the structural design of the surface acoustic wave device. Furthermore, the Q value can be modulated by using the main mode energy concentration region, thereby improving Q value fluctuations between the resonance point and the antiresonance point and enhancing the Q value stability of the surface acoustic wave device. The surface acoustic wave device will be described in detail below.

[0035] It can be understood that the surface acoustic wave device of the present application can be a surface acoustic wave resonator, such as a conventional surface acoustic wave resonator, a temperature-compensated surface acoustic wave resonator, a surface acoustic wave resonator with a piezoelectric substrate including a multi-layer thin film structure, a resonator structure with a piezoelectric substrate having a cavity or a groove, or a longitudinally coupled resonator, a dual-mode or multi-mode surface acoustic wave filter, or a ladder filter or duplexer including the above-mentioned surface acoustic wave resonator, etc., which is not specifically limited in the present application.

[0036] See also Figure 2 and Figure 3 , Figure 2 is a schematic structural diagram of a surface acoustic wave device provided in an embodiment of the present application, Figure 3 It is a schematic structural diagram of another surface acoustic wave device provided in an embodiment of the present application.

[0037] like Figure 2 and Figure 3As shown, the surface acoustic wave device 100 includes a piezoelectric substrate 10 and an interdigital transducer 20 disposed on the surface of the piezoelectric substrate 10. The interdigital transducer 20 includes a first bus bar 21 and a second bus bar 22 disposed opposite to each other; an electrode finger 23 is disposed between the first bus bar 21 and the second bus bar 22. The electrode finger 23 includes a plurality of first electrode fingers 231 and a plurality of second electrode fingers 232. One end of the first electrode finger 231 is electrically connected to the first bus bar 21, and the other end of the first electrode finger 231 is spaced apart from the second bus bar 22. One end of the second electrode finger 232 is electrically connected to the second bus bar 22. The other end of the second electrode finger 232 is spaced from the first bus bar 21, and multiple first electrode fingers 231 and multiple second electrode fingers 232 are arranged alternately and spaced in sequence; in the extension direction of the electrode fingers 23, there is an overlapping area A between the first bus bar 21 and the second bus bar 22, and the overlapping area A is the area where the first electrode finger 231 and the second electrode finger 232 overlap with each other. A first area B1 is included between the overlapping area A and the first bus bar 21, and a second area B2 is included between the overlapping area A and the second bus bar 22. The first area B1 and the second area B2 are respectively adjacent to the two ends of the overlapping area A.

[0038] The piezoelectric substrate 10 may include at least one of lithium niobate (LiNbO3) and lithium tantalate (LiTaO3), which are not specifically limited herein. A first region B1 and a third region B3 are located between the overlapping region A and the first bus bar 21, and a second region B2 and a fourth region B4 are located between the overlapping region A and the second bus bar 22. The first region B1 and the second region B2 are adjacent to both ends of the overlapping region A, respectively. The third region B3 also adjoins the first region B1 and the first bus bar 21. The fourth region B4 also adjoins the second region B2 and the second bus bar 22.

[0039] The critical positions of the overlapping area A and the first area B1 and the second area B2 form a first curve and a second curve respectively. The edges of the first area B1 and the second area B2 away from the overlapping area A respectively form a third curve and a fourth curve. The first curve and the second curve are symmetrically distributed with the center line of the interdigital transducer 20 as the symmetry axis. The third curve and the fourth curve are symmetrically distributed with the center line of the interdigital transducer 20 as the symmetry axis. The center line is perpendicular to the extension direction of the electrode finger 23. The difference between the maximum length and the minimum length of the first area B1 along the extension direction of the electrode finger 23 is less than or equal to 3λ, where λ is the wavelength of the sound wave.

[0040] For example, the area formed between the first and third curves is the first area B1, the area formed between the second and fourth curves is the second area B2, the area formed between the third curve and the first bus bar 21 is the third area B3, and the area formed between the fourth curve and the second bus bar 22 is the fourth area B4. The overlapping area A may be the area formed between the first and second curves.

[0041] Illustratively, the first area B1 may also be adjacent to the overlapping area A and the first bus bar 21, respectively, that is, the area between the overlapping area A and the first bus bar 21 is the first area B1, and the second area B2 may also be adjacent to the overlapping area A and the second bus bar 22, respectively, that is, the area between the overlapping area A and the second bus bar 22 is the second area B2.

[0042] It is understood that, in the extension direction of the electrode fingers 23, the straight-line distance between any point on the first curve and the third curve can be considered the length of the first region B1 along the extension direction of the electrode fingers 23. On the first curve, there is a point with the largest straight-line distance from the third curve, namely d1. In this case, d1 is the maximum length of the first region B1 along the extension direction of the electrode fingers 23. On the first curve, there is also a point with the smallest straight-line distance from the third curve, namely d2. In this case, d2 is the minimum length of the first region B1 along the extension direction of the electrode fingers 23. In this embodiment of the present application, d1-d2≤3λ.

[0043] It should be noted that the difference between the maximum length and the minimum length of the first region B1 along the extension direction of the electrode finger 23 is less than or equal to 3λ. Since the first region B1 and the second region B2 are symmetrically distributed with the center line of the interdigital transducer 20 as the symmetry axis, the area of the second region B2 is the same as that of the first region B1, that is, the difference between the maximum length and the minimum length of the second region B2 along the extension direction of the electrode finger 23 is also less than or equal to 3λ.

[0044] The surface acoustic wave device 100 provided in the present application can change the aperture length of the electrode fingers 23 so that the interdigital transducer 20 presents apodized first and second regions B1 and B2 at both ends of the overlapping region A. The difference between the maximum length and the minimum length of the first region B1 along the extension direction of the electrode fingers 23 is controlled to be less than or equal to 3λ. This can make the equivalent area of the main mode energy concentration region (i.e., the overlapping region A) approximately equal to the area of the overlapping region A before apodization, thereby simplifying the structural design of the surface acoustic wave device 100. At the same time, the Q value can be modulated by the main mode energy concentration region, thereby improving the Q value fluctuation between the resonance point and the antiresonance point. The improvement effect on the Q value fluctuation near the antiresonance point is particularly significant, thereby improving the Q value stability of the surface acoustic wave device 100.

[0045] In some embodiments, the maximum length and the minimum length of the first region B1 along the extending direction of the electrode fingers 23 are equal.

[0046] Specifically, the lengths of the first regions B1 along the extension direction of the electrode fingers 23 are all equal. Although the edges of the first regions B1 are the first and third apodized curves, the periods of the first and third curves can be controlled to be the same by, for example, controlling the aperture lengths of the electrode fingers 23. This ensures that the lengths of the first regions B1 along the extension direction of the electrode fingers 23 are all equal. This design optimizes the improvement of Q-value fluctuations between the resonant and antiresonant points, and also ensures that the equivalent area of the main mode energy concentration region is approximately equal to, or 80% to 120% of, the area of the overlap region A before apodization. This simplifies the structural design of the surface acoustic wave device 100.

[0047] It is understood that, in the extension direction of the electrode fingers 23, the straight-line distance between any point on the first curve and the third curve can be considered to be the length of the first region B1 along the extension direction of the electrode fingers 23. On the first curve, there is a point with the largest straight-line distance from the third curve, namely d1. In this case, d1 is the maximum length of the first region B1 along the extension direction of the electrode fingers 23. On the first curve, there is also a point with the smallest straight-line distance from the third curve, namely d2. In this case, d2 is the minimum length of the first region B1 along the extension direction of the electrode fingers 23. In the embodiment of the present application, d1 = d2, meaning that in the extension direction of the electrode fingers 23, the straight-line distance between any point on the first curve and the third curve is equal.

[0048] It should be noted that since the maximum length and the minimum length of the first region B1 along the extension direction of the electrode finger 23 are equal, and the first region B1 and the second region B2 are symmetrically distributed with the center line of the interdigital transducer 20 as the symmetry axis, the maximum length and the minimum length of the second region B2 along the extension direction of the electrode finger 23 are also equal.

[0049] In some embodiments, the IDT 20 further includes a first gap electrode 24 and a second gap electrode 25, wherein the first end of the first gap electrode 24 is connected to the first bus bar 21, and a first region B1 is formed between the second end of the first gap electrode 24 and the overlapping region A; the first end of the second gap electrode 25 is connected to the second bus bar 22, and a second region B2 is formed between the second end of the first gap electrode 24 and the overlapping region A.

[0050] Specifically, the first gap electrode 24 can be used to divide the first area B1 and the third area B3. The first area B1 is formed between the second end of the first gap electrode 24 and the overlapping area A, and the third area B3 is formed between the second end of the first gap electrode 24 and the first bus bar 21. Therefore, the first gap electrode 24 is arranged in the third area B3, and the second end of each first gap electrode 24 is used to form a first curve; the second gap electrode 25 can be used to divide the second area B2 and the fourth area B4. The second area B2 is formed between the second end of the second gap electrode 25 and the overlapping area A, and the fourth area B4 is formed between the second end of the second gap electrode 25 and the second bus bar 22. Therefore, the second gap electrode 25 is arranged in the fourth area B4, and the second end of each second gap electrode 25 is used to form a second curve.

[0051] It should be noted that the length of the first region B1 along the extension direction of the electrode finger 23 includes but is not limited to the distance from the second end of the first gap electrode 24 to the corresponding second electrode finger 232, and the length of the second region B2 along the extension direction of the electrode finger 23 includes but is not limited to the distance from the second end of the second gap electrode 25 to the corresponding first electrode finger 231. Therefore, the range of the first region B1 and the second region B2 can be adjusted by adjusting each first gap electrode 24, the second gap electrode 25 and the electrode finger 23.

[0052] like Figure 4 As shown, in some embodiments, the interdigital transducer 20 further includes a first intermediate electrode 26 and / or a second intermediate electrode 27; along the extension direction of the first intermediate electrode 26, the first end of the first intermediate electrode 26 is connected to the second end of the first gap electrode 24, the second end of the first intermediate electrode 26 is connected to the first electrode finger 231, and the extension direction of the first intermediate electrode 26 intersects with the extension direction of the electrode finger 23; along the extension direction of the second intermediate electrode 27, the first end of the second intermediate electrode 27 is connected to the second end of the second gap electrode 25, the second end of the second intermediate electrode 27 is connected to the second electrode finger 232, and the extension direction of the second intermediate electrode 27 intersects with the extension direction of the electrode finger 23.

[0053] Specifically, the first electrode fingers 231 and the first gap electrodes 24 are spaced apart on opposite sides of the first intermediate electrode 26 in the direction in which the first intermediate electrode 26 extends, and the first gap electrodes 24 are spaced apart from the second electrode fingers 232. The second electrode fingers 232 and the second gap electrodes 25 are spaced apart on opposite sides of the second intermediate electrode 27 in the direction in which the second intermediate electrode 27 extends, and the second gap electrodes 25 are spaced apart from the first electrode fingers 231. The provision of the gap electrodes and intermediate electrodes can suppress stray modes in the first region B1, the second region B2, the third region B3, and the fourth region B4 to a certain extent.

[0054] Preferably, the extending direction of the first intermediate electrode 26 and the extending direction of the second intermediate electrode 27 may be perpendicular or approximately perpendicular to the extending direction of the electrode fingers 23 .

[0055] like Figure 5 and Figure 6 As shown, in some embodiments, the IDT 20 further includes a first dummy finger 261 and / or a second dummy finger 271. The first end of the first dummy finger 261 is connected to the first end of the first intermediate electrode 26 and the second end of the first gap electrode 24, and a first region B1 is formed between the second end of the first dummy finger 261 and the overlapping region A. The first end of the second dummy finger 271 is connected to the first end of the second intermediate electrode 27 and the second end of the second gap electrode 25, and a second region B2 is formed between the second end of the second dummy finger 271 and the overlapping region A. By providing the first dummy finger 261 and / or the second dummy finger 271, the Q value of the surface acoustic wave device 100 can be improved, energy leakage can be reduced, and the cross-mode suppression effect on the first region B1, the second region B2, the third region B3, and the fourth region B4 can be further enhanced.

[0056] Specifically, the first end of the first dummy finger 261 is connected to the first end of the first intermediate electrode 26 and the second end of the first gap electrode 24, and the first dummy finger 261 can be arranged on a side close to the overlapping area A, that is, the first dummy finger 261 and the first gap electrode 24 are respectively arranged on both sides of the first intermediate electrode 26, so that a first area B1 is formed between the second end of the first dummy finger 261 and the overlapping area A; the first end of the second dummy finger 271 is connected to the first end of the second intermediate electrode 27 and the second end of the second gap electrode 25, and the second dummy finger 271 can be arranged on a side close to the overlapping area A, that is, the second dummy finger 271 and the second gap electrode 25 are respectively arranged on both sides of the second intermediate electrode 27, so that a second area B2 is formed between the second end of the second dummy finger 271 and the overlapping area A.

[0057] It should be noted that a first dummy finger 261 may be provided on each first intermediate electrode 26 , and a second dummy finger 271 may be provided on each second intermediate electrode 27 ; a first dummy finger 261 may be provided only on a specific first intermediate electrode 26 , and a second dummy finger 271 may be provided only on a specific second intermediate electrode 27 ; and multiple first dummy fingers 261 may be provided on the first intermediate electrode 26 , and multiple second dummy fingers 271 may be provided on the second intermediate electrode 27 , without specific limitation herein.

[0058] In some embodiments, the lengths of the first dummy fingers 261 in the extending direction of the electrode fingers 23 are equal, and / or the lengths of the second dummy fingers 271 in the extending direction of the electrode fingers 23 are equal.

[0059] Exemplarily, the IDT 20 may include multiple first pseudo fingers 261 and multiple second pseudo fingers 271 , and the lengths of the first pseudo fingers 261 in the extension direction of the electrode fingers 23 are equal, while the lengths of the second pseudo fingers 271 in the extension direction of the electrode fingers 23 are not completely equal.

[0060] Exemplarily, the IDT 20 may include multiple first pseudo fingers 261 and multiple second pseudo fingers 271 , and the lengths of the first pseudo fingers 261 in the extension direction of the electrode fingers 23 are not completely equal, and the lengths of the second pseudo fingers 271 in the extension direction of the electrode fingers 23 are equal.

[0061] Exemplarily, the interdigital transducer 20 may include multiple first pseudo fingers 261 and multiple second pseudo fingers 271, and the length of each first pseudo finger 261 in the extension direction of the electrode finger 23 is equal, and the length of each second pseudo finger 271 in the extension direction of the electrode finger 23 is equal; the length of the first pseudo finger 261 in the extension direction of the electrode finger 23 and the length of the second pseudo finger 271 in the extension direction of the electrode finger 23 may be equal or unequal.

[0062] Specifically, the periods of the first and third curves can be controlled to be the same by controlling the length of the gap electrode, the length of the dummy finger, the aperture length of the electrode finger 23, etc., so that the length of the first region B1 along the extension direction of the electrode finger 23 is equal. This design can optimize the improvement effect of the Q value fluctuation between the resonance point and the antiresonance point, and can also make the equivalent area of the main mode energy concentration region approximately equal to the area of the overlapping region A before tracking, or 80%-120% of the area before tracking, thereby simplifying the structural design of the surface acoustic wave device 100.

[0063] It should be noted that in order to achieve the same period of the first curve and the third curve, the straight-line distance between any point on the first curve and the third curve must be equal. Generally, the period of the first curve and the third curve can be made the same by controlling the distance between the first gap electrode 24 and its corresponding second electrode finger 232.

[0064] For example, the distance between the first gap electrode 24 and its corresponding second electrode finger 232 can be changed by changing one or more of the length of the first gap electrode 24, the length of the first dummy finger 261, and the aperture length of the second electrode finger 232. For example, the distance between the first gap electrode 24 and its corresponding second electrode finger 232 can be changed by changing only the length of the first gap electrode 24; the distance between the first gap electrode 24 and its corresponding second electrode finger 232 can also be changed by changing the length of the first gap electrode 24 and the aperture length of the second electrode finger 232; or the distance between the first gap electrode 24 and its corresponding second electrode finger 232 can be changed by simultaneously changing the length of the first gap electrode 24, the length of the first dummy finger 261, and the aperture length of the second electrode finger 232. By changing the above parameters, the periods of the first and third curves can be changed, thereby controlling the difference between the maximum and minimum lengths of the first region B1 along the extension direction of the electrode finger 23 to be less than or equal to 3λ, and controlling the maximum and minimum lengths of the first region B1 along the extension direction of the electrode finger 23 to be equal. The specific settings can be determined based on actual conditions.

[0065] See also Figure 3 and Figure 7 In some embodiments, the first electrode finger 231 is connected to the first bus bar 21, and the first gap electrode 24 is located between two adjacent first electrode fingers 231 and spaced apart from the second electrode finger 232; the second electrode finger 232 is connected to the second bus bar 22, and the first gap electrode 24 is located between two adjacent first electrode fingers 231 and spaced apart from the second electrode finger 232.

[0066] Specifically, one end of the first electrode finger 231 is connected to the first bus bar 21, and the other end is spaced apart from the second bus bar 22. One end of the second electrode finger 232 is connected to the second bus bar 22, and the other end is spaced apart from the first bus bar 21. The first gap electrode 24 is located between two adjacent first electrode fingers 231, parallel to the first electrode fingers 231, and spaced apart from the second electrode fingers 232. The second gap electrode 25 is located between two adjacent second electrode fingers 232, parallel to the second electrode fingers 232, and spaced apart from the first electrode fingers 231. In this manner, the first gap electrode 24 and the second gap electrode 25 can further form a low-speed zone in the area where the first gap electrode 24 and the second gap electrode 25 are located, thereby further suppressing the transverse mode of the surface acoustic wave device 100.

[0067] like Figure 7As shown, in some embodiments, the overlapping area A includes a middle area A1 and edge areas A2 located on both sides of the middle area A1 in the extension direction of the electrode finger 23, and the electrode finger 23 located in the edge area A2 includes a widened portion 233; the interdigital transducer 20 also includes an auxiliary structure 28, and the auxiliary structure 28 is located in the edge area A2; wherein, within the same edge area A2, the projections of the widened portion 233 and the auxiliary structure 28 in the top view direction are at least partially staggered along the extension direction of the electrode finger 23, and the acoustic impedance of the area where the widened portion 233 is provided is different from the acoustic impedance of the area where the auxiliary structure 28 is provided.

[0068] The overlapping region A includes a middle region A1 and edge regions A2 located on both sides of the middle region A1 in the extending direction of the electrode fingers 23 .

[0069] like Figure 3 and Figure 7 As shown, the endpoint of the widened portion 233 close to one end of the gap electrode is used to fit the first curve and the second curve. At this time, the length of the first region B1 along the extension direction of the electrode finger 23 can be the distance between the first gap electrode 24 and the widened portion 233. Specifically, the distance between the first gap electrode 24 and the widened portion 233 can be changed by changing one or more of the length of the first gap electrode 24 and the aperture length of the second electrode finger 232.

[0070] Specifically, within the same edge area A2, the projections of the widening portion 233 and the auxiliary structure 28 in the top view direction are at least partially staggered along the extension direction of the electrode finger 23, and the acoustic impedance of the area with the widening portion 233 is different from the acoustic impedance of the area with the auxiliary structure 28. For example, the acoustic impedance of the area with the widening portion 233 is low acoustic impedance, and the acoustic impedance of the area with the auxiliary structure 28 is high acoustic impedance, or the acoustic impedance of the area with the widening portion 233 is high acoustic impedance, and the acoustic impedance of the area with the auxiliary structure 28 is low acoustic impedance, so as to adjust the acoustic impedance distribution of the sound wave in the edge area A2, thereby further suppressing the heterogeneous mode of the interdigital transducer 20.

[0071] It should be noted that the auxiliary structure 28 can be arranged in the thickness direction of the electrode finger 23. In this case, the electrode finger 23 is equivalent to being thickened. For example, the auxiliary structure 28 can be located above the electrode finger 23, or below the electrode finger 23, or both above and below the electrode finger 23. No specific limitation is made here.

[0072] The auxiliary structure 28 can be a plurality of mass blocks, in which the projection of each mass block on the edge area A2 overlaps with the projection of at least one electrode finger on the edge area A2 in the thickness direction of the electrode finger 23, and the plurality of mass blocks are arranged at intervals from each other; the auxiliary structure can also be a dielectric strip, in which the length of the dielectric strip is at least equal to the length of the edge area A2 in the length extension direction of the dielectric strip (i.e., the arrangement direction of the electrode fingers 23).

[0073] In some embodiments, when the area between the overlapping area A and the first bus bar 21 is the first area B1, and the area between the overlapping area A and the second bus bar 22 is the second area B2, one end of the first electrode finger 231 is connected to the first bus bar 21, and the other end is spaced from the second bus bar 22; one end of the second electrode finger 232 is connected to the second bus bar 22, and the other end is spaced from the first bus bar 21. At this time, the interdigital transducer is not provided with the first gap electrode 24 and the second gap electrode 25, and the electrode finger 23 located in the edge area A2 includes a widened portion 233; the interdigital transducer 20 also includes an auxiliary structure 28, and the auxiliary structure 28 is located in the edge area A2; wherein, within the same edge area A2, the projections of the widened portion 233 and the auxiliary structure 28 in the top view direction are at least partially staggered along the extension direction of the electrode finger 23, and the acoustic impedance of the area where the widened portion 233 is provided is different from the acoustic impedance of the area where the auxiliary structure 28 is provided. In the embodiment of the present application, the Q value may be modulated by the main mode energy concentration region, thereby improving the Q value fluctuation between the resonance point and the antiresonance point, thereby improving the Q value stability of the surface acoustic wave device 100 .

[0074] The specific embodiments of the widened portion 233 and the auxiliary structure 28 may refer to the above embodiments, and will not be repeated here.

[0075] Specifically, the endpoint of the widened portion 233 near one end of the gap electrode is used to fit the first and second curves. In this case, the length of the first region B1 along the extension direction of the electrode fingers 23 can be the distance between the first bus bar 21 and the widened portion 233. Specifically, the distance between the first bus bar 21 and the widened portion 233 can be changed by changing the aperture length of the second electrode fingers 232. In the embodiment of the present application, by providing the widened portion 233 and the auxiliary structure 28 in the edge region A2, the acoustic impedance distribution of the sound wave in the edge region A2 can be adjusted, thereby further suppressing the stray modes of the interdigital transducer 20.

[0076] like Figure 8As shown, in some embodiments, when the IDT 20 further includes a first intermediate electrode 26 and / or a second intermediate electrode 27, the electrode finger 23 located in the edge area A2 includes a widened portion 233; the IDT 20 further includes an auxiliary structure 28, and the auxiliary structure 28 is located in the edge area A2; wherein, within the same edge area A2, the projections of the widened portion 233 and the auxiliary structure 28 in the top view direction are at least partially staggered along the extension direction of the electrode finger 23, and the acoustic impedance of the area where the widened portion 233 is provided is different from the acoustic impedance of the area where the auxiliary structure 28 is provided.

[0077] The specific embodiments of the first intermediate electrode 26 and the second intermediate electrode 27 may refer to the above embodiments, and will not be repeated here.

[0078] Specifically, the endpoint of the widened portion 233 near one end of the gap electrode is used to fit the first and second curves. In this case, the length of the first region B1 along the extension direction of the electrode finger 23 can be the distance between the second end of the first gap electrode 24 or the second end of the first dummy finger 261 and the widened portion 233. Specifically, the distance between the first gap electrode 24 and the widened portion 233 can be changed by changing one or more of the length of the first gap electrode 24, the length of the first dummy finger 261, and the aperture length of the second electrode finger 232. In the embodiment of the present application, by providing the widened portion 233 and the auxiliary structure 28 in the edge region, the acoustic impedance distribution of the sound wave in the edge region A2 can be adjusted, thereby further suppressing the stray modes of the interdigital transducer 20.

[0079] In some embodiments, the first bus bar 21 forms a fifth curve near the edge of the overlapping area A, and the second bus bar 22 forms a sixth curve near the edge of the overlapping area A. The fifth curve and the sixth curve are symmetrically distributed with the center line as the symmetry axis, thereby reducing energy scattering in the bus bar area and achieving the effect of energy confinement.

[0080] The edge of the first bus bar 21 near the overlapping area A is the critical position between the first bus bar 21 and the third area B3 , and the edge of the second bus bar 22 near the overlapping area A is the critical position between the second bus bar 22 and the fourth area B4 .

[0081] Specifically, the difference between the maximum length and the minimum length of the first region B1 along the extension direction of the electrode finger 23 can be controlled to be less than or equal to 3λ by adjusting the length of the gap electrode and the length of the electrode finger 23. Preferably, the maximum length and the minimum length of the first region B1 along the extension direction of the electrode finger 23 are controlled to be equal.

[0082] It should be noted that the fifth curve and the sixth curve may not be symmetrically distributed with the center line as the axis of symmetry, that is, they may be asymmetrically distributed. It is only necessary to control the difference between the maximum length and the minimum length of the first area B1 along the extension direction of the electrode finger 23 to be less than or equal to 3λ. Preferably, the fifth curve and the sixth curve are symmetrically distributed with the center line as the axis of symmetry, which can further reduce the energy scattering in the busbar area and achieve the effect of energy confinement.

[0083] In some embodiments, the first curve and the second curve satisfy a first function, and the expression of the first function is Y A (x) = Y A1 (x)*Y A2 (x), the third and fourth curves satisfy the second function, and the expression of the second function is Y B (x) = Y B1 (x)Y B2 (x); where Y A2 (x) and Y B2 (x) is a periodic function; the number of periods of the periodic function is less than or equal to 50, and / or the periodic function is an integer period.

[0084] For example, Y A1 (x), Y B1 (x) can be a non-periodic function or a periodic function, Y A1 (x) and Y B1 (x) can satisfy A, ax n +b, Acos(αx+θ), Asin(αx+θ), etc. First functions; Y A2 (x), Y B2 (x) can satisfy Second functions such as Acos(αx+θ) and Asin(αx+θ) are given below. Where A, T, a, b, and n are constants.

[0085] Exemplarily, the functions satisfied by the first curve and the second curve may be the same or different. In the case where the functions satisfied by the first curve and the second curve are different, it is sufficient to control d1-d2≤3λ. Preferably, the functions satisfied by the first curve and the second curve are the same. Since the first curve, the second curve, the third curve, and the fourth curve are symmetrically distributed with the midline as the axis of symmetry, the functions satisfied by the first curve, the second curve, the third curve, and the fourth curve are all the same, thereby facilitating acoustic wave energy confinement.

[0086] For example, when the first curve and the second curve satisfy the same function, the periods of the functions satisfied by the first curve and the second curve can be staggered to control d1-d2≤3λ, that is, the difference between the maximum length and the minimum length of the first region B1 along the extension direction of the electrode finger 23 is less than or equal to 3λ.

[0087] Exemplarily, when the first curve and the second curve satisfy the same function, their periods are controlled to be consistent so that d1 = d2 , that is, the maximum length and the minimum length of the first region B1 along the extension direction of the electrode fingers 23 are equal.

[0088] In some embodiments, the fifth curve and the sixth curve satisfy a third function, and the expression of the third function is Y C (x) = Y C1 (x)*Y C2 (x).

[0089] Among them, Y C1 (x), Y C2 (x) can be a non-periodic function or a periodic function, Y C1 (x) and Y C2 (x) can satisfy A, ax n +b, Acos(αx+θ), Asin(αx+θ), etc. Where A, T, a, b, and n are constants.

[0090] Specifically, if Y C2 (x) is a periodic function, and the periodic function is an integer period; Y C2 The period of (x) and Y A2 (x) and Y B2 (x) has different periods. Generally, Y C2 The period of (x) is greater than Y A2 (x) and Y B2 (x) period.

[0091] It should be noted that, assuming Y A (x), Y B (x) and Y C (x) all satisfy Asin(αx+θ), from Figure 2 It can be seen that although Y A (x), Y B (x) and Y C (x) The function types corresponding to the first and third curves are the same, but due to different periods, the periods of the functions satisfied by the first and fifth curves are consistent, while the periods of the first and fifth curves are staggered.

[0092] like Figure 9 and Figure 10As shown, in some embodiments, the overlapping area A includes a middle area A1 and edge areas A2 located on both sides of the middle area A1 in the extension direction of the electrode finger 23; the interdigital transducer 20 also includes an acoustic impedance adjustment structure 29, the acoustic impedance adjustment structure 29 is located in the edge area A2, and the acoustic impedance of the edge area A2 is less than the acoustic impedance of the middle area A1.

[0093] Among them, the endpoint of the acoustic impedance adjustment structure 29 close to one end of the gap electrode is used to fit the first curve and the second curve. At this time, the length of the first region B1 along the extension direction of the electrode finger 23 can be the distance between the first gap electrode 24 or the first dummy finger 261 and the acoustic impedance adjustment structure 29. Specifically, the distance between the first gap electrode 24 or the first dummy finger 261 and the acoustic impedance adjustment structure 29 can be changed by changing one or more of the length of the first gap electrode 24, the length of the first dummy finger 261 and the aperture length of the second electrode finger 232.

[0094] Specifically, by setting the acoustic impedance adjustment structure 29 in the edge area A2, the acoustic impedance of the edge area A2 is smaller than the acoustic impedance of the middle area A1, so that the propagation speed of the sound wave in the edge area A2 can be made smaller than the propagation speed in the middle area A1. At the same time, it can also effectively improve the Q value fluctuation between the resonance point and the anti-resonance point, thereby improving the Q value stability of the surface acoustic wave device 100.

[0095] Exemplarily, the acoustic impedance adjustment structure 29 may be, for example, thickening the electrode fingers 23 in the edge area A2 to form a piston thickening structure, widening the electrode fingers 23 in the edge area A2, or widening the electrode fingers 23 in the edge area A2 and thickening them at the widened position, or widening the electrode fingers in the edge area A2 with different widths to form a T-shaped piston structure, or widening a portion of the same electrode finger in the edge area A2 and thickening both the widened portion and the non-widened portion to form a T-shaped piston structure, without specific limitation herein.

[0096] Exemplarily, when the area between the overlapping area A and the first bus bar 21 is the first area B1, and the area between the overlapping area A and the second bus bar 22 is the second area B2, one end of the first electrode finger is connected to the first bus bar, and the other end is spaced from the second bus bar, and one end of the second electrode finger is connected to the second bus bar, and the other end is spaced from the first bus bar. At this time, the interdigital transducer is not provided with the first gap electrode 24 and the second gap electrode 25, and a portion of the same electrode finger 23 located in the edge area A2 is widened and both the widened part and the non-widened part are thickened to form a T-type piston structure, or the electrode fingers in the edge area A2 are widened with different widths to form a T-type piston structure.

[0097] For example, the acoustic impedance adjustment structure 29 can be provided in the thickness direction of the electrode finger 23. In this manner, the electrode finger 23 is equivalent to being thickened. Specifically, the acoustic impedance adjustment structure 29 can be located above the electrode finger 23, below the electrode finger 23, or both above and below the electrode finger 23. The width direction of the electrode finger 23 is perpendicular to the extension direction of the electrode finger 23.

[0098] For example, the acoustic impedance adjustment structure 29 may be provided in the width direction of the electrode finger 23. In this manner, the electrode finger 23 is effectively widened. Specifically, the acoustic impedance adjustment structure 29 may be located on one side of the electrode finger 23 in the width direction, or on both sides of the electrode finger 23 in the width direction. The width direction of the electrode finger 23 is perpendicular to the extension direction of the electrode finger 23.

[0099] by Figure 9 and Figure 10 Taking the acoustic impedance adjustment structure 29 in the structure as an example, this structure is formed by widening and thickening the electrode fingers 23 in the edge region A2. In this embodiment, the acoustic impedance adjustment structure 29 is provided in both the thickness and width directions of the electrode fingers 23. In this manner, the electrode fingers 23 are effectively widened and thickened at the widened locations.

[0100] It should be noted that the acoustic impedance adjustment structure 29 can be in direct contact with the electrode finger 23, or the acoustic impedance adjustment structure 29 and the electrode finger 23 can be separated by other membrane layers, wherein the membrane layer used to separate the acoustic impedance adjustment structure 29 and the electrode finger 23 can be at least one of a temperature compensation layer and a frequency modulation layer.

[0101] like Figure 11 As shown, in some embodiments, when the first electrode finger 231 is connected to the first bus bar 21, the first gap electrode 24 is located between two adjacent first electrode fingers 231 and is spaced apart from the second electrode finger 232; and the second electrode finger 232 is connected to the first bus bar 21, the first gap electrode 24 is located between two adjacent first electrode fingers 231 and is spaced apart from the second electrode finger 232, the interdigital transducer 20 further includes an acoustic impedance adjustment structure 29, and the acoustic impedance adjustment structure 29 is located in the edge area A2, and the acoustic impedance of the edge area A2 is less than the acoustic impedance of the middle area A1.

[0102] Specifically, the endpoint of the acoustic impedance adjustment structure 29 near one end of the gap electrode is used to fit the first curve and the second curve. In this case, the length of the first region B1 along the extension direction of the electrode fingers 23 can be the distance between the first gap electrode 24 and the acoustic impedance adjustment structure 29. Specifically, the distance between the first gap electrode 24 and the acoustic impedance adjustment structure 29 can be changed by changing one or more of the length of the first gap electrode 24 and the aperture length of the second electrode fingers 232. In the embodiment of the present application, by arranging the acoustic impedance adjustment structure 29 in the edge region A2, the acoustic impedance of the edge region A2 is smaller than that of the middle region A1, thereby making the propagation speed of the acoustic wave in the edge region A2 smaller than that in the middle region A1. At the same time, the Q value fluctuation between the resonance point and the antiresonance point can be effectively improved, thereby improving the Q value stability of the surface acoustic wave device 100.

[0103] In some embodiments, the minimum length of the overlapping region A in the extending direction of the electrode fingers 23 is greater than or equal to 5λ, thereby improving the energy confinement effect of the main mode of the surface acoustic wave.

[0104] Specifically, by setting the minimum length of the overlapping region A in the extension direction of the electrode finger 23 to be greater than or equal to 5λ, that is, the length of the overlapping region A in the extension direction of the electrode finger 23 is greater than or equal to 5λ, the equivalent area of the main mode energy concentration region can be prevented from being too small, thereby improving the main mode energy confinement effect of the surface acoustic wave.

[0105] In some embodiments, a difference between a maximum length and a minimum length of the overlapping region A in the extending direction of the electrode fingers 23 is greater than or equal to 0.1λ and less than or equal to 15λ.

[0106] Specifically, by setting the minimum length of the overlapping region A in the extension direction of the electrode finger 23 to be greater than or equal to 5λ, the amplitude difference between the first curve and the second curve can be controlled so that the equivalent area of the main mode energy concentration region is not too small, thereby improving the main mode energy confinement effect of the surface acoustic wave.

[0107] The following simulation experiment is used to test the embodiment 1 ( Figure 5 ) and Example 2 ( Figure 9 ) and the surface acoustic wave device 100 provided in Comparative Example 1 ( Figure 1a )’s Q value change curve is compared.

[0108] like Figure 12 As shown in the figure, the simulation experiment shows that compared with the surface acoustic wave device 100 provided in the comparative example 1, it can be seen that the surface acoustic wave device 100 provided in the embodiment 1 has a smaller Q value fluctuation between the resonance point and the antiresonance point, especially the improvement effect on the Q value fluctuation near the antiresonance point is more obvious.max The right side of the value has a good improvement, Q max The left side of the value can improve sharp fluctuations.

[0109] like Figure 13 As shown, the simulation experiment shows that compared with the surface acoustic wave device 100 provided in the comparative example 1, the surface acoustic wave device 100 provided in the embodiment 2 has a smaller Q value fluctuation between the resonance point and the antiresonance point, and the improvement effect on the Q value fluctuation near the antiresonance point is more obvious. max The right side of the value has a good improvement, Q max The left side of the value can improve the sharp fluctuation. Compared with the surface acoustic wave device 100 provided in Example 1, the surface acoustic wave device 100 provided in Example 2 can also improve Q max Value and Q max The depression and fluctuation on the left side of the value can also further improve the Q value fluctuation between the resonance point and the antiresonance point.

[0110] It can be seen from this that the surface acoustic wave device 100 provided in the present application can modulate the Q value by the main mode energy concentration area, thereby improving the Q value fluctuation between the resonance point and the antiresonance point, especially the improvement effect on the Q value fluctuation near the antiresonance point is more obvious, thereby improving the Q value stability of the surface acoustic wave device 100.

[0111] In the case where the surface acoustic wave device is a filter, the filter provided in the embodiment of the present application will be described in detail below.

[0112] The filter includes multiple series-arm surface acoustic wave devices 100 connected in series between an input and an output, and multiple parallel-arm surface acoustic wave devices 100, one end of which is connected to the series-arm surface acoustic wave device 100 and the other end is connected to a ground terminal. At least one of the series-arm surface acoustic wave device 100 and the parallel-arm surface acoustic wave device 100 can be the surface acoustic wave device 100 provided in any of the above-mentioned embodiments. The filter can reduce Q-value fluctuations between the resonance point and the antiresonance point, thereby improving the Q-value stability of the surface acoustic wave device 100.

[0113] The present application also provides an RF front-end module, comprising the surface acoustic wave device 100 described in any of the above embodiments. This RF front-end module can improve the Q-value fluctuation between the resonant and antiresonant points, thereby increasing the Q-value stability of the surface acoustic wave device 100 and thereby improving the reliability, safety, and practicality of the RF front-end module.

[0114] Among them, the RF front-end module may include an antenna end, a power amplifier, a low-noise amplifier, a switch, a filter, etc., which are not specifically limited here.

[0115] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present application, and such modifications or substitutions should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A surface acoustic wave device, characterized in that: The surface acoustic wave device includes a piezoelectric substrate and an interdigital transducer arranged on the surface of the piezoelectric substrate, and the interdigital transducer includes: A first bus bar and a second bus bar arranged opposite to each other; Electrode fingers are arranged between the first bus bar and the second bus bar, the electrode fingers including a plurality of first electrode fingers and a plurality of second electrode fingers, one end of the first electrode finger is electrically connected to the first bus bar, the other end of the first electrode finger is spaced from the second bus bar, one end of the second electrode finger is electrically connected to the second bus bar, the other end of the second electrode finger is spaced from the first bus bar, the plurality of first electrode fingers and the plurality of second electrode fingers are alternately arranged in sequence; in the extension direction of the electrode fingers, there is an overlapping area between the first bus bar and the second bus bar, the overlapping area is an area where the first electrode fingers and the second electrode fingers overlap with each other, a first area is included between the overlapping area and the first bus bar, a second area is included between the overlapping area and the second bus bar, and the first area and the second area are respectively adjacent to two ends of the overlapping area; In which, the critical positions of the overlapping area and the first area and the second area form a first curve and a second curve respectively, the edges of the first area and the second area away from the overlapping area respectively form a third curve and a fourth curve, the first curve and the second curve are symmetrically distributed with the center line of the interdigital transducer as the symmetry axis, the third curve and the fourth curve are symmetrically distributed with the center line as the symmetry axis, the center line is perpendicular to the extension direction of the electrode finger, and the difference between the maximum length and the minimum length of the first area along the extension direction of the electrode finger is less than or equal to 3λ, where λ is the wavelength of the sound wave.

2. The surface acoustic wave device according to claim 1, wherein The maximum length and the minimum length of the first region along the extending direction of the electrode fingers are equal.

3. The surface acoustic wave device according to claim 1, wherein The IDT further includes a first gap electrode and a second gap electrode, wherein a first end of the first gap electrode is connected to the first bus bar, and the first region is formed between the second end of the first gap electrode and the overlapping region; The first end of the second gap electrode is connected to the second bus bar, and the second region is formed between the second end of the first gap electrode and the overlapping region.

4. The surface acoustic wave device according to claim 3, wherein The interdigital transducer further includes a first middle electrode and / or a second middle electrode; Along an extension direction of the first intermediate electrode, a first end of the first intermediate electrode is connected to a second end of the first gap electrode, and a second end of the first intermediate electrode is connected to the first electrode finger, and the extension direction of the first intermediate electrode intersects with an extension direction of the electrode finger; Along the extension direction of the second intermediate electrode, the first end of the second intermediate electrode is connected to the second end of the second gap electrode, the second end of the second intermediate electrode is connected to the second electrode finger, and the extension direction of the second intermediate electrode intersects with the extension direction of the electrode fingers.

5. The surface acoustic wave device according to claim 4, wherein The interdigital transducer further includes a first pseudo finger and / or a second pseudo finger; The first end of the first dummy finger is connected to the first end of the first intermediate electrode and the second end of the first gap electrode, and the first region is formed between the second end of the first dummy finger and the overlapping region; The first end of the second dummy finger is connected to the first end of the second middle electrode and the second end of the second gap electrode, and the second region is formed between the second end of the second dummy finger and the overlapping region.

6. The surface acoustic wave device according to claim 5, wherein The lengths of the first dummy fingers in the extending direction of the electrode fingers are equal, and / or the lengths of the second dummy fingers in the extending direction of the electrode fingers are equal.

7. The surface acoustic wave device according to claim 3, wherein The first electrode finger is connected to the first bus bar, the first gap electrode is located between two adjacent first electrode fingers and is spaced apart from the second electrode finger; the second electrode finger is connected to the second bus bar, the first gap electrode is located between two adjacent first electrode fingers and is spaced apart from the second electrode finger.

8. The surface acoustic wave device according to claim 1 or 7, characterized in that The overlapping region includes a middle region and edge regions located on both sides of the middle region in the extending direction of the electrode fingers, and the electrode fingers located in the edge regions include widened portions; The IDT further includes an auxiliary structure, and the auxiliary structure is located in the edge area; In the same edge area, the projections of the widened portion and the auxiliary structure in the top view are at least partially staggered along the extension direction of the electrode finger, and the acoustic impedance of the area where the widened portion is provided is different from the acoustic impedance of the area where the auxiliary structure is provided.

9. The surface acoustic wave device according to claim 1, wherein The first curve and the second curve satisfy a first function, and the expression of the first function is Y A (x) = Y A1 (x)*Y A2 (x), the third curve and the fourth curve satisfy the second function, the expression of the second function is Y B (x) = Y B1 (x)Y B2 (x); Among them, Y A2 (x) and Y B2 (x) is a periodic function; The number of periods of the periodic function is less than or equal to 50, and / or the periodic function is an integer period.

10. The surface acoustic wave device according to claim 1, wherein The first bus bar forms a fifth curve near the edge of the overlapping area, and the second bus bar forms a sixth curve near the edge of the overlapping area. The fifth curve and the sixth curve are symmetrically distributed with the center line as the axis of symmetry.

11. The surface acoustic wave device according to claim 10, wherein The fifth curve and the sixth curve satisfy a third function, and the expression of the third function is Y C (x) = Y C1 (x)*Y C2 (x); Among them, Y C2 (x) is a periodic function, and the periodic function is an integer period; Y C2 The period of (x) and Y A2 (x) and Y B2 The period of (x) is different.

12. The surface acoustic wave device according to claim 1 or 3, characterized in that The overlapping region includes a middle region and edge regions located on both sides of the middle region in the extending direction of the electrode fingers; The IDT further includes an acoustic impedance adjustment structure, which is located in the edge region. The acoustic impedance of the edge region is smaller than the acoustic impedance of the middle region.

13. The surface acoustic wave device according to claim 1, wherein The minimum length of the overlapping region in the extending direction of the electrode fingers is greater than or equal to 5λ.

14. The surface acoustic wave device according to claim 1, wherein A difference between a maximum length and a minimum length of the overlapping region in an extending direction of the electrode fingers is greater than or equal to 0.1λ and less than or equal to 15λ.

15. A radio frequency front-end module, characterized in that: The surface acoustic wave device comprises the surface acoustic wave device according to any one of claims 1 to 14.

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