Surface acoustic wave filter and electronic device
By employing a parallel arm resonator with a thickness greater than that of the IDT electrode in the series arm resonator in the surface acoustic wave filter, and combining high-velocity acoustic materials and double-film thickness technology, the problems of large passband insertion loss and poor rectangularity in the high-frequency band of the IPD filter are solved, resulting in a filter with wider bandwidth, lower insertion loss, and smaller size.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2026-03-06
AI Technical Summary
Existing IPD filters suffer from problems such as large passband insertion loss and poor rectangularity in the high-frequency band.
A surface acoustic wave filter is employed, comprising a piezoelectric substrate, a series arm resonator, and a parallel arm resonator. The IDT electrode thickness of the parallel arm resonator is greater than that of the series arm resonator. By combining high-velocity acoustic materials and double-film thickness technology, the distance between fs and fu is optimized, enhancing out-of-band suppression capability while maintaining low insertion loss characteristics.
It achieves wider bandwidth and lower in-band insertion loss, reduces interference from bulk waves on the signal, has smaller device size, and improves communication quality.
Smart Images
Figure CN223978631U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of filter technology, and more specifically, to a surface acoustic wave filter and electronic device. Background Technology
[0002] As communication technology has evolved from 2G to 5G, the number of communication frequency bands has gradually increased (from 4 bands in 2G to over 50 bands in 5G). To improve the compatibility of smartphones with different communication standards, the amount of filters required for 5G smartphones will increase significantly, driving large-scale growth in the filter market. With the surge in demand for performance and stability in 5G communication systems, such as N77, N78, N79, and 5G Wi-Fi bands, the demand for SAW (Surface Acoustic Wave) filter devices to manufacture ultra-high frequency filters is also increasing daily.
[0003] SAW (Self-Aided Filter) is currently widely used in RF filters below 3 GHz, but for higher frequency bands (>3 GHz), it is mostly implemented using IPD (Integrated Passive Device). However, IPD is limited by its lack of good rectangularity and large size, making it unsuitable for high-end devices. As a common filter method used in high-frequency bands, IPD typically suffers from high insertion loss and poor rectangularity in its passband. Utility Model Content
[0004] The main objective of this application is to provide a surface acoustic wave filter and electronic device to solve the problems of large insertion loss and poor rectangularity in the high-frequency passband of the existing IPD filter.
[0005] To achieve the above objectives, according to one aspect of this application, a surface acoustic wave filter is provided, comprising: a piezoelectric substrate; a series arm resonator located on a portion of the surface of the piezoelectric substrate, the series arm resonator including a first IDT (Interdigital Transducer) electrode; and a parallel arm resonator located on a portion of the surface of the piezoelectric substrate, the parallel arm resonator including a second IDT electrode, the thickness of the second IDT electrode being greater than the thickness of the first IDT electrode.
[0006] Optionally, the thickness of the first IDT electrode is 50 nm to 120 nm.
[0007] Optionally, the thickness of the second IDT electrode is 100 nm to 200 nm.
[0008] Optionally, the series arm resonator includes the first IDT electrodes arranged in parallel and the first reflective grid array disposed at both ends of the first IDT electrodes.
[0009] Optionally, the parallel arm resonator includes the second IDT electrodes arranged in parallel and the second reflective grid array disposed at both ends of the second IDT electrodes.
[0010] Optionally, the piezoelectric substrate includes a substrate and a piezoelectric layer stacked sequentially, the series arm resonator is located on a portion of the piezoelectric layer away from the substrate, the parallel arm resonator is located on a portion of the piezoelectric layer away from the substrate, and both the substrate and the piezoelectric layer are made of high-velocity materials.
[0011] Optionally, the substrate is made of silicon carbide, and the piezoelectric layer is made of lithium niobate.
[0012] Optionally, the thickness of the substrate is 200nm to 700nm, and the thickness of the piezoelectric layer is 100nm to 500nm.
[0013] Optionally, the first IDT electrode has a first tilt angle and a first rotation angle, and the second IDT electrode has a second tilt angle and a second rotation angle, wherein the first tilt angle, the second tilt angle, the first rotation angle, and the second rotation angle are all non-zero.
[0014] According to another aspect of this application, an electronic device is provided, comprising any of the surface acoustic wave filters described herein.
[0015] Using the technical solution of this application, the surface acoustic wave filter includes a piezoelectric substrate, a series arm resonator, and a parallel arm resonator. The series arm resonator and the parallel arm resonator are both located on a portion of the surface of the piezoelectric substrate. The series arm resonator includes a first IDT electrode, and the parallel arm resonator includes a second IDT electrode. The thickness of the second IDT electrode is greater than the thickness of the first IDT electrode. Compared with the existing IPD filters, which suffer from large insertion loss and poor rectangularity in the high-frequency passband, the thickness of the second IDT electrode in this application is greater than that of the first IDT electrode. This ensures a larger distance between fs (resonant point) and fu (volume wave radiation point), which is beneficial for the frequency of the volume wave to deviate from the passband, thereby reducing the interference of the volume wave on the signal within the passband. Furthermore, the parallel arm and the series arm in the SAW filter respectively undertake the responsibilities of out-of-band suppression and in-band transmission. Increasing the thickness of the parallel arm electrode (i.e., the second IDT electrode) can improve its out-of-band frequency suppression capability while maintaining the low insertion loss characteristics of the series arm, thereby optimizing the frequency response of the entire filter, achieving a wider bandwidth and lower in-band insertion loss. Thus, the size of the filter can also be smaller for the same bandwidth. Attached Figure Description
[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:
[0017] Figure 1 A schematic cross-sectional view of a surface acoustic wave filter according to an embodiment of this application is shown.
[0018] Figure 2 An embodiment of this application is shown, which provides a method for... Figure 1 A top view of the corresponding surface acoustic wave filter;
[0019] Figure 3 A cross-sectional schematic diagram of a specific surface acoustic wave filter according to an embodiment of this application is shown;
[0020] Figure 4(a) shows the admittance curves of a series arm resonator and a parallel arm resonator in a surface acoustic wave filter according to an embodiment of the present application;
[0021] Figure 4(b) shows the real part plot of the admittance corresponding to Figure 4(a) according to an embodiment of this application;
[0022] Figure 5 A performance comparison diagram is shown between a surface acoustic wave filter provided according to an embodiment of this application and a filter designed by IPD in the prior art;
[0023] Figure 6 A schematic diagram of a wafer provided according to an embodiment of this application is shown;
[0024] Figure 7 A schematic diagram of an electrode rotation angle provided according to an embodiment of this application is shown;
[0025] Figure 8 A schematic diagram of an electrode tilt angle provided according to an embodiment of this application is shown;
[0026] The above figures include the following reference numerals:
[0027] 11. Piezoelectric substrate; 12. Series arm resonator; 13. Parallel arm resonator; 121. First IDT electrode; 122. First reflective grating array; 131. Second IDT electrode; 132. Second reflective grating array; 111. Substrate; 112. Piezoelectric layer. Detailed Implementation
[0028] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, 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 pertains.
[0029] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0030] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element may be directly on the other element, or there may be an intermediate element present. Furthermore, in the specification and claims, when an element is described as being "connected" to another element, the element may be "directly connected" to the other element, or "connected" to the other element via a third element.
[0031] As described in the background section, existing IPD filters suffer from large insertion loss and poor rectangularity in the high-frequency passband. To address these issues, embodiments of this application provide a surface acoustic wave filter and an electronic device.
[0032] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.
[0033] This application provides a surface acoustic wave filter, such as... Figure 1 and Figure 2 As shown, it includes:
[0034] Piezoelectric substrate 11;
[0035] A series arm resonator 12 is located on a portion of the surface of the piezoelectric substrate 11, and the series arm resonator 12 includes a first IDT electrode 121.
[0036] Parallel arm resonator 13 is located on a portion of the surface of the piezoelectric substrate 11. The parallel arm resonator 13 includes a second IDT electrode 131, the thickness of which is greater than the thickness of the first IDT electrode 121.
[0037] According to the above embodiments, the surface acoustic wave filter includes a piezoelectric substrate, a series arm resonator, and a parallel arm resonator. The series arm resonator and the parallel arm resonator are both located on a portion of the surface of the piezoelectric substrate. The series arm resonator includes an IDT electrode, and the parallel arm resonator includes a second IDT electrode. The thickness of the second IDT electrode is greater than the thickness of the first IDT electrode. Compared with the existing IPD filters, which suffer from large insertion loss and poor rectangularity in the high-frequency passband, the thickness of the second IDT electrode in this application is greater than that of the first IDT electrode. This ensures a larger distance between fs (resonant point) and fu (volume wave radiation point), which is beneficial for the frequency of the volume wave to deviate from the passband, thereby reducing the interference of the volume wave on the signal within the passband. Furthermore, the parallel arm and the series arm in the SAW filter respectively undertake the responsibilities of out-of-band suppression and in-band transmission. Increasing the thickness of the parallel arm electrode (i.e., the second IDT electrode) can improve its out-of-band frequency suppression capability while maintaining the low insertion loss characteristics of the series arm, thereby optimizing the frequency response of the entire filter, achieving a wider bandwidth and lower in-band insertion loss. Thus, the size of the filter can also be smaller for the same bandwidth.
[0038] Specifically, such as Figure 1 As shown, the thickness of the parallel arm resonator 13 is greater than the thickness of the series arm resonator 12.
[0039] Specifically, such as Figure 1 and Figure 2 As shown, the thickness in this application is the length in a predetermined direction.
[0040] Specifically, the surface acoustic wave filter of this application can realize the application of SAW in high frequency bands such as N77 and N78.
[0041] Specifically, a dual-thickness technique is employed, using electrodes of different thicknesses on the series and parallel arms. By adjusting the electrode thickness, the distance between fs (resonant point) and fu (bulk wave radiation point) can be optimized, thereby achieving lower insertion loss (signal loss) and wider bandwidth in the high-frequency band. Specifically, in the high-frequency band, due to the high bandwidth requirements, bulk waves radiate into the passband, leading to increased loss on the right side of the passband. Increasing the electrode thickness increases the distance between fs and fu, allowing the bulk wave to radiate out of the passband, thus not affecting the right side of the passband loss.
[0042] In one alternative embodiment, the thickness of the first IDT electrode is 50 nm to 120 nm. In this embodiment, the thickness of the first IDT electrode has a direct impact on the frequency selectivity of the filter. Within the range of 50 nm to 120 nm, the rectangularity of the filter can be further optimized, which means that the filter can transmit signals more effectively in the passband and suppress signals more effectively in the stopband.
[0043] Specifically, the thinner design of the first IDT electrode helps reduce insertion loss when the signal passes through the filter, which is crucial for maintaining signal strength and improving communication quality.
[0044] According to some exemplary embodiments of this application, the thickness of the second IDT electrode is 100nm to 200nm. In this embodiment, by adjusting the thickness of the second IDT electrode to 100nm to 200nm, the out-of-band rejection capability can be further improved while maintaining the in-band transmission efficiency, further optimizing the performance of the entire filter, and further achieving better communication quality and smaller device size.
[0045] According to some further exemplary embodiments of this application, such as Figure 2 As shown, the series arm resonator 12 includes the first IDT electrodes 121 arranged in parallel and a first reflective grating array 122 disposed at both ends of the first IDT electrodes 121. In this embodiment, the arrangement of the first reflective grating array helps to reflect surface acoustic waves, reduce wave loss, and thus enhance the signal processing capability of the filter.
[0046] In another alternative, such as Figure 2 As shown, the parallel arm resonator 13 includes the second IDT electrodes 131 arranged in parallel and a second reflective grating array 132 disposed at both ends of the second IDT electrodes 131. In this embodiment, the arrangement of the second reflective grating array helps to further reflect surface acoustic waves, further reduce wave loss, and thus further enhance the signal processing capability of the filter.
[0047] Specifically, Figure 1 For along Figure 2 A schematic diagram of the cross-sectional structure of the SAW filter obtained by longitudinally cutting along the dashed line L. Figure 2 The piezoelectric substrate 11 and Figure 1 The piezoelectric substrate 11 in it is the same.
[0048] In some of the alternative solutions of this application, such as Figure 3 As shown, the piezoelectric substrate 11 includes a substrate 111 and a piezoelectric layer 112 stacked sequentially. The series arm resonator 12 is located on the portion of the piezoelectric layer 112 away from the substrate 111, and the parallel arm resonator 13 is located on the portion of the piezoelectric layer 112 away from the substrate 111. Both the substrate 111 and the piezoelectric layer 112 are made of high-velocity acoustic materials. In this embodiment, both the substrate and the piezoelectric layer are made of high-velocity acoustic materials. High sound velocity means that at the same frequency, the SAW device can have a shorter wavelength, which is beneficial for further realizing smaller device sizes. At the same time, high sound velocity also helps to reduce bulk wave interference.
[0049] In other embodiments, the substrate is made of silicon carbide, and the piezoelectric layer is made of lithium niobate. In this embodiment, the substrate is made of silicon carbide, and the piezoelectric layer is made of lithium niobate. Lithium niobate is a material with a high electromechanical coupling coefficient, which means that it can more effectively convert electrical energy into acoustic energy. In surface acoustic wave (SAW) devices, a high electromechanical coupling coefficient can improve the conversion efficiency of the filter and reduce energy loss during signal transmission, thereby achieving low insertion loss. Silicon carbide is a material with a very high velocity of sound. A high velocity of sound means that at the same frequency, SAW devices can have a shorter wavelength, which is beneficial for further realizing smaller device sizes. At the same time, the high velocity of sound also helps to reduce the interference of bulk waves. The low loss characteristics of SiC also help to reduce energy loss during signal transmission.
[0050] Specifically, SiC material has a high sound velocity, and LN (lithium niobate) has a large electromechanical coupling coefficient, thus enabling wide-bandwidth filtering performance in the high-frequency range.
[0051] In some alternative embodiments of this application, the thickness of the substrate is 200 nm to 700 nm, and the thickness of the piezoelectric layer is 100 nm to 500 nm. In this embodiment, by precisely controlling the thickness of the substrate and the piezoelectric layer, the propagation characteristics of surface acoustic waves in the filter, including propagation speed and attenuation, can be further optimized, thereby improving the performance of the filter.
[0052] In other embodiments, the first IDT electrode has a first tilt angle and a first rotation angle, and the second IDT electrode has a second tilt angle and a second rotation angle, wherein the first tilt angle, the second tilt angle, the first rotation angle and the second rotation angle are all non-zero.
[0053] Specifically, Figure 4(a) shows the admittance curves of a series arm resonator and a parallel arm resonator in a surface acoustic wave filter according to an embodiment of this application; Figure 4(b) shows the real part admittance curve corresponding to Figure 4(a). From the perspective of the resonators, in Figures 4(a) and 4(b), the solid line represents the series arm resonator, the dashed line represents the parallel arm resonator, fu1 is the bulk wave radiation point of the series arm resonator using a thin film, fu2 is the bulk wave radiation point of the parallel arm resonator using a thick film, and fs is the resonant point. In Figure 4(a), the horizontal axis freq represents the frequency in Hz, and the vertical axis represents the admittance gain in dB. In Figure 4(b), the horizontal axis freq represents the frequency in Hz, and the vertical axis represents the real part admittance gain in dB. As can be seen from Figures 4(a) and 4(b), when the parallel arm resonator uses a thick film (i.e., the film thickness of the parallel arm resonator is greater than that of the series arm resonator), the distance between fs and fu will increase, which can allow the bulk wave to radiate out of the band, thus not affecting the right-side loss of the passband.
[0054] Specifically, Figure 5 shows a performance comparison diagram between a surface acoustic wave filter provided according to an embodiment of this application and a filter designed by IPD in the prior art. Figure 5 In the diagram, the solid line represents the surface acoustic wave filter of this application (i.e., the film thickness of the parallel arm resonator is greater than that of the series resonator), and the dashed line represents the filter designed by IPD in the prior art (the film thickness of the parallel arm resonator is equal to that of the series resonator). Figure 5 (b) shows the admittance curve for the entire band. Figure 5 (a) indicates and Figure 5 (b) Admittance curves of the corresponding local band (i.e., passband band); Figure 5 (a) and Figure 5 In (b), the horizontal axis freq represents frequency in GHz, and the vertical axis represents admittance gain in dB. Figure 5 (c) shows the Smith chart at the filter input. Figure 5 (d) shows the Smith chart at the filter output. From Figure 5 (a) and Figure 5 (b) It can be seen that the surface acoustic wave filter of this application (i.e., solid line) has lower passband loss and better out-of-band suppression compared to the filter designed by IPD in the prior art (i.e., dashed line) (i.e., when the loss is reduced and the bandwidth is widened, the out-of-band suppression will also be better). From Figure 5 (c) and Figure 5 (d) It can be seen that the surface acoustic wave filter of this application (i.e., solid line) is more convergent at the center and has a lower filter impedance compared to the filter designed by IPD in the prior art (i.e., dashed line).
[0055] Specifically, when the resonator is tilted, the IDT electrode and the reflective grating array located at both ends of the IDT electrode tilt together; when the resonator is rotated, the IDT electrode and the reflective grating array located at both ends of the IDT electrode rotate together.
[0056] Specifically, during wafer fabrication, the wafer orientation needs to be defined; therefore, a fixed notch is typically left in a certain direction, such as... Figure 6 As shown in the dashed box, for ease of explanation, upward is defined as the positive direction. Figure 7 The diagram illustrates the definition of the electrode rotation angle. It is stipulated that when the direction of the IDT electrode interdigitation point in the resonator is consistent with the positive direction, the resonator has a 0° rotation angle; when the direction of the IDT electrode interdigitation point in the resonator rotates clockwise along the positive direction, the resonator is rotating in the positive direction, and the rotation angle is the positive rotation angle; when the direction of the IDT electrode interdigitation point in the resonator rotates counterclockwise along the positive direction, the resonator is rotating in the negative direction, and the rotation angle is the negative rotation angle. Figure 8The diagram illustrates the definition of the electrode tilt angle. The tilt angle is defined as follows: the interdigitated direction of the IDT electrodes in the resonator is always aligned with the positive direction. It is stipulated that when the interdigitated direction of the IDT electrodes in the resonator is aligned with the positive direction, the resonator has a 0° tilt angle. When the entire resonator tilts clockwise along the positive direction (left side of the reflector array is higher than right side), the resonator is positively tilted, and the angle of rotation is a positive tilt angle. When the entire resonator tilts counterclockwise along the positive direction (left side of the reflector array is lower than right side), the resonator is negatively tilted, and the angle of rotation is a negative tilt angle.
[0057] Specifically, Figure 7 and Figure 8 The resonator in the circuit is either a series arm resonator or a parallel arm resonator. Figure 7 and Figure 8 wafers and Figure 6 The wafers in the same container are identical.
[0058] In summary, the surface acoustic wave filter composed of a high-velocity SiC substrate, a high-velocity piezoelectric LN layer with double film thickness (i.e., the film thickness of the parallel arm resonator is greater than that of the series arm resonator), a tilted electrode, and a rotating electrode can be applied to the high-frequency band.
[0059] This application also provides an electronic device including any of the above-described surface acoustic wave filters.
[0060] Specifically, the aforementioned electronic devices include, but are not limited to, smartphones, tablets, and sensors.
[0061] As can be seen from the above description, the embodiments of this application achieve the following technical effects:
[0062] In the surface acoustic wave filter of this application, the surface acoustic wave filter includes a piezoelectric substrate, a series arm resonator and a parallel arm resonator, wherein the series arm resonator and the parallel arm resonator are both located on a portion of the surface of the piezoelectric substrate, the series arm resonator includes a first IDT electrode, and the parallel arm resonator includes a second IDT electrode, the thickness of the second IDT electrode being greater than the thickness of the first IDT electrode. Compared with the existing IPD filters, which suffer from large insertion loss and poor rectangularity in the high-frequency passband, the thickness of the second IDT electrode in this application is greater than that of the first IDT electrode. This ensures a larger distance between fs (resonant point) and fu (volume wave radiation point), which is beneficial for the frequency of the volume wave to deviate from the passband, thereby reducing the interference of the volume wave on the signal within the passband. Furthermore, the parallel arm and the series arm in the SAW filter respectively undertake the responsibilities of out-of-band suppression and in-band transmission. Increasing the thickness of the parallel arm electrode (i.e., the second IDT electrode) can improve its out-of-band frequency suppression capability while maintaining the low insertion loss characteristics of the series arm, thereby optimizing the frequency response of the entire filter, achieving a wider bandwidth and lower in-band insertion loss. Thus, the size of the filter can also be smaller for the same bandwidth.
[0063] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A surface acoustic wave filter, characterized by, The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter.
2. The surface acoustic wave filter according to claim 1, characterized by, The application relates to a surface acoustic wave filter.
3. The surface acoustic wave filter according to claim 2, characterized by, The application relates to a surface acoustic wave filter.
4. The surface acoustic wave filter according to claim 1, characterized by, The application relates to a surface acoustic wave filter.
5. The surface acoustic wave filter according to claim 1, wherein The application relates to a surface acoustic wave filter.
6. The surface acoustic wave filter according to claim 1, wherein The application relates to a surface acoustic wave filter.
7. The surface acoustic wave filter according to claim 6, characterized by, The application relates to a surface acoustic wave filter.
8. The surface acoustic wave filter according to claim 6, wherein The application relates to a surface acoustic wave filter.
9. The surface acoustic wave filter according to claim 1, wherein, The application relates to a surface acoustic wave filter.
10. An electronic device, comprising: The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. The application relates to a surface acoustic wave filter. 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