Interdigital transducer, filter and electronic device

Abstract

The invention relates to an interdigital transducer, a filter and an electronic device. The interdigital transducer comprises first electrode fingers and second electrode fingers, wherein the first electrode fingers and the second electrode fingers are sequentially and alternately distributed at intervals in the first direction; wherein the interdigital transducer is provided with at least two partitions which are not overlapped with each other in a first direction, each partition comprises at least one electrode group, and each electrode group comprises a first electrode finger and a second electrode finger which are adjacent to each other in the first direction; in the at least two subareas, at least one electrode group of one subarea and at least one electrode group of the other subarea are different in period and duty ratio, excited surface acoustic wave frequencies are the same, and at least the transverse mode component in the transducer can be effectively inhibited.

Description

Technical Field

[0001] The present application relates to the field of surface acoustic wave technology, and in particular to an interdigital transducer, a filter and an electronic device. Background Art

[0002] With the increasing level of mobile communication technology, the number of communication frequency bands has also increased dramatically, making the frequency bands very crowded and the protection intervals between frequency bands of different communication systems getting smaller and smaller. In order to avoid mutual interference between frequency bands and achieve a steep transition band, higher out-of-band suppression and lower passband loss, surface acoustic wave filters based on piezoelectric-on-insulator (POI) substrates are usually used. Compared with conventional surface acoustic wave filters, they have higher energy utilization efficiency and a larger electromechanical coupling coefficient, and can be applied to the design of large-bandwidth devices.

[0003] However, the transducer in the POI-based surface acoustic wave filter has problems with lateral energy leakage and beam deflection, which will seriously deteriorate the steepness of the filter's transition band and the flatness within the passband, while causing stray resonances in the resonator, reducing the device's Q value, and especially generating a large number of obvious glitches within the passband. Summary of the invention

[0004] Based on this, it is necessary to provide an IDT, a filter and an electronic device that can at least effectively suppress the lateral mode components in the transducer and have a wider range of applications in order to address the problems in the above-mentioned background technology.

[0005] One aspect of the present application provides an IDT, comprising first electrode fingers and second electrode fingers alternately distributed in sequence along a first direction; wherein the IDT has at least two non-overlapping partitions in the first direction, each partition comprising at least one electrode group, and one electrode group comprising first electrode fingers and second electrode fingers adjacent to each other along the first direction; in at least two partitions, at least one electrode group in one partition has different periods and duty cycles from at least one electrode group in another partition, and the frequencies of the excited surface acoustic waves are the same.

[0006] In the IDT in the above embodiment, the IDT has at least two non-overlapping partitions in the first direction, each partition includes at least one electrode group, and one electrode group includes a first electrode finger and a second electrode finger adjacent to each other along the first direction; the periods and duty cycles of the electrode groups in at least two partitions are different and the frequencies of the excited surface acoustic waves are the same. Due to the design of variable duty cycle and variable period, the transverse mode components will not be accumulated and superimposed at the same frequency, but will be dispersed to different frequency positions in the passband. At the same time, the electrode index in each period is greatly reduced, thereby greatly weakening the intensity of the excited transverse mode components; ultimately, smaller burrs are exhibited in the overall filter performance.

[0007] In one of the embodiments, at least two partitions are symmetrical in the first direction about a symmetry axis passing through the center point of the IDT, thereby reducing the manufacturing complexity and cost of the IDT, so that the transverse mode components of the electrode group in the partitions that are symmetrical in the first direction will not be accumulated and superimposed at the same frequency, but will be dispersed to different frequency positions in the passband. At the same time, the electrode index in each period is greatly reduced, thereby greatly weakening the intensity of the excited transverse mode components.

[0008] In one of the embodiments, in the direction along the first direction toward the symmetry axis, the duty ratios of different partitions gradually decrease or increase, so as to simplify the complexity of the internal partition design of the IDT.

[0009] In one of the embodiments, in the direction along the first direction toward the symmetry axis, the duty ratios of different partitions are sequentially reduced by a fixed amount or linearly decreased.

[0010] In one of the embodiments, in the direction along the first direction toward the symmetry axis, the duty cycles of different partitions are sequentially increased by a fixed amount or linearly increased.

[0011] In one embodiment, at least two partitions are configured as:

[0012] Along the first direction, the duty ratios of different partitions are successively reduced by a fixed amount or linearly decreased; or

[0013] Along the first direction, the duty cycles of different partitions are sequentially increased by a fixed amount or linearly increased.

[0014] In one embodiment, the duty ratios and periods of different first electrode fingers are different; the duty ratios and periods of different second electrode fingers are different; and the duty ratios and periods of the first electrode fingers and the second electrode fingers are different.

[0015] In one embodiment, the thickness of different first electrode fingers is the same; the thickness of different second electrode fingers is the same; and the thickness of the first electrode finger and the second electrode finger is the same. In one embodiment, the interdigital transducer also includes a first bus bar and a second bus bar spaced along the second direction and extending along the first direction; the first electrode finger and the second electrode finger are both located between the first bus bar and the second bus bar; the first electrode finger is configured to have a first end and a second end opposite to each other along the second direction, the first end is connected to the first bus bar, and the second end is spaced from the second bus bar; the second electrode finger is configured to have a first end and a second end opposite to each other along the second direction, the first end is connected to the second bus bar, and the second end is spaced from the first bus bar.

[0016] One aspect of the present application provides a filter, comprising an IDT according to any one of the embodiments of the present application. By setting the periods and duty cycles of at least two partitioned electrode groups in the IDT to be different and the excited surface acoustic wave frequencies to be the same, the transverse mode components will not be accumulated and superimposed at the same frequency due to the design of variable duty cycle and variable period, but will be dispersed to different frequency positions in the passband, and at the same time, the electrode index in each period is greatly reduced, so that the intensity of the excited transverse mode components is greatly weakened, ensuring the steepness of the transition band of the filter and the flatness in the passband, and avoiding a large number of obvious burrs inside the passband.

[0017] In one embodiment, the first reflection grating and the second reflection grating are symmetrical in a first direction about a symmetry axis passing through the center point of the IDT, so as to ensure the steepness of the transition band of the filter and the flatness in the passband and reduce the complexity of the filter structure.

[0018] In one of the embodiments, the first reflection grating includes third electrode fingers that are spaced apart in sequence along the first direction; the first reflection grating has at least two non-overlapping sub-regions in the first direction, and the sub-regions include at least one third electrode finger; the periods and duty cycles of the third electrode fingers in at least two sub-regions are different and the frequencies of the excited surface acoustic waves are the same, so that the transverse mode components of the third electrode fingers in different sub-regions in the first reflection grating will not be accumulated and superimposed at the same frequency, but will be dispersed to different frequency positions in the passband, and at the same time, the electrode index in each period is greatly reduced, thereby greatly weakening the intensity of the excited transverse mode components, and ultimately showing smaller glitches in the overall filter performance.

[0019] In one of the embodiments, the second reflection grating includes fourth electrode fingers that are spaced apart in sequence along the first direction; the second reflection grating has at least two non-overlapping sub-regions in the first direction, and the sub-regions include at least one fourth electrode finger; the periods and duty cycles of the fourth electrode fingers in at least two sub-regions are different and the frequencies of the excited surface acoustic waves are the same, so that the transverse mode components of the fourth electrode fingers in different sub-regions in the second reflection grating will not be accumulated and superimposed at the same frequency, but will be dispersed to different frequency positions in the passband, and at the same time, the electrode index in each period is greatly reduced, thereby greatly weakening the intensity of the excited transverse mode components, and ultimately showing smaller burrs in the overall filter performance.

[0020] Another aspect of the present application provides an electronic device, comprising a filter according to any of the embodiments of the present application. By setting the periods and duty cycles of at least two partitioned electrode groups in the interdigital transducer to be different and the excited surface acoustic wave frequencies to be the same, the transverse mode components will not be accumulated and superimposed at the same frequency due to the design of variable duty cycle and variable period, but will be dispersed to different frequency positions in the passband, and at the same time, the electrode index in each period is greatly reduced, so that the intensity of the excited transverse mode components is greatly weakened, the steepness of the transition band of the filter and the flatness in the passband are guaranteed, and a large number of obvious burrs are avoided in the passband, thereby improving the performance and reliability of the electronic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, drawings of other embodiments can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 is a schematic top view of an interdigital transducer with a fixed period and duty cycle;

[0023] Figure 2 for Figure 1 A schematic diagram of the structure of the longitudinal section parallel to the ox direction of the structure shown in FIG.

[0024] Figure 3a is a schematic top view of an interdigital transducer with a variable period and duty cycle in one embodiment;

[0025] Figure 3b For Figure 3a A schematic top view of the structure obtained by adding fake fingers on the basis of FIG.

[0026] Figure 4 is a schematic top view of an interdigital transducer with a variable period and duty cycle in another embodiment;

[0027] Figure 5a for Figure 4 Schematic diagram of the change of duty cycle of different partitions with position;

[0028] Figure 5b Schematic diagram of correlation curves between periods and duty cycles in different regions of an IDT in one embodiment;

[0029] Figure 5c A schematic diagram of the variation of the period of different regions in an IDT with respect to position in one embodiment;

[0030] Figure 6A schematic top view of an interdigital transducer with a variable period and duty cycle in yet another embodiment;

[0031] Figure 7a For the general Figure 6 Schematic diagram of the comparison of the waveforms of the surface acoustic wave obtained when the duty ratio MR of the internal partition of the interdigital transducer is set to 0.4;

[0032] Figure 7b For the general Figure 6 Schematic diagram of the comparison of the waveforms of the surface acoustic wave obtained when the duty ratio MR of the internal partition of the interdigital transducer is set to 0.45;

[0033] Figure 7c For the general Figure 6 Schematic diagram of the comparison of the waveforms of the surface acoustic wave obtained when the duty ratio MR of the internal partition of the interdigital transducer is set to 0.5;

[0034] Figure 7d For the general Figure 6 Schematic diagram of the comparison of the waveforms of the surface acoustic wave obtained when the duty cycle MR of the internal partition of the interdigital transducer is set to 0.6;

[0035] Figure 8 is a schematic top view of a filter in one embodiment;

[0036] Figure 9a It is a schematic diagram of the change of the duty cycle of the first filter with the position;

[0037] Figure 9b for Figure 9a Schematic diagram of the change of the period of the corresponding filter with position;

[0038] Fig.9c It is a schematic diagram of the change of the duty cycle of the second filter with the position;

[0039] Figure 9d for Fig.9c Schematic diagram of the change of the period of the corresponding filter with position;

[0040] Fig.9e It is a schematic diagram of the change of the duty cycle of the third filter with the position;

[0041] Figure 9f for Fig.9e Schematic diagram of the change of the period of the corresponding filter with position;

[0042] Figure 9g is a schematic diagram of the change of the duty cycle of the fourth filter with position;

[0043] Figure 9h is a schematic diagram of the change of the duty cycle of the fifth filter with position;

[0044] Fig.10a A schematic diagram for comparing waveforms of surface acoustic waves obtained when the duty ratios and periods of at least two partitions in the filter are set to be different;

[0045] Fig.10b for Fig.10a A partial enlarged schematic diagram of the waveform in the middle rectangular frame.

[0046] Description of reference numerals:

[0047] 100. IDT; 10. Substrate; 11. Dielectric layer; 12. Piezoelectric material layer; 21. First electrode finger; 22. Second electrode finger; 20. Electrode group; 31 / 31' / 31a. First bus bar; 32 / 32' / 32a. Second bus bar; 41. First reflection grating; 42. Second reflection grating; 51. First dummy finger; 52. Second dummy finger; 411. Third electrode finger; 412. Third complementary electrode finger; 421. Fourth electrode finger; 422. Fourth complementary electrode finger; 200. Filter. DETAILED DESCRIPTION

[0048] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0050] The term "and / or" used herein includes any and all combinations of one or more of the related listed items. In the case of using "including", "having", and "comprising" described herein, another component may be added unless a clear limiting term such as "only", "consisting of", etc. is used. Unless mentioned to the contrary, a term in the singular form may include a plural form and is not to be understood as having one number.

[0051] It should be understood that although the terms "first", "second", etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of the present disclosure.

[0052] In the description of the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0053] In addition, in the description of the present application, unless otherwise specified, “several,” “overlap,” “stacked,” “layered,” “mutually” or “mutually” means two or more.

[0054] It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present disclosure in a schematic manner. Although the illustrations only show components related to the present disclosure and are not drawn according to the number, shape and size of components in actual implementation, the type, quantity and proportion of each component in actual implementation may be changed arbitrarily, and the component layout type may also be more complicated.

[0055] As the number of communication frequency bands increases, the frequency bands become more and more crowded, and the protection intervals between frequency bands of different communication systems are getting smaller and smaller. For example, for the duplexer frequency bands (Band2, 3, 8, 25) including the transmitter Tx and the receiver Rx, the frequency interval between the transmitter Tx and the receiver Rx is very narrow. In order to avoid mutual interference between frequency bands, surface acoustic wave filters based on POI substrates can usually be used to improve the energy utilization efficiency of the filter. However, the transducer in the POI-based surface acoustic wave filter has problems with lateral energy leakage and beam deflection, which will seriously deteriorate the steepness of the filter's transition band and the flatness within the passband, while causing stray resonances to the resonator, reducing the device Q value, and especially generating a large number of obvious burrs within the passband. In order to suppress the lateral mode components of the transducer in the POI-based surface acoustic wave filter, the following three technical solutions are generally adopted:

[0056] Solution 1: Weighting the overlapping area of ​​the fingers of the interdigital transducer (IDT), for example, using a cosine function or a sinusoidal function to weight the overlapping area of ​​the fire and ground electrodes to change the length of the acoustic-to-electric conversion area.

[0057] Solution 2: Process the ends of the metal fingers to increase the metal duty cycle, or add a second layer of metal.

[0058] Solution three: Dig grooves in the piezoelectric layer substrate below the metal finger tips to physically block the propagation path of the sound waves and achieve transverse mode suppression.

[0059] Among the three common transverse mode suppression schemes mentioned above, scheme one will increase the size of the device and reduce the Q value of the transducer; scheme two has a good transverse mode suppression effect, but if the duty cycle is too large or the second layer is not accurately positioned, a short circuit may occur, causing device failure; scheme three has high requirements for process accuracy, which will significantly increase the manufacturing cost.

[0060] The present disclosure aims to provide an interdigital transducer, a filter and an electronic device, which can at least effectively suppress the transverse mode component in the transducer.

[0061] like Figure 1-Figure 2 As shown, in some embodiments, an IDT 100 includes first electrode fingers 21 and second electrode fingers 22 that are alternately and evenly spaced in sequence along a first direction; the first electrode fingers 21 and the second electrode fingers 22 form an electrode group 20; the first electrode fingers 21 and the second electrode fingers 22 have the same shape, size, duty cycle and period. Figure 1 Where p is the abbreviation of pitch, which indicates the repetitive period of the first electrode finger 21 and the second electrode finger 22, which is half of the wavelength; the duty cycle is used to indicate the metallization rate, which can be represented by MR, which is the ratio of the width a of the first electrode finger 21 or the second electrode finger 22 to the period p, MR=a / p.

[0062] As an example, please refer to Figure 1-Figure 2 The interdigital transducer 100 is located on a substrate 10. A laminated dielectric layer 11 and a piezoelectric material layer 12 are provided between the interdigital transducer 100 and the substrate 10. The dielectric layer 11 is used to isolate the piezoelectric material layer 12 from the substrate 10, so as to facilitate damage or contamination of the substrate 10 during the preparation of the piezoelectric material layer 12. The interdigital transducer 100 is shaped like a pair of crossed fingers, and converts electroacoustic signals through the piezoelectric effect. The interdigital transducer 100 includes a plurality of electrode groups 20 spaced apart to form a grating-like structure, and the spacing d between the gratings determines the wavelength of the generated surface acoustic wave. The vibration of the surface acoustic wave can cause the piezoelectric material layer 12 to vibrate, thereby transmitting the surface acoustic wave outward.

[0063] As an example, please refer to Figure 1-Figure 2The substrate 10 may be made of semiconductor material, insulating material, conductor material or any combination of their material types. The substrate 10 may be a single-layer structure or a multi-layer structure. For example, the substrate 10 may be a silicon (Si) substrate, a silicon germanium (SiGe) substrate, a silicon germanium carbon (SiGeC) substrate, a silicon carbide (SiC) substrate, a gallium arsenide (Gas) substrate, an indium arsenide (InAs) substrate, an indium phosphide (InP) substrate or other III / V semiconductor substrates or II / VI semiconductor substrates. Alternatively, for example, the substrate 10 may be a layered substrate including a stack of Si and SiGe, a stack of Si and SiC, a silicon on insulator (SOI) or a silicon germanium on insulator. The material of the dielectric layer 11 may include silicon dioxide, silicon nitride, silicon oxynitride, silicon carbide or any combination thereof. The material of the piezoelectric material layer 12 may include at least one of a piezoelectric crystal, a piezoelectric ceramic and a piezoelectric polymer.

[0064] As an example, see Figure 3a An IDT 100 includes first electrode fingers 21 and second electrode fingers 22 which are alternately and evenly spaced in sequence along a first direction; the IDT 100 has non-overlapping partitions S1, S2 and S3 in the first direction, each of which includes at least one electrode group 20, and an electrode group 20 includes first electrode fingers 21 and second electrode fingers 22 which are adjacent to each other along the first direction; the periods and duty cycles of the electrode groups 20 in the partitions S1, S2 and S3 are different and the frequencies of the excited surface acoustic waves are the same.

[0065] It should be noted that the first direction may be parallel to the ox direction shown in the figure, the acoustic wave propagation direction may be parallel to the first direction, the second direction may be parallel to the oy direction shown in the figure, and the thickness direction of the substrate may be perpendicular to the ox direction and the oy direction.

[0066] As an example, please refer to Figure 3a By setting the interdigital transducer 100 to have non-overlapping partitions S1, S2 and S3 in the first direction, each of the partitions S1, S2 and S3 includes at least one electrode group 20, and one electrode group 20 includes a first electrode finger 21 and a second electrode finger 22 adjacent to each other along the first direction; the periods and duty cycles of the electrode groups 20 in the partitions S1, S2 and S3 are different and the frequencies of the excited surface acoustic waves are the same, so that the transverse mode components of the electrode groups 20 in different partitions will not be accumulated and superimposed at the same frequency, but will be dispersed to different frequency positions in the passband, and at the same time, the electrode index in each period is greatly reduced, so that the intensity of the excited transverse mode components is greatly weakened, and finally a smaller burr is shown in the overall filter performance.

[0067] As an example, please refer to Figure 3b An IDT 100 further includes dummy fingers (not shown), the dummy fingers include a first dummy finger 51 and a second dummy finger 52; the first dummy finger 51 is arranged one-to-one with the first electrode finger 21, and the second dummy finger 52 is arranged one-to-one with the second electrode finger 22; the period and duty cycle of the first dummy finger 51 are the same as the period and duty cycle of the corresponding first electrode finger 21, and the period and duty cycle of the second dummy finger 52 are the same as the period and duty cycle of the corresponding second electrode finger 22. The periods and duty cycles of the dummy fingers in the partitions S1, S2, and S3 are different and the frequencies of the excited surface acoustic waves are the same, so that the transverse mode components of the dummy fingers in different partitions will not be accumulated and superimposed at the same frequency, which is conducive to suppressing the transverse mode components.

[0068] As an example, see Figure 4 An IDT 100 includes first electrode fingers 21 and second electrode fingers 22 which are alternately and evenly spaced in sequence along a first direction; the first electrode fingers 21 and the second electrode fingers 22 form an electrode group 20; the IDT 100 has non-overlapping partitions S1', S2', and S3' in the first direction, and the partitions S1', S2', and S3' all include first electrode fingers 21 and second electrode fingers 22 adjacent to each other along the first direction. The partitions S1', S2', and S3' of the IDT 100 are symmetrical in the first direction with a symmetry axis L1 passing through the center point of the IDT 100, so that the transverse mode components of the electrode group 20 in the partitions symmetrical in the first direction will not be accumulated and superimposed at the same frequency, but will be dispersed to different frequency positions in the passband, and at the same time, the electrode index in each period is greatly reduced, so that the intensity of the excited transverse mode components is greatly weakened, and finally a smaller burr is shown in the overall filter performance, thereby reducing the preparation complexity and cost of the IDT 100.

[0069] As an example, please refer to Figure 3a In the direction along the first direction toward the symmetry axis L1, the duty cycle of partition S3, partition S2, and partition S1 gradually decreases and the period p gradually increases, so that the transverse mode components of the electrode group 20 in the partitions symmetrical in the first direction will not be accumulated and superimposed at the same frequency, but will be dispersed to different frequency positions in the passband. At the same time, the electrode index in each period is greatly reduced, thereby greatly weakening the intensity of the excited transverse mode components.

[0070] As an example, please refer to Figure 3a In the direction from the first direction to the symmetry axis L1, the duty ratios of different partitions can be set to decrease by a fixed amount or linearly decrease in sequence, so as to simplify the complexity of the internal partition design of the IDT 100.

[0071] As an example, see Figure 4In the direction along the first direction toward the symmetry axis L1, the duty cycle of partition S3', partition S2', and partition S1' gradually increases and the period p gradually decreases, so that the transverse mode components of the electrode group 20 in the partitions symmetrical in the first direction will not be accumulated and superimposed at the same frequency, but will be dispersed to different frequency positions in the passband. At the same time, the electrode index in each period is greatly reduced, thereby greatly weakening the intensity of the excited transverse mode components and improving the efficiency of transverse mode suppression.

[0072] As an example, please refer to Figure 4 In the direction along the first direction toward the symmetry axis L1, the duty ratios of different partitions are increased by a fixed amount or linearly increased in sequence, so as to simplify the complexity of the internal partition design of the IDT 100.

[0073] Those skilled in the art will appreciate that, in some embodiments, the multiple partitions of the IDT may be configured such that: along the first direction, the duty cycles of different partitions are sequentially reduced by a fixed amount or linearly decreased. In some other embodiments, the multiple partitions of the IDT may be configured such that: along the first direction, the duty cycles of different partitions are sequentially increased by a fixed amount or linearly increased.

[0074] As an example, please refer to Figure 3a and Figure 5a , Figure 5a The horizontal axis represents Figure 3a The positions of the electrode fingers in the middle interdigital transducer 100, the vertical axis is the duty cycle, it can be seen that the duty cycle gradually increases from the middle to the two ends, mirror symmetry. The duty cycles of different partitions are different, but it is necessary to ensure that the surface acoustic wave frequencies excited by different partitions are the same.

[0075] As an example, please refer to Figure 5b The horizontal axis represents the duty cycle of different zones in the IDT 100, and the vertical axis represents the period of different zones in the IDT 100. The electrode fingers in each zone of the IDT 100 should be evenly distributed, and different duty cycles correspond to different periods. Figure 5b The middle dotted line represents a schematic diagram of a curve showing a change in duty cycle of different regions in the improved interdigital transducer 100 with respect to a period; Figure 5b The solid line in the middle shows the change curve of the duty ratio of different areas in the improved interdigital transducer 100 with the period. The duty ratio and period can be set to change linearly, that is, the duty ratio and period of each finger in the resonator are different, which can be adjusted according to the Figure 5b It is calculated using the fitting formula.

[0076] As an example, please refer to Figure 4 , Figure 5c , Figure 5c The horizontal axis represents Figure 4The position of the electrode fingers in the interdigital transducer 100, the vertical axis is the duty cycle, it can be seen that the duty cycle gradually decreases from the middle to the two ends, mirror symmetry. The duty cycles of different partitions are different. Since it is necessary to ensure that the frequency of the surface acoustic waves excited by different partitions in the interdigital transducer 100 is the same, the change trend of the period of different partitions is opposite to the change trend of the duty cycle.

[0077] As an example, see Figure 6 The IDT 100 includes a plurality of unit regions r1 arranged in sequence in a first direction, each unit region r1 includes at least one partition, and the partitions in different unit regions r1 are arranged in the same manner. Figure 6 The middle unit area r1 includes three electrode groups 20 , and the arrangement of the partitions in the two unit areas r1 is the same.

[0078] As an example, different partitions in the interdigital transducer can be arranged irregularly, as long as the periods and duty cycles of the electrode groups in at least two partitions are different and the frequencies of the excited surface acoustic waves are the same. Moreover, when a resonator is composed of electrode fingers with different duty cycles, the lateral mode components excited under different duty cycles and periods will not be accumulated and superimposed at the same frequency point compared with the previously fixed duty cycle and period. The electrode index under each duty cycle is reduced, thereby weakening the amplitude of the lateral mode component, so as to show a smoother passband response in the filter response.

[0079] In one embodiment, the duty cycles and periods of different first electrode fingers are different; the duty cycles and periods of different second electrode fingers are different; and the duty cycles and periods of the first electrode fingers and the second electrode fingers are different, so as to maximize the degree of suppression of the lateral mode components of the resonator.

[0080] As an example, please refer to Figure 3a , Figure 4 and Figure 6 , the thicknesses of different first electrode fingers 21 are the same; the thicknesses of different second electrode fingers 22 are the same; and the thicknesses of the first electrode fingers 21 and the second electrode fingers 22 are the same, so as to reduce the complexity of the manufacturing process.

[0081] As an example, please refer to Figure 3a , Figure 4 and Figure 6The interdigital transducer 100 also includes a first bus bar 31 and a second bus bar 32 spaced apart along the second direction and extending along the first direction; the first electrode finger 21 and the second electrode finger 22 are both located between the first bus bar 31 and the second bus bar 32; the first electrode finger 21 is configured as: having a first end and a second end opposite to each other along the second direction, the first end being connected to the first bus bar 31, and the second end being spaced apart from the second bus bar 32; the second electrode finger 22 is configured as: having a first end and a second end opposite to each other along the second direction, the first end being connected to the second bus bar 32, and the second end being spaced apart from the first bus bar 31.

[0082] As an example, please refer to Figure 4 , Figure 7a-7d , you can set Figure 4 The duty cycle MR1 of the middle partition S1' is 0.55, the duty cycle MR2 of the partition S2 is 0.5, and the duty cycle MR3 of the partition S3 is 0.45. Correspondingly, the period p1 of the partition S1' is 2.5427um, the period p2 of the partition S2 is 2.5527um, and the period p3 of the partition S3 is 2.5642um.

[0083] Figure 7a-7d The following are schematic diagrams of the waveform comparison of the surface acoustic wave obtained by setting the duty ratio MR of different partitions in the interdigital transducer to 0.4, 0.45, 0.5, and 0.6, respectively, where curve X1 is a schematic diagram of the waveform curve after improvement, and curve X2 is a schematic diagram of the waveform curve before improvement. It can be seen that the shear wave mode of the resonator behaves differently under different duty ratios; when different duty ratios are used for the metal fingers in the same resonator, the frequency and strength of the shear wave mode will change accordingly. Figure 7a-7d The amplitude of the surface acoustic wave obtained after changing the duty cycle MR and the period pitch (please refer to curve X1) is greater than the amplitude of the surface acoustic wave of the resonator with fixed duty cycle and period before improvement (please refer to curve X2), and the waveform is obviously smoother and has fewer burrs.

[0084] As an example, see Figure 8The present application provides a filter 200, comprising any one of the IDT 100, the first reflection grating 41 and the second reflection grating 42 described in the embodiments of the present application, wherein the first reflection grating 41 and the second reflection grating 42 are spaced apart along the first direction, and the IDT 100 is located between the first reflection grating 41 and the second reflection grating 42. By setting the periods and duty cycles of the electrode groups 20 of at least two partitions in the IDT 100 to be different and the excited surface acoustic wave frequencies to be the same, the transverse mode components of the electrode groups 20 in different partitions will not be accumulated and superimposed at the same frequency, but will be dispersed to different frequency positions in the passband, and at the same time, the electrode index in each period is greatly reduced, so that the intensity of the excited transverse mode components is greatly weakened, thereby ensuring the steepness of the transition band of the filter 200 and the flatness in the passband, and avoiding a large number of obvious burrs in the passband.

[0085] As an example, please refer to Figure 8 The first reflection grating 41 and the second reflection grating 42 are symmetrical in a first direction about a symmetry axis L1 passing through the center point of the IDT 100 , so as to ensure the steepness of the transition band of the filter 200 and the flatness in the passband and reduce the complexity of the structure of the filter 200 .

[0086] As an example, please refer to Figure 8 The first reflection grating 41 includes third electrode fingers 411 that are sequentially spaced and distributed along the first direction; the first reflection grating 41 has at least two non-overlapping sub-areas z1 in the first direction, and the sub-area z1 includes at least one third electrode finger 411; the periods and duty cycles of the third electrode fingers 411 in at least two sub-areas z1 are different and the frequencies of the excited surface acoustic waves are the same, so that the transverse mode components of the third electrode fingers 411 in different sub-areas z1 in the first reflection grating 41 will not be accumulated and superimposed at the same frequency, but will be dispersed to different frequency positions in the passband, and at the same time, the electrode index in each period is greatly reduced, so that the intensity of the excited transverse mode component is greatly weakened.

[0087] As an example, please refer to Figure 8The first reflector 41 includes a first bus bar 31' and a second bus bar 32' spaced apart along the second direction and extending along the first direction; the third electrode fingers 411 are located between the first bus bar 31' and the second bus bar 32'; the third electrode fingers 411 are configured to have a first end and a second end opposite to each other along the second direction, the first end is connected to the first bus bar 31', and the second end is spaced apart from the second bus bar 32'. The first reflector 41 may also include a third complementary electrode finger 412, the third complementary electrode finger 412 and the third electrode finger 411 form an electrode finger pair; the third complementary electrode finger 412 is configured to have a first end and a second end opposite to each other along the second direction, the first end is connected to the second bus bar 32', and the second end is spaced apart from the first bus bar 31', at least one electrode finger pair is included in the sub-area z1, and the periods and duty cycles of different sub-areas z1 are different and the frequencies of the excited surface acoustic waves are the same.

[0088] As an example, please refer to Figure 8 The second reflection grating 42 includes fourth electrode fingers 421 that are sequentially spaced and distributed along the first direction; the second reflection grating 42 has at least two non-overlapping sub-areas z2 in the first direction, and the sub-area z2 includes at least one fourth electrode finger 421; the periods and duty cycles of the fourth electrode fingers 421 in at least two sub-areas z2 are different and the frequencies of the excited surface acoustic waves are the same, so that the transverse mode components of the fourth electrode fingers 421 in different sub-areas z2 in the second reflection grating 42 will not be accumulated and superimposed at the same frequency, but will be dispersed to different frequency positions in the passband, and at the same time, the electrode index in each period is greatly reduced, so that the intensity of the excited transverse mode component is greatly weakened.

[0089] As an example, please refer to Figure 8 The second reflector 42 includes a first bus bar 31a and a second bus bar 32a spaced along the second direction and extending along the first direction; the fourth electrode fingers 421 are located between the first bus bar 31a and the second bus bar 32a; the fourth electrode fingers 421 are configured to have a first end and a second end opposite to each other along the second direction, the first end is connected to the first bus bar 31a, and the second end is spaced from the second bus bar 32a. The second reflector 42 may also include a fourth complementary electrode finger 422, the fourth electrode finger 421 and the fourth complementary electrode finger 422 form an electrode finger pair; the fourth complementary electrode finger 422 is configured to have a first end and a second end opposite to each other along the second direction, the first end is connected to the second bus bar 32a, and the second end is spaced from the first bus bar 31a. The sub-area z2 includes at least one electrode finger pair, and the periods and duty cycles of different sub-areas z2 are different and the frequencies of the excited surface acoustic waves are the same.

[0090] As an example, see Figure 8 , Figure 9a and Figure 9b , you can set Figure 8In the IDT 100, the duty ratios of different partitions increase by a fixed amount in sequence in the direction along the first direction toward the symmetry axis L1, such as Figure 9a As shown; can be set Figure 8 In the interdigital transducer 100, in the direction along the first direction toward the symmetry axis L1, the periods of different partitions are successively reduced by a fixed amount, such as Figure 9b As shown, the frequencies of surface acoustic waves excited in different partitions are guaranteed to be the same; you can set Figure 8 The pitch and duty cycle of the first reflective grating 41 and the second reflective grating 42 are correspondingly equal, the pitch and duty cycle of different electrode fingers in the first reflective grating 41 remain unchanged, and the pitch and duty cycle of different electrode fingers in the second reflective grating 42 remain unchanged.

[0091] As an example, see Figure 8 , Fig.9c and Figure 9d , you can set Figure 8 In the IDT 100 , the duty cycles of different partitions are asymmetric in the direction along the first direction toward the symmetry axis L1 .

[0092] Specifically, Fig.9c As shown, in the first direction from left to right, with the middle position of the IDT of the IDT as a reference, from one reflection grid to the middle of the IDT, the duty cycles of different partitions gradually increase, from the middle of the IDT to another reflection grid, the duty cycles of the first two partitions gradually increase, and the duty cycles of the last three partitions also gradually increase, but the duty cycles of the first two partitions are greater than those of the last three partitions. Therefore, the duty cycle can be gradually increased, and can be increased with different duty cycles as starting points; wherein, the gradual increase can be understood as a linear increase or an increase of a fixed amount; in addition, in other embodiments, along the first direction, the duty cycles of different partitions can change randomly.

[0093] Specifically, Figure 9d As shown, in the first direction from left to right, with the middle position of the IDT of the IDT as a reference, from one reflection grid to the middle of the IDT, the duty cycles of different partitions gradually decrease, and from the middle of the IDT to another reflection grid, the duty cycles of the first two partitions gradually decrease, and the duty cycles of the last three partitions also gradually decrease, but the duty cycles of the first two partitions are smaller than those of the last three partitions. Therefore, the duty cycle may gradually increase, and may increase from different duty cycles as starting points; wherein, gradually increasing may be understood as a linear increase or an increase of a fixed amount. In addition, in other embodiments, along the first direction, the duty cycles of different partitions may change randomly.

[0094] Therefore, along the first direction, the duty ratios of different partitions may be successively reduced by a fixed amount or linearly decreased, or may be successively increased by a fixed amount or linearly increased, or may be randomly changed.

[0095] As an example, see Figure 8 , Fig.9e and Figure 9f , you can set Figure 8 The IDT 100 in the first direction increases from left to right, and the duty ratios of different partitions increase by a fixed amount, and the pitches of different partitions decrease by a fixed amount. Figure 8 The pitch and duty cycle of the first reflective grating 41 and the second reflective grating 42 are correspondingly equal, the pitch and duty cycle of different electrode fingers in the first reflective grating 41 remain unchanged, and the pitch and duty cycle of different electrode fingers in the second reflective grating 42 remain unchanged.

[0096] As an example, see Figure 8 , Figure 9g-9h , you can set Figure 8 The first reflection grating 41 and the second reflection grating 42 are symmetrical in the first direction with a symmetry axis L1 passing through the center point of the IDT 100. Figure 8 The periods (pitch) and duty ratios of the first reflective grating 41 and the second reflective grating 42 are correspondingly equal, the periods and duty ratios of different electrode fingers in the first reflective grating 41 remain unchanged, and the periods and duty ratios of different electrode fingers in the second reflective grating 42 remain unchanged. Figure 9g shown.

[0097] As an example, see Figure 9h , you can set Figure 8 The first reflective grid 41 includes two sub-areas z1, and the duty ratios of the two sub-areas z1 increase from left to right along the first direction. The second reflective grid 42 includes two sub-areas z2, and the duty ratios of the two sub-areas z2 decrease from left to right along the first direction.

[0098] As an example, see Figure 10a-Figure 10b , Fig.10a The middle dotted line shows the waveform curve diagram obtained by using a filter with a fixed period and duty cycle. Fig.10a The solid line in the middle represents a schematic diagram of a waveform curve obtained by using the filter described in the above embodiment, wherein the horizontal axis represents frequency (freq), in MHz, and the vertical axis represents decibel (dB); Fig.10b for Fig.10a The enlarged schematic diagram of the part in the rectangular box. Figure 10a-Figure 10b From the dotted waveform curve and the solid waveform curve in the figure, it can be clearly found that the solid waveform curve has better smoothness and fewer burrs.

[0099] As an example, the present application provides an electronic device, including a filter according to any of the embodiments of the present application. By setting the period and duty cycle of the electrode groups of at least two partitions in the interdigital transducer to be different and the excited surface acoustic wave frequency to be the same, due to the design of variable duty cycle and variable period, the transverse mode components will not be accumulated and superimposed at the same frequency, but dispersed to different frequency positions in the passband, and the electrode index in each period is greatly reduced, so that the intensity of the excited transverse mode component is greatly weakened, ensuring the steepness of the transition band of the filter and the flatness in the passband, avoiding a large number of obvious burrs inside the passband, thereby improving the performance and reliability of the electronic device. The electronic device is, for example, but not limited to, suitable types of electronic products such as consumer electronic products, home electronic products, vehicle-mounted electronic products, financial terminal products, and duplexers containing filters according to any of the embodiments of the present application, and some electronic products containing the duplexers. Among them, consumer electronic products are such as mobile phones, tablet computers, laptops, desktop monitors, all-in-one computers, etc. Home electronic products are such as smart door locks, televisions, refrigerators, wearable devices, etc. Car-mounted electronic products include car navigation systems, car DVD players, etc. Financial terminal products include ATM machines, self-service terminals, etc.

[0100] Please note that for the sake of simplicity of the specification, in the structural schematic diagrams given in the embodiments below, unless the corresponding cross-sectional structural schematic diagrams are given separately, other structural schematic diagrams of different perspectives of structures related to the inventive points of the embodiments of the present disclosure can refer to each other.

[0101] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0102] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. An interdigital transducer, characterized in that: It comprises first electrode fingers and second electrode fingers which are alternately and spacedly distributed in sequence along a first direction; The IDT has at least two non-overlapping partitions in the first direction, each partition includes at least one electrode group, and the electrode group includes the first electrode finger and the second electrode finger adjacent to each other along the first direction; In the at least two partitions, the periods and duty ratios of at least one electrode group in one partition and at least one electrode group in another partition are different, and the frequencies of the excited surface acoustic waves are the same.

2. The interdigital transducer according to claim 1, characterized in that: The at least two partitions are symmetrical in the first direction about a symmetry axis passing through a center point of the IDT.

3. The interdigital transducer according to claim 2, characterized in that: In a direction along the first direction toward the symmetry axis, the duty ratios of different partitions gradually decrease or increase.

4. The interdigital transducer according to claim 3, characterized in that: In the direction along the first direction toward the symmetry axis, the duty ratios of different partitions are successively reduced by a fixed amount or linearly decreased; or In the direction along the first direction toward the symmetry axis, the duty ratios of different partitions are sequentially increased by a fixed amount or linearly increased.

5. The interdigital transducer according to claim 1, characterized in that: The at least two partitions are configured as: Along the first direction, the duty ratios of different partitions are successively reduced by a fixed amount or linearly decreased; or Along the first direction, the duty cycles of different partitions are sequentially increased by a fixed amount or linearly increased.

6. The interdigital transducer according to any one of claims 1 to 5, characterized in that: The duty ratios and periods of different first electrode fingers are different; The duty ratios and periods of different second electrode fingers are different; and The duty ratios and periods of the first electrode fingers and the second electrode fingers are different.

7. The interdigital transducer according to any one of claims 1 to 5, characterized in that: The thicknesses of the different first electrode fingers are the same; The thicknesses of the second electrode fingers are different from each other; and The first electrode fingers and the second electrode fingers have the same thickness.

8. A filter, characterized in that: include: A first reflection grating and a second reflection grating spaced apart along a first direction, and an IDT according to any one of claims 1 to 6 located between the first reflection grating and the second reflection grating.

9. The filter according to claim 8, characterized in that The first reflection grating and the second reflection grating are symmetrical in the first direction about a symmetry axis passing through a center point of the IDT.

10. The filter according to claim 8, characterized in that: The first reflection grating comprises third electrode fingers sequentially spaced and distributed along the first direction; the first reflection grating has at least two non-overlapping sub-regions in the first direction, each of which comprises at least one third electrode finger; the periods and duty cycles of the third electrode fingers in at least two of the sub-regions are different and the frequencies of the excited surface acoustic waves are the same; and / or The second reflection grating includes fourth electrode fingers that are sequentially spaced and distributed along the first direction; the second reflection grating has at least two non-overlapping sub-regions in the first direction, and the sub-regions include at least one of the fourth electrode fingers; the periods and duty cycles of the fourth electrode fingers in at least two of the sub-regions are different and the frequencies of the excited surface acoustic waves are the same.

11. An electronic device, characterized in that: include: A filter as claimed in any one of claims 8 to 10.

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