Surface Acoustic Wave Resonators and Their Design Methods

Abstract

This invention discloses a surface acoustic wave (SAW) resonator and its design method. The SAW resonator includes: two reflectors located on opposite sides; a transducer located between the two reflectors; the transducer is divided into different zones, and at least two of the zones have interdigitated electrodes with different pitches and coverage. The pitch and coverage of the interdigitated electrodes in each zone are set to satisfy the following relationship: for a specified stray mode frequency, the pitch setting causes the stray mode to deviate from the dominant mode frequency by a preset value, thereby suppressing it; and the pitch and coverage settings together maintain the dominant mode at a desired frequency. The above-described SAW resonator and its design method achieve the goal of suppressing stray modes while maintaining the frequency of the dominant mode.

Description

Technical Field

[0001] This invention relates to the field of surface acoustic wave (SAW) resonators, and particularly to a SAW resonator and its design method. Background Technology

[0002] Acoustic resonators are widely used in signal processing in the telecommunications field due to their ability to operate with high precision and stability over a wide frequency range, while also being compact, cost-effective, and efficient. Acoustic devices based on interdigital transducers rely on the interaction between sound waves propagating along the surface of a piezoelectric material. The performance of an acoustic resonator depends on the interaction between these sound waves and the resonator's structural design.

[0003] With the increasing demand for higher frequencies, smaller device sizes, and superior performance, multilayer substrate designs have emerged. These designs add an extra layer beneath the piezoelectric material to enhance the mechanical, thermal, and electrical properties of the device. However, these multilayer structures often introduce unwanted stray modes, stemming from both more pronounced transverse modes and bulk wave reflections at the interface between the piezoelectric layer and the extra substrate layer. These stray modes interfere with the desired acoustic waves, leading to performance degradation, reduced selectivity, and limited operating bandwidth of the acoustic resonator.

[0004] To address these challenges, various techniques have been proposed in the design and fabrication of interdigital transducer-based acoustic resonators to suppress or reduce the influence of stray modes. These techniques include reducing stray mode coupling, matching the excitation shape to the dominant mode shape, dispersion curve engineering, interfering with stray mode conversion, and dissipating stray mode energy. However, many of these techniques, while completely eliminating interference caused by stray modes, struggle to maintain the performance characteristics required by the dominant acoustic mode. Summary of the Invention

[0005] Therefore, it is necessary to provide a surface acoustic wave resonator and its design method to address the problem that it is impossible to simultaneously suppress stray modes and maintain the performance characteristics of the dominant modes.

[0006] A surface acoustic wave resonator, comprising:

[0007] Two reflectors located on opposite sides;

[0008] A transducer located between the two reflectors; the transducer is divided into different zones, and the interdigitated electrodes in at least two of the zones have different pitches and coverage.

[0009] The pitch and coverage settings of the interdigitated electrodes in each partition satisfy the following relationship: for a specified spurious mode frequency, the pitch setting causes the spurious mode to deviate from the main mode frequency by more than a preset value and thus be suppressed, and the pitch and coverage settings together keep the main mode at the expected frequency.

[0010] In one embodiment, the number of partitions within the transducer corresponds to the number of stray modes to be suppressed, and the pitch and coverage of the interdigitated electrodes in each partition correspond to the stray modes to be suppressed.

[0011] In one embodiment, the two reflectors include gate electrodes, and the number of gate electrodes in the two reflectors is the same, which is different from the number of interdigitated electrodes in each partition.

[0012] In one embodiment, the pitch and coverage are the same within the same partition.

[0013] In one embodiment, the resonator includes <110> A cross-sectioned silicon substrate, and a lithium tantalate piezoelectric layer with a YX|42° cross-section on the silicon substrate.

[0014] In one embodiment, the resonator has a single-layer or multi-layer substrate.

[0015] A design method for a surface acoustic wave (SAW) resonator, the SAW resonator comprising two reflectors located on opposite sides and a transducer located between the two reflectors, the transducer comprising interdigitated electrodes, the design method comprising:

[0016] Determine the expected frequency and dominant mode characteristics of the surface acoustic wave resonator;

[0017] Set initial parameters for the pitch and coverage of the interdigital electrodes in the transducer that conform to the expected frequency and main mode characteristics;

[0018] Based on the initial parameters, if there are bulk stray modes that affect the frequency response of the main mode, the pitch of the interdigitated electrodes is adjusted to adjust the bulk stray modes to a frequency far from the expected frequency of the main mode.

[0019] If the frequency of the dominant mode deviates from the expected frequency due to pitch adjustment, the coverage of the interdigitated electrodes is adjusted to bring the frequency of the dominant mode back to the expected frequency.

[0020] In one embodiment, adjusting the pitch of the interdigitated electrodes to adjust the bulk stray modes to a frequency far removed from the expected frequency of the dominant mode includes:

[0021] Set the frequency difference to be adjusted for the stray modes of the body wave;

[0022] The pitch of the interdigital transducer is adjusted according to the frequency difference; wherein the frequency difference of the bulk stray modes and the pitch change of the interdigital transducer satisfy the following relationship:

[0023]

[0024] in: Indicates the frequency difference. This indicates the sensitivity of stray modes to pitch variations. This indicates the pitch adjustment amount.

[0025] In one embodiment, adjusting the coverage of the interdigitated electrodes to adjust the frequency of the dominant mode to the desired frequency includes:

[0026] Obtain the frequency deviation of the main mode caused by pitch adjustment;

[0027] The coverage of the interdigital transducer is adjusted according to the frequency deviation; wherein the frequency deviation of the main mode and the change in the coverage of the interdigital transducer satisfy the following relationship:

[0028]

[0029] in: This indicates the change in the coverage of the interdigital electrodes. This indicates the frequency deviation of the dominant mode. This indicates the sensitivity of the dominant mode to pitch changes. This indicates the sensitivity of the dominant mode to changes in coverage. This indicates the pitch adjustment amount.

[0030] A design method for a surface acoustic wave (SAW) resonator, the SAW resonator comprising two reflectors located on opposite sides and a transducer located between the two reflectors, the transducer comprising interdigitated electrodes, the design method comprising:

[0031] Determine the expected frequency and dominant mode characteristics of the surface acoustic wave resonator;

[0032] Set initial parameters for the pitch and coverage of the interdigital electrodes in the transducer that conform to the expected frequency and main mode characteristics;

[0033] The frequency difference to be adjusted for the stray modes is set according to the adjustment target;

[0034] Adjust the pitch of the interdigital electrodes according to the frequency difference;

[0035] The coverage of the interdigital electrodes is adjusted according to the frequency difference; wherein the coverage and the frequency difference satisfy the following relationship:

[0036]

[0037] in: This indicates the change in the coverage of the interdigital electrodes. This indicates the sensitivity of the dominant mode to pitch changes. This indicates the sensitivity of the dominant mode to changes in electrode coverage. This indicates the sensitivity of stray modes to pitch variations. This represents the frequency difference between stray modes.

[0038] The aforementioned surface acoustic wave resonator and its design method, including the pitch and coverage settings of the interdigitated electrodes of the active transducer, aim to "suppress stray modes and stabilize the dominant mode." Since pitch adjustment has a similar impact on the frequencies of the dominant and stray modes, but coverage adjustment has a much greater impact on the dominant mode than on the stray modes, pitch adjustment first suppresses the response of stray modes at specific frequencies. Although the frequency of the dominant mode deviates at this point, it can be restored by adjusting the coverage, while the stray mode remains unchanged. This achieves the goal of suppressing stray modes while maintaining the frequency of the dominant mode. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the basic structure of a surface acoustic wave resonator according to an embodiment;

[0040] Figure 2 A schematic diagram of the functional partitioning of the electrode layer of a surface acoustic wave resonator according to an embodiment;

[0041] Figure 3 A schematic diagram illustrating the effects of stray modes on a surface acoustic wave resonator;

[0042] Figure 4 This is a schematic diagram of the partitioned structure of the input transducer of a surface acoustic wave resonator according to an embodiment.

[0043] Figure 5 A schematic diagram of the interdigital transducer cell structure parameters of a surface acoustic wave resonator according to an embodiment;

[0044] Figure 6A and Figure 6B These are schematic diagrams illustrating the effects of pitch and coverage adjustments on frequency response.

[0045] Figure 7 This is a schematic diagram of a specific example structure of a surface acoustic wave resonator;

[0046] Figure 8A and Figure 8B These are schematic diagrams comparing simulation and experimental admittance plots;

[0047] Figure 9A flowchart illustrating the design method of a surface acoustic wave resonator according to one embodiment;

[0048] Figure 10 This is a flowchart illustrating the design method of a surface acoustic wave resonator according to another embodiment. Detailed Implementation

[0049] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0051] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, parts, regions, layers, doping types, and / or portions, these elements, parts, regions, layers, doping types, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, part, region, layer, doping type, or portion from another element, part, region, layer, doping type, or portion. Therefore, without departing from the teachings of this invention, the first element, component, region, layer, doping type, or portion discussed below may be represented as a second element, component, region, layer, or portion; for example, the first doping type may be referred to as the second doping type, and similarly, the second doping type may be referred to as the first doping type; the first doping type and the second doping type are different doping types, for example, the first doping type may be P-type and the second doping type may be N-type, or the first doping type may be N-type and the second doping type may be P-type.

[0052] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as “below,” “under,” or “below” will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both above and below orientations. Furthermore, the device may also include other orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptive terms used herein will be interpreted accordingly.

[0053] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, in this specification, the term “and / or” includes any and all combinations of the associated listed items.

[0054] Embodiments of the invention are described herein with reference to cross-sectional views illustrating ideal embodiments (and intermediate structures) of the invention, thus allowing for variations in the illustrated shape due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of the invention should not be limited to the specific shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing techniques. For instance, implantation regions shown as rectangular typically have rounded or curved features at their edges and / or implantation concentration gradients, rather than a binary change from implantation regions to non-implantation regions. Similarly, the buried regions formed by implantation can result in some implantation in the region between the buried region and the surface traversed during implantation. Therefore, the regions shown in the figures are substantially schematic, and their shapes do not represent the actual shapes of regions of the device and do not limit the scope of the invention.

[0055] like Figure 1 As shown, a surface acoustic wave (SAW) resonator is an electronic component that utilizes the propagation characteristics of SAW waves to achieve frequency selection; it can be manufactured using semiconductor processes. A piezoelectric layer 200 and an electrode layer 100 are sequentially formed on a silicon substrate 300. Figure 1 The piezoelectric layer 200 contains multiple unit cells with basic structures, and the repetition of these unit cell structures forms the aforementioned functional layers. Commonly used materials for the piezoelectric layer 200 include quartz and lithium niobate. These materials can undergo mechanical deformation under the influence of an electric field, or generate an electric field through mechanical deformation, thus exhibiting the piezoelectric effect.

[0056] like Figure 2 As shown, according to the direction of sound wave propagation, the electrode layer 100 sequentially defines a reflector 102, an input transducer 104, and an output transducer 106. The input transducer 104 and output transducer 106 each include multiple alternately arranged metal electrodes, connected at their ends to a signal input or signal output terminal via a busbar. These metal electrodes are called interdigitated electrodes, and the spacing between them is related to the wavelength of the surface acoustic wave (SAW) and determines the resonant frequency. Both the input transducer 104 and output transducer 106 can be called active transducers due to their electro-acoustic and acoustic-electric conversion capabilities. When the input transducer 104 is connected to an alternating electric field (input signal), the piezoelectric layer 200 is excited by the electric field, generating mechanical vibrations and forming surface acoustic waves propagating along its surface. The SAW propagates along the piezoelectric layer 200 to the output transducer 106, causing deformation of the piezoelectric layer 200. Through the piezoelectric effect, the mechanical vibration is converted into an alternating electric field (output signal). When the input signal frequency matches the natural frequency of the surface acoustic wave in the piezoelectric layer 200, the system resonates, and the output signal amplitude is significantly enhanced, thereby achieving the selection and filtering of signals at specific frequencies and completing the functions of frequency stabilization or signal gating. The function of the reflector 102 is to reflect the surface acoustic wave back and forth to form a standing wave to enhance the resonance effect.

[0057] like Figure 3 As shown, the stray modes present in the surface acoustic wave resonator affect the frequency response performance of the resonator (spurious modes A / B / C in the figure cause spikes in the admittance diagram). It is necessary to suppress the stray modes without affecting the frequency response performance of the resonator's main modes.

[0058] To achieve this objective, in this embodiment of the application, the input transducer 104 and the output transducer 106 are divided into different partitions, and the interdigitated electrodes in at least two of the partitions have different pitches and coverage.

[0059] The partitioning method of input transducer 104 and output transducer 106 is similar; the explanation will take input transducer 104 as an example. Figure 4 As shown, the input transducer 104 includes interdigitated electrodes arranged in a cross pattern and connected to a busbar at its outer end, through which the input signal is connected. The input transducer 104 is divided into multiple zones, such as zone A, zone B, and zone C. The pitch and coverage of the interdigitated electrodes in at least two zones are different. For example, the pitch and coverage of the interdigitated electrodes in zones A and B are the same, but they are different from those in zone C (the interdigitated electrodes in zone C are more compactly spaced).

[0060] Figure 5 This is a schematic diagram of a unit cell of an interdigital transducer. (Reference) Figure 5In an interdigital transducer, the gap is the distance between two adjacent interdigital fingers (leading from different busbars), and the pitch is the length of the smallest repeating unit in the interdigital electrode arrangement, i.e., the total width of a complete "electrode finger + gap," a parameter describing the periodicity of the interdigital electrode structure. Coverage is the proportion of the width of a single interdigital electrode within a pitch. Different pitch and coverage settings directly affect the frequency characteristics of the resonator. Therefore, different pitch and coverage settings in each section will affect the resonator's ability to suppress different specific stray modes.

[0061] In this embodiment, the pitch and coverage settings are required to meet specific requirements to achieve the suppression effect on spurious modes. That is, for a specified spurious mode frequency, the pitch setting enables the spurious mode to move away from the dominant mode frequency, and the pitch and coverage settings together keep the dominant mode at the expected frequency.

[0062] The pitch and coverage settings of the interdigital electrodes of the input transducer 104 are designed to "suppress stray modes and stabilize the dominant mode." The pitch and coverage settings affect both the dominant and stray modes. Through extensive experiments and calculations, the applicant observed that pitch adjustment has a similar impact on the frequencies of the dominant and stray modes (e.g., ...). Figure 6A (as shown), but the effect of coverage adjustment on the dominant mode is much greater than on the stray modes (such as...). Figure 6B As shown in the figure, the effect is particularly significant on the volume wave stray modes. The effect of coverage adjustment on the volume wave stray modes is negligible. Therefore, the response of the stray modes at a specific frequency can be suppressed first by adjusting the pitch. At this time, although the frequency of the main mode has deviated, the frequency of the main mode can be restored by adjusting the coverage, but the stray modes will not change due to the adjustment of the coverage.

[0063] In practical applications, the pitch and coverage of the surface acoustic wave resonator in this embodiment need to be adjusted according to specific frequency requirements, and are not limited to specific parameters.

[0064] In some embodiments, the number of partitions within the input transducer 104 and the output transducer 106 corresponds to the number of spurious modes to be suppressed, and the pitch and coverage settings of the interdigitated electrodes in each partition correspond to the spurious modes to be suppressed. For example, if the resonator generates two spurious modes (e.g., 1905MHz and 1940MHz) during operation, the transducer needs to be divided into two partitions to address these two types of interference respectively. The pitch and coverage settings of the interdigitated electrodes in each partition also need to be matched to the specific spurious mode to be suppressed. Taking the partition suppressing the 1905MHz spurious mode as an example, the pitch needs to be fine-tuned to the appropriate value to suppress the spurious mode first, while the coverage is set to a suitable value to restore the frequency of the main mode to the expected frequency; while for the partition suppressing the 1940MHz spurious mode, the pitch needs to be adjusted to another value to suppress the spurious mode first, while the coverage is set to a suitable value to restore the frequency of the main mode to the expected frequency, thereby achieving directional suppression.

[0065] In some embodiments, the two reflectors 102 include grid electrodes, and the number of grid electrodes in both reflectors 102 is the same, differing from the number of interdigitated electrodes in each zone. That is, the reflectors 102 are also formed from electrodes similar to those in the input transducer 104 and output transducer 106, referred to as grid electrodes. The number of grid electrodes in the reflectors 102 differs from the interdigitated electrodes in the transducer zone, and the pitch and coverage may also differ. For example, in one example, the two reflectors 102 on each side have 21 grid electrodes, while the middle transducer zone contains 210 interdigitated electrodes. The interdigitated electrodes in the transducer zone can perform electro-acoustic or acoustic-electric conversion, referred to as active transducers. That is, active transducers include the input transducer 104 and the output transducer 106. Using interdigitated electrodes with similar structures in both the reflectors 102 and the active transducers allows for a unified process and simplifies the manufacturing process.

[0066] The following examples illustrate the effect of the resonator described above. In a specific example, such as... Figure 7 As shown, the resonator includes a silicon substrate 300 ( <110> A lithium tantalate piezoelectric layer 200 (YX|42° cross-section) is placed on the silicon substrate 300. The piezoelectric layer 200 has a thickness of 10 μm, and the silicon substrate 300 has a thickness of 675 μm. Each interdigitated electrode consists of a stacked 20 nm titanium layer and a 160 nm aluminum-copper layer. The passivation layer is a 20 nm silicon dioxide layer.

[0067] In this specific example, the active transducer region of the resonator is divided into three sections, each containing 70 interdigitated electrodes. From left to right, the pitches of each section are 1090 nm, 1079 nm, and 1073 nm, with coverages of 40%, 50%, and 60%, respectively, corresponding to electrode widths of 436 nm, 539.5 nm, and 643.8 nm. Each cell within the same section has the same pitch and coverage. The reflector 102 on the left includes 21 gate electrodes with a pitch of 1090 nm and a coverage of 40%, corresponding to an electrode width of 436 nm. The reflector 102 on the right includes 21 gate electrodes with a pitch of 1073 nm and a coverage of 60%, corresponding to an electrode width of 643.8 nm.

[0068] according to Figure 8A The simulated admittance diagrams shown are Figure 8B The experimental admittance plots shown, comparing the admittance frequency responses with and without pitch-coverage adjustment, reveal that the spikes before adjustment become smooth after pitch-coverage adjustment. This indicates that stray modes were effectively suppressed, while the dominant mode did not deviate significantly.

[0069] In the above example, a single-layer substrate is used for illustration. In other embodiments, the substrate may also be a multilayer substrate.

[0070] This application also provides a design method for a surface acoustic wave resonator to obtain the resonator described in the above embodiments. For example... Figure 9 As shown, the method includes:

[0071] S102: Determine the expected frequency and dominant mode characteristics required for the surface acoustic wave resonator.

[0072] S104: Set initial parameters for the pitch and coverage of the interdigitated electrodes in the active transducer that conform to the expected frequency and main mode characteristics.

[0073] S106: Based on the initial parameters, if there are bulk stray modes that affect the frequency response of the main mode, adjust the pitch of the interdigitated electrodes to adjust the bulk stray modes to a frequency far from the expected frequency of the main mode.

[0074] S108: If the frequency of the main mode deviates from the expected frequency due to pitch adjustment, the coverage of the interdigital transducer is adjusted to adjust the frequency of the main mode to the expected frequency.

[0075] In step S102, the expected frequency refers to the target frequency that the resonator needs to output. This parameter is determined by the application scenario of the electronic device. For example, the Bluetooth module of a smartwatch requires low-power, low-frequency signals, and the expected frequency may be set below 1 GHz; while 5G base stations require high-frequency, high-stability signals, and the expected frequency may be as high as 6 GHz or above. The solution of this application has relatively good spurious mode suppression for low-frequency applications.

[0076] In step S104, the pitch and coverage parameters directly determine the frequency and energy of the surface acoustic wave excited by the interdigital transducer, and are key parameters for achieving the expected frequency, dominant mode characteristics, and actual device performance. The propagation speed (v) of the surface acoustic wave is determined by the dominant mode characteristics and the medium material; for example, the propagation speed of Rayleigh waves in a quartz crystal is approximately 3200 m / s. Assuming the expected frequency is 1.8 GHz, the dominant mode is Rayleigh waves, and the propagation speed v = 3200 m / s, the pitch p can be calculated to be approximately 8.89 × 10⁻⁶. -7 m (i.e., 889nm). This is the basis for calculating the initial pitch parameter. Then, adjustments are made based on actual conditions or empirical values. The initial coverage parameter setting needs to comprehensively consider energy conversion efficiency and frequency stability. A larger coverage results in a larger contact area between the electrode and the dielectric, leading to higher energy conversion efficiency for surface acoustic waves. However, excessive coverage can increase the capacitance between the electrodes, affecting frequency stability. Conversely, a smaller coverage results in better frequency stability, but lower energy conversion efficiency. In practical designs, for surface acoustic wave resonators with Rayleigh wave as the dominant mode used in communication equipment, the initial coverage value is typically set between 0.4 and 0.6, ensuring both high energy conversion efficiency and meeting frequency stability requirements.

[0077] In step S106, a bulk stray mode refers to an acoustic signal that does not propagate along the surface of the medium but passes through the entire interior of the medium. This bulk stray mode competes for energy with the dominant mode, causing noise in the frequency response of the dominant mode. The core idea of ​​adjusting the pitch is to adjust the frequency of the bulk stray mode to a range far away from the expected frequency of the dominant mode.

[0078] In one embodiment, adjusting the pitch of the interdigital transducer to adjust the bulk stray modes to frequencies far from the expected frequencies of the dominant modes includes:

[0079] Set the frequency difference to be adjusted for the stray modes;

[0080] The pitch of the interdigital electrodes is adjusted according to the frequency difference; wherein the frequency difference of the stray modes and the pitch change of the interdigital transducer satisfy the following relationship:

[0081]

[0082] in: Indicates the frequency difference. This indicates the sensitivity of stray modes to pitch variations. This indicates the pitch adjustment amount.

[0083] This frequency difference represents the numerical change in frequency at which the stray mode is adjusted, and how far it is from the dominant mode. This frequency difference needs to suppress the stray mode without making subsequent adjustments to the dominant mode difficult to recover. Once the target frequency difference is determined, the desired pitch adjustment can be obtained based on the relationship between the frequency change of the stray mode and the pitch change of the interdigitated electrodes.

[0084] In step S108, since the pitch adjustment simultaneously causes frequency changes in both the dominant mode and the stray mode, in one embodiment, adjusting the coverage of the interdigital transducer to adjust the frequency of the dominant mode to the expected frequency includes:

[0085] Obtain the frequency deviation of the main mode caused by pitch adjustment;

[0086] The coverage of the interdigital transducer is adjusted according to the frequency deviation; wherein the frequency deviation of the dominant mode and the change in the coverage of the interdigital transducer satisfy the following relationship:

[0087]

[0088] in: This indicates the change in the coverage of the interdigital electrodes. This indicates the frequency deviation of the dominant mode. This indicates the sensitivity of the dominant mode to pitch changes. This indicates the sensitivity of the dominant mode to changes in coverage. This indicates the pitch adjustment amount.

[0089] Since the frequency deviation of the main mode is affected by both pitch and coverage, the aforementioned pitch adjustment has already been determined. After obtaining the frequency deviation, the coverage adjustment amount can be calculated using the above formula. The calculated coverage adjustment amount should be assessed based on the actual situation to determine its suitability. If the calculated coverage adjustment amount is unsuitable, the pitch needs to be readjusted, and the above process repeated to obtain a new coverage, until the overall pitch and coverage settings allow the resonator to meet the design requirements. At this point, the pitch and coverage adjustments are complete.

[0090] The design method for the surface acoustic wave resonator described above is a step-by-step adjustment approach. First, the pitch is adjusted to gradually suppress stray modes. Then, the coverage is adjusted based on the frequency deviation of the dominant mode to attempt to restore its frequency. The pitch and coverage are adjusted iteratively, gradually approaching the desired frequency. After these adjustments, the resulting resonator satisfies the requirements of suppressing stray modes while maintaining the dominant mode.

[0091] This application also provides a design method for a surface acoustic wave resonator to obtain the resonator described in the above embodiments. For example... Figure 10 As shown, the method includes the following steps:

[0092] S202: Determine the expected frequency and dominant mode characteristics required for the surface acoustic wave resonator.

[0093] S204: Set initial parameters for the pitch and coverage of the interdigitated electrodes in the active transducer that conform to the expected frequency and main mode characteristics.

[0094] S206: Set the frequency difference to be adjusted for the stray modes according to the adjustment target.

[0095] S208: Adjust the pitch of the interdigital electrodes according to the frequency difference.

[0096] S210: Adjust the coverage of the interdigitated electrodes according to the frequency difference; wherein the coverage and the frequency difference satisfy the following relationship:

[0097]

[0098] in: This indicates the change in the coverage of the interdigital electrodes. This indicates the sensitivity of the dominant mode to pitch changes. This indicates the sensitivity of the dominant mode to changes in electrode coverage. This indicates the sensitivity of stray modes to pitch variations. This represents the frequency difference between stray modes.

[0099] The steps S202-S204 described above are the same as steps S102-S104 in the previous embodiment, and will not be repeated here.

[0100] Starting from step S206, you can first determine the frequency difference of the stray mode to be adjusted, that is, how far the stray mode should be moved from the main mode.

[0101] In step S208, the required adjustment amount for the pitch can be obtained based on the relationship between the frequency change of the spurious frequency and the pitch change. The pitch is then adjusted directly.

[0102] In step S210, the required adjustment amount for coverage can be obtained based on the relationship between spurious frequency changes and coverage changes. Coverage is then directly adjusted. Since the factors influencing coverage changes in the formula include the dominant mode's sensitivity to pitch and coverage, the coverage adjustment amount can be directly obtained based on spurious frequency changes, while simultaneously maintaining the dominant mode. This is because of the following formula:

[0103]

[0104]

[0105] Pitch adjustment amount These are common factors, and the frequency deviation of the main mode must be 0. Synthesizing these factors yields the adjustment formula for step S210.

[0106] The above-described surface acoustic wave resonator design method involves directly pre-determining the frequency difference of stray modes and then directly obtaining the pitch adjustment and coverage adjustment amounts based on theoretical formulas. While the method is similar in principle to the previous embodiment, the adjustment process differs. This adjustment method can also yield a resonator that suppresses stray modes while maintaining the dominant mode frequency.

[0107] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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.

[0108] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A surface acoustic wave resonator, characterized by, The resonator comprises: two reflectors located on opposite sides; a transducer located between the two reflectors; the transducer is divided into different zones, and the interdigital electrodes in at least two of the zones have different pitches and coverages; the coverage is the proportion of the width of a single interdigital electrode in a pitch; the pitches and coverages of the interdigital electrodes in each zone satisfy the following relationship: for a given spurious mode frequency, the pitch is set to cause the spurious mode to deviate from the main mode frequency by more than a predetermined value so as to be suppressed, including adjusting the pitch of the interdigital electrodes to adjust the bulk wave spurious mode to a frequency far from the expected frequency of the main mode, and the pitch and coverage are set together to keep the main mode at the expected frequency, including if the frequency of the main mode deviates from the expected frequency due to pitch adjustment, adjusting the coverage of the interdigital electrodes to adjust the frequency of the main mode to the expected frequency.

2. The surface acoustic wave resonator according to claim 1, characterized by, The number of zones in the transducer corresponds to the number of spurious modes to be suppressed, and the pitch and coverage of the interdigital electrodes in each zone correspond to the spurious modes to be suppressed.

3. The surface acoustic wave resonator according to claim 1, wherein The two reflectors include gate electrodes, and the number of gate electrodes of the two reflectors is the same, and is different from the number of interdigital electrodes in each zone.

4. The surface acoustic wave resonator according to claim 1, wherein The pitch and coverage in the same zone are the same.

5. The surface acoustic wave resonator of claim 1, wherein, The resonator comprises a silicon substrate on a <110> cut surface, and a lithium tantalate piezoelectric layer on a YX|42° cut surface of the silicon substrate.

6. The surface acoustic wave resonator of claim 1, wherein, The resonator has a single-layer or multi-layer substrate.

7. A design method of a surface acoustic wave resonator, the surface acoustic wave resonator comprising two reflectors located on opposite sides and a transducer located between the two reflectors, the transducer comprising interdigital electrodes, the design method comprising: determining the expected frequency and main mode characteristics required by the surface acoustic wave resonator; setting initial parameters of the pitch and coverage of the interdigital electrodes in the transducer that meet the expected frequency and main mode characteristics; based on the initial parameters, if there is a bulk wave spurious mode affecting the frequency response of the main mode, adjusting the pitch of the interdigital electrodes to adjust the bulk wave spurious mode to a frequency far from the expected frequency of the main mode; if the frequency of the main mode deviates from the expected frequency due to pitch adjustment, adjusting the coverage of the interdigital electrodes to adjust the frequency of the main mode to the expected frequency.

8. The design method of a surface acoustic wave resonator according to claim 7, wherein The adjustment of the pitch of the interdigital electrodes to adjust the bulk wave spurious mode to a frequency far from the expected frequency of the main mode comprises: setting the frequency difference to be adjusted by the bulk wave spurious mode; adjusting the pitch of the interdigital transducer according to the frequency difference; wherein the frequency difference of the bulk wave spurious mode and the change of the pitch of the interdigital transducer satisfy the following relationship: wherein: represents the frequency difference, represents the sensitivity of the spurious mode to the pitch variation, represents the pitch adjustment amount.

9. The design method of a surface acoustic wave resonator according to claim 8, wherein The adjustment of the coverage of the interdigital electrodes to adjust the frequency of the main mode to the expected frequency comprises: obtaining the frequency deviation of the main mode caused by adjusting the pitch; adjusting the coverage of the interdigital transducer according to the frequency deviation; wherein the frequency deviation of the main mode and the change of the coverage of the interdigital transducer satisfy the following relationship: wherein: represents a change in the coverage of the interdigital electrode, represents a frequency deviation of the main mode, represents a sensitivity of the main mode to a pitch change, represents a sensitivity of the main mode to a coverage change, represents a pitch adjustment amount.

10. A design method of a surface acoustic wave resonator, the surface acoustic wave resonator comprising two reflectors on opposite sides and a transducer between the two reflectors, the transducer comprising interdigital electrodes, the design method comprising: determining an expected frequency and a main mode characteristic required for the surface acoustic wave resonator; setting initial parameters of a pitch and an overlap of the interdigital electrodes in the transducer in accordance with the expected frequency and the main mode characteristic; setting a frequency difference value to be adjusted for a spurious mode in accordance with an adjustment target; adjusting the pitch of the interdigital electrodes in accordance with the frequency difference value; adjusting the overlap of the interdigital electrodes in accordance with the frequency difference value; wherein the overlap and the frequency difference value satisfy the following relationship: wherein: represents the amount of change in the overlap of the interdigital electrodes, represents the sensitivity of the main mode to the pitch change, represents the sensitivity of the main mode to the change in the overlap of the electrodes, represents the sensitivity of the spurious mode to the pitch change, represents the frequency difference of the spurious mode.

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