Surface acoustic wave resonator for suppressing parasitic mode and filter thereof
By splitting a single resonator into multiple resonators and adjusting their wavelengths and areas, the impact of parasitic SH wave modes on the filter's passband performance was resolved, thereby improving the filter's performance.
Patent Information
- Application Number
- CN202511793188.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-01
- Publication Date
- 2026-04-14
AI Technical Summary
In existing surface acoustic wave resonators, parasitic SH wave modes affect the passband performance of the filter, causing downward spikes in the passband curve and thus impacting the filter's performance.
A single resonator is split into multiple split resonators, and the influence of parasitic modes is reduced by adjusting the wavelength and area of each split resonator while keeping the overall electrical performance basically unchanged.
It effectively eliminates the spikes in the passband curve, improves the passband performance of the filter, and maintains the stability of the overall electrical performance.
Smart Images
Figure CN121864049A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of resonator technology, specifically relating to a surface acoustic wave resonator and filter for suppressing parasitic modes. Background Technology
[0002] The primary function of radio frequency (RF) filters is to attenuate signals in unwanted frequency bands while minimizing the impact on signals in desired frequency bands. RF filters are used in communication systems that transmit information via wireless links. For example, RF filters can be found in the RF front-end of cellular base stations, mobile phones and computing devices, satellite transceivers and terrestrial base stations, IoT (Internet of Things) devices, laptops and tablets, fixed-point radio links, and other communication systems. RF filters are also used in radar, as well as electronic and information warfare systems.
[0003] High-performance RF filters used in current communication systems typically include acoustic resonators, such as surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators, thin-film bulk acoustic wave (FBAR) resonators, and laterally excited membrane bulk acoustic wave (XBAR) resonators. To improve the temperature characteristics of SAW resonators, a temperature-compensated SAW (TC-SAW) resonator is formed by covering its interdigital transducer (IDT) with a temperature compensation layer. Due to the presence of the temperature compensation layer, the temperature characteristics of TC-SAW are significantly improved compared to SAW. Connecting multiple SAWs in series and parallel yields an SAW filter, and connecting multiple TC-SAWs in series and parallel yields a TC-SAW filter.
[0004] The structure of a conventional surface acoustic wave resonator is as follows: Figure 1 As shown, the filter includes an input electrode (IN), an output electrode (OUT), an interdigital transducer located between the input and output electrodes, and reflective grids located on both sides of the interdigital transducer. The interdigital transducer includes a pair of parallel busbars and interdigital electrodes staggered between the busbars. Applying an electric field to the interdigital transducer will generate stress in all possible directions, thereby exciting various vibration modes that the piezoelectric material can support. The common dominant mode in TC-SAW is Rayleigh wave, with parasitic SH waves. Parasitic SH waves can affect the passband performance of the filter, such as... Figure 2 As shown, within the filter passband, this manifests as a downward spike in the passband curve (e.g., Figure 2 Peak 1 in the middle. Summary of the Invention
[0005] To address at least one of the aforementioned problems, this invention proposes a surface acoustic wave resonator and its filter for suppressing parasitic modes. By splitting a single resonator into two or more resonators, the parasitic effects can be significantly reduced within the filter passband while maintaining the overall electrical performance approximately unchanged.
[0006] The technical solution adopted in this invention is as follows: In the first aspect, this application discloses a surface acoustic wave resonator that suppresses parasitic modes, comprising: Input electrodes and output electrodes; A split resonator Each split resonator is connected in parallel between the input electrode and the output electrode, and the wavelengths of each split resonator are not equal. when At that time, the wavelengths of each split resonator are respectively , The areas of each split resonator are respectively , ;when At that time, the wavelengths of each split resonator are respectively , , The areas of each split resonator are respectively , , ;when At that time, the wavelengths of each split resonator are respectively , , , The areas of each split resonator are respectively , , , ,satisfy:
[0007]
[0008] in, The area of a single resonator. The wavelength of a single resonator.
[0009] As an optional technical solution, when At that time, the wavelengths of each split resonator and the single resonator satisfy:
[0010]
[0011] in, For structural parameters, .
[0012] As an optional technical solution, when At that time, the wavelengths of each split resonator and the single resonator satisfy:
[0013]
[0014]
[0015] As an optional technical solution, each of the split resonators includes a first bus bar and a second bus bar arranged in parallel, a first interdigital electrode and a second interdigital electrode staggered between the first bus bar and the second bus bar, and a reflective grid distributed on both sides of the first bus bar and the second bus bar; the first interdigital electrode is electrically connected to the first bus bar, and the second interdigital electrode is electrically connected to the second bus bar.
[0016] As an optional technical solution, the gaps between adjacent first interdigital electrodes and second interdigital electrodes are equal. The width of each of the first interdigital electrodes and each of the second interdigital electrodes is equal. The wavelength of each of the aforementioned split resonators is... .
[0017] As an optional technical solution, for each of the split resonators, the number of its first interdigital electrodes is: The number of its second interdigital electrodes is ,satisfy:
[0018] in, This represents the total number of interdigitated electrodes in a single resonator.
[0019] As an optional technical solution, when At that time, for each of the aforementioned split resonators, the overlap length of its finger strips is equal, and is always... ;when At that time, for each of the aforementioned split resonators, the overlap length of its finger strips is equal, and is always... ;when At that time, for each of the aforementioned split resonators, the overlap length of its finger strips is equal, and is always... And satisfy:
[0020] in, It is the overlap length of the finger strips of a single resonator.
[0021] In a second aspect, this application also discloses a filter comprising a surface acoustic wave resonator for suppressing parasitic modes as described in the first aspect above.
[0022] The beneficial effects of this application are as follows: In this application, a single resonator is split into multiple split resonators. Through structural design, the overall electrical performance of the split resonators remains approximately unchanged from that of the original single resonator, while suppressing parasitic modes and eliminating the spikes in the passband curve caused by parasitic modes. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of an existing surface acoustic wave resonator structure.
[0024] Figure 2 It is the passband curve of a filter constructed from existing surface acoustic wave resonators.
[0025] Figure 3 This is a schematic diagram of the structure of a surface acoustic wave resonator after splitting a single resonator into two resonators in an exemplary embodiment.
[0026] Figure 4 yes Figure 3 A schematic diagram of the passband curve of a filter composed of a surface acoustic wave resonator.
[0027] Figure 5 This is a schematic diagram of the structure of a surface acoustic wave resonator after splitting a single resonator into three resonators in an exemplary embodiment.
[0028] Figure 6 yes Figure 5 A schematic diagram of the passband curve of a filter composed of a surface acoustic wave resonator. Detailed Implementation
[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components and steps of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. 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.
[0030] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. The present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0031] Example Existing surface acoustic wave resonator structures such as Figure 1 As shown, it includes a pair of reflective gratings, an input electrode (IN), an output electrode (OUT), and an interdigital transducer (IDT) located between the input and output electrodes on a piezoelectric substrate. The interdigital transducer includes a pair of busbars and a plurality of interdigital electrodes that are staggered and equally spaced between the pair of busbars. The single resonator described in this application refers to... Figure 1 The diagram shows a structure consisting of a pair of reflective gratings and an interdigital transducer located between them. The area of the single resonator is S = a × b, the total number of its interdigital electrodes is N, and its finger overlap length (i.e., the aperture aperture) is... The width of each interdigitated electrode is equal, and the gap width between adjacent interdigitated electrodes is equal. The wavelength of this single resonator is twice the sum of the width of the interdigitated electrodes and the gap width (i.e., as shown in the image). Figure 1 As shown, a wavelength contains exactly two interdigitated electrodes and two gap widths. Applying an electric field to the interdigitated transducer (IDT) will generate stress in all possible directions, thereby exciting various vibration modes that the piezoelectric material can support. For example, the common dominant mode in TC-SAW is Rayleigh wave, with parasitic SH waves. Parasitic SH waves can affect the passband performance of the filter, such as... Figure 2 As shown, within the filter passband, this manifests as a downward spike 1 in the passband curve. Figure 2 In the diagram, curve 1 is the filter transmission coefficient curve, curve 2 is a magnified view of the vertical axis of curve 1 by 10 times, and curve 3 is the conductance curve of the split resonator.
[0032] To improve the passband performance of the filter and eliminate the downward spikes in the passband curve, the technical solution adopted in this embodiment is to split the single resonator into... A split resonator. After splitting, the total area of the resonator remains unchanged, and the average wavelength is equal to that of the original single resonator, but the area of each split resonator becomes one-third of the area of the original single resonator. The number of interdigitated electrodes (including the first and second interdigitated electrodes) in each split resonator is the same as the number of interdigitated electrodes in the original single resonator, and the aperture aperture of each split resonator is [amount missing] times that of the original single resonator. .
[0033] After splitting, the area of a split resonator is only that of the original single resonator. This means that the effective region for applying an electric field to a single split resonator is significantly reduced. The volume of piezoelectric material capable of participating in the inverse piezoelectric effect and generating strain is also correspondingly reduced, and the absolute intensity of parasitic modes weakens as the overall excitation intensity decreases. Simultaneously, by staggering the wavelengths of the split resonators (i.e., the wavelengths are not equal), the parasitic waves of each split resonator will also experience frequency misalignment. Thus, the parasitic effects of the split resonators cannot be superimposed in the filter passband, resulting in a significant reduction in parasitic effects within the filter passband. Furthermore, the total area of the split resonators remains unchanged, and the average wavelength is equal to that of the original single resonator, ensuring that the overall electrical performance is approximately equivalent to that of the original single resonator. In other words, this application can reduce the impact of parasitic waves on the passband while maintaining approximately the same overall electrical performance.
[0034] The following is based on Taking this example, we will explain this embodiment.
[0035] like Figure 3 As shown, when At the same time, the surface acoustic wave resonator with suppressed parasitic modes provided in this embodiment The system includes: a piezoelectric substrate 10, an input electrode 20, an output electrode 30, and two split resonators 40 fabricated on the piezoelectric substrate 10; each split resonator 40 includes a first busbar 401 and a second busbar 402 arranged in parallel, a first interdigital electrode 403 and a second interdigital electrode 404 distributed alternately and at equal intervals between the first busbar 401 and the second busbar 402, and a reflective grating 405 distributed on both sides of the first busbar 401 and the second busbar 402; the first interdigital electrode 403 is electrically connected to the first busbar 401, and the second interdigital electrode 404 is electrically connected to the second busbar 402; the first busbar 401 is electrically connected to the input electrode 20, and the second busbar 402 is electrically connected to the output electrode 30. The number of first interdigital electrodes 403 in each split resonator is... The number of second interdigital electrodes 404 is The total number of interdigital electrodes remains unchanged, equal to the total number N of interdigital electrodes in the original single resonator, i.e. .
[0036] The two split resonators have essentially the same structure; the only difference is their wavelengths. For example... Figure 3 As shown, the wavelengths of the two split resonators are respectively , The wavelengths of each resonator are the sum of the width of a first interdigital electrode 403, the width of a second interdigital electrode 404, and the two spacing widths, where the spacing width is the distance between adjacent first interdigital electrodes 403 and second interdigital electrodes 404. To control the wavelength of each split resonator, the width of the interdigital electrode and the spacing width are controlled. To avoid parasitic waves overlapping within the passband, the wavelengths of the two split resonators are... , They cannot be equal. As a preferred implementation, the wavelengths of the two split resonators and the single resonator satisfy the following:
[0037]
[0038] in, For structural parameters, , The wavelength of a single resonator is given. In this structure, a significant frequency misalignment occurs between the split resonators. The average wavelength of the two split resonators is... That is, the wavelength is equal to that of the original single resonator, and at the same time, the lengths of each split resonator are equal. Each split resonator has the same width. The areas of the two split resonators are approximately equal. ,Keep , Then the total area of the two split resonators is This means that the area of the resonator remains essentially unchanged after splitting. Furthermore, the aperture diameter of each split resonator is equal. Then the sum of the apertures of the two split resonators is The aperture is the same as that of the original single resonator. With the average wavelength, aperture, and total area remaining approximately constant, the overall electrical performance of the split resonator can remain largely unchanged.
[0039] like Figure 4 As shown, the wavelengths of the two split resonators are respectively , A schematic diagram of the passband curve of the filter constructed by time. For example... Figure 2 Wavelength The schematic diagram of the passband curve of the filter composed of a single resonator shows that, by comparing curve 2 and curve 5, peak 1 is basically eliminated. Figure 4 In the diagram, curve 4 is the filter transmission coefficient curve, curve 5 is a magnified view of the vertical axis of curve 4 by 10 times, and curves 6 and 7 are the conductance curves of the two split resonators after splitting.
[0040] The following is based on Taking this example, we will explain this embodiment.
[0041] like Figure 5 As shown, when At the same time, the surface acoustic wave resonator with suppressed parasitic modes provided in this embodiment The system includes: a piezoelectric substrate 10, an input electrode 20, an output electrode 30, and three split resonators 40 fabricated on the piezoelectric substrate 10; each split resonator 40 includes a first busbar 401 and a second busbar 402 arranged in parallel, a first interdigital electrode 403 and a second interdigital electrode 404 distributed alternately and at equal intervals between the first busbar 401 and the second busbar 402, and a reflective grating 405 distributed on both sides of the first busbar 401 and the second busbar 402; the first interdigital electrode 403 is electrically connected to the first busbar 401, and the second interdigital electrode 404 is electrically connected to the second busbar 402; the first busbar 401 is electrically connected to the input electrode 20, and the second busbar 402 is electrically connected to the output electrode 30. The number of first interdigital electrodes 403 in each split resonator is... The number of second interdigital electrodes 404 is The total number of interdigital electrodes remains unchanged, equal to the total number N of interdigital electrodes in the original single resonator, i.e. .
[0042] The three split resonators have essentially the same structure; the only difference is their wavelengths. For example... Figure 5 As shown, the wavelengths of the three split resonators are respectively , , The wavelengths of the three split resonators are the sum of the widths of a first interdigital electrode 403, a second interdigital electrode 404, and two spacing widths, where the spacing width is the distance between adjacent first interdigital electrodes 403 and second interdigital electrodes 404. To control the wavelengths of each split resonator, the widths of the interdigital electrodes and the spacing widths are controlled. To avoid parasitic waves overlapping within the passband, the wavelengths of the three split resonators are... , , They cannot be equal. As a preferred implementation, the wavelengths of the three split resonators and the single resonator satisfy the following:
[0043]
[0044]
[0045] in, For structural parameters, In this structure, a significant frequency misalignment occurs among the split resonators. The average wavelength of the three split resonators is... That is, the wavelength is equal to that of the original single resonator. At the same time, the length and width of each of the three split resonators are respectively... , Then the areas of the three split resonators are each equal. ,Keep , The total area of the three split resonators is This means that the area of the resonator remains unchanged after splitting. Furthermore, the aperture of each split resonator is equal. Then the sum of the apertures of the three split resonators is The aperture is the same as that of the original single resonator. With the average wavelength, total area, and aperture remaining unchanged, the overall electrical performance of the split resonator can remain roughly unchanged.
[0046] like Figure 6 As shown, the wavelengths of the three split resonators are respectively , , A schematic diagram of the passband curve of the filter constructed by time. Figure 6 In the diagram, curve 8 is the filter transmission coefficient curve, curve 9 is a magnified view of the vertical axis of curve 8 by 10 times, and curves 10, 11, and 12 are the conductance curves of the three split resonators after the split.
[0047] It should be noted that, with As the value of increases, the difficulty and cost of the processing will gradually increase. Therefore, considering factors such as process cost, The value is controlled within Better.
[0048] Finally, this embodiment also discloses a filter, including a surface acoustic wave resonator for suppressing parasitic modes as described in the above embodiments.
[0049] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. All technical solutions that fall within the scope of the claims of this invention are within the scope of protection of this invention.
Claims
1. A surface acoustic wave resonator that suppresses parasitic modes, characterized in that, include: Input electrodes and output electrodes; A split resonator Each split resonator is connected in parallel between the input electrode and the output electrode, and the wavelengths of each split resonator are not equal. when At that time, the wavelengths of each split resonator are respectively , The areas of each split resonator are respectively , ;when At that time, the wavelengths of each split resonator are respectively , , The areas of each split resonator are respectively , , ;when At that time, the wavelengths of each split resonator are respectively , , , The areas of each split resonator are respectively , , , ,satisfy: in, The area of a single resonator. The wavelength of a single resonator.
2. The surface acoustic wave resonator for suppressing parasitic modes according to claim 1, characterized in that: when At that time, the wavelengths of each split resonator and the single resonator satisfy: in, For structural parameters, .
3. The surface acoustic wave resonator for suppressing parasitic modes according to claim 2, characterized in that: when At that time, the wavelengths of each split resonator and the single resonator satisfy: 。 4. The surface acoustic wave resonator for suppressing parasitic modes according to claim 1, characterized in that: Each of the split resonators includes a first bus bar and a second bus bar arranged in parallel, a first interdigital electrode and a second interdigital electrode staggered between the first bus bar and the second bus bar, and a reflective grid distributed on both sides of the first bus bar and the second bus bar; the first interdigital electrode is electrically connected to the first bus bar, and the second interdigital electrode is electrically connected to the second bus bar.
5. The surface acoustic wave resonator for suppressing parasitic modes according to claim 4, characterized in that: The gaps between adjacent first and second interdigital electrodes are equal. The width of each of the first interdigital electrodes and each of the second interdigital electrodes is equal. ; The wavelength of each of the aforementioned split resonators is .
6. The surface acoustic wave resonator for suppressing parasitic modes according to claim 4, characterized in that: For each of the split resonators, the number of its first interdigitated electrodes is The number of its second interdigital electrodes is ,satisfy: in, This represents the total number of interdigitated electrodes in a single resonator.
7. The surface acoustic wave resonator for suppressing parasitic modes according to any one of claims 4-6, characterized in that: when At that time, for each of the aforementioned split resonators, the overlap length of its finger strips is equal, and is always... ;when At that time, for each of the aforementioned split resonators, the overlap length of its finger strips is equal, and is always... ;when At that time, for each of the aforementioned split resonators, the overlap length of its finger strips is equal, and is always... And satisfy: in, It is the overlap length of the finger strips of a single resonator.
8. A filter, characterized in that: Includes a surface acoustic wave resonator that suppresses parasitic modes as described in any one of claims 1-7.