Filter, radio frequency front-end module and electronic device

Abstract

The present application relates to a filter, a radio frequency front-end module and an electronic device. The filter comprises a piezoelectric substrate, and a first reflector grating and two interdigital transducers, which are arranged on a surface of the piezoelectric substrate. The two interdigital transducers are respectively arranged on two opposite sides of the first reflector grating. The first reflector grating comprises first fingers, second fingers and third fingers, which are connected to each other, the first fingers and the second fingers respectively being arranged on two sides of the third fingers in a first direction, wherein the spacing between the central axis of a third finger adjacent to the first fingers and the central axis of an adjacent first finger is a first spacing, the spacing between the central axis of a third finger adjacent to the second fingers and the central axis of an adjacent second finger is a second spacing, and the first spacing is not equal to the second spacing.

Description

Filters, RF front-end modules and electronic devices

[0001] This application is based on and claims priority to Chinese patent application No. 202510025764.4 filed on January 8, 2025, entitled "Filters, RF Front-End Modules and Electronic Devices". Technical Field

[0002] This application relates to the field of radio frequency, and more particularly to a filter, a radio frequency front-end module including the filter, and an electronic device including the radio frequency front-end module. Background Technology

[0003] In the field of radio frequency (RF), filters typically consist of a piezoelectric substrate and multiple interdigital transducers. Through the interaction of each interdigital transducer with the piezoelectric substrate, the conversion between electrical signals and acoustic signals is achieved. To confine the surface acoustic waves generated by the interdigital transducers during operation, a reflective grating is placed on each opposite side of each interdigital transducer to form a resonator.

[0004] In related technologies, to achieve filter miniaturization, two resonators typically share a single reflector grating. When the parameters of the two resonators differ, sharing the reflector grating causes the dominant modes of the two resonators to interfere with each other, thereby degrading the filter's quality factor (Q value).

[0005] Application content

[0006] In view of the shortcomings of the above-mentioned related technologies, the purpose of this application is to provide a solution for improving the Q value of a filter, specifically including the following technical solution:

[0007] In a first aspect, embodiments of this application provide a filter, including a piezoelectric substrate, a first reflective grating disposed on the surface of the piezoelectric substrate, and two interdigital transducers, the two interdigital transducers being arranged on opposite sides of the first reflective grating;

[0008] The first reflective grating includes a first finger strip, a second finger strip, and a third finger strip connected together, with the first and second finger strips arranged on either side of the third finger strip along a first direction; wherein...

[0009] The distance between the central axis of a third finger adjacent to the first finger and the central axis of the adjacent first finger is the first distance, and the distance between the central axis of a third finger adjacent to the second finger and the central axis of the adjacent second finger is the second distance. The first distance and the second distance are not equal.

[0010] The filter of this application arranges two interdigital transducers on opposite sides of a first reflective grating, so that the first reflective grating can simultaneously constrain the propagation range of surface acoustic waves generated when the two interdigital transducers are working, thereby improving the performance of the two interdigital transducers and facilitating the miniaturization of the filter of this application.

[0011] The filter in this application further adjusts the spacing between the first, second, and third interdigital transducers within the first reflective grating, making the first spacing between adjacent first and third interdigital transducers unequal to the second spacing between adjacent second and third interdigital transducers. This avoids the mutual interference of surface acoustic waves generated when the two interdigital transducers are operating, thereby improving the Q value of the filter in this application.

[0012] Secondly, embodiments of this application provide a filter, including a piezoelectric substrate, a first reflective grating disposed on the surface of the piezoelectric substrate, and two interdigital transducers, the two interdigital transducers being arranged on opposite sides of the first reflective grating; the first reflective grating includes a first finger strip, a second finger strip, and a third finger strip connected together, the first finger strip and the second finger strip being arranged on both sides of the third finger strip along a first direction; wherein, the number of first finger strips is less than the number of second finger strips, and the number of first finger strips is greater than or equal to the number of third finger strips.

[0013] The filter provided in this application improves the Q value of the filter by setting a relatively small number of third fingers between multiple first fingers and multiple second fingers, while ensuring the overall size of the first reflective grating, by using the third fingers to block the mutual influence of surface acoustic waves generated when the two interdigital transducers are working.

[0014] Thirdly, embodiments of this application provide a radio frequency front-end module, including a filter as described in the first or second aspect.

[0015] Fourthly, embodiments of this application provide an electronic device, including a radio frequency front-end module.

[0016] Understandably, the RF front-end module provided in the third aspect and the electronic device provided in the fourth aspect of this application, because they employ the surface acoustic wave devices provided in the first and second aspects of this application, also possess better Q values. Attached Figure Description

[0017] Figure 1 is a schematic diagram of the structure of an electronic device provided in one embodiment of this application;

[0018] Figure 2 is a schematic diagram of the structure of the radio frequency front-end module provided in one embodiment of this application;

[0019] Figure 3 is a schematic diagram of the structure of the filter provided in one embodiment of this application;

[0020] Figure 4 is a top view of the filter provided in one embodiment of this application;

[0021] Figure 5 is a partial structural diagram of the filter provided in one embodiment of this application;

[0022] Figure 6 is a top view of another embodiment of the filter provided in this application;

[0023] Figure 7 is a schematic diagram of another partial structure of the filter provided in one embodiment of this application;

[0024] Figure 8 is a top view of another embodiment of the filter provided in this application;

[0025] Figure 9 is a partial structural diagram of the filter provided in one embodiment of this application;

[0026] Figure 10 is a schematic diagram of another partial structure of the filter provided in one embodiment of this application;

[0027] Figure 11 is a schematic diagram of another partial structure of the filter provided in one embodiment of this application;

[0028] Figure 12 is a schematic diagram of a partially magnified structure of the filter provided in one embodiment of this application;

[0029] Figure 13 is a schematic diagram of another partially enlarged structure of the filter provided in one embodiment of this application;

[0030] Figure 14 is a schematic diagram of another structure of the filter provided in one embodiment of this application;

[0031] Figure 15 is a schematic diagram of the filter arrangement structure provided in one embodiment of this application;

[0032] Figure 16 is a partial top view of the filter provided in one embodiment of this application;

[0033] Figure 17 is a comparison of the conductivity curves of Comparative Example 1 and Reference Example 1 in the related art;

[0034] Figure 18 is a comparison of the conductivity curves of Comparative Example 2 and Reference Example 1 in the related art;

[0035] Figure 19 is a comparison of the conductivity curves of Comparative Example 3 and Reference Example 1 in the related art;

[0036] Figure 20 is a comparison of the conductivity curves of Embodiment 1 and Reference Example 1 provided in one embodiment of this application;

[0037] Figure 21 is a comparison of the conductivity curves of Embodiment 2 and Reference Example 1 provided in one embodiment of this application;

[0038] Figure 22 is a comparison of the conductivity curves of Embodiment 3 and Reference Example 1 provided in one embodiment of this application;

[0039] Figure 23 is a comparison of the Q-value curves of Comparative Example 1 and Reference Example 1 in the related art;

[0040] Figure 24 is a comparison of the Q-value curves of Comparative Example 2 and Reference Example 1 in the related art;

[0041] Figure 25 is a comparison of the Q-value curves of Comparative Example 3 and Reference Example 1 in the related art;

[0042] Figure 26 is a comparison of the Q-value curves of Embodiment 1 and Reference Example 1 provided in one embodiment of this application;

[0043] Figure 27 is a comparison of the Q-value curves of Embodiment 2 and Reference Example 1 provided in one embodiment of this application;

[0044] Figure 28 is a comparison of the Q-value curves of Embodiment 3 and Reference Example 1 provided in one embodiment of this application;

[0045] Figure 29 is a comparison of the admittance curves of Comparative Examples 1-3 and Reference Example 1 in the related art;

[0046] Figure 30 is a comparison of admittance curves between Embodiments 1-3 and Reference Example 1 provided in one embodiment of this application;

[0047] Figure 31 is a comparison of the conductivity curves of Comparative Example 4 and Reference Example 2 in the related art;

[0048] Figure 32 is a comparison of the conductivity curves of Comparative Example 5 and Reference Example 2 in the related art;

[0049] Figure 33 is a comparison of the conductivity curves of Comparative Example 6 and Reference Example 2 in the related art;

[0050] Figure 34 is a comparison of the conductivity curves of Embodiment 4 and Reference Example 2 provided in one embodiment of this application;

[0051] Figure 35 is a comparison of the conductivity curves of Embodiment 5 and Reference Example 2 provided in one embodiment of this application;

[0052] Figure 36 is a comparison of the conductivity curves of Embodiment 6 and Reference Example 2 provided in one embodiment of this application;

[0053] Figure 37 is a comparison of the conductivity curves of Embodiment 7 and Reference Example 2 provided in one embodiment of this application;

[0054] Figure 38 is a comparison of the Q-value curves of Comparative Example 4 and Reference Example 2 in the related art;

[0055] Figure 39 is a comparison of the Q-value curves of Comparative Example 5 and Reference Example 2 in the related art;

[0056] Figure 40 is a comparison of the Q-value curves of Comparative Example 6 and Reference Example 2 in the related art;

[0057] Figure 41 is a comparison of the Q-value curves of Embodiment 4 and Reference Example 2 provided in one embodiment of this application;

[0058] Figure 42 is a comparison of the Q-value curves of Embodiment 5 and Reference Example 2 provided in one embodiment of this application;

[0059] Figure 43 is a comparison of the Q-value curves of Embodiment 6 and Reference Example 2 provided in one embodiment of this application;

[0060] Figure 44 is a comparison of the Q-value curves of Embodiment 7 and Reference Example 2 provided in one embodiment of this application. Detailed Implementation

[0061] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0062] The following descriptions of the embodiments are based on the accompanying illustrations and are used to illustrate specific embodiments in which this application can be implemented. The component designations used herein, such as "first," "second," etc., are merely for distinguishing the described objects and have no sequential or technical meaning. Unless otherwise specified, the terms "connection" and "linkage" used in this application include both direct and indirect connections (linkages). Directional terms used in this application, such as "up," "down," "front," "rear," "left," "right," "inner," "outer," "side," etc., are merely for reference to the accompanying illustrations. Therefore, the use of directional terms is for better and clearer explanation and understanding of this application, and does not indicate or imply that the referred device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this application.

[0063] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joint" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. It should be noted that the terms "first," "second," etc., in the specification, claims, and drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising," "may include," "include," or "may include" used in this application indicate the presence of the corresponding disclosed function, operation, element, etc., and do not limit one or more other functions, operations, elements, etc. Moreover, the terms "comprising" or "include" indicate the presence of the corresponding features, numbers, steps, operations, elements, components, or combinations thereof disclosed in the specification, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, and are intended to cover non-exclusive inclusion.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0065] Please refer to Figure 1, which shows a schematic diagram of the structure of an electronic device 300 provided in one embodiment of this application.

[0066] As shown in Figure 1, the electronic device 300 of this application includes a transceiver, an antenna, and a radio frequency front-end module 200. The radio frequency front-end module is connected between the transceiver and the antenna and is used to amplify the radio frequency signal output by the transceiver to obtain a sufficiently large radio frequency output power and transmit the amplified radio frequency signal to the antenna for radiation; and / or, to amplify the weak radio frequency signal received by the antenna with a low noise figure and transmit it to the transceiver.

[0067] For example, electronic device 300 includes at least one of computers, mobile phones, tablets, smartwatches, and navigators, etc., and this application does not specifically limit it.

[0068] Please refer to Figure 2, which shows a schematic diagram of the structure of the radio frequency front-end module 200 provided in one embodiment of this application.

[0069] An RF front-end module is a component that integrates one or more discrete devices such as RF switches, low-noise amplifiers, filters, duplexers, and power amplifiers into an independent module, thereby improving integration and hardware performance, and miniaturizing the size.

[0070] As shown in Figure 2, the RF front-end module 200 of this embodiment includes a signal terminal 201, a switch 202, an amplifier 203, and a filter 100. The signal terminal 201 is used to receive external signals or transmit RF signals. Exemplarily, the signal terminal 201 can be a port for connecting an antenna, also known as an antenna port. The RF front-end module can connect to an antenna in an electronic device through the signal terminal 201, thereby receiving or transmitting RF signals through the antenna.

[0071] Switch 202 is communicatively connected between signal terminal 201 and filter 100 to control signal transmission between signal terminal 201 and filter 100.

[0072] The number of amplifiers 203 can be one or more. Optionally, amplifier 203 may include at least one low-noise amplifier, or one or more power amplifiers, or at least one power amplifier and at least one low-noise amplifier.

[0073] The number of filters 100 can also be one or more. When there are multiple filters 100, different filters 100 can be used to filter signals on different signal transmission paths, wherein the different signal transmission paths can be transmission paths and reception paths of the same frequency band, or transmission paths and reception paths of different frequency bands, or transmission paths of different frequency bands, or reception paths of different frequency bands.

[0074] The switch 202 may include multiple switching paths, and the common terminal of the multiple switching paths is connected to the signal terminal 201 to switch the connection of filters on different signal transmission paths to the signal terminal 201.

[0075] When amplifier 203 is a low-noise amplifier, filter 100 is used to receive the external signal received by signal terminal 201 when switch 202 is closed, and to filter it to output a signal with a preset frequency. Amplifier 203 is electrically connected to filter 100 to amplify the signal processed by filter 100 and output it to a subsequent stage (e.g., a receiver in an electronic device).

[0076] When amplifier 203 is a power amplifier, filter 100 is used to receive the radio frequency signal amplified by amplifier 203, filter the received radio frequency signal, and then transmit the filtered radio frequency signal to signal terminal 201 through closed switch 202.

[0077] In one embodiment, the RF front-end module 200 includes a plurality of filters 100, at least two of which can be integrated together to form a duplexer or multiplexer. That is, the RF front-end module 200 also includes a multiplexer, which includes a plurality of filters 100.

[0078] It is worth noting that in the embodiments of this application and subsequent embodiments, the number of structures is multiple, meaning that the number of the structures is two or more.

[0079] In one embodiment, the filter 100 of this application includes a piezoelectric substrate 10, interdigital transducers 20, and a first reflective grating 30. The number of interdigital transducers 20 is plurality of, and the plurality of interdigital transducers 20 and the first reflective grating 30 are arranged at intervals on the surface of the piezoelectric substrate 10. Specifically, the number of interdigital transducers 20 is at least two, with at least two interdigital transducers 20 positioned on opposite sides of the first reflective grating 30.

[0080] For example, please refer to Figures 3 and 4, where Figure 3 is a structural schematic diagram of the filter 100 provided in one embodiment of the present application, and Figure 4 is a top view structural schematic diagram of the filter 100 provided in one embodiment of the present application.

[0081] As shown in Figures 3 and 4, there are two interdigital transducers 20 in filter 100.

[0082] For ease of description, the embodiments of this application and subsequent embodiments are described in terms of two adjacent interdigital transducers 20 disposed on the surface of the piezoelectric substrate 10.

[0083] Please refer to Figure 5 for a partial structural diagram of the filter 100 provided in one embodiment of this application.

[0084] As shown in Figure 5, each interdigital transducer 20 includes two parallel and spaced-apart busbars 21 and a plurality of parallel and spaced-apart electrode fingers 22. One of the two busbars 21 is used to receive external signals, and the other busbar 21 is used to output signals. The plurality of electrode fingers 22 are located between the two busbars 21. Some of the electrode fingers 22 are connected to one busbar 21, and other electrode fingers 22 are connected to the other busbar 21.

[0085] For ease of description, the busbar 21 used for receiving external signals is defined as the first busbar 21a, and the busbar 21 used for outputting signals is defined as the second busbar 21b. The electrode finger 22 connected to the first busbar 21a is defined as the first electrode 221, and the electrode finger 22 connected to the second busbar 21b is defined as the second electrode 222.

[0086] Specifically, the first electrode 221 and the second electrode 222 are arranged alternately along the first direction 001. Both the first electrode 221 and the second electrode 222 extend along the second direction 002. Specifically, as shown in Figure 4, along the first direction 001, there is a second electrode 222 between any two adjacent first electrodes 221, and there is a first electrode 221 between any two adjacent second electrodes 222.

[0087] Wherein, the first direction 001 is the extension direction of the busbars, that is, both the first busbar 21a and the second busbar 21b extend along the first direction 001. The second direction 002 intersects the first direction 001. For example, the second direction 002 and the first direction 001 can be perpendicular to each other, so that each electrode finger 22 has a 90° angle with the busbar it is connected to. For example, the second direction 002 and the first direction 001 can also not be perpendicular, so that each electrode finger 22 has an angle greater than 90° with the busbar it is connected to.

[0088] In this embodiment, when an external excitation signal is applied to the interdigital transducer 20, the interdigital transducer 20 converts the electrical signal into a surface acoustic wave. The surface acoustic wave propagates along the surface of the piezoelectric substrate 10 and is reflected by the reflective grating, and is then converted back into an electrical signal by the interdigital transducer 20 for output.

[0089] Surface acoustic waves (SAWs) are used to achieve the frequency selection and signal processing functions of the filter 100 in this application. During SAW propagation, the primary propagation direction is the first direction 001. However, in practice, due to edge effects and acoustic diffraction, the propagation direction of the SAW formed on the surface of the piezoelectric substrate 10 may also be other directions. In one embodiment, SAWs propagating in other directions are absorbed by a sound-absorbing material (not shown in the figure).

[0090] It is understood that this application can be applied to devices including interdigital transducers, such as high-Q piezoelectric thin-film surface acoustic wave filters (POI SAW filters), conventional surface acoustic wave filters (NSAW filters), temperature-compensated surface acoustic wave filters (TCSAW filters), and filter devices formed by interconnecting them through a certain topology. This application does not limit the application in this regard.

[0091] In one embodiment, the first direction 001 is the arrangement direction of the two interdigital transducers 20.

[0092] In this embodiment, along the first direction 001, the first reflective grating 30 is located on one side of the interdigital transducer 20. When the surface acoustic wave generated by the interdigital transducer 20 operates, it propagates along the first direction 001 and is transmitted into the first reflective grating 30. The first reflective grating 30 is used to reflect the surface acoustic wave propagating to the first reflective grating 30, so as to confine the surface acoustic wave within the interdigital transducer 20 that generates the surface acoustic wave.

[0093] Since the first reflective grating 30 is located between the two interdigital transducers 20, it is understood that the first reflective grating 30 can simultaneously reflect the surface acoustic waves generated by the two interdigital transducers 20 during operation, thus constraining the propagation range of the surface acoustic waves generated by the two interdigital transducers 20, thereby improving the performance of the two interdigital transducers. This, in turn, improves the operating performance of the filter in this application.

[0094] Meanwhile, compared with the related technologies where each interdigital transducer independently uses a pair of identical reflective gratings for reflection and different interdigital transducers use different reflective gratings, the filter 100 of this application uses a first reflective grating 30 to constrain the surface acoustic waves generated when the two interdigital transducers 20 are working. It is also beneficial to reduce the spacing between the two interdigital transducers 20, which is beneficial to the miniaturization of the filter 100 of this application.

[0095] Please refer to Figures 6 and 7, where Figure 6 is a top view of another structure of the filter 100 provided in one embodiment of this application, and Figure 7 is a partial structure of another structure of the filter 100 provided in one embodiment of this application.

[0096] As shown in Figures 6 and 7, the first reflective grating 30 includes a first finger strip 31, a second finger strip 32, and a third finger strip 33. Along the first direction 001, the first finger strip 31 and the second finger strip 32 are arranged on both sides of the third finger strip 33. In this embodiment, one of the two interdigital transducers 20 is located on one side of the third finger strip 33 along with the first finger strip 31, and the other interdigital transducer 20 is located on the other side of the third finger strip 33 along with the second finger strip 32.

[0097] For ease of description, the interdigital transducer 20 on the same side as the first finger strip 31 is defined as the first interdigital transducer 20a. The interdigital transducer 20 on the same side as the second finger strip 32 is defined as the second interdigital transducer 20b.

[0098] As shown in Figures 6 and 7, the surface acoustic wave generated when the first interdigital transducer 20a is working propagates toward the first finger strip 31. When the dominant mode of the surface acoustic wave reaches the first finger strip 31, the first finger strip 31 reflects the dominant mode. This confines the dominant mode of the surface acoustic wave generated by the first interdigital transducer 20a within the first interdigital transducer 20a.

[0099] When the second interdigital transducer 20b is operating, the surface acoustic wave generated propagates toward the second interdigital strip 32. When the dominant mode of the surface acoustic wave reaches the second interdigital strip 32, the second interdigital strip 32 reflects the dominant mode. This confines the dominant mode of the surface acoustic wave generated by the second interdigital transducer 20b within the second interdigital transducer 20b.

[0100] In one embodiment, the distance between a third finger 33 adjacent to the first finger 31 and the central axis of the adjacent first finger 31 is a first distance D1, and the distance between a third finger 33 adjacent to the second finger 32 and the central axis of the adjacent second finger 32 is a second distance D2. The first distance D1 and the second distance D2 are not equal.

[0101] It is worth noting that the number of first finger strips 31, second finger strips 32, and third finger strips 33 can be one or more. A third finger strip 33 adjacent to a first finger strip 31 and an adjacent first finger strip 31 refers to the third finger strip 33 closest to the first finger strip 31 among all third finger strips 33, and the first finger strip 31 closest to the third finger strip 33 among all first finger strips 31. For convenience, this will also be referred to below as "adjacent third finger strip 33 and first finger strip 31". Similarly, a third finger strip 33 adjacent to a second finger strip 32 and an adjacent second finger strip 32 refers to the third finger strip 33 closest to the second finger strip 32 among all third finger strips 33, and the second finger strip 32 closest to the third finger strip 33 among all second finger strips 32. For convenience, this will also be referred to below as "adjacent third finger strip 33 and second finger strip 32".

[0102] The wavelength range of surface acoustic waves reflected by the reflective grating is related to the distance between the central axes of adjacent fingers in the grating. When surface acoustic waves propagate to the fingers of the grating, the grating mainly reflects surface acoustic waves with wavelengths matching the distance between the central axes of two adjacent fingers. Some of the mismatched surface acoustic waves are blocked by the fingers, while others propagate directly through the grating and gradually attenuate as the propagation distance increases.

[0103] In this embodiment, the first finger strip 31 is configured to match the master mode of the first interdigital transducer 20a, and the second finger strip 32 is configured to match the master mode of the second interdigital transducer 20b.

[0104] It is worth noting that the master mode described in the embodiments of this application and subsequent embodiments refers to the portion of surface acoustic waves whose frequency matches that of the master mode.

[0105] In the illustrations shown in Figures 6 and 7, there is one of each of the first finger strip 31, the second finger strip 32, and the third finger strip 33. Correspondingly, a third finger strip 33 adjacent to the first finger strip 31 and an adjacent first finger strip 31 are adjacent third finger strip 33 and first finger strip 31, and a third finger strip 33 adjacent to the second finger strip 32 and an adjacent second finger strip 32 are adjacent third finger strip 33 and second finger strip 32.

[0106] In this embodiment of the application, when the first interdigital transducer 20a is working, the first finger strip 31 of the first reflective grating 30 can reflect the main mode in the surface acoustic wave generated by the first interdigital transducer 20a into the first interdigital transducer 20a.

[0107] In this embodiment, by setting the first spacing D1 and the second spacing D2 to be unequal, the main modes not reflected by the first finger strip 31 and the second finger strip 32 can be prevented from affecting each other, thereby ensuring the performance of the filter 100 and improving the Q value of the filter 100.

[0108] Similarly, when the second interdigital transducer 20b is operating, the filter 100 of this application also helps to ensure the performance of the second interdigital transducer 20b by setting the first spacing D1 and the second spacing D2 to be unequal. This ensures the performance of the filter 100 of this application and improves the Q value of the filter 100 of this application.

[0109] Based on the above description, it is worth mentioning that when there are multiple of one or more of the first finger strip 31, the second finger strip 32, and the third finger strip 33, in the description of adjacent first finger strips 31 and third finger strips 33, the third finger strip 33 refers to the third finger strip 33 adjacent to the first finger strip 31, and the first finger strip 31 refers to the first finger strip 31 with the smallest distance from the third finger strip 33, that is, the first finger strip 31 adjacent to the third finger strip 33.

[0110] In the description of the adjacent second finger strip 32 and third finger strip 33, the third finger strip 33 refers to a third finger strip 33 that is adjacent to the second finger strip 32, and the second finger strip 32 refers to the second finger strip 32 that has the smallest distance from the third finger strip 33, that is, the second finger strip 32 that is adjacent to the third finger strip 33.

[0111] Please refer to Figures 8 and 9 for further details. Figure 8 is a top view of the filter 100 provided in one embodiment of this application, and Figure 9 is a partial view of the filter 100 provided in one embodiment of this application.

[0112] As shown in Figures 8 and 9, there are multiple first finger strips 31 and second finger strips 32, and one third finger strip 33. The multiple first finger strips 31, third finger strips 33, and multiple second finger strips 32 are arranged at intervals along the first direction 001.

[0113] Understandably, the arrangement of multiple first finger strips 31 can increase the reflection efficiency of the first finger strips 31 on the surface acoustic waves generated when the first interdigital transducer 20a is operating, thereby improving the performance of the first interdigital transducer 20a and increasing its Q value. Similarly, the arrangement of multiple second finger strips 32 can increase the reflection efficiency of the second finger strips 32 on the surface acoustic waves generated when the second interdigital transducer 20b is operating, thereby improving the performance of the second interdigital transducer 20b and increasing its Q value. This, in turn, improves the Q value of the filter 100 of this application.

[0114] In this embodiment, the distance between the central axes of two adjacent first finger strips 31 is the first finger spacing F1, and the distance between the central axes of two adjacent second finger strips 32 is the second finger spacing F2. The first finger spacing F1 is used to define the reflection frequency of the surface acoustic wave generated by the first reflective grating 30 when the first interdigital transducer 20a is working, and the second finger spacing F2 is used to define the reflection frequency of the surface acoustic wave generated by the first reflective grating 30 when the second interdigital transducer 20b is working.

[0115] The difference between twice the first finger spacing D1 and the first finger spacing F1 is defined as the third finger spacing F3, i.e., D1 = 1 / 2(F1 + F3). And / or, the difference between twice the second finger spacing D2 and the second finger spacing F2 is defined as the third finger spacing F3, i.e., D2 = 1 / 2(F2 + F3). Wherein, the third finger spacing F3 is greater than the first finger spacing F1 and the second finger spacing F2.

[0116] That is, the third interdigital transducer 33 has a relatively large gap with the first interdigital transducer 31 and the second interdigital transducer 32. On the one hand, this allows the main mode not reflected by the first interdigital transducer 31 to gradually attenuate before propagating to the third interdigital transducer 33, thereby reducing the mutual influence of the main modes of the two interdigital transducers 20. On the other hand, the relatively large gap also makes it less likely that the portion of the main mode generated by the two interdigital transducers 20 that passes through the first interdigital transducer 31 and the second interdigital transducer 32 will pass through the third interdigital transducer 33 and propagate to the interdigital transducer 20 on the other side. This allows the third interdigital transducer 33 to block the mutual influence of the surface acoustic waves when the two interdigital transducers 20 are operating. This, in turn, improves the Q value of the filter 100 of this application.

[0117] In one embodiment, the difference between twice the first spacing D1 and the first finger spacing F1 is equal to the difference between twice the second spacing D2 and the second finger spacing F2.

[0118] Please refer to Figure 10 for another partial structural diagram of the filter 100 provided in one embodiment of this application.

[0119] As shown in Figure 10, there are multiple first finger strips 31, multiple second finger strips 32, and multiple third finger strips 33, which are arranged at intervals along the first direction 001. The distance between the central axes of two adjacent first finger strips 31 is the first finger spacing F1, the distance between the central axes of two adjacent second finger strips 32 is the second finger spacing F2, and the distance between the central axes of two adjacent third finger strips 33 is the third finger spacing F3. The third finger spacing F3 is greater than the first finger spacing F1 and the second finger spacing F2.

[0120] Along the first direction 001, multiple first finger strips 31 are arranged at equal intervals, multiple second finger strips 32 are arranged at equal intervals, and multiple third finger strips 33 are arranged at equal intervals. The first finger spacing F1 corresponding to the multiple equally spaced first finger strips 31 is typically matched with the dominant mode of the first interdigital transducer 20a. That is, the dominant mode in the surface acoustic wave generated when the first interdigital transducer 20a is working is reflected by the multiple first finger strips 31, thereby increasing the Q value of the first interdigital transducer 20a.

[0121] The second finger spacing F2 corresponding to the multiple equally spaced second finger strips 32 is usually matched with the main mode of the second interdigital transducer 20b. That is, the portion of the surface acoustic wave that matches the main mode frequency in the surface acoustic wave generated when the second interdigital transducer 20b is working will be reflected by the multiple second finger strips 32, thereby improving the Q value of the second interdigital transducer 20b.

[0122] The multiple equally spaced third finger strips 33 increase the spacing between the first finger strip 31 and the second finger strip 32, reducing the impact of the dominant mode not reflected by the first finger strip 31 and the second finger strip 32 on the two interdigital transducers 20. Simultaneously, the cooperation of the multiple third finger strips 33 further improves the blocking efficiency of the dominant mode of surface acoustic waves passing through the first finger strip 31 and the second finger strip 32, further preventing the dominant mode from propagating to the other interdigital transducer 20 during operation. This improves the Q value of the filter in this application.

[0123] In one embodiment, the first spacing D1 is equal to half the sum of the third finger spacing F3 and the first finger spacing F1; the second spacing D2 is equal to half the sum of the third finger spacing F3 and the second finger spacing F2.

[0124] For surface acoustic waves (SAWs), when they propagate on the surface of the piezoelectric substrate 10, they gradually attenuate with increasing propagation time without the influence of other structures. Typically, the intensity of the SAW gradually decreases during this attenuation process. In this embodiment, when the dominant mode of the SAW generated by the interdigital transducer 20 propagates between the first and third interdigital strips 31 and 33, and between the second and third interdigital strips 32 and 33, the intensity of the dominant mode gradually decreases.

[0125] Understandably, the larger the first spacing D1 and the second spacing D2, the lower the intensity of the main mode when it propagates to the third interdigital transducer 33, and correspondingly, the smaller the mutual influence between the main modes of the two interdigital transducers 20. The larger the first spacing D1 and the second spacing D2, the larger the size of the first reflective grating 30, and the larger the spacing between the first interdigital transducer 20a and the second interdigital transducer 20b, which is not conducive to the miniaturization of the filter 100 of this application.

[0126] That is, by limiting the size of the first spacing D1 and the second spacing D2, the filter 100 of this application can improve the Q value of the filter 100 while facilitating its miniaturization.

[0127] In one embodiment, the width of the third finger strip 33 is greater than the width of the second finger strip 32. That is, the first reflective grating 30 of the filter 100 of this application adjusts the relationship between the third finger spacing F3 and the second finger spacing F2 by adjusting the width of the third finger strip 33. This ensures that the third finger strip 33 blocks the surface acoustic waves generated when the second interdigital transducer 20b is working, thereby improving the Q value of the filter 100 of this application.

[0128] In one embodiment, the width of the third finger strip 33 is greater than the width of the first finger strip 31. That is, the first reflective grating 30 of the filter 100 of this application adjusts the relationship between the third finger spacing F3 and the first finger spacing F1 by adjusting the width of the third finger strip 33. This ensures that the third finger strip 33 blocks the surface acoustic waves generated when the first interdigital transducer 20a is working, thereby improving the Q value of the filter 100 of this application.

[0129] Please refer to Figure 11 for another partial structural diagram of the filter 100 provided in one embodiment of this application.

[0130] As shown in Figure 11, along the first direction 001, the gap size between two adjacent first finger strips 31 is the first gap size G1, and the gap size between a third finger strip 33 adjacent to the first finger strip 31 and the adjacent first finger strip 31 is greater than the first gap size G1.

[0131] That is, the first reflective grating 30 of the filter 100 of this application adjusts the relationship between the third finger spacing F3 and the first finger spacing F1 by adjusting the adjacent third finger strips 33 and first finger strips 31. This ensures that the third finger strips 33 block the surface acoustic waves generated when the first interdigital transducer 20a is working, thereby improving the Q value of the filter 100 of this application.

[0132] In one embodiment, along the first direction 001, the gap size between two adjacent second finger strips 32 is the second gap size G2, and the gap size between a third finger strip 33 adjacent to the second finger strip 32 and the adjacent second finger strip 32 is greater than the second gap size G2.

[0133] That is, the first reflective grating 30 of the filter 100 of this application adjusts the gap size between adjacent third finger strips 33 and second finger strips 32 to adjust the relationship between the third finger spacing F3 and the second finger spacing F2. This ensures that the third finger strip 33 blocks the surface acoustic waves generated when the second interdigital transducer 20b is working, thereby improving the Q value of the filter 100 of this application.

[0134] In one embodiment, the width of the third finger strip 33 is greater than the width of the first finger strip 31, and the width of the third finger strip 33 is greater than the width of the second finger strip 32. Along the first direction 001, the gap between a third finger strip 33 adjacent to the first finger strip 31 and the adjacent first finger strip 31 is greater than the first gap size G1, and the gap between a third finger strip 33 adjacent to the second finger strip 32 and the adjacent second finger strip 32 is greater than the second gap size G2.

[0135] In one embodiment, the widths of the third finger strip 33, the first finger strip 31, and the second finger strip 32 are all equal. Along the first direction 001, the gap between a third finger strip 33 adjacent to the first finger strip 31 and the adjacent first finger strip 31 is greater than the first gap size G1, and the gap between a third finger strip 33 adjacent to the second finger strip 32 and the adjacent second finger strip 32 is greater than the second gap size G2.

[0136] In one embodiment, the width of the third finger strip 33 is greater than the width of the first finger strip 31, and the width of the third finger strip 33 is greater than the width of the second finger strip 32. Along the first direction 001, the gap between a third finger strip 33 adjacent to the first finger strip 31 and the adjacent first finger strip 31 is equal to the first gap size G1, and the gap between a third finger strip 33 adjacent to the second finger strip 32 and the adjacent second finger strip 32 is equal to the second gap size G2.

[0137] In one embodiment, the ratio of the third interdigital spacing F3 to the first interdigital spacing F1 is greater than or equal to 1.01. That is, the filter 100 of this application controls the ratio of the third interdigital spacing F3 to the first interdigital spacing F1 so that the intensity of the main mode propagating to the third interdigital strip 33 is relatively weak, thereby reducing the mutual influence between the main modes of the two interdigital transducers 20 and improving the Q value of the filter 100 of this application.

[0138] Meanwhile, the ratio of the third finger spacing F3 to the first finger spacing F1 is greater than or equal to 1.01, which also ensures the blocking effect of the third finger strip 33 on the main modes of the two interdigital transducers 20. This avoids the surface acoustic waves generated by the two interdigital transducers 20 from interfering with each other during operation, thus improving the Q value of the filter 100 of this application.

[0139] In one embodiment, the third finger spacing F3 is less than or equal to 1.04 times the first finger spacing F1 to control the first spacing D1 and the second spacing D2, thereby reducing the overall size of the first reflective grating 30 and facilitating the miniaturization of the filter 100 of this application.

[0140] In one embodiment, the third finger spacing F3 is less than or equal to 1.1 times the first finger spacing F1.

[0141] In one embodiment, referring back to Figures 4 and 5, the first interdigital transducer 20a includes a plurality of first electrode fingers 22a. The finger spacing of the first interdigital transducer 20a is equal to the first finger spacing F1. The distance between the central axis of the first finger strip 31 adjacent to the first interdigital transducer 20a and the adjacent first electrode finger 22a is equal to the first finger spacing F1.

[0142] Since the frequency of the dominant mode of the first interdigital transducer 20a is determined by the finger spacing between two adjacent first electrode fingers 22a within the first interdigital transducer 20a, the filter 100 of this application sets the finger spacing between two adjacent first electrode fingers 22a and the distance between the central axis of the first finger strip 31 adjacent to the first interdigital transducer 20a and the adjacent first electrode finger 22a as a first finger spacing F1, thereby ensuring that the multiple first finger strips 31 can reflect the dominant mode of the first interdigital transducer 20a.

[0143] In one embodiment, as shown in Figures 4 and 5, the second interdigital transducer 20b includes a plurality of second electrode fingers 22b, the finger spacing of the second interdigital transducer 20b is equal to the second finger spacing F2, and the distance between the central axis of the second finger strip 32 adjacent to the second interdigital transducer 20b and the adjacent second electrode finger 22b is equal to the second finger spacing F2.

[0144] Since the frequency of the dominant mode of the second interdigital transducer 20b is determined by the finger spacing between two adjacent second electrode fingers 22b within the second interdigital transducer 20b, the filter 100 of this application sets the finger spacing between two adjacent second electrode fingers 22b and the distance between the central axis of the second finger strip 32 adjacent to the second interdigital transducer 20b and the adjacent second electrode finger 22b as a second finger spacing F2, thereby ensuring that multiple second finger strips 32 can reflect the dominant mode of the second interdigital transducer 20b.

[0145] In one embodiment, the finger spacing of the two interdigital transducers 20 is unequal. For example, in one embodiment, the first finger spacing F1 is greater than the second finger spacing F2. That is, the first reflective grating 30 of this application can simultaneously reflect surface acoustic waves from two interdigital transducers 20 with different dominant modes. This improves the operating range of the filter 100 of this application.

[0146] In one embodiment, there are multiple first finger strips 31 and multiple second finger strips 32, and the number of first finger strips 31 and the number of second finger strips 32 are both greater than or equal to the number of third finger strips 33.

[0147] Multiple first finger strips 31 are used to reflect the dominant mode of the surface acoustic wave generated when the first interdigital transducer 20a is working, and multiple second finger strips 32 are used to reflect the dominant mode of the surface acoustic wave generated when the second interdigital transducer 30b is working.

[0148] The more fingers a reflective grating has, the better its reflection effect on the corresponding surface acoustic waves. In this embodiment, the filter 100 improves the reflection effect of the first reflective grating 30 on the surface acoustic waves generated by the first interdigital transducer 20a and the second interdigital transducer 30b when they are working by setting a relatively large number of first fingers 31 and second fingers 32, thereby ensuring the performance of the filter 100.

[0149] In one embodiment, the number of first finger strips 31 is less than or equal to the number of second finger strips 32. Since a smaller finger spacing of the interdigital transducer results in a smaller wavelength of the surface acoustic wave generated during operation, the number of reflective gratings should be increased accordingly to match the wavelength of the surface acoustic wave. Furthermore, because the first finger spacing F1 is greater than the second finger spacing F2, the relationship between the number of first finger strips 31 and second finger strips 32 is adjusted so that the first finger strips 31 and second finger strips 32 match the dominant modes of the surface acoustic waves from the corresponding two interdigital transducers 20. This ensures the reflection effect of the first reflective grating 30 on the two interdigital transducers 20.

[0150] Since the first finger spacing F1 is greater than the second finger spacing F2, it is understandable that setting a relatively small number of first finger strips 31 can reduce the size occupied by multiple first finger strips 31 along the first direction 001 while ensuring the Q value of the filter 100 of this application, which is beneficial to the miniaturization of the filter 100 of this application.

[0151] In one embodiment, the ratio of the number of second finger strips 32, the number of third finger strips 33, and the number of first finger strips 31 is 2:1:1. Based on the first finger spacing F1, the second finger spacing F2, and the third finger spacing F3, the filter 100 of this application adjusts the ratio of the number of first finger strips 31, second finger strips 32, and third finger strips 33 to further improve the Q value of the filter 100 while ensuring the reflection effect of the first reflective grating 30 on the main modes of the two interdigital transducers 20.

[0152] In one embodiment, the sum of the numbers of the first finger strip 31, the second finger strip 32, and the third finger strip 33 is greater than or equal to 10. Since the number of fingers in the reflective grating is positively correlated with the reflective effect of the reflective grating on surface acoustic waves (SAW), the filter 100 of this application ensures that the first finger strip 31 and the second finger strip 32 reflect the SAW generated by the corresponding interdigital transducers 20 during operation, and that the third finger strip 33 blocks the SAW generated by the two interdigital transducers 20 during operation, by controlling the sum of the numbers of the first finger strip 31, the second finger strip 32, and the third finger strip 33 to be greater than 10. This ensures the Q value of the filter 100 of this application.

[0153] In one embodiment, the sum of the number of the first finger strip 31, the second finger strip 32 and the third finger strip 33 is less than or equal to 40, so as to reduce the overall size of the first reflective grating 30, which is beneficial to the miniaturization of the filter 100 of this application.

[0154] In one embodiment, the sum of the number of the first finger strip 31, the second finger strip 32 and the third finger strip 33 is greater than or equal to 10 and less than or equal to 40, so as to reduce the overall size of the first reflective grating 30 while ensuring the Q value of the filter 100 of this application, which is beneficial to the miniaturization of the filter 100 of this application.

[0155] In one embodiment, as shown in FIG4, the filter 100 of this application further includes a second reflective grating 40 and a third reflective grating 50. Along the first direction 001, the first interdigital transducer 20a and the second reflective grating 40 are located on the first side of the first reflective grating 30, and the second interdigital transducer 20b and the third reflective grating 50 are located on the second side of the first reflective grating.

[0156] Along the first direction 001, a first reflective grating 30 and a second reflective grating 40 are respectively provided on opposite sides of the first interdigital transducer 20a. The first reflective grating 30 and the second reflective grating 40 cooperate with each other to constrain the surface acoustic wave generated when the first interdigital transducer 20a is working. Specifically, during the operation of the filter 100 of this application, the main mode of the surface acoustic wave generated when the first interdigital transducer 20a is working will propagate along the first direction 001 to the first reflective grating 30 and the second reflective grating 40 respectively, and the main mode propagating to the first reflective grating 30 will be reflected by multiple first finger strips 31.

[0157] The second reflective grating 40 includes multiple fourth finger strips 41. The main mode propagating to the second reflective grating 40 is reflected towards the first interdigital transducer 20a under the action of the multiple fourth finger strips 41. This achieves constraint on the main mode generated by the first interdigital transducer 20a and improves the Q value of the first interdigital transducer 20a.

[0158] Along the first direction 001, a first reflective grating 30 and a third reflective grating 50 are respectively provided on opposite sides of the second interdigital transducer 20b. The first reflective grating 30 and the third reflective grating 50 cooperate to constrain the surface acoustic wave generated when the second interdigital transducer 20b is working. Specifically, during the operation of the filter 100 of this application, the main mode of the surface acoustic wave generated when the second interdigital transducer 20b is working will propagate along the first direction 001 to the first reflective grating 30 and the third reflective grating 50 respectively, and the main mode propagating to the first reflective grating 30 will be reflected by multiple second finger strips 32.

[0159] The third reflector grating 50 includes multiple fifth fingers 51. Surface acoustic waves propagating to the third reflector grating 50 are reflected towards the second interdigital transducer 20b under the action of the multiple fifth fingers 51. This achieves constraint on the dominant mode generated by the second interdigital transducer 20b, thereby improving the Q value of the second interdigital transducer 20b.

[0160] In one embodiment, the sum of the number of the first finger strip 31, the second finger strip 32, and the third finger strip 33 is greater than or equal to the minimum of the number of the fourth finger strip 41 and the number of the fifth finger strip 51.

[0161] In one embodiment, the sum of the number of the first finger strip 31, the second finger strip 32, and the third finger strip 33 is less than or equal to the largest of the number of the fourth finger strip 41 and the number of the fifth finger strip 51.

[0162] Based on the limitations of the two embodiments described above, the filter 100 of this application adjusts the relationship between the total number of the first reflective grating 30 and the number of the fourth and fifth reflective gratings 41 and 51. This ensures the reflection effect of the first and second reflective gratings 31 and 32 on the two interdigital transducers 20. Furthermore, it controls the overall size of the first reflective grating 30, facilitating the miniaturization of the filter 100.

[0163] Please refer to Figure 12 for a partially magnified schematic diagram of the filter 100 provided in one embodiment of this application.

[0164] As shown in Figure 12, along the first direction 001, the distance between the central axes of two adjacent fourth finger strips 41 is the fourth finger distance F4, the distance between the central axes of two adjacent first electrode fingers 22a in the first interdigital transducer 20a is equal to the fourth finger distance F4, and the distance between the central axes of adjacent fourth finger strips 41 and first electrode fingers 22a is equal to the fourth finger distance F4.

[0165] Since the frequency of the main mode of the first interdigital transducer 20a is determined by the finger spacing between two adjacent first electrode fingers 22a within the first interdigital transducer 20a, the filter 100 of this application sets the finger spacing between two adjacent first electrode fingers 22a, the distance between the central axis of the adjacent fourth finger strip 41 and the first electrode finger 22a, and the finger spacing between two adjacent fourth finger strips 41 as a fourth finger spacing F4, thereby ensuring that multiple fourth finger strips 41 can reflect the main mode of the first interdigital transducer 20a.

[0166] Please refer to Figure 13 for another partially enlarged structural schematic diagram of the filter 100 provided in one embodiment of this application.

[0167] As shown in Figure 13, along the first direction 001, the distance between the central axes of two adjacent fifth finger strips 51 is the fifth finger distance F5. The distance between the central axes of two adjacent second electrode fingers 22b in the second interdigital transducer 20b is equal to the fifth finger distance F5. The distance between the central axes of adjacent fifth finger strips 51 and second electrode fingers 22b is equal to the fifth finger distance F5.

[0168] Since the frequency of the dominant mode of the second interdigital transducer 20b is determined by the finger spacing between two adjacent second electrode fingers 22b within the second interdigital transducer 20b, the filter 100 of this application ensures that multiple fifth finger strips 51 can reflect the dominant mode of the second interdigital transducer 20b by setting the finger spacing between two adjacent second electrode fingers 22b, the distance between the central axis of an adjacent fifth finger strip 51 and the second electrode finger 22b, and the finger spacing between two adjacent fifth finger strips 51 as a fifth finger spacing F5.

[0169] In one embodiment, referring back to Figure 5, along the arrangement direction of the two busbars 21, the distance between the ends of any two adjacent electrode fingers 22 in each interdigital transducer 20 that are not connected to the busbar 21 is the aperture size L, and the aperture size L of the two interdigital transducers 20 is equal.

[0170] In one embodiment, the spacing between the two busbars 21 of each interdigital transducer 20 is equal, and the length of the first finger bar 31, the length of the second finger bar 32, and the length of the third finger bar 33 are all equal to the spacing between the two busbars 21 of any interdigital transducer 20.

[0171] Along the arrangement direction of the two busbars 21, the length of each finger bar of the first reflective grating 30 is set equal to the distance between the two busbars 21, thereby limiting the length of each finger bar within the first reflective grating 30, which facilitates the miniaturization of the filter 100 of this application. Simultaneously, the length of each finger bar within the first reflective grating 30 is matched with that of the interdigital transducer 20a to ensure the reflection effect of the first reflective grating 30 on surface acoustic waves.

[0172] The filter 100 of this application includes a piezoelectric substrate 10, interdigital transducers 20, and a first reflective grating 30. There are multiple interdigital transducers 20, and the multiple interdigital transducers 20 and the first reflective grating 30 are arranged at intervals along the planar direction of the piezoelectric substrate 10 on the surface of the piezoelectric substrate 10.

[0173] For example, please refer to Figures 14 and 15, where Figure 14 is another structural schematic diagram of the filter 100 provided in one embodiment of this application, and Figure 15 is a schematic diagram of the arrangement structure of the filter 100 provided in one embodiment of this application.

[0174] As shown in Figures 14 and 15, there are two interdigital transducers 20, positioned on opposite sides of the first reflective grating 30. Each interdigital transducer 20 includes two parallel and spaced-apart busbars 21 and a plurality of parallel and spaced-apart electrode fingers 22. One of the two busbars 21 is used to receive external signals, while the other busbar 21 is used to output signals. The plurality of electrode fingers 22 are located between the two busbars 21. Some of the electrode fingers 22 are connected to one busbar 21, and other electrode fingers 22 are connected to the other busbar 21.

[0175] For ease of description, the busbar 21 used for receiving external signals is defined as the first busbar 21a, and the busbar 21 used for outputting signals is defined as the second busbar 21b. The electrode finger 22 connected to the first busbar 21a is defined as the first electrode 221, and the electrode finger 22 connected to the second busbar 21b is defined as the second electrode 222.

[0176] Specifically, the first electrode 221 and the second electrode 222 are arranged alternately along the first direction 001. Both the first electrode 221 and the second electrode 222 extend along the second direction 002. Specifically, as shown in Figure 15, along the first direction 001, there is a second electrode 222 between any two adjacent first electrodes 221, and there is a first electrode 221 between any two adjacent second electrodes 222.

[0177] Both the first busbar 21a and the second busbar 21b extend along a first direction 001, wherein a second direction 002 intersects the first direction 001. Exemplarily, the second direction 002 and the first direction 001 may be perpendicular to each other, such that each electrode finger 22 has a 90° angle with its connected busbar. Exemplarily, the second direction 002 and the first direction 001 may also not be perpendicular, such that each electrode finger 22 has an angle greater than 90° with its connected busbar.

[0178] In this embodiment, when an external excitation signal is applied to the first busbar 21a of the interdigital transducer 20, each first electrode 221 converts the electrical signal into a surface acoustic wave. The surface acoustic wave propagates along the surface of the piezoelectric substrate 10 and is converted into an electrical signal by each second electrode 222, and then output by the second busbar 21b.

[0179] Surface acoustic waves (SAWs) are used to achieve the frequency selection and signal processing functions of the filter 100 in this application. During SAW propagation, the primary propagation direction is the first direction 001. However, in practice, due to edge effects and acoustic diffraction, the propagation direction of the SAW formed on the surface of the piezoelectric substrate 10 may also be other directions. In one embodiment, SAWs propagating in other directions are absorbed by a sound-absorbing material (not shown in the figure). In one embodiment, the first direction 001 is the arrangement direction of the two interdigital transducers 20.

[0180] In this embodiment, along the first direction 001, the first reflective grating 30 is located on one side of the interdigital transducer 20. When the surface acoustic wave generated by the interdigital transducer 20 operates, it propagates along the first direction 001 and is transmitted into the first reflective grating 30. The first reflective grating 30 is used to reflect the surface acoustic wave propagating to the first reflective grating 30, so as to confine the surface acoustic wave within the interdigital transducer 20 that generates the surface acoustic wave.

[0181] Since the first reflective grating 30 is located between the two interdigital transducers 20, it is understood that the first reflective grating 30 can simultaneously reflect the surface acoustic waves generated when the two interdigital transducers 20 are operating, thereby constraining the propagation range of the surface acoustic waves generated when the two interdigital transducers 20 are operating, thus improving the performance of the two interdigital transducers. This, in turn, improves the operating performance of the filter in this application.

[0182] Meanwhile, compared with the related technologies where each interdigital transducer independently uses a pair of identical reflective gratings and different interdigital transducers use different reflective gratings, the filter 100 of this application uses a first reflective grating 30 to constrain the surface acoustic waves generated when the two interdigital transducers 20 are working. It is also beneficial to reduce the spacing between the two interdigital transducers 20, which is beneficial to the miniaturization of the filter 100 of this application.

[0183] Please refer to Figure 16 for a partial top view of the filter 100 provided in one embodiment of this application.

[0184] As shown in Figures 15 and 16, the first reflective grating 30 includes a first finger strip 31, a second finger strip 32, and a third finger strip 33. Along the first direction 001, the first finger strip 31 and the second finger strip 32 are arranged on both sides of the third finger strip 33. In this embodiment, one of the two interdigital transducers 20 is located on one side of the third finger strip 33 along with the first finger strip 31, and the other interdigital transducer 20 is located on the other side of the third finger strip 33 along with the second finger strip 32.

[0185] For ease of description, the interdigital transducer 20 on the same side as the first finger strip 31 is defined as the first interdigital transducer 20a. The interdigital transducer 20 on the same side as the second finger strip 32 is defined as the second interdigital transducer 20b.

[0186] As shown in Figures 15 and 16, the surface acoustic wave generated when the first interdigital transducer 20a is working propagates towards the first finger strip 31. When the dominant mode of the surface acoustic wave reaches the first finger strip 31, the first finger strip 31 reflects the dominant mode. This confines the dominant mode of the surface acoustic wave generated by the first interdigital transducer 20a within the first interdigital transducer 20a.

[0187] When the second interdigital transducer 20b is operating, the surface acoustic wave generated propagates toward the second interdigital strip 32. When the dominant mode of the surface acoustic wave reaches the second interdigital strip 32, the second interdigital strip 32 reflects the dominant mode. This confines the dominant mode of the surface acoustic wave generated by the second interdigital transducer 20b within the second interdigital transducer 20b.

[0188] In one embodiment, the number of first finger strips 31 is less than the number of second finger strips 32, and the number of first finger strips 31 is greater than or equal to the number of third finger strips 33. The third finger strips 33 are used to block the mutual interference of surface acoustic waves generated when the two interdigital transducers 20 are operating.

[0189] The first reflective grating 30 has a relatively large number of first finger strips 31 and second finger strips 32, which can ensure the reflection effect of the first reflective grating 30 on the two interdigital transducers 20. The third finger strip 33 is provided with a smaller number of third finger strips, which can block the mutual influence of the surface acoustic waves generated by the two interdigital transducers 20 when they are working, while ensuring the overall size of the first reflective grating 30, thereby improving the Q value of the filter 100 of this application.

[0190] In one embodiment, there are multiple first finger strips 31 and multiple second finger strips 32. The finger spacing between two adjacent first finger strips 31 is greater than the finger spacing between two adjacent second finger strips 32, so as to match the main modes of different interdigital transducers 20 respectively. This allows the first reflective grating 30 to simultaneously reflect surface acoustic waves from two interdigital transducers 20 with different main modes. This improves the operating range of the filter 100 of this application.

[0191] In one embodiment, the ratio of the number of second finger strips 32, the number of third finger strips 33, and the number of first finger strips 31 is 2:1:1. The filter 100 of this application adjusts the ratio of the number of first finger strips 31, second finger strips 32, and third finger strips 33 based on the finger spacing between two adjacent first finger strips 31 and the finger spacing between two adjacent second finger strips 32, in order to further improve the Q value of the filter 100 while ensuring the reflection effect of the first reflective grating 30 on the main modes of the two interdigital transducers 20.

[0192] In one embodiment, the sum of the numbers of the first finger strip 31, the second finger strip 32, and the third finger strip 33 is greater than or equal to 10. Since the number of fingers on the reflective grating is positively correlated with the reflective effect of the reflective grating on surface acoustic waves (SAW), the filter 100 of this application controls the sum of the numbers of the first finger strip 31, the second finger strip 32, and the third finger strip 33 to ensure the reflection effect of the first finger strip 31 and the second finger strip 32 on the SAW generated when the corresponding interdigital transducers 20 are operating, and the blocking effect of the third finger strip 33 on the SAW generated when the two interdigital transducers 20 are operating. This ensures the Q value of the filter 100 of this application.

[0193] In one embodiment, the sum of the number of the first finger strip 31, the second finger strip 32 and the third finger strip 33 is less than or equal to 40, so as to reduce the overall size of the first reflective grating 30, which is beneficial to the miniaturization of the filter 100 of this application.

[0194] In one embodiment, the first interdigital transducer 20a includes a plurality of first electrode fingers 22a, and the second interdigital transducer 20b includes a plurality of second electrode fingers 22b; wherein, the finger spacing of the first interdigital transducer 20a is a first finger spacing F1, and the distance between the central axis of the first finger strip 31 adjacent to the first interdigital transducer 20a and the adjacent first electrode finger 22a is equal to the first finger spacing F1; the finger spacing of the second interdigital transducer 20b is a second finger spacing F2, and the distance between the central axis of the second finger strip 32 adjacent to the second interdigital transducer 20b and the adjacent second electrode finger 22b is equal to the second finger spacing F2, and the first finger spacing F1 is greater than the second finger spacing F2.

[0195] Since the dominant mode frequency of the first interdigital transducer 20a is determined by the finger spacing between two adjacent first electrode fingers 22a within the first interdigital transducer 20a, the filter 100 of this application sets the finger spacing between two adjacent first electrode fingers 22a and the distance between the central axis of the first finger strip 31 adjacent to the first interdigital transducer 20a and the adjacent first electrode finger 22a as a first finger spacing F1, thereby ensuring that the multiple first finger strips 31 can reflect the dominant mode of the first interdigital transducer 20a.

[0196] Since the dominant mode frequency of the second interdigital transducer 20b is determined by the finger spacing between two adjacent second electrode fingers 22b within the second interdigital transducer 20b, the filter 100 of this application sets the finger spacing between two adjacent second electrode fingers 22b and the distance between the central axis of the second finger strip 32 adjacent to the second interdigital transducer 20b and the adjacent second electrode finger 22b as a second finger spacing F2, thereby ensuring that multiple second finger strips 32 can reflect the dominant mode of the second interdigital transducer 20b.

[0197] In one embodiment, the filter 100 of this application further includes a second reflective grating 40 and a third reflective grating 50. Along the first direction 001, the first interdigital transducer 20a and the second reflective grating 40 are located on the first side of the first reflective grating 30, and the second interdigital transducer 20b and the third reflective grating 50 are located on the second side of the first reflective grating.

[0198] Along the first direction 001, a first reflective grating 30 and a second reflective grating 40 are respectively provided on opposite sides of the first interdigital transducer 20a. The first reflective grating 30 and the second reflective grating 40 cooperate with each other to constrain the surface acoustic wave generated when the first interdigital transducer 20a is working. Specifically, during the operation of the filter 100 of this application, the main mode of the surface acoustic wave generated when the first interdigital transducer 20a is working will propagate along the first direction 001 to the first reflective grating 30 and the second reflective grating 40 respectively, and the main mode propagating to the first reflective grating 30 will be reflected by multiple first finger strips 31.

[0199] The second reflective grating 40 includes multiple fourth finger strips 41. The main mode propagating to the second reflective grating 40 is reflected towards the first interdigital transducer 20a under the action of the multiple fourth finger strips 41. This achieves constraint on the main mode generated by the first interdigital transducer 20a and improves the Q value of the first interdigital transducer 20a.

[0200] Along the first direction 001, a first reflective grating 30 and a third reflective grating 50 are respectively provided on opposite sides of the second interdigital transducer 20b. The first reflective grating 30 and the third reflective grating 50 cooperate to constrain the surface acoustic wave generated when the second interdigital transducer 20b is working. Specifically, during the operation of the filter 100 of this application, the main mode of the surface acoustic wave generated when the second interdigital transducer 20b is working will propagate along the first direction 001 to the first reflective grating 30 and the third reflective grating 50 respectively, and the main mode propagating to the first reflective grating 30 will be reflected by multiple second finger strips 32.

[0201] The third reflector grating 50 includes multiple fifth fingers 51. Surface acoustic waves propagating to the third reflector grating 50 are reflected towards the second interdigital transducer 20b under the action of the multiple fifth fingers 51. This achieves constraint on the dominant mode generated by the second interdigital transducer 20b, thereby improving the Q value of the second interdigital transducer 20b.

[0202] In one embodiment, the sum of the number of the first finger strip 31, the second finger strip 32, and the third finger strip 33 is greater than or equal to the minimum of the number of the fourth finger strip 41 and the number of the fifth finger strip 51.

[0203] In one embodiment, the sum of the number of the first finger strip 31, the second finger strip 32, and the third finger strip 33 is less than or equal to the largest of the number of the fourth finger strip 41 and the number of the fifth finger strip 51.

[0204] Based on the limitations of the two embodiments described above, the filter 100 of this application adjusts the relationship between the total number of the first reflective grating 30 and the number of the fourth and fifth reflective gratings 41 and 51. This ensures the reflection effect of the first and second reflective gratings 31 and 32 on the two interdigital transducers 20. Furthermore, it controls the overall size of the first reflective grating 30, facilitating the miniaturization of the filter 100.

[0205] In one embodiment, along the first direction 001, the distance between the central axes of two adjacent fourth finger strips 41 is the fourth finger distance F4, the distance between the central axes of two adjacent first electrode fingers 22a in the first interdigital transducer 20a is equal to the fourth finger distance F4, and the distance between the central axes of adjacent fourth finger strips 41 and first electrode fingers 22a is equal to the fourth finger distance F4.

[0206] Since the frequency of the main mode of the first interdigital transducer 20a is determined by the finger spacing between two adjacent first electrode fingers 22a within the first interdigital transducer 20a, the filter 100 of this application sets the finger spacing between two adjacent first electrode fingers 22a, the distance between the central axis of the adjacent fourth finger strip 41 and the first electrode finger 22a, and the finger spacing between two adjacent fourth finger strips 41 as a fourth finger spacing F4, thereby ensuring that multiple fourth finger strips 41 can reflect the main mode of the first interdigital transducer 20a.

[0207] In one embodiment, along the first direction 001, the distance between the central axes of two adjacent fifth finger strips 51 is the fifth finger distance F5, the distance between the central axes of two adjacent second electrode fingers 22b in the second interdigital transducer 20b is equal to the fifth finger distance F5, and the distance between the central axes of adjacent fifth finger strips 51 and second electrode fingers 22b is equal to the fifth finger distance F5.

[0208] Since the frequency of the dominant mode of the second interdigital transducer 20b is determined by the finger spacing between two adjacent second electrode fingers 22b within the second interdigital transducer 20b, the filter 100 of this application ensures that multiple fifth finger strips 51 can reflect the dominant mode of the second interdigital transducer 20b by setting the finger spacing between two adjacent second electrode fingers 22b, the distance between the central axis of an adjacent fifth finger strip 51 and the second electrode finger 22b, and the finger spacing between two adjacent fifth finger strips 51 as a fifth finger spacing F5.

[0209] Based on the limitations of the above embodiments, specifically, admittance can be used to describe the response process of an element to a signal. In the filter 100 of this application, conductivity is used to measure the acoustic wave loss propagating on the surface of the piezoelectric substrate 10, and Q value is used to describe the signal quality in the filter 100.

[0210] Figures 17-22 are comparison graphs of the conductance curves of the filter 100 of this application, the filter in the comparative example, and the filter in Reference Example 1 based on different surface acoustic wave frequencies. In Figures 17-22, the horizontal axis represents frequency in MHz, and the vertical axis represents conductance in dB. Figures 23-28 are comparison graphs of the Q values ​​of the filter 100 of this application, the filter in the comparative example, and the filter in Reference Example 1 based on different surface acoustic wave frequencies. In Figures 23-28, the horizontal axis represents frequency in MHz, and the vertical axis represents Q value.

[0211] For each embodiment, comparative example, and Reference Example 1, the filter includes two interdigital transducers, namely a first interdigital transducer and a second interdigital transducer. Specifically, for the first interdigital transducer, the finger spacing between two adjacent interdigital fingers is 2.8 μm, the duty cycle of the interdigital fingers is 0.42, the aperture size is 140 μm, the number of interdigital fingers is 131, the interdigital finger material is aluminum, the piezoelectric substrate material is LiTaO3, and the thickness of the interdigital fingers is 410 nm.

[0212] For the second interdigital transducer, the finger spacing between two adjacent electrode fingers is 2.5 μm, the duty cycle of the electrode fingers is 0.42, the aperture size is 140 μm, the number of electrode fingers is 131, the electrode finger material is aluminum, the piezoelectric substrate material is LiTaO3, and the thickness of the electrode fingers is 410 nm.

[0213] Based on the structure of the two interdigital transducers mentioned above, each comparative example includes three reflective gratings arranged at intervals. Each interdigital transducer is located between two adjacent reflective gratings, and each reflective grating has 20 fingers.

[0214] Three sets of comparative examples are provided, numbered 1 to 3, with different ratios of the number of reflective gratings between the two interdigital transducers in each example. In the comparative examples, each finger strip of the shared reflective grating consists of multiple first finger strips and multiple second finger strips. In these examples, the spacing between two adjacent first finger strips, the spacing between adjacent first finger strips and the electrode fingers of the first interdigital transducer, and the finger spacing between two adjacent electrode fingers within the first interdigital transducer are all equal. In this case, the number of first finger strips represents the number of finger strips allocated to the first interdigital transducer from the shared reflective grating. Similarly, the spacing between two adjacent second finger strips, the spacing between adjacent second finger strips and the electrode fingers of the second interdigital transducer, and the finger spacing between two adjacent electrode fingers within the second interdigital transducer are all equal. In this case, the number of second finger strips represents the number of finger strips allocated to the second interdigital transducer from the shared reflective grating. Therefore, the different distribution ratio of the number of reflective grids between the two interdigital transducers in each comparative example means that the ratio of the number of finger strips allocated to the first interdigital transducer to the number of finger strips allocated to the second interdigital transducer is different in different comparative examples, that is, the ratio of the number of first finger strips to the number of second finger strips is different in each comparative example.

[0215] Specifically, in Comparative Example 1, the ratio of the number of the first finger to the number of the second finger is 5:15. In Comparative Example 2, the ratio is 15:5. In Comparative Example 3, the ratio is 10:10.

[0216] Based on the structure of the two interdigital transducers 20 described above, each embodiment includes 20 finger strips in the first reflective grating 30, the second reflective grating 40, and the third reflective grating 50. There are three embodiments, namely Embodiment 1 to Embodiment 3, and the distribution ratio of the number of the first finger strips 31, the second finger strips 32, and the third finger strips 33 within the first reflective grating 30 differs in each embodiment. The spacing F3 between the third finger strips is 2.915 μm.

[0217] Specifically, in Embodiment 1, the ratio of the number of the first finger strip 31, the third finger strip 33, and the second finger strip 32 is 5:5:10. In Embodiment 2, the ratio of the number of the first finger strip 31, the third finger strip 33, and the second finger strip 32 is 10:5:5. In Embodiment 3, the ratio of the number of the first finger strip 31, the third finger strip 33, and the second finger strip 32 is 6:5:9.

[0218] Based on the structure of the two interdigital transducers described above, Reference Example 1 includes four reflective gratings. Each interdigital transducer has a reflective grating on each of its opposite sides, and the two interdigital transducers are spaced apart. Each reflective grating includes 20 finger strips.

[0219] Based on the above three comparative examples, three embodiments, and one reference example 1, the conductivity curves and Q-value curves were simulated and generated, forming the legends shown in Figures 17-28. Each legend includes a solid line representing the conductivity curve or Q-value curve corresponding to the first interdigital transducer, and a dashed line representing the conductivity curve or Q-value curve corresponding to the second interdigital transducer. It can be understood that the conductivity curves corresponding to Reference Example 1 are consistent in the legends of Figures 17-22, and the Q-value curves corresponding to Reference Example 1 are also consistent in the legends of Figures 23-28.

[0220] Specifically, Figures 17-19 are comparison graphs of the conductance curves corresponding to the two interdigital transducers in Comparative Examples 1-3 and Reference Example 1, respectively. Figures 20-22 are comparison graphs of the conductance curves corresponding to the two interdigital transducers in Examples 1-3 and Reference Example 1, respectively. Figures 23-25 ​​are comparison graphs of the Q-value curves corresponding to the two interdigital transducers in Comparative Examples 1-3 and Reference Example 1, respectively. Figures 26-28 are comparison graphs of the Q-value curves corresponding to the two interdigital transducers in Examples 1-3 and Reference Example 1, respectively.

[0221] As shown in Figures 17-19 and 23-25, the more fingers an interdigital transducer in Comparative Examples 1-3 has, the better the consistency between its conductivity curve or Q-value curve and that of Reference Example 1.

[0222] Comparing Figures 17-28, it can be seen that the conductivity curves and Q-value curves corresponding to Examples 1-3 are more consistent with those of Reference Example 1 than those of Comparative Examples 1-3. For example, a comparison of the conductivity curves of Comparative Example 1 and Example 1 is taken. Since Example 1 has the largest number of second interdigital transducers 32, comparing Figures 20 and 17 shows that the conductivity curve corresponding to the second interdigital transducer 20b of Example 1 is more consistent with the corresponding conductivity curve of Reference Example 1, while the conductivity curve corresponding to the first interdigital transducer 20a of Example 1 is significantly more consistent with that of Reference Example 1 than that of Comparative Example 1.

[0223] Similarly, referring to the above figures, it is clear that the conductivity curve obtained in Example 2 is in better agreement with that in Comparative Example 2 than with that in Comparative Example 1. The Q-value curves obtained in Examples 1 and 2 are also in better agreement with those in Comparative Examples 1 and 2 than with those in Comparative Examples 1 and 2.

[0224] This is because Embodiments 1 and 2 of this application provide a third finger strip 33, which blocks the mutual influence of surface acoustic waves generated by the two interdigital transducers 20 during operation, thereby improving the performance of the filter 100 and increasing the Q value of the filter 100.

[0225] In Comparative Examples 1-3, the conductivity curve and Q-value curve corresponding to Comparative Example 3 show good consistency with those corresponding to Reference Example 1. In the embodiments of this application, the number of second fingers 32 is greater than or equal to the number of third fingers 33, and less than or equal to the number of first fingers 31, which corresponds to the conductivity curve and Q-value curve corresponding to Example 3.

[0226] By comparing Figures 19 and 22, and Figures 25 and 28, it can be seen that the conductivity curve and Q-value curve corresponding to Example 3 are more consistent with those of Reference Example 1 than those of Comparative Example 3. This is because Example 3 of this application includes a third finger strip 33 and adjusts the quantitative relationship between the third finger strip 33 and the first finger strip 31 and the second finger strip 32, so as to make full use of the third finger strip 33 to block the mutual influence of the surface acoustic waves generated when the two interdigital transducers 20 are working, thereby improving the performance of the filter 100 of this application and increasing the Q-value of the filter 100 of this application.

[0227] It is worth noting that the finger-strip allocation schemes proposed in Comparative Examples 1-3 and Embodiments 1-3 of this application do not affect the resonant frequency, electromechanical coupling coefficient, static capacitance, or other characteristics of the filter. Therefore, the differences in consistency shown in Figures 17-28 do not originate from the resonant frequency, electromechanical coupling coefficient, static capacitance, or other characteristics of the filter.

[0228] Specifically, Figure 29 is a comparison of the admittance curves of Comparative Examples 1-3 and Reference Example 1. Figure 30 is a comparison of the admittance curves of Examples 1-3 and Reference Example 1. In Figures 29 and 30, the horizontal axis represents frequency in MHz, and the vertical axis represents admittance in dB. In Figures 29 and 30, solid lines represent the admittance curve corresponding to the first interdigital transducer, and dashed lines represent the admittance curve corresponding to the second interdigital transducer. To facilitate comparison of the consistency of the curves of each comparative example or embodiment with Reference Example 1, the vertical axis of the admittance curves corresponding to each comparative example and embodiment has been processed. This is reflected in the illustrations as a certain displacement along the vertical axis for each comparative example and embodiment. Specifically, in Figure 29, along the vertical axis towards -100dB, the curves are, in order, Comparative Example 3, Comparative Example 2, Comparative Example 1, and Reference Example 1. In Figure 30, along the vertical axis towards -100dB, the curves are, in order, Example 3, Example 2, Example 1, and Reference Example 1.

[0229] As shown in Figures 29 and 30, the admittance curves of each comparative example and each embodiment are consistent with the admittance curve of Reference Example 1. Correspondingly, the finger-strip allocation ratio schemes proposed in Comparative Examples 1-3 and Embodiments 1-3 of this application do not affect the resonant frequency, electromechanical coupling coefficient, static capacitance, and other characteristics of the filter.

[0230] To further support the viewpoint of this application, Figures 31-37 are comparative diagrams showing the conductance curves of the filter 100 of this application, the filter in the comparative example, and the filter in Reference Example 2 based on different surface acoustic wave frequencies. In Figures 31-37, the horizontal axis represents frequency in MHz, and the vertical axis represents conductance in dB. Figures 38-44 are comparative diagrams showing the Q values ​​of the filter 100 of this application, the filter in the comparative example, and the filter in Reference Example 2 based on different surface acoustic wave frequencies. In Figures 38-44, the horizontal axis represents frequency in MHz, and the vertical axis represents Q value.

[0231] There are three sets of comparative examples, namely Comparative Examples 4-6. There are four sets of exemplary examples, namely Exemplary Examples 4-7. The filters in Comparative Examples 4-6 and Exemplary Examples 4-7 all include two interdigital transducers, namely a first interdigital transducer and a second interdigital transducer. Specifically, for the first interdigital transducer, the finger spacing between two adjacent electrodes is 2.8 μm, the duty cycle of the electrodes is 0.42, the aperture size is 140 μm, the number of electrodes is 131, the electrode material is aluminum, the piezoelectric substrate material is LiTaO3, and the thickness of the electrodes is 410 nm.

[0232] For the second interdigital transducer, the finger spacing between two adjacent electrode fingers is 2.5 μm, the duty cycle of the electrode fingers is 0.42, the aperture size is 140 μm, the number of electrode fingers is 131, the electrode finger material is aluminum, the piezoelectric substrate material is LiTaO3, and the thickness of the electrode fingers is 410 nm.

[0233] Based on the structure of the two interdigital transducers described above, each comparative example includes three reflective gratings arranged at intervals, with each interdigital transducer located between two adjacent reflective gratings. Specifically, the reflective grating on the side of the first interdigital transducer furthest from the second interdigital transducer has 30 fingers, the reflective grating on the side of the second interdigital transducer furthest from the first interdigital transducer has 20 fingers, and the reflective grating between the first and second interdigital transducers has 25 fingers.

[0234] The number of reflective gratings allocated between the two interdigital transducers differs in each comparative example. Furthermore, the number of reflective gratings allocated to the shared gratings also differs. As mentioned above, each finger of the shared grating comprises multiple first fingers and multiple second fingers.

[0235] Specifically, in Comparative Example 4, the ratio of the number of the first finger to the number of the second finger is 8:17. In Comparative Example 5, the ratio is 17:8. In Comparative Example 6, the ratio is 12:13.

[0236] Based on the structure of the two interdigital transducers 20 described above, in each embodiment, the first reflective grating 30 includes 30 finger strips, the second reflective grating 40 includes 20 finger strips, and the third reflective grating 50 includes 25 finger strips. The distribution ratio of the number of the first finger strips 31, the second finger strips 32, and the third finger strips 33 within the first reflective grating 30 differs in each embodiment. The distance F3 between the third finger strips is equal to 2.915 μm.

[0237] Specifically, in Example 4, the ratio of the number of the first finger strip 31, the third finger strip 33, and the second finger strip 32 is 8:5:12. In Example 5, the ratio of the number of the first finger strip 31, the third finger strip 33, and the second finger strip 32 is 15:2:8. In Example 6, the ratio of the number of the first finger strip 31, the third finger strip 33, and the second finger strip 32 is 12:5:8. In Example 7, the ratio of the number of the first finger strip 31, the third finger strip 33, and the second finger strip 32 is 8:4:13.

[0238] Based on the structure of the two interdigital transducers described above, Reference Example 2 includes four reflective gratings. Each interdigital transducer has a reflective grating on each of its opposite sides, and the two interdigital transducers are spaced apart. The first interdigital transducer has 30 fingers on each of its two reflective gratings on opposite sides, and the second interdigital transducer has 20 fingers on each of its two reflective gratings on opposite sides.

[0239] Based on the above three comparative examples, four embodiments, and one reference example 2, the conductivity curves and Q-value curves were simulated and generated, forming the legends shown in Figures 31-44. Each legend includes a solid line representing the conductivity curve or Q-value curve corresponding to the first interdigital transducer, and a dashed line representing the conductivity curve or Q-value curve corresponding to the second interdigital transducer. It can be understood that the conductivity curve or Q-value curve corresponding to Reference Example 2 remains consistent in the legends of Figures 31-44.

[0240] Specifically, Figures 31-33 are comparison graphs of the conductance curves corresponding to the two interdigital transducers in Comparative Examples 4-6 and Reference Example 2, respectively. Figures 34-37 are comparison graphs of the conductance curves corresponding to the two interdigital transducers in Examples 4-7 and Reference Example 2, respectively. Figures 38-40 are comparison graphs of the Q-value curves corresponding to the two interdigital transducers in Comparative Examples 4-6 and Reference Example 2, respectively. Figures 41-44 are comparison graphs of the Q-value curves corresponding to the two interdigital transducers in Examples 4-7 and Reference Example 2, respectively.

[0241] Comparing the above figures, it is clear that the conductivity curves and Q-value curves obtained for Examples 4-7 are more consistent with those for Comparative Examples 4-6 than those for Reference Example 2. This is because Examples 4-7 of this application include a third finger strip 33, which blocks the mutual interference of surface acoustic waves generated by the two interdigital transducers 20 during operation, thereby improving the performance of the filter 100 and increasing its Q-value.

[0242] It should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0243] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0244] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Those skilled in the art will understand that implementing all or part of the processes of the above embodiments, and making equivalent changes according to the claims of this application, still falls within the scope of this application.

Claims

1. A filter, characterized in that, It includes a piezoelectric substrate, a first reflective grating disposed on the surface of the piezoelectric substrate, and two interdigital transducers, the two interdigital transducers being arranged on opposite sides of the first reflective grating; The first reflective grating includes a first finger strip, a second finger strip, and a third finger strip connected together, wherein the first finger strip and the second finger strip are arranged on both sides of the third finger strip along a first direction; wherein, The distance between the central axis of the third finger adjacent to the first finger and the central axis of the adjacent first finger is the first distance, and the distance between the central axis of the third finger adjacent to the second finger and the central axis of the adjacent second finger is the second distance. The first distance and the second distance are not equal.

2. The filter according to claim 1, characterized in that, The number of first finger strips and second finger strips is multiple, and the number of third finger strips is one. The multiple first finger strips, the third finger strips, and the multiple second finger strips are arranged at intervals along the first direction. The distance between the central axes of two adjacent first finger strips is the first finger spacing, and the distance between the central axes of two adjacent second finger strips is the second finger spacing. The difference between twice the first distance and the first finger distance is defined as the third finger distance; and / or, the difference between twice the second distance and the second finger distance is defined as the third finger distance; The third finger spacing is greater than the first finger spacing and the second finger spacing.

3. The filter according to claim 2, characterized in that, The difference between twice the first spacing and the first finger spacing is equal to the difference between twice the second spacing and the second finger spacing.

4. The filter according to claim 1, characterized in that, The number of the first finger strip, the second finger strip, and the third finger strip are all multiple, and the multiple first finger strips, the multiple third finger strips, and the multiple second finger strips are arranged at intervals along the first direction; The distance between the central axes of two adjacent first finger strips is the first finger spacing, the distance between the central axes of two adjacent second finger strips is the second finger spacing, and the distance between the central axes of two adjacent third finger strips is the third finger spacing, wherein the third finger spacing is greater than the first finger spacing and the second finger spacing.

5. The filter according to claim 4, characterized in that, The first spacing is equal to half the sum of the third finger spacing and the first finger spacing; the second spacing is equal to half the sum of the third finger spacing and the second finger spacing.

6. The filter according to any one of claims 2-5, characterized in that, The width of the third finger strip is greater than the width of the first finger strip, and the width of the third finger strip is greater than the width of the second finger strip; and / or, Along the first direction, the gap between two adjacent first finger strips is the first gap size, the gap between two adjacent second finger strips is the second gap size, the gap between a third finger strip adjacent to a first finger strip and an adjacent first finger strip is greater than the first gap size, and the gap between a third finger strip adjacent to a second finger strip and an adjacent second finger strip is greater than the second gap size.

7. The filter according to claim 6, characterized in that, The widths of the third finger strip, the first finger strip, and the second finger strip are all equal. Along the first direction, the gap between a third finger strip adjacent to the first finger strip and an adjacent first finger strip is greater than the first gap size, and the gap between a third finger strip adjacent to the second finger strip and an adjacent second finger strip is greater than the second gap size; or, The width of the third finger strip is greater than the width of the first finger strip, and the width of the third finger strip is greater than the width of the second finger strip. Along the first direction, the gap between a third finger strip adjacent to the first finger strip and an adjacent first finger strip is equal to the first gap size, and the gap between a third finger strip adjacent to the second finger strip and an adjacent second finger strip is equal to the second gap size.

8. The filter according to any one of claims 2-5, characterized in that, The ratio of the third finger spacing to the first finger spacing is greater than or equal to 1.

01.

9. The filter according to any one of claims 2-5, characterized in that, The third finger spacing is less than or equal to 1.04 times the first finger spacing.

10. The filter according to any one of claims 2-5, characterized in that, The third finger spacing is less than or equal to 1.1 times the first finger spacing.

11. The filter according to any one of claims 1-5, characterized in that, The two interdigital transducers include a first interdigital transducer and a second interdigital transducer. Along the first direction, the first interdigital transducer and the first finger strip are located on a first side of the third finger strip, and the second interdigital transducer and the second finger strip are located on a second side of the third finger strip. The first interdigital transducer includes a plurality of first electrode fingers, and the second interdigital transducer includes a plurality of second electrode fingers. The finger spacing of the first interdigital transducer is equal to the first finger spacing, and the distance between the central axis of the first finger strip adjacent to the first interdigital transducer and the adjacent first electrode finger is equal to the first finger spacing; The finger spacing of the second interdigital transducer is equal to the second finger spacing, the distance between the central axis of the second finger strip adjacent to the second interdigital transducer and the adjacent second electrode finger is equal to the second finger spacing, and the first finger spacing is greater than the second finger spacing.

12. The filter according to any one of claims 1-5, characterized in that, The number of the first finger strips is multiple, the number of the second finger strips is multiple, and the number of the first finger strips and the number of the second finger strips are both greater than or equal to the number of the third finger strips.

13. The filter according to claim 11, characterized in that, The number of the first finger strips is less than or equal to the number of the second finger strips.

14. The filter according to any one of claims 1-5, characterized in that, The ratio of the number of the second finger strips, the number of the third finger strips, and the number of the first finger strips is 2:1:1; and / or, The sum of the number of the first finger strip, the second finger strip, and the third finger strip is greater than or equal to 10; and / or, The sum of the number of the first finger strip, the second finger strip, and the third finger strip is less than or equal to 40.

15. The filter according to any one of claims 1-5, characterized in that, The first direction is the arrangement direction of the two interdigital transducers.

16. The filter according to any one of claims 1-5, characterized in that, The finger spacing of the two interdigital transducers is not equal.

17. The filter according to any one of claims 1-5, characterized in that, The filter further includes a second reflective grating and a third reflective grating. The two interdigital transducers include a first interdigital transducer and a second interdigital transducer. Along the first direction, the first interdigital transducer and the second reflective grating are located on a first side of the first reflective grating, and the second interdigital transducer and the third reflective grating are located on a second side of the first reflective grating. The second reflective grating includes a plurality of fourth finger strips, and the third reflective grating includes a plurality of fifth finger strips; The sum of the number of the first finger strip, the second finger strip, and the third finger strip is greater than or equal to the minimum of the number of the fourth finger strip and the number of the fifth finger strip; And / or, the sum of the number of the first finger strip, the second finger strip, and the third finger strip is less than or equal to the largest of the number of the fourth finger strip and the number of the fifth finger strip.

18. The filter according to claim 17, characterized in that, Along the first direction, the distance between the central axes of two adjacent fourth finger strips is the fourth finger spacing, the distance between the central axes of two adjacent electrode fingers in the first interdigital transducer is equal to the fourth finger spacing, and the distance between the central axes of adjacent fourth finger strips and electrode fingers is equal to the fourth finger spacing. Along the first direction, the distance between the central axes of two adjacent fifth finger strips is the fifth finger spacing, the distance between the central axes of two adjacent electrode fingers in the second interdigital transducer is equal to the fifth finger spacing, and the distance between the central axes of adjacent fifth finger strips and electrode fingers is equal to the fifth finger spacing.

19. The filter according to any one of claims 1-5, characterized in that, Each of the interdigital transducers includes two parallel and spaced-apart busbars and a plurality of electrode fingers located between the two busbars. Some of the electrode fingers are connected to one of the busbars, and other of the electrode fingers are connected to the other busbar. The electrode fingers connected to different busbars are arranged alternately. Along the arrangement direction of the two busbars, the distance between the ends of any two adjacent electrode fingers of each interdigital transducer that are not connected to the busbar is the aperture size, and the aperture sizes of the two interdigital transducers are equal.

20. The filter according to claim 19, characterized in that, The spacing between the two busbars of each interdigital transducer is equal, and the length of the first, second, and third finger bars is equal to the spacing between the two busbars of any interdigital transducer.

21. A filter, characterized in that, The device includes a piezoelectric substrate and a first reflective grating, a first interdigital transducer and a second interdigital transducer disposed on the surface of the piezoelectric substrate. Along a first direction, the first interdigital transducer and the second interdigital transducer are arranged on opposite sides of the first reflective grating, and the finger spacing of the first interdigital transducer is not equal to the finger spacing of the second interdigital transducer. The first reflective grating includes a plurality of first fingers, a plurality of second fingers, and a plurality of third fingers connected together, wherein the plurality of first fingers and the plurality of second fingers are arranged on both sides of the plurality of third fingers along a first direction; wherein, The distance between the central axes of two adjacent first finger strips is the first finger spacing, the distance between the central axes of two adjacent second finger strips is the second finger spacing, and the distance between the central axes of two adjacent third finger strips is the third finger spacing. The first finger spacing and the second finger spacing are not equal and are both less than the third finger spacing.

22. The filter according to claim 21, characterized in that, There are multiple first finger strips and multiple second finger strips, and the finger spacing between two adjacent first finger strips is greater than the finger spacing between two adjacent second finger strips.

23. The filter according to claim 21, characterized in that, The ratio of the number of the second finger strips, the number of the third finger strips, and the number of the first finger strips is 2:1:1; and / or, The sum of the number of the first finger strip, the second finger strip, and the third finger strip is greater than or equal to 10; and / or, The sum of the number of the first finger strip, the second finger strip, and the third finger strip is less than or equal to 40.

24. The filter according to any one of claims 21-23, characterized in that, The two interdigital transducers include a first interdigital transducer and a second interdigital transducer. Along the first direction, the first interdigital transducer and the first finger strip are located on a first side of the third finger strip, and the second interdigital transducer and the second finger strip are located on a second side of the third finger strip. The first interdigital transducer includes a plurality of first electrode fingers, and the second interdigital transducer includes a plurality of second electrode fingers. The finger spacing of the first interdigital transducer is the first finger spacing, and the distance between the central axis of the first finger strip adjacent to the first interdigital transducer and the adjacent first electrode finger is equal to the first finger spacing; The finger spacing of the second interdigital transducer is the second finger spacing. The distance between the central axis of the second finger strip adjacent to the second interdigital transducer and the adjacent second electrode finger is equal to the second finger spacing. The first finger spacing is greater than the second finger spacing.

25. The filter according to any one of claims 21-23, characterized in that, The filter further includes a second reflective grating and a third reflective grating. The two interdigital transducers include a first interdigital transducer and a second interdigital transducer. Along the first direction, the first interdigital transducer and the second reflective grating are located on a first side of the first reflective grating, and the second interdigital transducer and the third reflective grating are located on a second side of the first reflective grating. The second reflective grating includes a plurality of fourth finger strips, and the third reflective grating includes a plurality of fifth finger strips; The sum of the number of the first finger strip, the second finger strip, and the third finger strip is greater than or equal to the minimum of the number of the fourth finger strip and the number of the fifth finger strip; And / or, the sum of the number of the first finger strip, the second finger strip, and the third finger strip is less than or equal to the largest of the number of the fourth finger strip and the number of the fifth finger strip.

26. The filter according to claim 25, characterized in that, Along the first direction, the distance between the central axes of two adjacent fourth finger strips is the fourth finger spacing, the distance between the central axes of two adjacent electrode fingers in the first interdigital transducer is equal to the fourth finger spacing, and the distance between the central axes of adjacent fourth finger strips and electrode fingers is equal to the fourth finger spacing. Along the first direction, the distance between the central axes of two adjacent fifth finger strips is the fifth finger spacing, the distance between the central axes of two adjacent electrode fingers in the second interdigital transducer is equal to the fifth finger spacing, and the distance between the central axes of adjacent fifth finger strips and electrode fingers is equal to the fifth finger spacing.

27. A radio frequency front-end module, characterized in that, Includes the filter as described in any one of claims 1-26.

28. An electronic device, characterized in that, Includes the radio frequency front-end module as described in claim 27.

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