A surface acoustic wave resonator and a surface acoustic wave filter

Abstract

The present application relates to the technical field of resonator, and discloses a surface acoustic wave resonator and a surface acoustic wave filter, which comprise a piezoelectric layer, and an interdigital transducer and a reflective grating structure arranged on the piezoelectric layer and arranged along a first direction, the reflective grating structure being located at the side of the interdigital transducer; the reflective grating structure comprises a plurality of unit reflective gratings arranged along the first direction, and the finger strips of each unit reflective grating extend along a second direction; the structure of each unit reflective grating is an interdigital reflective grating, a short-circuit reflective grating or an open-circuit reflective grating; in the reflective grating structure, at least one unit reflective grating is an interdigital reflective grating, and the unit reflective gratings other than the interdigital reflective grating are one or both of a short-circuit reflective grating or an open-circuit reflective grating. The present application can weaken the influence of the longitudinal wave of the surface acoustic wave resonator on the filter passband, reduce the insertion loss, improve the flatness of the filter passband, and realize a surface acoustic wave device with high stability and low loss.

Description

Technical Field

[0001] This invention relates to the field of resonator technology, and more specifically to a surface acoustic wave resonator and a surface acoustic wave filter. Background Technology

[0002] As a core component of modern wireless communication systems, surface acoustic wave (SAW) filters are widely used in 5G RF front-ends, IoT, and satellite communications due to their advantages of high-frequency selectivity, low insertion loss, and miniaturization. With the increasingly complex electromagnetic environment in modern mobile communication systems, the performance requirements for SAW filters are constantly rising.

[0003] In related technologies, surface acoustic wave (SAW) filters use short-circuited reflective gratings on both sides of the interdigital transducer as acoustic mirrors to confine the acoustic waves excited by the interdigital transducer to the region between the two short-circuited reflective gratings. However, existing SAW resonators suffer from parasitic ripples generated by longitudinal wave modes, which deteriorate the filter's passband insertion loss. Related technologies cannot effectively suppress this ripple, leading to increased insertion loss and severely impacting the performance of communication equipment.

[0004] Therefore, a solution is needed to avoid parasitic ripples caused by the longitudinal wave mode of the surface acoustic wave filter and reduce the insertion loss of the surface acoustic wave filter. Summary of the Invention

[0005] This invention provides a surface acoustic wave resonator and a surface acoustic wave filter to solve the problem in related technologies where parasitic ripples generated by longitudinal wave modes in surface acoustic wave filters lead to the deterioration of filter passband insertion loss, which in turn increases insertion loss and seriously affects the performance of communication equipment.

[0006] In a first aspect, the present invention provides a surface acoustic wave resonator, comprising: A piezoelectric layer, and interdigitated transducers and a reflective grating structure arranged along a first direction disposed on the piezoelectric layer, wherein the reflective grating structure is located on the side of the interdigitated transducers; The reflective grating structure includes multiple unit reflective gratings arranged along a first direction, and the fingers of each unit reflective grating extend along a second direction; the structure of each unit reflective grating is an interdigitated reflective grating, a short-circuit reflective grating, or an open-circuit reflective grating; In the reflective grating structure, at least one unit reflective grating is an interdigitated reflective grating, and the other unit reflective gratings are either short-circuit reflective gratings or open-circuit reflective gratings, or both.

[0007] The surface acoustic wave (SAW) resonator provided by this invention has two aspects. Firstly, the reflector grating structure includes multiple unit reflector gratings. By utilizing different types of reflector gratings, the reflected waves from these multiple unit reflector gratings can be superimposed on the longitudinal wave propagation path, achieving multi-level destructive interference at the target longitudinal wave frequency. This effectively suppresses the longitudinal wave resonance peak or shifts the longitudinal wave peak to a frequency band further away from the stopband. Secondly, in the reflector grating structure, at least one unit reflector grating is an interdigital reflector grating. Using the interdigital reflector grating as the core for controlling the longitudinal wave position, it can provide electromechanical coupling reflection. This allows it to combine with short-circuit and / or open-circuit reflector gratings to form a gradient acoustic boundary, effectively adjusting the frequency spacing between the resonator's longitudinal wave and the resonant point. This reduces the impact of the resonator's longitudinal wave on the filter passband, lowers insertion loss, improves the filter passband flatness, and consequently reduces the loss of the SAW device, improving its stability and reliability.

[0008] In one alternative embodiment, the reflective grating structure includes at least one interdigital reflective grating and at least one short-circuit reflective grating, wherein the unit reflective grating closest to the interdigital transducer is the short-circuit reflective grating.

[0009] The surface acoustic wave resonator provided by this invention has a short-circuit reflector grid close to the interdigital transducer, which can suppress strongly excited low-frequency longitudinal waves, provide an equipotential boundary, and not interfere with the main electric field of the interdigital transducer. The interdigital reflector grid is located on the side of the short-circuit reflector grid facing away from the interdigital transducer, which can perform precise phase matching for the target longitudinal wave frequency point to the right of the anti-resonance point. The short-circuit reflector grid and the interdigital reflector grid can form a layered boundary, change the reflection path and standing wave mode of the longitudinal wave, cause the longitudinal wave resonant frequency to shift, and at the same time reduce its Q value and amplitude.

[0010] In one alternative implementation, along the direction away from the interdigital transducer, the unit reflective gratings at the beginning and end of the reflective grating structure are both short-circuit reflective gratings; the middle region of the reflective grating structure is configured with at least one interdigital reflective grating.

[0011] The surface acoustic wave (SAW) resonator provided by this invention has at least one interdigitated reflector in the middle region of the reflector grating structure, which serves as the core for controlling the position of the longitudinal wave and amplifying the reflection or suppression of longitudinal waves at a specific frequency. The unit reflectors at the beginning and end of the reflector grating structure are all short-circuit reflectors, which can form equipotential electrical boundaries before and after phase matching of the interdigitated reflectors. Multiple reflector units form multi-layered gradient acoustic boundaries, which can adjust the frequency spacing between the resonator's longitudinal wave and the resonant point, reduce the influence of the resonator's longitudinal wave on the filter passband, reduce insertion loss, improve the passband flatness of the filter, and thus reduce the loss of the SAW device and improve the stability and reliability of the SAW device.

[0012] In one alternative embodiment, along the direction away from the interdigital transducer, the reflective grating structure sequentially includes a short-circuit reflective grating, a plurality of interdigital reflective gratings, and another short-circuit reflective grating, wherein the periods of the plurality of interdigital reflective gratings are all different.

[0013] The surface acoustic wave (SAW) resonator provided by this invention has multiple interdigitated reflective gratings arranged between two short-circuit reflective gratings. By controlling the periods of the multiple interdigitated reflective gratings to be different, the frequency spacing between the longitudinal wave of the resonator and the resonant point can be further adjusted, the influence of the longitudinal wave of the resonator on the passband of the filter can be reduced, the insertion loss can be further reduced, the passband flatness of the filter can be improved, and thus the loss of the SAW device can be reduced, and the stability and reliability of the SAW device can be improved.

[0014] In one optional embodiment, the reflective grating structure includes at least one interdigital reflective grating, at least one short-circuit reflective grating, and at least one open-circuit reflective grating, wherein the unit reflective grating closest to the interdigital transducer is the short-circuit reflective grating. Along the direction away from the interdigital transducer, the reflective grating structure sequentially includes a short-circuit reflective grating, an interdigital reflective grating, and an open-circuit reflective grating to form a gradient acoustic boundary; The electric field reflection phase of an open-circuit reflector is opposite to that of a short-circuit reflector.

[0015] The surface acoustic wave resonator provided by this invention has a short-circuit reflector grid close to the interdigital transducer, which can suppress strongly excited low-frequency longitudinal waves, provide an equipotential boundary, and not interfere with the main electric field of the interdigital transducer. The interdigital reflector grid is located on the side of the short-circuit reflector grid facing away from the interdigital transducer, which can perform precise phase matching for the target longitudinal wave frequency point to the right of the anti-resonance point. The open-circuit reflector grid is located on the outermost side, and the phase difference between the open-circuit reflector grid and the first two types of reflector grids is used to perform secondary peak cancellation or frequency shifting of the residual high-frequency longitudinal waves. The short-circuit reflector grid, interdigital reflector grid, and open-circuit reflector grid can form a gradient acoustic boundary, realize multi-level destructive interference at the target longitudinal wave frequency, further change the reflection path and standing wave mode of the longitudinal wave, effectively suppress the longitudinal wave resonance peak, and shift the longitudinal wave resonance frequency away from the resonance point, which can simultaneously reduce its Q value and amplitude.

[0016] In one alternative embodiment, the reflective grating structure includes five unit reflective gratings along the direction away from the interdigital transducer, and the reflective grating structure sequentially includes a short-circuit reflective grating, an interdigital reflective grating, an open-circuit reflective grating, an interdigital reflective grating, and a short-circuit reflective grating.

[0017] The surface acoustic wave resonator provided by this invention comprises a reflector grating structure sequentially consisting of a short-circuit reflector grating, an interdigitated reflector grating, an open-circuit reflector grating, another interdigitated reflector grating, and a short-circuit reflector grating. The short-circuit reflector grating is positioned at the innermost and outermost edges to suppress strongly excited low-frequency longitudinal waves and provide an equipotential boundary. The interdigitated reflector grating is located on the side of the short-circuit reflector grating facing away from the interdigitated transducer, enabling precise phase matching for the target longitudinal wave frequency to the right of the anti-resonance point. The open-circuit reflector grating is located in the middle, forming a floating electrical boundary. It can combine with the interdigitated and open-circuit reflector gratings on both sides to create a phase difference, performing secondary peak reduction or frequency shifting for high-frequency longitudinal waves. The five unit reflector gratings can form a multi-boundary gradient acoustic boundary, achieving multi-level destructive interference at the target longitudinal wave frequency, further increasing the frequency spacing between the resonator's longitudinal wave and the resonant point, reducing the impact of the resonator's longitudinal wave on the filter passband, and lowering insertion loss.

[0018] In one alternative implementation, at least two unit reflective gratings have different combinations of parameters; the parameter combinations include one or more of the following: period, aperture, duty cycle, finger material, and finger thickness.

[0019] The surface acoustic wave resonator provided by this invention superimposes the reflected waves of multiple three types of gratings on the longitudinal wave propagation path. By precisely designing the spacing, period, and duty cycle of each reflecting grating unit, multi-level destructive interference can be achieved at the target longitudinal wave frequency, which can effectively suppress the longitudinal wave resonance peak or shift the longitudinal wave peak to a frequency band further away from the stopband.

[0020] In one optional embodiment, the interdigitated reflector includes a plurality of third finger strips and a plurality of fourth finger strips alternately spaced along a first direction, and a third busbar and a fourth busbar disposed opposite to each other along a second direction; the starting end of the third finger strip is connected to the third busbar and the ending end is close to the fourth busbar; the starting end of the fourth finger strip is connected to the fourth busbar and the ending end is close to the third busbar. The short-circuit reflector includes a plurality of fifth finger strips spaced apart along a first direction, and a fifth bus bar and a sixth bus bar arranged opposite to each other along a second direction; the starting end of the fifth finger strip is connected to the fifth bus bar and the ending end is connected to the sixth bus bar; The open-circuit reflective grid includes a plurality of sixth finger strips spaced apart along a first direction.

[0021] In one alternative implementation, each unit reflector is interconnected with the other unit via a target busbar on the same side along a first direction; Alternatively, each unit reflective grating is interconnected on both sides along the first direction via target busbars; Alternatively, each unit reflector grid is alternately connected to the adjacent unit reflector grid via a target busbar along a first side or a second side of a first direction.

[0022] The surface acoustic wave resonator provided by this invention allows adjacent reflector grid units in the reflector grid structure to be connected via single-sided target busbars, double-sided target busbars, or alternating connections. Different connection methods can alter the electric field boundary conditions, improving the longitudinal wave suppression effect and thus reducing the influence of longitudinal waves and lowering device insertion loss. Furthermore, different connection methods can be selected according to requirements to specifically modify the electric field boundary conditions, improving design flexibility and allowing for precise adjustment of the degree and position of longitudinal wave offset.

[0023] In a second aspect, the present invention provides a surface acoustic wave filter, including the surface acoustic wave resonator of the first aspect above or any corresponding embodiment thereof. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a top view schematic diagram of the structure of a surface acoustic wave resonator based on related technologies; Figure 2 This is a top view schematic diagram of the structure of a surface acoustic wave resonator according to an embodiment of the present invention; Figure 3 This is a top view schematic diagram of the reflector grating structure in another surface acoustic wave resonator according to an embodiment of the present invention; Figure 4 This is a top view schematic diagram of a reflective grating structure in another surface acoustic wave resonator according to an embodiment of the present invention; Figure 5 This is a top view schematic diagram of a reflective grating structure in a surface acoustic wave resonator according to an embodiment of the present invention; Figure 6 This is a top view schematic diagram of the reflector grating structure in a surface acoustic wave resonator according to Example 1 of the present invention; Figure 7 This is a schematic diagram of the topology of the surface acoustic wave filter tested in Example 1 and Comparative Example 1 according to the present invention. Figure 8 This is a schematic diagram comparing the admittance curves of the surface acoustic wave filters of Example 1 and Comparative Example 1 according to the present invention. Figure 9 This is a schematic diagram comparing the real part of the admittance curves of the surface acoustic wave filter in Example 1 and Comparative Example 1 according to the present invention. Figure 10This is a schematic diagram comparing the insertion loss curves of the surface acoustic wave filters of Example 1 and Comparative Example 1 according to the present invention.

[0026] Figure label: 100. Interdigitated transducer; 200. Reflective grating structure; 201. Interdigitated reflective grating; 202. Short-circuit reflective grating; 203. Open-circuit reflective grating; 300. Piezoelectric layer; 11. First finger bar; 12. Second finger bar; 13. Third finger bar; 14. Fourth finger bar; 15. Fifth finger bar; 16. Sixth finger bar; 21. First bus bar; 22. Second bus bar; 23. Third bus bar; 24. Fourth bus bar; 25. Fifth bus bar; 26. Sixth bus bar; 30. Target bus bar. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the invention and not all structures. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0028] In the following description, descriptions of well-known structures and techniques are omitted to avoid unnecessarily obscuring the concepts of the present invention. Various structural schematic diagrams according to embodiments of the present invention are shown in the accompanying drawings. These drawings are not to scale, and some details are enlarged for clarity, and some details may be omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed. In the context of the present invention, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intermediate layer / element between them. Additionally, if a layer / element is "on" another layer / element in one orientation, then when the orientation is reversed, the layer / element may be "below" the other layer / element.

[0029] With the continuous evolution of mobile communication technology, the number of communication frequency bands has shown a significant growth trend. In order to improve the ability of mobile communication devices to support multiple communication standards, the demand for filters in 5G communication devices has increased dramatically, and this trend has strongly promoted the vigorous development of the filter market.

[0030] Surface acoustic wave (SAW) filters, as core components of modern wireless communication systems, are widely used in 5G RF front-ends, IoT, and satellite communications due to their advantages of high-frequency selectivity, low insertion loss, and miniaturization. With the increasingly complex electromagnetic environment in modern mobile communication systems, the performance requirements for SAW filters are constantly rising.

[0031] Current surface acoustic wave resonator structures are as follows: Figure 1 As shown, the surface acoustic wave (SAW) resonator includes an interdigital transducer 2 and a reflective grating 3 located above the piezoelectric layer 1. The reflective gratings 3 on both sides of the interdigital transducer are short-circuit reflective gratings. This SAW resonator generates parasitic ripples excited by the longitudinal wave mode, which leads to the deterioration of the filter's passband insertion loss. This results in ripples appearing in the passband of the SAW device due to longitudinal wave excitation, thereby increasing the insertion loss and affecting the performance of communication equipment. Related technologies cannot effectively suppress this ripple.

[0032] Therefore, a solution is needed to avoid parasitic ripples caused by the longitudinal wave mode of the surface acoustic wave filter and reduce the insertion loss of the surface acoustic wave filter.

[0033] This invention provides a design method for a surface acoustic wave resonator, which can effectively adjust the frequency spacing between the longitudinal wave and the resonant point, reduce the influence of the longitudinal wave on the filter passband, reduce insertion loss, improve the passband flatness of the filter, and realize a surface acoustic wave device with high stability and low loss.

[0034] like Figure 2 As shown, this embodiment provides a surface acoustic wave resonator, including: The piezoelectric layer 300, and the interdigital transducer 100 and the reflective grating structure 200 disposed on the piezoelectric layer 300, wherein the reflective grating structure 200 is located on the side of the interdigital transducer 100. The reflective grating structure 200 includes a plurality of unit reflective gratings arranged along a first direction, and the fingers of each unit reflective grating extend along a second direction; the structure of each unit reflective grating is an interdigitated reflective grating 201, a short-circuited reflective grating 202, or an open-circuit reflective grating 203; In the reflective grating structure 200, at least one unit reflective grating is an interdigitated reflective grating 201, and the unit reflective gratings other than the interdigitated reflective grating 201 are one or both of short-circuit reflective grating 202 or open-circuit reflective grating 203.

[0035] In practice, by combining different types of unit reflective gratings, multi-level destructive interference can be achieved at the target longitudinal wave frequency, which can effectively suppress the longitudinal wave resonance peak and shift the longitudinal wave peak to a frequency band further away from the stopband, increase the frequency spacing between the longitudinal wave and the resonance point, and reduce the impact of the longitudinal wave on the filter passband.

[0036] Specifically, the reflection of surface acoustic waves by the interdigitated reflector 201 is a superposition of electromechanical coupling and mechanical load effects, resulting in more complex reflection intensity and phase characteristics. It is the only reflection structure that combines strong electromechanical coupling and frequency selectivity, making it the core component for controlling the position of longitudinal waves. The interdigitated reflector 201 can provide electromechanical coupling reflection, possessing strong electromechanical coupling that can amplify or suppress the reflection of longitudinal waves at specific frequencies. The reflection of surface acoustic waves by the short-circuit reflector 202 mainly originates from the mechanical load effect; that is, the local acoustic impedance can be changed through the fingers, while the constraint effect on the electric field is relatively weak, forming an equipotential electrical boundary. The reflection of surface acoustic waves by the open-circuit reflector 203 is a charge-bound reflection and mechanical load. Its electric field reflection phase is opposite to that of the short-circuit reflector 202, introducing an additional phase difference and forming a floating electrical boundary.

[0037] The reflector structure 200 includes at least an interdigital reflector 201, and also includes one or both of an open-circuit reflector 203 and a short-circuit reflector 202. It utilizes the strong electromechanical coupling of the interdigital reflector 201 to generate reflection, amplifying or suppressing the reflection of longitudinal waves at a specific frequency. Simultaneously, it uses the short-circuit reflector 202 to form an equipotential electrical boundary, and / or uses the open-circuit reflector 203 to form a floating electrical boundary, creating a gradient acoustic boundary. This adjusts the frequency spacing between the resonator's longitudinal wave and the resonant point, reducing the impact of the resonator's longitudinal wave on the filter's passband. Furthermore, the electric field reflection phases of the short-circuit reflector 202 and the open-circuit reflector 203 are opposite, both of which can be used to cancel the additional reflections of the interdigital reflector 201 in non-target frequency bands, avoiding the introduction of new parasitic resonances. Specifically, the short-circuit reflector 202 and / or the open-circuit reflector 203 are configured according to requirements.

[0038] The surface acoustic wave (SAW) resonator provided in this embodiment has two main aspects. Firstly, the reflector grating structure 200 includes multiple unit reflector gratings. By utilizing different types of reflector gratings, the reflected waves from these multiple unit reflector gratings can be superimposed on the longitudinal wave propagation path, achieving multi-level destructive interference at the target longitudinal wave frequency. This effectively suppresses the longitudinal wave resonance peak and shifts it to a frequency band further away from the stopband. Secondly, in the reflector grating structure 200, at least one unit reflector grating is an interdigital reflector grating 201. Using the interdigital reflector grating 201 as the core for controlling the longitudinal wave position, it can provide electromechanical coupling reflection. This allows it to combine with the short-circuit reflector grating 202 and / or the open-circuit reflector grating 203 to form a gradient acoustic boundary, effectively adjusting the frequency spacing between the resonator's longitudinal wave and the resonant point. This reduces the impact of the resonator's longitudinal wave on the filter passband, lowers insertion loss, improves the filter passband flatness, and consequently reduces the loss of the SAW device, thereby improving its stability and reliability.

[0039] In some alternative embodiments, the first direction is the extension direction of the busbars in the interdigital transducer 100 and the reflective grating structure 200, which is also the propagation direction of the surface acoustic wave. The second direction is the extension direction of the electrode fingers in the interdigital transducer 100 and the reflective grating structure 200.

[0040] In some alternative implementations, such as Figure 2 As shown, an interdigital transducer 100 and two reflective grating structures 200 are arranged alternately along a first direction on the piezoelectric layer 300; the interdigital transducer 100 is located between the two reflective grating structures 200.

[0041] In some alternative implementations, the two reflective grating structures 200 on both sides of the interdigital transducer 100 are symmetrically arranged.

[0042] In some alternative implementations, such as Figure 2 As shown, the interdigital transducer 100 includes a plurality of first finger strips 11 and a plurality of second finger strips 12 alternately spaced along a first direction, and a first busbar 21 and a second busbar 22 arranged opposite to each other along a second direction; the starting end of the first finger strip 11 is connected to the first busbar 21 and the ending end is close to the second busbar 22; the starting end of the second finger strip 12 is connected to the second busbar 22 and the ending end is close to the first busbar 21; In some alternative implementations, such as Figure 2 As shown, the interdigitated reflector 201 includes a plurality of third finger strips 13 and a plurality of fourth finger strips 14 alternately spaced along a first direction, and a third busbar 23 and a fourth busbar 24 arranged opposite to each other along a second direction; the starting end of the third finger strip 13 is connected to the third busbar 23 and the ending end is close to the fourth busbar 24; the starting end of the fourth finger strip 14 is connected to the fourth busbar 24 and the ending end is close to the third busbar 23.

[0043] In some alternative implementations, such as Figure 2 As shown, the short-circuit reflector 202 includes a plurality of fifth finger strips 15 spaced apart along a first direction, and a fifth busbar 25 disposed opposite to each other along a second direction; the starting end of the fifth finger strip 15 is connected to the fifth busbar 25 and the ending end is connected to the sixth busbar 26.

[0044] In some alternative implementations, such as Figure 2 As shown, the open-circuit reflective grid 203 includes a plurality of sixth fingers 16 that are alternately spaced along a first direction.

[0045] In some alternative implementations, such as Figures 2-6 As shown, the reflective grating structure 200 includes at least one interdigital reflective grating 201 and at least one short-circuit reflective grating 202, wherein the unit reflective grating closest to the interdigital transducer 100 is the short-circuit reflective grating 202.

[0046] In practice, the phase of the short-circuit reflector 202 is clean and stable, serving as the reference for the entire reflection system. It is used to cancel the extra reflections of the interdigital reflector 201 in the non-target frequency band, without introducing additional parasitic modes and protecting the main resonance.

[0047] The surface acoustic wave resonator provided in this embodiment has a short-circuit reflector 202 close to the interdigital transducer 100, which can suppress strongly excited low-frequency longitudinal waves, provide an equipotential boundary, and not interfere with the main electric field of the interdigital transducer 100. The interdigital reflector 201 is located on the side of the short-circuit reflector 202 away from the interdigital transducer 100, which can perform precise phase matching for the target longitudinal wave frequency point to the right of the anti-resonance point. The short-circuit reflector 202 and the interdigital reflector 201 can form a layered boundary, change the reflection path and standing wave mode of the longitudinal wave, cause the longitudinal wave resonant frequency to shift, and reduce its Q value and amplitude.

[0048] In some alternative implementations, such as Figure 2 As shown, the reflective grating structure 200 includes at least one interdigital reflective grating 201, at least one short-circuit reflective grating 202, and at least one open-circuit reflective grating 203, wherein the unit reflective grating closest to the interdigital transducer 100 is the short-circuit reflective grating 202; along the direction away from the interdigital transducer 100, the reflective grating structure 200 sequentially includes the short-circuit reflective grating 202, the interdigital reflective grating 201, and the open-circuit reflective grating 203 to form a gradient acoustic boundary; the electric field reflection phase of the open-circuit reflective grating 203 is opposite to the electric field reflection phase of the short-circuit reflective grating 202.

[0049] The surface acoustic wave resonator provided in this embodiment has a short-circuit reflector 202 located near the interdigital transducer 100, which can suppress strongly excited low-frequency longitudinal waves, provide an equipotential boundary, and not interfere with the main electric field of the interdigital transducer 100. The interdigital reflector 201 is located on the side of the short-circuit reflector 202 facing away from the interdigital transducer 100, which can perform precise phase matching for the target longitudinal wave frequency point to the right of the anti-resonance point. The open-circuit reflector 203 is located on the outermost side, and the phase difference between the open-circuit reflector 203 and the first two reflectors is used to perform secondary peak cancellation or frequency shifting of the residual high-frequency longitudinal wave. The short-circuit reflector 202, interdigital reflector 201, and open-circuit reflector 203 can form a gradient acoustic boundary, realize multi-level destructive interference at the target longitudinal wave frequency, further change the reflection path and standing wave mode of the longitudinal wave, effectively suppress the longitudinal wave resonance peak, and shift the longitudinal wave resonance frequency away from the resonance point, which can simultaneously reduce its Q value and amplitude.

[0050] In some alternative implementations, such as Figure 3 As shown, the reflective grating structure 200 includes five unit reflective gratings. Along the direction away from the interdigital transducer 100, the reflective grating structure 200 sequentially includes a short-circuit reflective grating 202, an interdigital reflective grating 201, an open-circuit reflective grating 203, an interdigital reflective grating 201, and a short-circuit reflective grating 202.

[0051] Specifically, Figure 3 The two reflective grating structures 200 on both sides of the interdigital transducer 100 are symmetrically arranged. The reflective grating structure 200 on the left side of the interdigital transducer 100 is symmetrical to the reflective grating structure 200 on the right side. For ease of explanation, the reflective grating structure 200 on the left side of the interdigital transducer 100 is simplified here.

[0052] The surface acoustic wave resonator provided in this embodiment includes a reflector grating structure 200 comprising, in sequence, a short-circuit reflector grating 202, an interdigital reflector grating 201, an open-circuit reflector grating 203, another interdigital reflector grating 201, and a short-circuit reflector grating 202. The short-circuit reflector grating 202 is positioned at the innermost and outermost edges to suppress strongly excited low-frequency longitudinal waves and provide an equipotential boundary. The interdigital reflector grating 201 is located on the side of the short-circuit reflector grating 202 facing away from the interdigital transducer 100, enabling precise phase matching for the target longitudinal wave frequency to the right of the anti-resonance point. The open-circuit reflector grating 203 is located in the middle, forming a floating electrical boundary. It can combine with the interdigital reflector gratings 201 and 203 on both sides to form a phase difference, performing secondary peak reduction or frequency shifting for high-frequency longitudinal waves. The five unit reflector gratings can form a multi-boundary gradient acoustic boundary, achieving multi-level destructive interference at the target longitudinal wave frequency, further increasing the frequency spacing between the resonator's longitudinal wave and the resonant point, reducing the influence of the resonator's longitudinal wave on the filter passband, and lowering insertion loss.

[0053] In some alternative implementations, such as Figure 4 , Figure 5 and Figure 6 As shown, along the direction away from the interdigital transducer 100, the unit reflective grids at the start and end of the reflective grid structure 200 are both short-circuit reflective grids 202; the middle region of the reflective grid structure 200 is configured with at least one interdigital reflective grid 201.

[0054] The surface acoustic wave (SAW) resonator provided in this embodiment has at least one interdigital reflector 201 in the middle region of the reflector grating structure 200, which serves as the core for controlling the position of the longitudinal wave and amplifying the reflection or suppression of longitudinal waves at a specific frequency. The unit reflectors at the beginning and end of the reflector grating structure 200 are all short-circuit reflectors 202, which can form an equipotential electrical boundary before and after phase matching of the interdigital reflectors 201. Multiple reflector units form a multi-layered gradient acoustic boundary, which can adjust the frequency spacing between the resonator's longitudinal wave and the resonant point, reduce the influence of the resonator's longitudinal wave on the filter passband, reduce insertion loss, improve the passband flatness of the filter, thereby reducing the loss of the SAW device and improving the stability and reliability of the SAW device.

[0055] In some alternative implementations, such as Figure 4As shown, along the direction away from the interdigital transducer 100, the reflective grating structure 200 sequentially includes a short-circuit reflective grating 202, an interdigital reflective grating 201, and a short-circuit reflective grating 202.

[0056] In some alternative implementations, such as Figure 5 and Figure 6 As shown, along the direction away from the interdigital transducer 100, the reflective grating structure 200 sequentially includes a short-circuit reflective grating 202, a plurality of interdigital reflective gratings 201, and a short-circuit reflective grating 202, and the periods of the plurality of interdigital reflective gratings 201 are all different.

[0057] The surface acoustic wave resonator provided in this embodiment has multiple interdigitated reflective gratings 201 disposed between two short-circuit reflective gratings 202. By controlling that the periods of the multiple interdigitated reflective gratings 201 are all different, the frequency spacing between the longitudinal wave of the resonator and the resonant point can be further adjusted, the influence of the longitudinal wave of the resonator on the passband of the filter can be weakened, the insertion loss can be further reduced, the passband flatness of the filter can be improved, and thus the loss of the surface acoustic wave device can be reduced, and the stability and reliability of the surface acoustic wave device can be improved.

[0058] In some alternative implementations, such as Figure 5 As shown, along the direction away from the interdigital transducer 100, the reflective grating structure 200 sequentially includes a short-circuit reflective grating 202, two interdigital reflective gratings 201, and a short-circuit reflective grating 202, with the periods of the two interdigital reflective gratings 201 being different.

[0059] In some alternative implementations, such as Figure 6 As shown, along the direction away from the interdigital transducer 100, the reflective grating structure 200 sequentially includes a short-circuit reflective grating 202, three interdigital reflective gratings 201, and a short-circuit reflective grating 202, with the three interdigital reflective gratings 201 having different periods.

[0060] In some alternative implementations, at least two unit reflective gratings have different combinations of parameters; these combinations include one or more of the following: period, aperture, duty cycle, finger material, and finger thickness.

[0061] The surface acoustic wave resonator provided in this embodiment superimposes the reflected waves of multiple three types of gratings on the longitudinal wave propagation path. By precisely designing the spacing, period, and duty cycle of each reflective grating unit, multi-level destructive interference can be achieved at the target longitudinal wave frequency, which can effectively suppress the longitudinal wave resonance peak or shift the longitudinal wave peak to a frequency band further away from the stopband.

[0062] In some alternative implementations, such as Figure 3 As shown, each unit reflector is interconnected on the same side along the first direction via a target busbar.

[0063] In specific implementation, such as Figure 3 As shown, along the first direction, multiple unit reflective gratings are interconnected on the same side via target busbars.

[0064] In some alternative implementations, such as Figure 3 As shown, the reflector structure 200 includes at least one interdigital reflector 201 and at least one short-circuit reflector 202; each interdigital reflector 201 and each short-circuit reflector 202 are interconnected by a target busbar 30 on the same side along a first direction.

[0065] In specific implementation, Figure 3 In the direction away from the interdigital transducer 100, the busbars on the lower side of each interdigital reflector 201 and short-circuit reflector 202 are connected through the target busbar 30. That is, the third busbar 23 and the fifth busbar 25 are connected through the target busbar 30. The electric field boundary conditions can be changed according to the requirements, thereby improving the design flexibility and precisely adjusting the degree and position of the longitudinal wave offset.

[0066] In some alternative implementations, such as Figure 4 As shown, each unit reflector is interconnected on both sides along the first direction via target busbars.

[0067] In specific implementation, such as Figure 4 As shown, along the first direction, the two sides of the multiple unit reflective gratings are interconnected by target busbars. Specifically, each unit reflective grating eye includes a first side and a second side that are opposite to each other along the first direction; along the first direction, the first sides of the multiple unit reflective gratings are interconnected by target busbars, and the second sides of the multiple unit reflective gratings are interconnected by target busbars.

[0068] In some alternative implementations, such as Figure 4 As shown, the reflective grid structure 200 includes at least one interdigital reflective grid 201 and at least one short-circuit reflective grid 202; the busbars on both sides of each interdigital reflective grid 201 and each short-circuit reflective grid 202 along the first direction are interconnected through target busbars 30.

[0069] In specific implementation, Figure 4 In the direction away from the interdigital transducer 100, the busbars on the lower side of each interdigital reflector 201 and each short-circuit reflector 202 are connected through the target busbar 30, and the busbars on the upper side of each interdigital reflector 201 and each short-circuit reflector 202 are also connected through the target busbar 30. That is, the third busbar 23 and the fifth busbar 25 are connected through the target busbar 30, and the fourth busbar 24 and the sixth busbar 26 are connected through the target busbar 30. The electric field boundary conditions can be changed according to requirements, thereby improving design flexibility and precisely adjusting the degree and position of the longitudinal wave offset.

[0070] In some alternative implementations, such as Figure 5 As shown, each unit reflector is alternately connected to its adjacent unit reflector via a target busbar along a first side or a second side of a first direction. Multiple unit reflectors are alternately connected via target busbars along a first side and a second side of a first direction.

[0071] In specific implementation, Figure 5 In the direction away from the interdigital transducer 100, the reflective grating structure 200 sequentially includes a first short-circuit reflective grating 202, two interdigital reflective gratings 201, and a second short-circuit reflective grating 202. The first side is... Figure 5 The upper side of the middle, the second side is Figure 5 The first short-circuit reflector 202 and the first interdigital reflector 201 are connected on the upper side via the target bus 30, the first interdigital reflector 201 and the second interdigital reflector 201 are connected on the lower side via the target bus 30, and the second interdigital reflector 201 and the second short-circuit reflector 202 are connected on the lower side via the target bus 30. That is, the sixth bus 26 of the first short-circuit reflector 202 and the fourth bus 24 of the first interdigital reflector 201 are connected via the target bus 30, the third bus 23 of the first interdigital reflector 201 and the third bus 23 of the second interdigital reflector 201 are connected via the target bus 30, and the fourth bus 24 of the second interdigital reflector 201 and the sixth bus 26 of the second short-circuit reflector 202 are connected via the target bus 30.

[0072] The surface acoustic wave resonator provided in this embodiment allows adjacent reflector grid units in the reflector grid structure to be connected via single-sided target busbars, double-sided target busbars, or alternating connections. Different connection methods can alter the electric field boundary conditions, improving the longitudinal wave suppression effect and thus reducing the influence of longitudinal waves and lowering device insertion loss. Furthermore, different connection methods can be selected according to requirements to specifically modify the electric field boundary conditions, improving design flexibility and allowing for precise adjustment of the degree and position of longitudinal wave offset.

[0073] In some alternative implementations, such as Figure 5 As shown, the interdigital reflector 201 and the short-circuit reflectors 202 on both sides are connected to the target busbar 30 on different sides, which can make the interdigital reflector 201 form different potentials, thereby changing the electric field boundary conditions below the interdigital reflector 201 and providing more suppression effect.

[0074] The present invention also provides a surface acoustic wave filter, including the surface acoustic wave resonator of any of the above embodiments.

[0075] In some alternative implementations, the surface acoustic wave (SAW) filter includes multiple series-arm resonators and multiple parallel-arm resonators, which form a trapezoidal topology. The aforementioned SAW resonators can serve as series-arm resonators (SR) and / or parallel-arm resonators (PR).

[0076] In some alternative implementations, the surface acoustic wave filter is a duplexer, including an antenna port ANT, a first port 1, and a second port 2. It also includes a first filter located between the antenna port ANT and the first port 1, and a second filter located between the antenna port ANT and the second port 2.

[0077] To verify the performance of the surface acoustic wave resonator provided in this embodiment, Example 1 and Comparative Example 1 are provided. The specific structure of the surface acoustic wave resonator in Example 1 is as follows: Figure 6 As shown, along the direction away from the interdigital transducer 100, the reflective grating structure 200 sequentially includes a short-circuit reflective grating 202, three interdigital reflective gratings 201, and another short-circuit reflective grating 202. The periods of the three interdigital reflective gratings 201 are all different. Furthermore, each unit reflective grating is interconnected along the same side of the first direction via a target busbar 30. The specific structure of the surface acoustic wave resonator in Comparative Example 1 is as follows... Figure 1 As shown, reflector grating 3 is a short-circuit reflector grating.

[0078] Example 1 and Comparative Example 1 are respectively formed Figure 7 The surface acoustic wave (SAW) filter was tested. In the SAW filter formed in Comparative Example 1, the specific structure of each SAW resonator (including the series arm resonator SR and the parallel arm resonator PR) is as follows... Figure 1 As shown. In the surface acoustic wave filter formed in Example 1, the specific structure of each parallel arm resonator is as follows. Figure 6 As shown, the structure of the series arm resonator SR is the same as that of Comparative Example 1.

[0079] Figure 8 This diagram illustrates a comparison of the admittance curves of the surface acoustic wave (SAW) filters in Example 1 and Comparative Example 1, where Example 1 is represented by a dashed line and Comparative Example 1 by a solid line. It can be seen that the longitudinal wave peak in Example 1 is further spaced from the resonator's resonant point, thus reducing its impact on the filter's passband.

[0080] Figure 9 This diagram illustrates a comparison of the real part admittance curves of surface acoustic wave filters in Example 1 and Comparative Example 1, where Example 1 is represented by a dashed line and Comparative Example 1 by a solid line. As can be seen from the black dashed circle, the longitudinal wave peak in Example 1 is further spaced from the resonator's resonant point, thus reducing its impact on the filter's passband.

[0081] Figure 10This is a comparative diagram showing the insertion loss curves (i.e., magnified passband views) of the surface acoustic wave (SAW) filters in Example 1 and Comparative Example 1, where Example 1 is represented by a dashed line and Comparative Example 1 by a solid line. As can be seen from the black dashed circle, Comparative Example 1 exhibits in-band peaking and higher insertion loss; compared to Comparative Example 1, Example 1 has a flatter in-band curve and lower insertion loss. Therefore, Example 1 can reduce the insertion loss of the filter.

[0082] In the description of this specification, the references to terms such as "this embodiment," "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0083] The above description does not provide detailed explanations of the technical aspects of each layer's patterning, etching, etc. However, those skilled in the art should understand that various technical means can be used to form layers and regions of the desired shape. Furthermore, to form the same structure, those skilled in the art can also design methods that are not entirely identical to those described above. Additionally, although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination.

[0084] The above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described above, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of protection of the present invention is determined by the scope of the appended claims.

Claims

1. A surface acoustic wave resonator, characterized in that, include: A piezoelectric layer, and interdigitated transducers and a reflective grating structure arranged along a first direction disposed on the piezoelectric layer, wherein the reflective grating structure is located on the side of the interdigitated transducers; The reflective grating structure includes a plurality of unit reflective gratings arranged along a first direction, and the fingers of each unit reflective grating extend along a second direction; each unit reflective grating is an interdigitated reflective grating, a short-circuit reflective grating, or an open-circuit reflective grating; In the reflective grating structure, at least one unit reflective grating is the interdigitated reflective grating, and the unit reflective gratings other than the interdigitated reflective grating are one or both of the short-circuit reflective grating and the open-circuit reflective grating.

2. The surface acoustic wave resonator according to claim 1, characterized in that, The reflective grating structure includes at least one interdigital reflective grating and at least one short-circuit reflective grating, wherein the unit reflective grating closest to the interdigital transducer is the short-circuit reflective grating.

3. The surface acoustic wave resonator according to claim 2, characterized in that, Along the direction away from the interdigital transducer, the unit reflective gratings located at the beginning and end of the reflective grating structure are both short-circuit reflective gratings; the middle region of the reflective grating structure is configured with at least one interdigital reflective grating.

4. The surface acoustic wave resonator according to claim 2, characterized in that, Along the direction away from the interdigital transducer, the reflective grating structure sequentially includes the short-circuit reflective grating, a plurality of interdigital reflective gratings, and the short-circuit reflective grating, wherein the periods of the plurality of interdigital reflective gratings are all different.

5. The surface acoustic wave resonator according to claim 1, characterized in that, The reflective grid structure includes at least one interdigital reflective grid, at least one short-circuit reflective grid, and at least one open-circuit reflective grid, wherein the unit reflective grid closest to the interdigital transducer is the short-circuit reflective grid; Along a direction away from the interdigital transducer, the reflective grating structure sequentially includes the short-circuit reflective grating, the interdigital reflective grating, and the open-circuit reflective grating to form a gradient acoustic boundary; The electric field reflection phase of the open-circuit reflector is opposite to that of the short-circuit reflector.

6. The surface acoustic wave resonator according to claim 1, characterized in that, The reflective grating structure includes five unit reflective gratings. Along the direction away from the interdigital transducer, the reflective grating structure sequentially includes the short-circuit reflective grating, the interdigital reflective grating, the open-circuit reflective grating, the interdigital reflective grating, and the short-circuit reflective grating.

7. The surface acoustic wave resonator according to claim 1, characterized in that, At least two of the unit reflective gratings have different combinations of parameters; the parameter combinations include one or more of the following: period, aperture, duty cycle, finger material, and finger thickness.

8. The surface acoustic wave resonator according to claim 1, characterized in that, The interdigitated reflector includes a plurality of third finger strips and a plurality of fourth finger strips alternately spaced along the first direction, and a third busbar and a fourth busbar arranged opposite to each other along the second direction; the starting end of the third finger strip is connected to the third busbar and the ending end is close to the fourth busbar; the starting end of the fourth finger strip is connected to the fourth busbar and the ending end is close to the third busbar; And / or, the short-circuit reflector includes a plurality of fifth finger strips spaced apart along the first direction, and a fifth bus strip and a sixth bus strip arranged opposite to each other along the second direction; the starting end of the fifth finger strip is connected to the fifth bus strip and the ending end is connected to the sixth bus strip; And / or, the open-circuit reflective grid includes a plurality of sixth fingers spaced apart along the first direction.

9. The surface acoustic wave resonator according to claim 2, characterized in that, Each of the unit reflective gratings is interconnected on the same side along the first direction via a target busbar; Alternatively, each of the unit reflective gratings is interconnected on both sides along the first direction via target busbars; Alternatively, each of the unit reflective grids is alternately connected to the adjacent unit reflective grids via a target busbar along a first side or a second side of the first direction.

10. A surface acoustic wave filter, characterized in that, The surface acoustic wave filter includes the surface acoustic wave resonator according to any one of claims 1 to 9.

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