Surface acoustic wave resonator, filter, multiplexer and radio frequency front-end module

Abstract

The present application relates to a surface acoustic wave resonator, a filter, a multiplexer and a radio frequency front-end module. In the present application, at least one of the reflection structures of the surface acoustic wave resonator is modulated, such that the distance between center lines of two adjacent reflection electrodes in each reflection structure fluctuates in units of reflection groups, and thus the fluctuations near an upper sideband frequency point of the surface acoustic wave resonator can be suppressed, thereby improving the performance of the resonator. In addition, the filter provided in the embodiments of the present application comprises the surface acoustic wave resonator, such that the passband performance of the filter, particularly the passband flatness and the out-of-band rejection level, can be improved.

Description

Surface acoustic wave resonators, filters, multiplexers and RF front-end modules

[0001] This application is based on the Chinese application No. 202410003391.6 filed on January 2, 2024, entitled “Surface Acoustic Wave Resonator, Filter, Multiplexer and RF Front-End Module”, and claims priority. Technical Field

[0002] The present application belongs to the field of radio frequency filtering technology, and in particular relates to a surface acoustic wave resonator, a filter, and a radio frequency front-end module. Background Art

[0003] The RF front-end modules of wireless communication devices typically include filters to filter RF signals. Acoustic wave filters are a type of filter, including surface acoustic wave (SAW) filters and bulk acoustic wave (BAW) filters. Surface acoustic wave (SAW) filters are widely used in RF front-ends due to their high operating frequency, wide bandwidth, excellent frequency selection characteristics, small size, light weight, simple manufacturing, and low cost.

[0004] Typically, a SAW resonator included in a SAW filter generally consists of two reflection gratings and at least one interdigital transducer (IDT) located between the two reflection gratings. Both the reflection gratings and the IDT are disposed on a piezoelectric substrate.

[0005] With the development of radio frequency technology, how to improve SAW resonators to improve resonator performance and filter performance has become an urgent problem to be solved.

[0006] Application Contents

[0007] In order to solve the above technical problems, the present application provides a surface acoustic wave resonator, a filter, a multiplexer and a radio frequency front-end module, which can improve the performance of the resonator and the filter.

[0008] In a first aspect, an embodiment of the present application provides a surface acoustic wave resonator, comprising an electric substrate, two reflective structures and at least one interdigital transducer arranged on the piezoelectric substrate, wherein the at least one interdigital transducer is located between the two reflective structures, wherein:

[0009] At least one of the reflective structures includes at least three reflective groups, each reflective group includes a plurality of reflective electrodes arranged at intervals, and the distance between the center lines of two adjacent reflective electrodes in the same reflective group is defined as the finger spacing of the reflective group. The finger spacings of the at least three reflective groups fluctuate.

[0010] A second aspect of an embodiment of the present application provides a surface acoustic wave resonator, comprising a piezoelectric substrate, two reflective structures and at least one interdigital transducer disposed on the piezoelectric substrate, wherein the at least one interdigital transducer is located between the two reflective structures, wherein:

[0011] The IDT comprises a plurality of interdigital electrodes arranged at intervals, and the distance between the midlines of two adjacent interdigital electrodes is defined as the finger spacing of the IDT;

[0012] At least one of the reflective structures includes at least one sixth reflective group and at least one seventh reflective group, each of the sixth reflective group and each of the seventh reflective groups includes a plurality of reflective electrodes arranged at intervals, and a distance between midlines of two adjacent reflective electrodes in the same reflective group is defined as a finger spacing of the reflective group;

[0013] The ratio of the finger spacing of the sixth reflection group to the finger spacing of the interdigital transducer is greater than 1, and the ratio of the finger spacing of the seventh reflection group to the finger spacing of the interdigital transducer is less than 1.

[0014] A third aspect of the embodiments of the present application provides a surface acoustic wave resonator, comprising a piezoelectric substrate, two reflective structures and at least one interdigital transducer arranged on the piezoelectric substrate, wherein the at least one interdigital transducer is located between the two reflective structures, wherein:

[0015] At least one of the reflective structures includes a first part close to one side of the interdigital transducer and a second part away from the interdigital transducer, the first part includes at least three reflective groups, each of the reflective groups includes a plurality of reflective electrodes arranged at intervals, the distance between the center lines of two adjacent reflective electrodes in the same reflective group is defined as the finger spacing of the reflective group, the ratio between the finger width of a reflective electrode in the same reflective group and the finger spacing of the reflective group is defined as the duty cycle of the reflective group, the duty cycles of the at least three reflective groups are the same, and the finger spacings of the at least three reflective groups fluctuate.

[0016] A fourth aspect of an embodiment of the present application provides a filter comprising a plurality of series resonators and a plurality of parallel resonators, wherein at least one of the plurality of parallel resonators is a surface acoustic wave resonator provided in any one of the first to third aspects above.

[0017] A fifth aspect of an embodiment of the present application provides a filter comprising a plurality of series resonators and a plurality of parallel resonators, wherein at least one of the plurality of series resonators is a surface acoustic wave resonator provided in any one of the first to third aspects above.

[0018] A sixth aspect of an embodiment of the present application provides a multiplexer, including a first filter and a second filter, wherein the operating frequency band of the first filter is greater than the operating frequency band of the second filter, and the second filter is the filter provided in the fifth aspect above.

[0019] A seventh aspect of an embodiment of the present application provides a radio frequency front-end module, comprising the surface acoustic wave resonator provided by any one of the first to third aspects above.

[0020] In the surface acoustic wave resonator provided in embodiments of the present application, at least one of the resonator's reflective structures is modulated so that the distance between the centerlines of two adjacent reflective electrodes in the reflective structure fluctuates according to the reflection group. This suppresses fluctuations near the upper edge frequency of the surface acoustic wave resonator, thereby improving resonator performance. Furthermore, the filter provided in embodiments of the present application, including the aforementioned surface acoustic wave resonator, can improve the filter's passband performance, particularly passband flatness and out-of-band suppression. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a schematic cross-sectional view of a surface acoustic wave resonator provided in an embodiment of the present application;

[0022] FIG2 is a cross-sectional schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present application;

[0023] FIG3 is a schematic structural diagram of a piezoelectric substrate provided in an embodiment of the present application;

[0024] FIG4 is a schematic top view of a surface acoustic wave resonator provided in an embodiment of the present application;

[0025] FIG5 is a schematic structural diagram of a reflective structure provided in an embodiment of the present application;

[0026] FIG6 is a schematic structural diagram of another reflective structure provided in an embodiment of the present application;

[0027] FIG7 is a schematic structural diagram of another reflective structure provided in an embodiment of the present application;

[0028] FIG8 is a schematic diagram showing a fluctuating variation in the spacing between fingers of a reflective group provided by an embodiment of the present application;

[0029] FIG9 is a schematic diagram of a variation in the spacing between fingers of each reflective group in a reflective structure provided in an embodiment of the present application;

[0030] FIG10 is a schematic diagram showing a variation in the finger spacing of each reflective group in another reflective structure provided in an embodiment of the present application;

[0031] FIG11 is a schematic diagram showing a variation in the spacing between fingers of each reflective group in another reflective structure provided in an embodiment of the present application;

[0032] FIG12 is a schematic diagram showing a variation in the spacing between fingers of a reflective group in another reflective structure provided in an embodiment of the present application;

[0033] FIG13 is a comparison diagram of the real part of impedance curves of the embodiment of the present application and the comparative example;

[0034] FIG14 is a comparison diagram of the Smith circles of the embodiment of the present application and the comparative example;

[0035] FIG15 is a schematic structural diagram of a filter provided in an embodiment of the present application;

[0036] FIG16 is a schematic structural diagram of a multiplexer provided in an embodiment of the present application;

[0037] FIG17 is a schematic structural diagram of a radio frequency front-end module provided in an embodiment of the present application.

[0038] Explanation of the accompanying drawings: 100, surface acoustic wave resonator; 10, piezoelectric substrate; 11, piezoelectric layer; 12, substrate; 13, intermediate layer; 20, interdigital transducer; 21, first bus bar; 22, interdigital electrode; 30, reflection structure; 31, second bus bar; 32, reflection electrode; 321-324, reflection group; 40, temperature compensation layer; 200, filter; 201, signal input terminal; 202, signal output terminal; 203, ground port; 300, multiplexer; 301, antenna terminal; 200a, transmit filter; 200b, receive filter; 302, first port; 303, second port; 400, RF front-end module; 401, signal terminal; 402, switch; 403, amplifier. DETAILED DESCRIPTION

[0039] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer and more understandable, the present application is further described in detail below with reference to the accompanying drawings and embodiments.

[0040] It should be understood that the embodiments set forth below represent the necessary information to enable those skilled in the art to implement the embodiments and to illustrate the best mode of implementing the embodiments. After reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the present disclosure and will recognize applications of these concepts not specifically mentioned herein. It should be understood that these concepts and applications fall within the scope of the present disclosure and the appended claims.

[0041] It should also be understood that although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of this disclosure. As used herein, the term "and / or" includes any and all combinations of one or more of the related listed items.

[0042] It should also be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements.

[0043] It should also be understood that the terms "upper", "lower", "left", "right", "front", "back", "bottom", "middle", "center", "top", etc. may be used in this document to describe various elements, and the indicated orientation or position relationship is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, so these elements should not be restricted by these terms.

[0044] These terms are only used to distinguish one element from another. For example, a first element can be referred to as an "upper" element, and similarly, a second element can be referred to as an "upper" element based on the relative orientation of these elements without departing from the scope of the present disclosure.

[0045] It is further understood that the terms “comprises,” “includes,” “includes,” and / or “comprising” when used herein specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0046] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that the terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the related art, and will not be interpreted in an idealized or overly formal sense unless expressly defined as such herein.

[0047] Usually, there will be fluctuations near the upper side frequency of the surface acoustic wave resonator. If the upper side frequency falls within the passband of the filter, it will cause ripples in the passband and reduce the flatness. If the upper side frequency (also called stopband) falls outside the passband of the filter, it will reduce the out-of-band suppression level of the filter and reduce the isolation from the filter in the adjacent operating frequency band.

[0048] The following describes some embodiments of the present application in detail with reference to Figures 1 to 17. The following embodiments and features of the embodiments may be combined with each other unless they conflict. It should be noted that the figures are for illustrative purposes only and may be used together unless they conflict.

[0049] The embodiments of the present application disclose a surface acoustic wave resonator, a filter, a duplexer, and a multiplexer, which can suppress fluctuations near the upper sideband of the resonator, thereby improving the passband flatness, out-of-band suppression level, and isolation of the filter, and further improving the performance of the multiplexer and the RF front-end module.

[0050] Please refer to Figure 1, which is a cross-sectional schematic diagram of a surface acoustic wave resonator provided in an embodiment of the present application. As shown in Figure 1, the surface acoustic wave resonator 100 includes a piezoelectric substrate 10, an interdigital transducer 20, and a reflective structure 30. The reflective structure 30 and the interdigital transducer 20 are both disposed on the surface of the piezoelectric substrate 10.

[0051] Specifically, the number of IDTs 20 can be one, or two or more, such as three or five, and is not limited in this embodiment. Referring to FIG. 4 , there are two reflective structures 30 on the piezoelectric substrate 10 , with the IDT 20 disposed between the two reflective structures 20 , for reflecting surface acoustic waves generated and propagating in the region where the IDT 20 is located, thereby confining the surface acoustic waves to the region where the IDT 20 is located.

[0052] In one embodiment, the piezoelectric substrate 10 can be a single-layer piezoelectric structure or a multi-layer piezoelectric structure. In the embodiment shown in FIG1 , the piezoelectric substrate 10 is a single-layer piezoelectric structure. The piezoelectric substrate 10 can be made of aluminum nitride, zinc oxide, lead zirconate titanate (PZT), or a rare earth element doped material of the above materials in a certain atomic ratio. Alternatively, a single crystal piezoelectric material such as single crystal aluminum nitride, lithium niobate, lithium tantalate, or quartz can be selected, and this application does not impose any specific restrictions on this.

[0053] In one embodiment, the interdigital transducer 20 can be a single metal material or a composite or alloy material of different metals. Optionally, the above material can be aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, tungsten, etc. or a composite of the above metals or an alloy thereof. The reflective structure 30 can also be a single metal material or a composite or alloy material of different metals. Optionally, the above material can be aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, tungsten, etc. or a composite of the above metals or an alloy thereof. The interdigital transducer 20 and the reflective structure 30 can be made of the same material or different materials. Preferably, the two are made of the same material to reduce process difficulty, reduce costs, and ensure performance consistency.

[0054] In the embodiment of the present application, the IDT 20 and the reflective structure 30 may be a single-layer metal film or a stacked metal film having multiple metal layers stacked thereon, and the present application does not impose any specific limitation thereto.

[0055] In one embodiment, the surface acoustic wave resonator 100 further includes a passivation layer (not shown in the figure), which is disposed on the piezoelectric substrate 10 and covers the interdigital transducer 20 and the reflective structure 30 to protect the surface acoustic wave resonator 100 and prevent water vapor and other substances in the external environment from corroding or contaminating the interdigital transducer 20, the reflective structure 30 and the piezoelectric substrate 10, thereby ensuring the working performance of the surface acoustic wave resonator 100 and improving the reliability of the structure of the surface acoustic wave resonator 100.

[0056] Specifically, the passivation layer can be silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, etc., and this application does not impose any specific limitation on this.

[0057] Please refer to Figure 2, which is a cross-sectional schematic diagram of another surface acoustic wave resonator provided in an embodiment of the present application. Figure 2 differs from Figure 1 in that the surface acoustic wave resonator 100 further includes a temperature compensation layer 40, which is disposed on the piezoelectric substrate 10 and covers at least the interdigital transducers 20.

[0058] Specifically, the temperature compensation layer 40 can be made of a material with a positive temperature compensation coefficient, or a material with a low temperature compensation coefficient. The material of the temperature compensation layer 40 can be at least one of dielectric materials with a positive temperature compensation coefficient, such as silicon oxide, silicon nitride, silicon oxynitride, tellurium dioxide, silicon oxyfluoride, etc. Among them, the material of the temperature compensation layer 40 is usually one of the above materials, that is, the material of the temperature compensation layer 40 is a single material. Of course, in some feasible embodiments, the material of the temperature compensation layer 40 can also be a mixed material. In this case, the material of the temperature compensation layer 40 can be a mixture of any of the above materials, or a mixture of one or more of the above materials with other materials.

[0059] Specifically, the temperature compensation layer 40 may completely cover the IDT 20, or may partially cover the IDT 20, for example, covering only the region where the electrode fingers of the IDT 20 are located, while the busbars are not covered by the temperature compensation layer 40. In this embodiment, the temperature compensation layer 40 completely covers the IDT 20 and the reflective structure 30. In other embodiments, the temperature compensation layer 40 may only cover the IDT 20.

[0060] By covering the IDT 20 with the temperature compensation layer 40 , the frequency shift of the SAW resonator 100 caused by temperature change can be reduced, thereby effectively improving the temperature stability of the SAW resonator 100 .

[0061] Please refer to Figure 3, which is a schematic diagram of the structure of a piezoelectric substrate provided in an embodiment of the present application. As shown in Figure 3, the piezoelectric substrate 10 may include a substrate 12 and a piezoelectric layer 11. The piezoelectric layer 11 may be a piezoelectric film, and the reflective structure 30 and the interdigital transducer 30 are arranged on the side of the piezoelectric layer 11 facing away from the substrate 12. The surface acoustic wave resonator 100 provided in an embodiment of the present application uses this piezoelectric substrate. Compared to traditional surface acoustic wave resonators, it can achieve a higher Q value, a lower frequency temperature coefficient, and good heat dissipation.

[0062] The substrate 12 may be made of single crystal silicon, polycrystalline silicon, quartz, glass, etc. Compared with the piezoelectric layer 11 , the substrate 12 may be a high acoustic velocity layer or a high acoustic impedance layer.

[0063] In some embodiments, an intermediate layer 13 may be provided between the substrate 12 and the piezoelectric layer 11. Specifically, the intermediate layer 13 may be a single-layer thin film layer, specifically a low acoustic velocity layer or a low acoustic impedance layer. The arrangement of the substrate 12 and the intermediate layer 13 may not only provide temperature compensation for the piezoelectric layer 11, but may also form an acoustic reflection structure below the piezoelectric layer 11, thereby reducing the longitudinal leakage of acoustic wave energy. The intermediate layer 13 may also be a multi-layer thin film layer, at least one of which is a single-layer thin film structure as described above. Of course, the multi-layer thin film layer may be a layer structure in which high and low acoustic impedance or high and low acoustic velocity are alternately stacked, thereby better suppressing the longitudinal leakage of acoustic wave energy. The longitudinal direction is roughly the thickness direction of the piezoelectric layer 11. The single-layer thin film layer may be made of materials such as silicon dioxide and silicon oxyfluoride.

[0064] Please refer to Figure 4, which is a top view schematic diagram of a surface acoustic wave resonator provided in an embodiment of the present application. Figure 4 takes an example of an interdigital transducer 20 between two reflective structures 30a and 30b. As shown in Figure 4, the transducer 20 includes two first bus bars 21 arranged opposite to each other, and a plurality of interdigital electrodes 22 between the two first bus bars 21. The plurality of interdigital electrodes 22 extend along the arrangement direction of the two bus bars 21. Among them, a portion of the interdigital electrodes 22 is connected to one first bus bar 21, and another portion of the interdigital electrodes 22 is connected to another first bus bar 21. The interdigital electrodes 22 connected to different first bus bars 21 are arranged alternately and spaced from each other. In the arrangement direction of the interdigital electrodes 22, an overlapping area is formed between the interdigital electrodes 22 connected to different first bus bars 21. The length K2 of this area in the direction of the two first bus bars 21 is the length of the aperture of the interdigital transducer 20.

[0065] Furthermore, the reflective structure 30 (30a and 30b) includes two second bus bars 31 arranged opposite each other, and a plurality of reflective electrodes 32 between the two second bus bars 31. The plurality of reflective electrodes 32 are spaced apart and extend along the arrangement direction of the two second bus bars 31. The ends of the reflective electrodes 32 are respectively connected to the two second bus bars 31. The length K1 of the reflective electrodes 32 in the extension direction can be regarded as the length of the aperture of the reflective structure (30a and 30b).

[0066] In some embodiments, one of the reflective structures 30a and 30b may not have the bus bar 31, that is, the reflective electrode 32 is open, and the other may have the bus bar 31; or both may have the bus bar 32 as shown in FIG. 4, that is, the reflective electrode 32 is short-circuited. This application does not impose any specific limitation on this.

[0067] In some embodiments, only one of the reflective structures 30a and 30b may have a reflective electrode 32, and the other may be a structure of other forms that can reflect surface acoustic waves to confine the surface acoustic waves to the area where the interdigital transducer 20 is located, such as a groove provided on the piezoelectric substrate 10. This application does not impose any specific restrictions on this.

[0068] In one embodiment, please refer to Figures 5 to 8. Figures 5 to 7 are schematic diagrams of the structures of the reflection structures provided in the embodiments of the present application. Figure 8 is a schematic diagram of the fluctuating spacing between the finger spacings of the reflection group provided in the embodiments of the present application. Figures 5 to 7 only show one reflection structure. In other embodiments, one of the reflection structures 30 may be improved, or two of the reflection structures 30 may be improved. At least one of the reflection structures 30 shown in the figures includes at least three reflection groups, each reflection group includes a plurality of reflection electrodes 32 arranged at intervals, and the distance between the center lines of two adjacent reflection electrodes 32 in the same reflection group is defined as the finger spacing of the reflection group (as shown in Figure 5, represented by P) . The finger spacings of at least three reflection groups fluctuate, thereby reducing the fluctuation near the upper side frequency point of the surface acoustic wave resonator 100.

[0069] Specifically, the embodiment of the present application divides the reflective structure 30 into at least three reflective groups. The figure schematically illustrates four reflective groups (321, 322, 323, and 324). Each reflective group includes multiple reflective electrodes 32. Specifically, the number of reflective electrodes 32 in each reflective group is greater than two, and can be 5, 7, 10, etc., which is not specifically limited in the embodiment of the present application. The number of reflective electrodes 32 in each reflective group can be equal or unequal, which is not specifically limited in the present application.

[0070] It is understandable that a portion of the reflective structure 30 may be divided into at least three reflective groups, or the entire reflective structure 30 may be divided into at least three reflective groups, thereby improving the finger spacing of the at least three reflective groups to make it fluctuate.

[0071] In a specific embodiment, the spacing between the fingers of at least three reflection groups varies in a sinusoidal function or a cosine function, which is beneficial for reducing the fluctuation near the upper side frequency of the surface acoustic wave resonator 100 and thus improving the working performance of the surface acoustic wave resonator 100.

[0072] In other embodiments, the spacing between fingers of at least three reflection groups varies in a wave function.

[0073] It should be noted that in the same reflective group, the distance between the center lines of any two adjacent reflective electrodes 32 can be the same or within a very small fluctuation range. If within a very small fluctuation range, the finger spacing of the reflective group can refer to the average distance between the center lines of each two adjacent reflective electrodes 32, or it can be the minimum distance or the maximum distance. This application does not make specific limitations.

[0074] Specifically, the spacing between the finger lines of the reflection groups fluctuates. It can be understood that the changes in the spacing between the finger lines of each reflection group can be regular changes that first increase and then decrease, regular changes that first decrease and then increase, or irregular changes.

[0075] For example, Figure 5 schematically illustrates the fluctuation trend of the finger spacings of multiple reflective groups. In Figure 5, the horizontal axis represents the reflective group, and the vertical axis represents the finger spacings of the reflective group. Figure 5 shows 10 reflective groups. In the curve shown in Method 1, the finger spacings of the 10 reflective groups fluctuate regularly, with the same fluctuation amplitude. That is, the finger spacings of reflective groups 1, 3, 5, 7, and 9 are large and equal, while the finger spacings of reflective groups 2, 4, 6, 8, and 10 are small and equal. Reflective groups with large finger spacings and reflective groups with small finger spacings are arranged alternately in the arrangement direction of the reflective electrodes 32. Of course, in other examples, the reflection groups can be interspersed with an equal number of reflection groups or with different numbers of reflection groups. In the curve shown in method 2, the finger spacing between reflection group 1 and reflection group 3 shows a downward trend, the finger spacing between reflection group 3 and reflection group 5 shows an upward trend, the finger spacing between reflection group 5 and reflection group 8 shows a downward trend, and the finger spacing between reflection group 8 and reflection group 10 shows an upward trend. In method 2, the finger spacing between reflection group 1 and reflection group 5 is not equal, and the finger spacing between reflection group 3 and reflection group 8 is also not equal. The decrease rate between the finger spacing from reflection group 1 to reflection group 3 and the finger spacing from reflection group 5 to reflection group 8 is different. Of course, in other examples, the finger spacing between reflection group 1 and reflection group 5 can also be equal, and the finger spacing between reflection group 3 and reflection group 8 can also be equal. In the curve shown in the third embodiment, the finger spacing between reflective groups 1 to 10 first increases, then decreases, and finally increases continuously. The finger spacing of reflective group 10 is greater than that of reflective group 2, and the finger spacing of reflective group 5 is less than that of reflective group 1. Of course, in other examples, the finger spacing of reflective group 10 can also be less than or equal to that of reflective group 2, and the finger spacing of reflective group 5 can also be greater than or equal to that of reflective group 1. In the curve shown in the fourth embodiment, the finger spacing between reflective groups 1 to 8 first increases and then decreases. The finger spacing between reflective groups 8 and 10 remains unchanged, and the finger spacing of reflective group 8 is less than that of reflective group 1. Of course, in other examples, the finger spacing of reflective group 8 can also be equal to that of reflective group 1.

[0076] By improving the reflective structure 30 so that the finger spacings of the multiple reflective groups fluctuate, the fluctuation near the upper sideband of the surface acoustic wave resonator 100 can be reduced, thereby improving the working performance of the surface acoustic wave resonator 100.

[0077] In an exemplary embodiment, the at least three reflection groups include a first reflection group, a second reflection group and a third reflection group, the second reflection group is located between the first reflection group and the third reflection group, and the finger spacing of the second reflection group is smaller than or larger than the finger spacing of the first reflection group and the finger spacing of the third reflection group.

[0078] In some embodiments, the finger spacing of the first reflection group is the same as the finger spacing of the third reflection group. Of course, in other embodiments, the finger spacing of the first reflection group is different from the finger spacing of the third reflection group.

[0079] It should be noted that the first reflection group, the second reflection group and the third reflection group are any three reflection groups as long as the second reflection group is located between the first reflection group and the third reflection group in the arrangement direction of the reflection electrodes 32 .

[0080] In one embodiment, the second reflection group is adjacent to the first reflection group and the third reflection group respectively. That is, the first reflection group, the second reflection group and the third reflection group are arranged adjacent to each other in sequence.

[0081] In other embodiments, there may be other reflection groups between the first reflection group and the second reflection group. Similarly, there may be other reflection groups between the second reflection group and the third reflection group. This application does not make any specific limitations.

[0082] With reference to Figures 5 to 7, for example, the finger spacing of reflection group 321 is defined as P1, the finger spacing of reflection group 322 is defined as P2, the finger spacing of reflection group 323 is defined as P3, the finger spacing of reflection group 324 is defined as P4, and so on. One approach is to consider reflection group 321, reflection group 322, and reflection group 324 as the first reflection group, the second reflection group, and the third reflection group, respectively. Then, if P2 is smaller than P1 and P4, P3 can be larger than or smaller than P2, and P1 can be larger than or smaller than P4; if P2 is larger than P1 and P4, P3 can be larger than or smaller than P2, and P1 can be larger than or smaller than P4. Another way is to regard reflection group 321, reflection group 322 and reflection group 323 as the first reflection group, the second reflection group and the third reflection group respectively. Then, when P2 is less than or greater than P1 and P3, P1 and P3 can be equal or unequal, P4 can be less than P3 or greater than P3, and P4 can be greater than or less than P2.

[0083] It should be noted that other reflection groups may exist on the side of the third reflection group facing away from the second reflection group, and the relationship between the finger spacings of the other reflection groups may be the same as the relationship between the finger spacings of the first reflection group, the second reflection group, and the third reflection group. That is, in the reflection structure, there may be multiple reflection groups, and the finger spacings of the reflection groups may be arranged alternately with larger and smaller ones. The change between the finger spacings of each reflection group is represented by a curve, and the curve has peaks and troughs, wherein at least one of the change curves between the peaks and the troughs (which may also be called the envelope of the change curve between the finger spacings of each reflection group) may remain unchanged, or may change with an increasing or decreasing trend, or may change with a wave function such as a sine / cosine function. The change curve between the troughs may be symmetrical or asymmetrical with the change curve between the peaks. Similarly, other reflection groups may exist on the side of the first reflection group facing away from the second reflection group, and the relationship between the finger spacings of the other reflection groups may be the same as described above, and this application will not repeat them here.

[0084] In this embodiment, the finger spacing of the second reflection group is set to be smaller than or larger than the finger spacing of the first reflection group and the finger spacing of the third reflection group, so that the finger spacings of multiple reflection groups fluctuate, thereby reducing the fluctuation near the upper side frequency point of the surface acoustic wave resonator 100 to a certain extent.

[0085] In a specific embodiment, the at least three reflection groups further include at least one fourth reflection group, which is located between the first reflection group and the second reflection group, and the finger spacing of each fourth reflection group is between the finger spacing of the first reflection group and the finger spacing of the second reflection group.

[0086] In a specific embodiment, the at least three reflection groups further include at least one fifth reflection group, which is located between the second reflection group and the third reflection group, and the finger spacing of each fifth reflection group is between the finger spacing of the second reflection group and the finger spacing of the third reflection group.

[0087] In a specific embodiment, the at least three reflection groups further include at least one fourth reflection group and at least one fifth reflection group. The fourth reflection group and the fifth reflection group are respectively located between the first reflection group and the second reflection group and between the second reflection group and the third reflection group.

[0088] Specifically, the fourth reflection group can be one or more, the fifth reflection group can be one or more, and the number of the fourth reflection groups can be equal to or different from the number of the fifth reflection groups, which is not specifically limited in this application.

[0089] For example, when the finger spacing of the second reflection group is greater than the finger spacing of the first reflection group and the finger spacing of the third reflection group, the finger spacing of each fourth reflection group can be greater than the finger spacing of the first reflection group and smaller than the finger spacing of the second reflection group, and the finger spacing of each fifth reflection group can be smaller than the finger spacing of the second reflection group and greater than the finger spacing of the third reflection group. The finger spacings between the fourth reflection groups can be equal or unequal. From the order of the fourth reflection groups from the first reflection group to the second reflection group, the finger spacings between the fourth reflection groups can gradually increase or decrease, or can first increase and then decrease, or can first decrease and then increase (i.e., fluctuating changes). Similarly, the finger spacings between the fifth reflection groups can be equal or unequal. From the order of the fifth reflection groups from the second reflection group to the third reflection group, the finger spacings between the fifth reflection groups can gradually increase or decrease, or can first increase and then decrease, or can first decrease and then increase (i.e., fluctuating changes).

[0090] Of course, in some feasible implementations, the finger spacing of each fourth reflection group may not be between the finger spacing of the first reflection group and the finger spacing of the second reflection group, for example, the finger spacing of some or all of the fourth reflection groups in all fourth reflection groups is greater than the larger of the finger spacing of the first reflection group and the finger spacing of the second reflection group, or is smaller than the smaller of the finger spacing of the first reflection group and the finger spacing of the second reflection group. The finger spacing of each fifth reflection group may also not be between the finger spacing of the second reflection group and the finger spacing of the third reflection group, for example, the finger spacing of some or all of the fifth reflection groups in all fifth reflection groups is greater than the larger of the finger spacing of the second reflection group and the finger spacing of the third reflection group, or is smaller than the smaller of the finger spacing of the second reflection group and the finger spacing of the third reflection group. This application does not make specific limitations.

[0091] In a specific embodiment, along the arrangement direction from the first reflection group to the second reflection group, there is a first change trend between the finger spacing of each fourth reflection group in at least one fourth reflection group, and the first change trend is the change trend from the finger spacing of the first reflection group to the finger spacing of the second reflection group.

[0092] In a specific embodiment, along the arrangement direction from the second reflection group to the third reflection group, the finger spacing of each fifth reflection group in at least one fifth reflection group has a second change trend, and the second change trend is the change trend from the finger spacing of the second reflection group to the finger spacing of the third reflection group.

[0093] It can be understood that if the finger spacing of the second reflection group is smaller than the finger spacing of the first reflection group and the finger spacing of the third reflection group, then along the arrangement direction from the first reflection group to the second reflection group, the finger spacing of each fourth reflection group is smaller than the finger spacing of the first reflection group and larger than the finger spacing of the second reflection group, and the finger spacing of each fourth reflection group gradually decreases, that is, the first change trend is a decreasing trend. Along the arrangement direction from the second reflection group to the third reflection group, the finger spacing of each fifth reflection group is larger than the finger spacing of the second reflection group and smaller than the finger spacing of the third reflection group, and the finger spacing of each fifth reflection group gradually increases, that is, the second change trend is an increasing trend.

[0094] It can be understood that the first change trend and the second change trend are opposite.

[0095] In this embodiment, the finger spacing of each fourth reflection group gradually increases, and the finger spacing of each fifth reflection group gradually decreases, or the finger spacing of each fourth reflection group gradually decreases, and the finger spacing of each fifth reflection group gradually increases, so that the finger spacing of each reflection group in the reflection structure 30 changes smoothly and regularly, which can further reduce the fluctuation near the upper sideband point of the surface acoustic wave resonator 100.

[0096] In some embodiments, the ratio of the finger width of a reflective electrode 32 in the same reflective group to the finger spacing of the reflective group is defined as the duty cycle of the reflective group. The duty cycles of the at least three reflective groups can be the same or different. Preferably, the duty cycles of the at least three reflective groups are the same.

[0097] Specifically, referring to FIG. 5 , in the reflective structure 30 , the width of the reflective electrode 32 is D, the distance between the center lines of two adjacent reflective electrodes 32 is P, and the duty cycle of the reflective electrode 32 is D / P. That is, the duty cycle of the reflective group can be understood as the duty cycle of the reflective electrode 32 in the reflective group.

[0098] In this embodiment, when the duty cycles of the reflection groups are the same, the finger spacings of the reflection groups are set to fluctuate, which is more conducive to reducing fluctuations near the upper sideband of the surface acoustic wave resonator 100 .

[0099] It should be noted that a portion of the reflective electrode 32 in the reflective structure 30 may be divided into at least three reflective groups, or all of the reflective electrodes 32 may be divided into at least three reflective groups, so that the finger spacing of the at least three reflective groups is set to fluctuate to reduce the fluctuation near the upper sideband point of the surface acoustic wave resonator 100.

[0100] In one specific embodiment, the reflective structure 30 includes a first portion close to one side of the IDT 20 and a second portion away from the IDT 20 . The first portion includes at least three reflective groups, and the distance between the center lines of two adjacent reflective electrodes 32 in the second portion remains consistent.

[0101] In this embodiment, as shown in Figures 5 and 6, the left side of the reflective structure 30 is close to the IDT 20. The reflective electrodes 32 on the side of the reflective structure 30 close to the IDT 20 are divided into multiple reflective groups (reflective group 321, reflection group 322, reflection group 323, reflection group 324, etc.), and the finger spacing between each reflection group is set to fluctuate. The reflective electrodes 32 on the side away from the IDT 20 are not improved, so that the distance between the center lines of any two adjacent reflective electrodes 32 remains unchanged. In this embodiment, only the reflective electrodes 32 on the side close to the IDT 20 are improved, divided into at least three reflection groups, and the finger spacing between the reflection groups fluctuates. This not only helps reduce fluctuations near the upper sideband of the surface acoustic wave resonator 100, but also reduces process difficulty and avoids the need to improve all reflective electrodes.

[0102] In other embodiments, as shown in FIG7 , the reflection electrode 32 in the middle portion of the reflection structure 30 may be improved by dividing it into at least three reflection groups (such as reflection group 321, reflection group 322, reflection group 323, etc.) so that the spacing between the fingers of the reflection group fluctuates. Instead of improving the reflection electrodes on both sides of the reflection structure, the distance between the center lines of any two adjacent reflection electrodes on both sides remains unchanged. This can also reduce the fluctuation near the upper sideband of the surface acoustic wave resonator 100 to a certain extent.

[0103] It is understandable that all the reflective electrodes 32 in the reflective structure 30 can be set to be open-circuited, that is, the reflective structure 30 is an open-circuited reflective grid, or all can be set to be short-circuited, that is, the reflective structure 30 is a short-circuited reflective grid, or some of the reflective electrodes 32 can be open-circuited and some of the reflective electrodes 32 can be short-circuited.

[0104] In some embodiments, the reflective electrode 32 of at least one of the at least three reflective groups is open-circuited, and / or the reflective electrode 32 of at least one of the at least three reflective groups is short-circuited.

[0105] Specifically, among the at least three reflection groups, the reflection electrodes 32 of some reflection groups can be open-circuited, and the reflection electrodes 32 of the remaining reflection groups can be short-circuited. Alternatively, the reflection electrodes 32 of all reflection groups can be open-circuited, or the reflection electrodes 32 of all reflection groups can be short-circuited. This application does not limit this.

[0106] For example, in Figure 5 , the reflective electrodes of all reflective groups (including reflective group 321, reflective group 322, reflective group 323, and reflective group 324) are short-circuited, that is, both ends of the reflective electrodes 32 along their length are connected to the second busbar 31. As shown in Figure 6 , the reflective electrodes 32 of reflective groups 321 and 322 are short-circuited, while the reflective electrodes 32 of reflective groups 322 and 323 are open-circuited, that is, both ends of the reflective electrode 32 of reflective group 323 are not connected to the second busbar 31 along their length. As shown in Figure 7 , the reflective electrode 32 of reflective group 321 is open-circuited, while the reflective electrodes 32 of reflective groups 322 and 323 are short-circuited.

[0107] In some embodiments, when both reflective structures 30a and 30b are improved, the two reflective structures can be arranged axially symmetrically with the IDT 20 as the axis of symmetry. This approach can improve the reflection effect of surface acoustic waves, better confine the surface acoustic waves to the area where the IDT 20 is located, and can be more conducive to reducing fluctuations near the upper sideband points of the surface acoustic wave resonator 100.

[0108] In some embodiments, the ratio between the aperture K1 of the reflective structure 30 and the aperture of the IDT 20 is in the range of [0.5, 2], for example, it can be 0.5, 0.7, 1, 1.5, 2, etc., which can better confine the sound waves to the area where the IDT 20 is located, and reduce the diffraction of the sound waves from the IDT 20 to the two sides of the reflective structure 20.

[0109] In some embodiments, the finger spacing of each reflection group of the reflection structure 300 can also be improved so that the ratio of the finger spacing of each reflection group in each reflection group to the finger spacing of the IDT fluctuates. The finger spacing of the IDT 20 refers to the distance between the center lines of two adjacent interdigital electrodes in the IDT 20. Specifically, the distance between the center lines of any two adjacent interdigital electrodes can be kept consistent. In other words, the finger spacing of the IDT 20 is a fixed value. In some embodiments, the IDT 20 can be set up in different regions, and the finger spacing in different regions (i.e., the distance between the center lines of two adjacent interdigital electrodes) is different. Then, the finger spacing of the IDT 20 can refer to the average value of the finger spacing of all regions, or the maximum value of the finger spacing of all regions, or the minimum value of the finger spacing of all regions. This application does not make any specific limitation on this.

[0110] It is understandable that the description of the fluctuation between the ratio of the finger spacing of the reflection group and the finger spacing of the interdigital transducer can also refer to the relevant descriptions in the above embodiments without conflict, and this application will not repeat them here.

[0111] Exemplarily, the change in the ratio of the finger spacing of the reflection group to the finger spacing of the interdigital transducer can be referred to Figures 9 to 12. Among them, the horizontal axes of Figures 9 to 12 all show 10 reflection groups, and the vertical axes show the ratio of the finger spacing of the reflection group to the finger spacing of the interdigital transducer. As shown in Figure 9, the ratio of the finger spacing of each reflection group to the finger spacing of the interdigital transducer is greater than or equal to 1. On this basis, the ratio of the finger spacing of each reflection group to the finger spacing of the interdigital transducer fluctuates; of course, in other embodiments, the ratio of the finger spacing of some or all reflection groups to the finger spacing of the interdigital transducer can also be less than 1. As shown in Figure 10, the reflection groups whose ratios of the finger spacing of the reflection group to the finger spacing of the interdigital transducer are greater than 1 and less than 1 are alternately arranged, showing a regular fluctuating change. As shown in FIG11 , although the ratio of the finger spacing of each reflection group to the finger spacing of the IDT fluctuates, the ratio generally shows an upward trend. Of course, in other embodiments, the ratio of the finger spacing of each reflection group to the finger spacing of the IDT may also generally show a downward trend. As shown in FIG12 , the ratio of the finger spacing of each reflection group to the finger spacing of the IDT first increases, then decreases, and ultimately remains unchanged.

[0112] By improving the finger spacing of each reflection group of the reflection structure 300, the ratio of the finger spacing of each reflection group to the finger spacing of the interdigital transducer fluctuates, which is beneficial to reducing the fluctuation near the upper sideband point of the surface acoustic wave resonator 100.

[0113] In another embodiment, please refer to Figures 1 to 7. This embodiment also provides a surface acoustic wave resonator, which includes a piezoelectric substrate 10 and two reflection structures 30 and at least one IDT 20 arranged on the piezoelectric substrate 10. The at least one IDT 20 is located between the two reflection structures 30, wherein the IDT 20 includes a plurality of interdigital electrodes 22 arranged at intervals, and the distance between the center lines of two adjacent interdigital electrodes 22 is defined as the finger pitch of the IDT 20; at least one of the reflection structures 30 includes at least one sixth reflection group and at least one seventh reflection group, each sixth reflection group and each seventh reflection group includes a plurality of reflection electrodes 32 arranged at intervals, and the distance between the center lines of two adjacent reflection electrodes 32 in the same reflection group is defined as the finger pitch of the reflection group; the ratio between the finger pitch of the sixth reflection group and the finger pitch of the IDT 20 is greater than 1, and the ratio between the finger pitch of the seventh reflection group and the finger pitch of the IDT 20 is less than 1.

[0114] It is understandable that in this embodiment, the relevant descriptions of the piezoelectric substrate 10 and the interdigital transducer 20 can refer to the previous embodiment, and, under the premise of no conflict, other features of the reflective structure 30 can also refer to the previous embodiment, which will not be repeated in this application.

[0115] Specifically, referring to FIG. 10 to FIG. 12 , one of the reflective structures 30 may be improved, the other reflective structure may include a reflective electrode, or may be a reflective structure in other forms, or both reflective structures 30 may be improved.

[0116] In this embodiment, the sixth reflection group may be one, two, three, or more. Similarly, the seventh reflection group may be one, two, three, or more. The number of the sixth reflection group and the number of the seventh reflection group may be the same or different.

[0117] For example, the ratio of the finger spacing of the sixth reflection group to the finger spacing of the interdigital transducer 20 is greater than 1, which can be 1.1, 1.2, 1.5, 1.8, 2, etc. The ratio of the finger spacing of the seventh reflection group to the finger spacing of the interdigital transducer 20 is less than 1, which can be 0.9, 0.8, 0.6, 0.5, etc. This application does not make any specific limitations on this.

[0118] In this embodiment, the finger spacing of the reflection group is improved so that the ratio between the finger spacing of the partial reflection group and the finger spacing of the interdigital transducer is greater than 1, and the ratio between the finger spacing of the partial reflection group and the finger spacing of the interdigital transducer 20 is less than 1, which is beneficial to reducing the fluctuation near the upper sideband point of the surface acoustic wave resonator 100, thereby improving the working performance of the surface acoustic wave resonator 100.

[0119] It will be understood that in this embodiment, the ratio of the finger spacing of a reflection group to the finger spacing of the IDT is defined as the spacing ratio of the reflection group. Therefore, the ratio of the finger spacing of the sixth reflection group to the finger spacing of the IDT is the spacing ratio M of the sixth reflection group, and the ratio of the finger spacing of the seventh reflection group to the finger spacing of the IDT is the spacing ratio N of the seventh reflection group. The spacing ratios M of the sixth reflection groups can be equal or different. Similarly, the spacing ratios N of the seventh reflection groups can be equal or different, and are not specifically limited unless otherwise specified in the present application.

[0120] In some embodiments, the sixth reflection group and the seventh reflection group may be arranged so that the ratio between the finger spacing of each reflection group and the finger spacing of the interdigital transducer 20 fluctuates, thereby facilitating reduction of fluctuations near the upper sideband of the surface acoustic wave resonator 100.

[0121] In some embodiments, the sixth reflective group and the seventh reflective group are alternately arranged in the arrangement direction of the reflective electrodes.

[0122] That is to say, the sixth reflection group with a spacing ratio M greater than 1 and the seventh reflection group with a spacing ratio N less than 1 can be arranged alternately, so that the ratio of the finger spacing of each reflection group to the finger spacing of the interdigital transducer fluctuates, as shown in Figures 10 and 11.

[0123] In a specific embodiment, the sixth reflective group and the seventh reflective group are adjacently arranged in the arrangement direction of the reflective electrodes 32 , as specifically shown in FIG. 10 .

[0124] In another specific embodiment, the reflective structure 30 further includes an eighth reflective group, there is at least one eighth reflective group between the sixth reflective group and the eighth reflective group, and the finger spacing of the eighth reflective group is between the finger spacing of the sixth reflective group and the finger spacing of the seventh reflective group.

[0125] That is, other reflection groups may exist between the sixth reflection group and the seventh reflection group, and the spacing ratios of the other reflection groups may be between the spacing ratio M of the sixth reflection group and the spacing ratio N of the seventh reflection group, as specifically shown in FIG11 . Of course, the spacing ratios of the other reflection groups may be 1, greater than 1, or less than 1, and this application does not impose any specific limitation thereto.

[0126] For example, the spacing ratios of other reflection groups that are closer to the sixth reflection group are closer to the spacing ratio M of the sixth reflection group, and the spacing ratios of other reflection groups that are closer to the seventh reflection group are closer to the spacing ratio N of the seventh reflection group, so that the spacing ratios of the sixth reflection group and the seventh reflection group change more slowly, which is beneficial to reducing the fluctuations near the upper sideband points of the surface acoustic wave resonator 100.

[0127] In some embodiments, the sixth reflection group is closer to the IDT 20 than the seventh reflection group.

[0128] Specifically, all the sixth reflection groups may be close to the IDT 20 , and all the seventh reflection groups may be far away from the IDT 20 , that is, all the sixth reflection groups are closer to the IDT 30 than all the seventh reflection groups.

[0129] Preferably, the sixth reflection group and the seventh reflection group are arranged alternately in the arrangement direction of the reflection electrodes 32, and the sixth reflection group is closer to the interdigital transducer 20 than the seventh reflection group. This can further help reduce the fluctuation near the upper sideband of the surface acoustic wave resonator 100, thereby improving the operating performance of the surface acoustic wave resonator 100.

[0130] It should be noted that, in this embodiment, the arrangement of the sixth reflection group and the seventh reflection group is not limited. Of course, all the reflection groups close to the IDT 20 may be seventh reflection groups, and all the sixth reflection groups may be far away from the IDT 20 .

[0131] In other embodiments, the sixth and seventh reflective groups, which are improvements to the reflective electrodes 32, are located on both sides of the reflective structure 30, and the distance between the centerlines of the reflective electrodes located in the middle region of the reflective structure 30 remains unchanged. Alternatively, the sixth and seventh reflective groups, which are improvements to the reflective electrodes 32, are located in the middle region of the reflective structure 30, and the distance between the centerlines of the reflective electrodes located on both sides of the reflective structure 30 remains unchanged.

[0132] In a specific embodiment, the number of the sixth reflection group is not less than 2, and the finger spacings of the sixth reflection group have a first envelope.

[0133] In another specific embodiment, the number of the seventh reflection group is not less than 2, and the finger spacings of the seventh reflection group have a second envelope.

[0134] In another specific embodiment, the spacing between fingers of the sixth reflection group has a first envelope, and the number of the seventh reflection group is not less than 2, and the spacing between fingers of the seventh reflection group has a second envelope.

[0135] That is, on the basis that the spacing ratio of the sixth reflection group is greater than 1 and the spacing ratio of the seventh reflection group is less than 1, there can be two or more sixth reflection groups, and the spacing between the fingers of each sixth reflection group forms a first envelope, which can satisfy a sine function, a cosine function, an exponential function, a linear function, etc.; there can also be two or more seventh reflection groups. The spacing between the fingers of each seventh reflection group forms a second envelope, which can satisfy a sine function, a cosine function, an exponential function, a linear function, etc.

[0136] Of course, the finger spacings of each sixth reflection group may also be equal, and the finger spacings of each seventh reflection group may also be equal, and this application does not make specific limitations.

[0137] It can be understood that the sixth reflective group and the seventh reflective group may be arranged alternately in the arrangement direction of the reflective electrodes 32 , or may be arranged non-alternatingly.

[0138] In a preferred embodiment, the reflection structure 30 has two sixth reflection groups and two seventh reflection groups on the side close to the interdigital transducer 20, and the reflection electrode 32 on the side away from the interdigital transducer 20 is not divided into reflection groups. The sixth reflection group and the seventh reflection group are alternately arranged in the arrangement direction of the reflection electrode 32, and the sixth reflection group is adjacent to the interdigital transducer 20. Through this embodiment, the fluctuation near the upper sideband point of the surface acoustic wave resonator 100 can be reduced, and the process complexity can be reduced, which is convenient for manufacturing.

[0139] In some embodiments, the ratio of the finger width of a reflective electrode 32 in the same reflective group to the finger spacing of the reflective group is defined as the duty cycle of the reflective group. The duty cycle of the sixth reflective group is the same as the duty cycle of the seventh reflective group.

[0140] Specifically, on the basis that the spacing ratio of the sixth reflection group is greater than 1 and the spacing ratio of the seventh reflection group is less than 1, the duty cycle of each reflection group remains consistent, which can further reduce the fluctuation near the upper sideband point of the surface acoustic wave resonator 100, thereby improving the working performance of the surface acoustic wave resonator 100.

[0141] In some embodiments, the two reflective structures 30 are arranged symmetrically about the IDT 20. This arrangement can improve the reflection effect on surface acoustic waves, better confine the surface acoustic waves to the area where the IDT 20 is located, and further help reduce fluctuations near the upper sideband of the surface acoustic wave resonator 100.

[0142] In another embodiment, referring to FIG. 1 to FIG. 7 , this embodiment further provides a surface acoustic wave resonator. The surface acoustic wave resonator 100 includes a piezoelectric substrate 10, two reflective structures 30 disposed on the piezoelectric substrate 10, and at least one interdigital transducer 20. The at least one interdigital transducer 20 is located between the two reflective structures 30.

[0143] At least one of the reflective structures 30 includes a first portion close to one side of the interdigital transducer 20 and a second portion away from the interdigital transducer 20. The first portion includes at least three reflective groups, each reflective group includes a plurality of reflective electrodes arranged at intervals. The distance between the center lines of two adjacent reflective electrodes 32 in the same reflective group is defined as the finger spacing of the reflective group. The ratio between the finger width of a reflective electrode 32 in the same reflective group and the finger spacing of the reflective group is defined as the duty cycle of the reflective group. The duty cycles of at least three reflective groups are the same, and the finger spacings of at least three reflective groups fluctuate.

[0144] It is understandable that in this embodiment, the relevant descriptions of the piezoelectric substrate 10 and the interdigital transducer 20 can refer to the above two embodiments, and, under the premise of no conflict, other features of the reflective structure 30 can also refer to the above two embodiments, which will not be repeated in this application.

[0145] It can be understood that in this embodiment, the reflection electrode 32 on the side of the reflection structure 30 close to the IDT 20 is improved and divided into at least three reflection groups. On the basis of the same duty cycle of each reflection group, the finger spacing of the reflection group close to the IDT 20 side fluctuates, which can be more conducive to reducing the fluctuation near the upper sideband point of the surface acoustic wave resonator 100, thereby improving the working performance of the surface acoustic wave resonator 100.

[0146] It should be understood that, in this embodiment, the description of the fluctuating spacing between the finger strips of at least three reflective groups can also be referred to the above two embodiments, and this application will not elaborate on them here.

[0147] In this embodiment, the second portion includes a plurality of reflective electrodes 32. The distance between two adjacent reflective electrodes 32 in the second portion is defined as the finger pitch of the second portion. The ratio of the finger width of a reflective electrode 32 in the second portion to the finger pitch of the second portion is defined as the duty cycle of the second portion. The duty cycle of the first portion (i.e., the duty cycle of each reflective group) can be the same as or different from the duty cycle of the second portion (i.e., the duty cycle of the reflective electrodes 32 in the second portion).

[0148] In some embodiments, the duty cycle of the second portion is the same as the duty cycle of the first portion, and the finger spacing of at least one reflection group in the first portion is different from the finger spacing of the second portion.

[0149] That is to say, the duty cycle in the reflection structure 30 remains unchanged, and the first part close to the IDT 20 is divided into multiple reflection groups. The finger spacing of each reflection group fluctuates, which is beneficial to reducing the fluctuation near the upper sideband point of the surface acoustic wave resonator 100.

[0150] It can be understood that the finger spacing of the second part remains consistent, and the finger spacing of one reflection group in the first part may be different from the finger spacing of the second part, or the finger spacing of two or more, or even all reflection groups are different from the finger spacing of the second part. This application does not make specific restrictions on this.

[0151] To further understand the present application, the embodiment of the present application will be compared with the comparative example using the impedance diagram and Smith chart of the surface acoustic wave resonator. In the comparative example, the surface acoustic wave resonator does not divide the reflective structure into reflective groups, and the spacing between the finger strips does not fluctuate.

[0152] Please refer to Figure 13, which is a comparison of the real impedance curves of the embodiment of the present application and the comparative example. The horizontal axis represents frequency in GHz, and the vertical axis represents the real impedance in dB. The solid line represents the comparative example, and the dashed line represents the embodiment of the present application. As can be seen from Figure 13, the area indicated by the dashed box represents the upper sideband of the surface acoustic wave resonator. Near this upper sideband (2.65 GHz to 2.7 GHz), the comparative example exhibits significant fluctuations, while the fluctuations at this location are significantly reduced in the embodiment.

[0153] Please refer to Figure 14, which is a Smith circle comparison chart of the embodiment of the present application and the comparative example. The left side of Figure 14 shows the Smith circle comparison chart, while the right side shows a partial enlargement of the portion indicated by the dashed box on the left. The dashed line represents the embodiment of the present application, while the solid line represents the comparative example. Figure 14 shows that near the upper edge frequency of the surface acoustic wave resonator (2.5 GHz to 2.7 GHz), the comparative example has an inward concave curve, while the embodiment is closer to the outside of the circle, resulting in a smoother curve.

[0154] It should be understood that Figures 13 and 14 illustrate only the impedance diagram and Smith chart of a surface acoustic wave resonator. Different surface acoustic wave resonators have different resonant frequencies and thus different upper sidebands. As can be seen from Figures 13 and 14, the embodiments of the present application can reduce fluctuations near the upper sideband of a surface acoustic wave resonator.

[0155] Please refer to Figure 15, which is a schematic diagram of the structure of a filter 200 provided in an embodiment of the present application. As shown in Figure 15, the filter 200 of the present application includes a signal input terminal 201, a signal output terminal 202, a ground port 203 and a plurality of resonators. Among them, a part of the resonators are connected in series between the signal input terminal 201 and the signal output terminal 202, and one end of the other part of the resonators is connected to the ground port 203, and the other end is connected to the series circuit between the signal input terminal 201 and the signal output terminal 202. It can be understood that the mutual series and parallel connection of multiple resonators can realize the filtering function of the filter 200 of the present application for the signal of the preset frequency.

[0156] It is understandable that the filter 200 may further include a dual-mode surface acoustic wave filter, which is connected in series between the signal input terminal 201 and the signal output terminal 202 .

[0157] It is understandable that the filter 200 can be a transmitting filter or a receiving filter, and this application does not make any specific limitation.

[0158] In one embodiment, the filter 200 includes a plurality of series resonators and a plurality of parallel resonators, wherein at least one of the plurality of parallel resonators is the surface acoustic wave resonator 100 in the above embodiment.

[0159] In this embodiment, by improving at least one parallel resonator in the filter 200, for example, improving one of the parallel resonators, or improving all the parallel resonators, so that the finger spacing between each reflection group of its reflection structure fluctuates, the depression in the passband of the filter 200 can be solved and the passband flatness can be improved.

[0160] In one embodiment, the plurality of series resonators include a first series resonator, the difference between the resonant frequency of the first series resonator and the resonant frequency of the parallel resonator is within a preset range, and the first series resonator is the surface acoustic wave resonator 100 in the above embodiment.

[0161] Specifically, the preset range may mean that the resonant frequency of the first series resonator is close to the resonant frequency of the parallel resonator, for example, the resonant frequency difference is within the range of 10 MHz, or within the range of 50 MHz, etc. The resonant frequency of the parallel resonance may be the average resonant frequency of multiple parallel resonators, or the maximum resonant frequency, or the minimum resonant frequency. The first series resonator may be one or more. This application does not impose any specific restrictions on this.

[0162] It can be understood that in the filter 200, the resonant frequency of the series resonator is usually greater than the resonant frequency of the parallel resonator. When there is a first series resonator with a resonant frequency close to that of the parallel resonator in the series resonator, the first series resonator can also be improved so that the finger spacing between each reflection group of its reflection structure fluctuates, which can solve the notch in the passband of the filter 200.

[0163] In another embodiment, the filter 200 includes a plurality of series resonators and a plurality of parallel resonators, wherein at least one of the plurality of series resonators is the surface acoustic wave resonator 100 in the above embodiment.

[0164] In this embodiment, by improving at least one series resonator in the filter 200, for example, improving one of the series resonators, or improving all the series resonators, so that the finger spacing between each reflection group of its reflection structure fluctuates, the out-of-band suppression level and passband rectangularity of the filter 200 can be improved.

[0165] Please refer to Figure 16, which is a schematic diagram of the structure of a multiplexer 300 provided in an embodiment of the present application. As shown in Figure 16, the multiplexer 300 of the present application can be a duplexer or a triplexer, etc., and the multiplexer 300 includes an antenna 301, a transmit filter 200a, and a receive filter 200b. Among them, the transmit filter 200a and the receive filter 200b each include a first port 302 and a second port 303 relative to each other, and the first port 302 of the transmit filter 200a and the receive filter 200b are both communicatively connected to the antenna 301.

[0166] For the transmit filter 200a, the first port 302 is used to transmit signals, and the second port 303 is used to receive signals. For the receive filter 200b, the first port 302 is used to receive signals, and the second port 303 is used to transmit signals.

[0167] When signals with different frequencies are input to the receiving filter 200b and the transmitting filter 200a from the first port 302 and the second port 303, respectively, the receiving filter 200b and the transmitting filter 200a process the signals of the corresponding frequencies and transmit them outward from the second port 303 and the first port 302, respectively. Since the transmitting filter 200a and the receiving filter 200b are spaced apart from each other, it is understandable that the multiplexer 300 of the present application enables the transmitting filter 200a and the receiving filter 200b to operate simultaneously. In other words, the multiplexer 300 of the present application can receive signals and transmit signals at the same time.

[0168] At least one of the transmit filter 200 a and the receive filter 200 b may be the filter 200 described above, thereby improving the operating performance of the multiplexer 300 .

[0169] In one embodiment, the multiplexer 300 includes a first filter and a second filter. The operating frequency band of the first filter is greater than the operating frequency band of the second filter. The second filter is the filter 200 in the above embodiment.

[0170] That is, in this embodiment, the first filter is a receiving filter and the second filter is a transmitting filter. Improving the reflective structure of at least part of the resonators in the transmitting filter can help improve the working performance of the multiplexer 300.

[0171] In a specific embodiment, the reflective structure of at least part of the series resonators in the second filter (ie, the transmitting filter) is improved, which is beneficial to improving the isolation of the receiving filter.

[0172] Please refer to Figure 17, which is a structural diagram of a radio frequency front-end module 400 provided in an embodiment of the present application. As shown in Figure 17, the radio frequency front-end module 400 of the present application includes a signal terminal 401, a switch 402, an amplifier 403 and a filter 200. Among them, the signal terminal 401 is used to receive and transmit external signals. The switch 402 is communicatively connected between the signal terminal 401 and the filter 200 to control the signal transmission between the signal terminal 401 and the filter 200. The filter 200 is used to transmit a signal to the filter 200 and output a signal with a preset frequency. The amplifier 403 is electrically connected to the filter 200 to amplify the signal processed by the filter 200 and output it to the subsequent structure. Among them, the signal terminal 401 can be set as an antenna.

[0173] It is understandable that, in another embodiment, there may be one or more filters 200, and multiple filters 200 may constitute the multiplexer 300. This application does not impose any particular limitation on this.

[0174] The improvement of the reflective structure of the surface acoustic wave resonator in the present application can help improve the working performance of the RF front-end module 400.

[0175] The present application also provides an electronic device including any of the filters described in the above embodiments. It should be understood that the electronic device includes, but is not limited to, intermediate products such as RF front-end modules and filter amplifier modules, and terminal products such as mobile phones, tablet computers, and drones.

[0176] In the present application, by improving at least one reflection structure of a surface acoustic wave resonator, the finger spacing of each reflection group of the reflection structure fluctuates, or the ratio of the finger spacing of a part of the reflection groups to the finger spacing of the interdigital transducer is greater than 1, and the ratio of the finger spacing of a part of the reflection groups to the finger spacing of the interdigital transducer is less than 1, thereby reducing the fluctuation near the upper sideband point of the surface acoustic wave resonator, thereby improving the passband flatness, out-of-band suppression level and rectangularity of the filter, and also improving the isolation of the filter, thereby improving the working performance of the RF front-end module.

[0177] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0178] Those skilled in the art will recognize that any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included in the scope of protection of this application.

Claims

1. A surface acoustic wave resonator, wherein, It includes a piezoelectric substrate, two reflection structures disposed on the piezoelectric substrate, and at least one interdigital transducer, and the at least one interdigital transducer is located between the two reflection structures, wherein, At least one of the reflection structures includes at least three reflection groups, each reflection group includes a plurality of reflection electrodes arranged at intervals, and the distance between the midlines of two adjacent reflection electrodes in the same reflection group is defined as the finger bar pitch of this reflection group, and the finger bar pitches of the at least three reflection groups vary in a fluctuating manner.

2. The surface acoustic wave resonator according to claim 1, wherein, The at least three reflection groups include a first reflection group, a second reflection group, and a third reflection group, the second reflection group is located between the first reflection group and the third reflection group, and the finger bar pitch of the second reflection group is less than or greater than the finger bar pitch of the first reflection group and the finger bar pitch of the third reflection group.

3. The surface acoustic wave resonator according to claim 2, wherein, The at least three reflection groups further include at least one fourth reflection group and / or at least one fifth reflection group; the fourth reflection group is located between the first reflection group and the second reflection group, and the fifth reflection group is located between the second reflection group and the third reflection group; The finger bar pitch of each fourth reflection group is between the finger bar pitch of the first reflection group and the finger bar pitch of the second reflection group; the finger bar pitch of each fifth reflection group is between the finger bar pitch of the second reflection group and the finger bar pitch of the third reflection group.

4. The surface acoustic wave resonator according to claim 3, wherein, Along the arrangement direction from the first reflection group to the second reflection group, there is a first change trend among the finger bar pitches of the at least one fourth reflection group, and the first change trend is the change trend from the finger bar pitch of the first reflection group to the finger bar pitch of the second reflection group; Along the arrangement direction from the second reflection group to the third reflection group, there is a second change trend among the finger bar pitches of the at least one fifth reflection group, and the second change trend is the change trend from the finger bar pitch of the second reflection group to the finger bar pitch of the third reflection group.

5. The surface acoustic wave resonator according to claim 2, wherein, The second reflection group is adjacent to the first reflection group and the third reflection group respectively.

6. The surface acoustic wave device according to claim 2, wherein The finger bar pitch of the first reflection group is the same as the finger bar pitch of the third reflection group.

7. The surface acoustic wave device according to claim 1, wherein, The ratio of the finger bar width of a reflection electrode in the same reflection group to the finger bar pitch of this reflection group is defined as the duty cycle of this reflection group, and the duty cycles of the at least three reflection groups are the same.

8. The surface acoustic wave resonator according to claim 1, wherein, The reflection structure includes a first part close to the interdigital transducer side and a second part far from the interdigital transducer, the first part includes the at least three reflection groups, and the distance between the midlines of two adjacent reflection electrodes in the second part remains consistent.

9. The surface acoustic wave resonator according to claim 1, wherein, At least one of the reflection groups in the at least three reflection groups has an open-circuit reflection electrode, and / or at least one of the reflection groups in the at least three reflection groups has a short-circuit reflection electrode.

10. The surface acoustic wave resonator according to any one of claims 1-9, wherein, The interdigital transducer includes a plurality of interdigital electrodes arranged at intervals, and the distance between the midlines of two adjacent interdigital electrodes is defined as the finger bar pitch of the interdigital transducer; The finger bar pitch of the interdigital transducer is different from the finger bar pitch of at least one of the at least three reflection groups.

11. The surface acoustic wave resonator according to any one of claims 1-9, wherein, The finger bar spacings of the at least three reflection groups vary in a sine function or a cosine function.

12. The surface acoustic wave resonator according to any one of claims 1-9, wherein, The two reflection structures are arranged axially symmetrically with the interdigital transducer as the axis of symmetry.

13. The surface acoustic wave resonator according to any one of claims 1-9, wherein, The ratio between the aperture of the reflection structure and the aperture of the interdigital transducer is in the range of [0.5, 2].

14. The surface acoustic wave resonator according to claim 1, wherein, The surface acoustic wave resonator further includes a temperature compensation layer, which is disposed on the piezoelectric substrate and covers at least the interdigital transducer.

15. The surface acoustic wave resonator according to claim 1, wherein, The surface acoustic wave resonator further includes a passivation layer, which is disposed on the piezoelectric substrate and covers the interdigital transducer and the reflection structure.

16. The surface acoustic wave resonator according to claim 1, wherein, The piezoelectric substrate includes a substrate and a piezoelectric layer stacked, and the reflection structure and the interdigital transducer are located on the side of the piezoelectric layer away from the substrate.

17. A surface acoustic wave resonator, wherein, Comprising a piezoelectric substrate and two reflection structures and at least one interdigital transducer disposed on the piezoelectric substrate, the at least one interdigital transducer is located between the two reflection structures, wherein, The interdigital transducer includes a plurality of interdigital electrodes arranged at intervals, and the distance between the midlines of two adjacent interdigital electrodes is defined as the finger bar spacing of the interdigital transducer; At least one of the reflection structures includes at least one sixth reflection group and at least one seventh reflection group, and each of the sixth reflection group and each of the seventh reflection group includes a plurality of reflection electrodes arranged at intervals, and the distance between the midlines of two adjacent reflection electrodes in the same reflection group is defined as the finger bar spacing of this reflection group; The ratio between the finger bar spacing of the sixth reflection group and the finger bar spacing of the interdigital transducer is greater than 1, and the ratio between the finger bar spacing of the seventh reflection group and the finger bar spacing of the interdigital transducer is less than 1.

18. The surface acoustic wave resonator according to claim 17, wherein, The sixth reflection group and the seventh reflection group are alternately arranged in the arrangement direction of the reflection electrodes.

19. The surface acoustic wave resonator according to claim 17 or 18, wherein The sixth reflection group is closer to the interdigital transducer than the seventh reflection group.

20. The surface acoustic wave resonator according to claim 17 or 18, wherein, The number of the sixth reflection groups is not less than 2, and there is a first envelope between the finger bar spacings of the sixth reflection groups; and / or, the number of the seventh reflection groups is not less than 2, and there is a second envelope between the finger bar spacings of the seventh reflection groups.

21. The surface acoustic wave resonator according to claim 17, wherein, The ratio between the finger bar width of a reflection electrode in the same reflection group and the finger bar spacing of this reflection group is defined as the duty ratio of this reflection group, and the duty ratio of the sixth reflection group is the same as the duty ratio of the seventh reflection group.

22. The surface acoustic wave resonator according to claim 17, wherein, The two reflection structures are axially symmetrically distributed with the interdigital transducer as the axis of symmetry.

23. The surface acoustic wave resonator according to claim 17, wherein, The reflection structure further includes an eighth reflection group, and there is at least one eighth reflection group between the sixth reflection group and the eighth reflection group, and the finger bar spacing of the eighth reflection group is between the finger bar spacing of the sixth reflection group and the finger bar spacing of the seventh reflection group.

24. A surface acoustic wave resonator, wherein, Comprising a piezoelectric substrate and two reflection structures and at least one interdigital transducer disposed on the piezoelectric substrate, the at least one interdigital transducer is located between the two reflection structures, wherein, At least one of the reflection structures includes a first portion near one side of the interdigital transducer and a second portion far from the interdigital transducer. The first portion includes at least three reflection groups, each reflection group includes a plurality of reflection electrodes arranged at intervals. The distance between the midlines of two adjacent reflection electrodes in the same reflection group is defined as the finger pitch of the reflection group. The ratio of the finger width of a reflection electrode in the same reflection group to the finger pitch of the reflection group is defined as the duty cycle of the reflection group. The duty cycles of the at least three reflection groups are the same, and the finger pitches of the at least three reflection groups vary in a fluctuating manner.

25. The surface acoustic wave resonator according to claim 24, wherein, The second portion includes a plurality of reflection electrodes. The duty cycle of the second portion is the same as that of the first portion. The distance between two adjacent reflection electrodes in the second portion is defined as the finger pitch of the second portion. The finger pitch of at least one reflection group in the first portion is different from the finger pitch of the second portion.

26. A filter, wherein, It includes a plurality of series resonators and a plurality of parallel resonators, wherein at least one of the plurality of parallel resonators is a surface acoustic wave resonator as described in any one of claims 1-25.

27. The filter according to claim 26, wherein, The plurality of series resonators includes a first series resonator. The difference between the resonance frequency of the first series resonator and the resonance frequency of the parallel resonator is within a preset range. The first series resonator is a surface acoustic wave resonator as described in any one of claims 1-25.

28. A filter, wherein, It includes a plurality of series resonators and a plurality of parallel resonators, wherein at least one of the plurality of series resonators is a surface acoustic wave resonator as described in any one of claims 1-25.

29. A multiplexer, wherein, It includes a first filter and a second filter. The operating frequency band of the first filter is greater than that of the second filter. The second filter is a filter as described in claim 28.

30. A radio frequency front-end module, wherein, It includes a surface acoustic wave resonator as described in any one of claims 1-25.

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