Cascade resonator and preparation method thereof, and filter

Abstract

The invention provides a cascade resonator and a preparation method thereof, and a filter. The cascade resonator comprises a plurality of interdigital transducers arranged along a surface acoustic wave propagation direction; wherein any interdigital transducer is divided into a first bus bar, an interdigital electrode and a second bus bar along a specified direction; the specified direction is parallel to the extension direction of the interdigital electrode; in the plurality of interdigital transducers, the first bus bars and the second bus bars of any two adjacent interdigital transducers are electrically connected with each other. According to the invention, the linearity of the cascade resonator and the filter can be improved.

Description

Technical Field

[0001] The embodiments in the present application relate to the technical field of surface acoustic wave filters, and particularly to a cascaded resonator, a preparation method thereof, and a filter. Background Art

[0002] With the development of mobile communication technology, the number of communication frequency bands has increased sharply, and the frequency interval between adjacent channels has become smaller and smaller. In mobile communication terminals, more and more filters are applied to the radio frequency front end. The surface acoustic wave (SAW) filter is one of them, which plays a key role in filtering out useless signals and retaining useful signals in the radio frequency front end module, and is widely used in mobile communication devices.

[0003] In 5G radio frequency communication, in addition to having high requirements for signal transmission quality indicators such as the insertion loss, isolation, and out-of-band attenuation of the SAW filter, at the same time, in order to ensure the inter-band uplink carrier aggregation and high-power signal transmission, the linearity requirement for the SAW filter is also getting higher and higher.

[0004] In the related art, usually, methods such as increasing the resonator segments and externally connecting capacitors are used to improve the linearity of the SAW filter, but there are also problems such as additional area occupation and affecting other performances of the SAW filter. Summary of the Invention

[0005] In view of this, multiple embodiments of the present application are committed to providing a cascaded resonator, a preparation method thereof, and a filter, which can improve the linearity of the cascaded resonator and the surface acoustic wave filter to a certain extent without additional area occupation and without affecting the main performances.

[0006] An embodiment of the present application provides a cascaded resonator, which includes a plurality of interdigital transducers arranged along the surface acoustic wave propagation direction; wherein, any one of the interdigital transducers is divided into a first bus bar, an interdigital electrode, and a second bus bar along a specified direction; the specified direction is parallel to the extension direction of the interdigital electrode; among the plurality of interdigital transducers, the first bus bar and the second bus bar of any two adjacent interdigital transducers are electrically connected to each other.

[0007] Optionally, among the plurality of interdigital transducers, between the first bus bar and the second bus bar of any two adjacent interdigital transducers, electrical connection to each other is achieved through one or more common fingers; when the electrical connection to each other is achieved through a plurality of common fingers, the plurality of common fingers form a reflection grating located between two adjacent interdigital transducers.

[0008] Optionally, the bus bar connecting the common fingers is used to access an intermediate potential point between the signal bus bar and the ground bus bar of the cascaded resonator.

[0009] Optionally, in any of the interdigital transducers, the length of the aperture in the extending direction of the interdigital electrodes ranges from 20 μm to 150 μm, and the number of the interdigital electrodes in the interdigital transducer ranges from 100 to 600.

[0010] Optionally, among the multiple interdigital transducers of the cascaded resonator, at least two interdigital transducers have different finger spacings and duty cycles.

[0011] Another embodiment of the present application provides a method for manufacturing a target cascaded resonator, where the target cascaded resonator is the cascaded resonator as described above; the manufacturing method includes: obtaining the reference specification data of a reference cascaded resonator corresponding to the target cascaded resonator; where the reference cascaded resonator includes multiple reference interdigital transducers arranged along the extending direction of the reference interdigital electrodes in the reference interdigital transducer; the reference specification data includes first reference data representing the aperture size of the reference interdigital transducer and second reference data representing the number of the reference interdigital electrodes in the reference interdigital transducer; determining the specification data of the target cascaded resonator according to the first reference data and the second reference data; the specification data includes: first target data representing the aperture size of the interdigital transducer in the target cascaded resonator and second target data representing the number of the interdigital electrodes in the interdigital transducer; the first target data is greater than the first reference data, and the second target data is less than the second reference data; where the product of the first target data and the second target data is equal to the product of the first reference data and the second reference data; manufacturing the target cascaded resonator with the corresponding specification based on the specification data.

[0012] Optionally, the first target data is a specified integer multiple of the first reference data; and the second reference data is a specified integer multiple of the second target data; where the specified integer is greater than or equal to 2.

[0013] Optionally, the interdigital transducer in the target cascaded resonator has the same impedance as the reference interdigital transducer.

[0014] Optionally, the filter includes the cascaded resonator as described in the foregoing embodiment.

[0015] Optionally, the filter includes multiple paths connected in parallel to the antenna terminal; where in at least one path, the cascaded resonator connected to the antenna terminal is provided.

[0016] Optionally, the multiple paths include paths of different frequency bands and an absorption load path; the cascaded resonator is provided in the absorption load path.

[0017] Another embodiment of the present application provides an electronic device, including the cascaded resonator as described above, or the filter as described above.

[0018] In multiple embodiments provided by the present application, multiple interdigital transducers are arranged along the propagation direction of the surface acoustic wave to form a cascaded resonator with an acoustic cascade. And relative to the reference cascaded resonator formed by arranging multiple reference interdigital transducers along the extension direction of the reference interdigital electrodes, on the premise that the product of the aperture of the interdigital transducer and the number of interdigital electrodes remains unchanged, by setting a larger aperture of the interdigital transducer and a smaller number of interdigital electrodes, the transverse wave mode in the end region of the interdigital electrodes is weakened, and the excitation of non-linear second harmonics and non-linear third harmonics is suppressed, so as to achieve the improvement of the linearity of the cascaded resonator and the surface acoustic wave filter to a certain extent while the occupied area and the main performance remain basically unchanged. Description of the Drawings

[0019] Figure 1 and Figure 2 It is a schematic diagram for analyzing the non-linear effect of the surface acoustic wave resonator provided by an embodiment of the present application.

[0020] Figure 3 It is a schematic diagram of the preparation method of the cascaded resonator provided by an embodiment of the present application.

[0021] Figure 4 It is a schematic diagram of the structure of the reference cascaded resonator provided by an embodiment of the present application.

[0022] Figure 5 It is a schematic diagram of the structure of a cascaded resonator provided by an embodiment of the present application.

[0023] Figure 6 It is a schematic diagram of the structure of another cascaded resonator provided by an embodiment of the present application.

[0024] Figure 7 It is a schematic diagram of the structure topology of a filter provided by an embodiment of the present application.

[0025] Figure 8 It is a schematic diagram for comparing the test results of the filter topology structure in the present application.

[0026] Description of the Reference Signs:

[0027] 101. Finger tip region; 102. Passband frequency band; 10. Reference cascaded resonator; 11. First reference interdigital transducer; 12. Second reference interdigital transducer; 13. Reference reflection grating; 20. Cascaded resonator; 21. First interdigital transducer; 211. First bus bar; 22. Second interdigital transducer; 222. Second bus bar; 23. Reflection grating; 24. Common finger bar; A-A. Surface acoustic wave propagation direction; B-B. Extension direction of interdigital electrodes. Detailed implementation manners

[0028] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0029] In the present application, the accompanying drawings are not necessarily drawn to scale, and local features can be enlarged or reduced to more clearly show the details of local features.

[0030] Unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as commonly understood by those skilled in the technical field of the present application. The terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the scope of the present application. The term "and / or" used in the embodiments of the present application and the appended claims includes any and all combinations of one or more of the related listed items. The singular forms "a", "above-mentioned" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0031] In the description of the present application, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the embodiments of the present application, the meaning of "a plurality" is two or more, unless otherwise specifically defined.

[0032] In the description of the present application, the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "height", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of simplifying the description of the present application, rather than indicating that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, that is, it cannot be understood as a limitation to the present application.

[0033] In the description of the present application, unless otherwise clearly defined, terms such as "installation", "connection", "linkage", "fixation", "setting", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and can also be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0034] In the related art, in order to improve the linearity of a surface acoustic wave filter, methods such as increasing resonator segments and externally connecting capacitors are usually adopted. However, although this method can improve the linearity of the filter to a certain extent, since new components are added, the overall area of the surface acoustic wave filter will increase, which is not conducive to reducing the size and cost.

[0035] In addition, by increasing the proportion of Ti content in the interdigital electrodes of the surface acoustic wave filter or resonator and changing the finger width of the interdigital electrodes, the purpose of improving linearity can also be achieved, but it will affect other performances of the surface acoustic wave filter or resonator. For example, changing the finger width of the interdigital electrodes will cause changes in local capacitance and period, and may have an impact on various performances of the surface acoustic wave filter or resonator, such as impedance characteristics, bandwidth, insertion loss, frequency selectivity, etc., making it difficult to meet the requirements of the original performance indicators.

[0036] Therefore, how to improve the linearity of the surface acoustic wave filter without increasing additional area occupation and without affecting the main performance indicators is an urgent problem to be solved in the design and manufacturing processes of the surface acoustic wave filter and the surface acoustic wave resonator.

[0037] Please refer to Figure 1 and Figure 2 . Technicians found in experiments and research that an interdigital electrode end region 101 is formed between the interdigital electrodes and the bus bar of the SAW resonator (if true and false fingers are provided, the interdigital electrode end region 101 is formed between the true and false fingers). There is coupling between the electric field and the lateral scattered wave in this interdigital electrode end region 101. Under high-power working conditions, it is easy to excite non-linear second harmonics and non-linear third harmonics, resulting in the linearity of the SAW resonator being affected. Especially for the SAW resonator with a POI (piezoelectric-on-insulator) substrate as shown in Figure 1 , since the transverse wave mode in its interdigital electrode end region 101 is stronger, the non-linear effect is more obvious. From Figure 2It can be seen that for the SAW resonator on the POI substrate, when a high-power signal is input, due to the strong transverse wave mode in the end region 101 of the finger bars, the intensities of the non-linear second harmonic H2 and non-linear third harmonic H3 excited within the passband frequency band 102 are relatively large.

[0038] In the SAW on the POI substrate, the H2 / H3 excited by the IDT is related to the power borne by the IDT. To withstand high power, cascaded resonators generally adopt Figure 4 a connection method. However, through simulation analysis, the transverse mode has a mode propagation manner similar to the main mode, propagating simultaneously in the length direction of the interdigital electrodes and forming a standing wave. Multiple transverse modes are formed within the entire passband frequency band. The coupling between the electrostatic field of the electrode finger bars and the strain field of the transverse mode of the surface acoustic wave will affect the non-linearity of the resonator. The stronger the electrostatic field, the higher the coupling degree, and the stronger its non-linearity.

[0039] After research, technicians found that: the intensity of the end effect of the interdigital finger bars is proportional to the number of finger bars of the interdigital and inversely proportional to the aperture. Reducing the number of interdigital electrodes and increasing the aperture are beneficial for improving non-linearity.

[0040] Please refer to Figure 3 for details. An embodiment of the present application provides a method for fabricating a target cascaded resonator. The target cascaded resonator includes a plurality of sub-resonators, and each sub-resonator may include an interdigital transducer (IDT).

[0041] In this embodiment, the target cascaded resonator can be formed by cascading a plurality of interdigital transducers to withstand high power. Among them, the cascading method between the interdigital transducers in the target cascaded resonator is a longitudinal coupling method, that is, a plurality of interdigital transducers are cascaded along the surface acoustic wave propagation direction (such as Figure 5 the A-A direction shown in

[0042] to form the cascaded resonator.

[0043] Optionally, in the cascaded resonator, the number of interdigital transducers cascaded along the surface acoustic wave propagation direction is 2, that is, the cascaded resonator includes 2 sub-resonators.

[0043] In this embodiment, any one of the interdigital transducers is divided into a first bus bar, interdigital electrodes, and a second bus bar along a specified direction; the specified direction is parallel to the extension direction of the interdigital electrodes (such as Figure 5 the B-B direction shown in

[0044] In this embodiment, in the target cascaded resonator, each interdigital transducer may have two bus bars, and the interdigital electrodes are arranged between the two bus bars, and adjacent interdigital electrodes are respectively connected to different bus bars. Specifically, the two bus bars in the same interdigital transducer can be divided into a first bus bar and a second bus bar according to their positions along the extending direction of the interdigital electrodes.

[0045] In the target cascaded resonator, between two adjacent interdigital transducers, the first bus bar of one interdigital transducer can be electrically connected to the second bus bar of the other interdigital transducer to achieve the cascading of the interdigital transducers. Among them, the electrical connection method can be by setting a common finger bar connecting the first bus bar and the second bus bar, or the first bus bar and the second bus bar can also be connected by leads or wires. The present application does not limit the specific electrical connection method.

[0046] In this embodiment, the preparation method may include the following steps.

[0047] S110: Obtain the reference specification data of the reference cascaded resonator corresponding to the target cascaded resonator; wherein, the reference cascaded resonator includes a plurality of reference interdigital transducers, and the plurality of reference interdigital transducers are arranged along the extending direction of the reference interdigital electrodes in the reference interdigital transducers; the reference specification data includes first reference data representing the aperture size of the reference interdigital transducers and second reference data representing the number of reference interdigital electrodes in the reference interdigital transducers.

[0048] In this embodiment, the reference cascaded resonator is used as a reference benchmark in the process of designing and preparing the target cascaded resonator. The reference cascaded resonator can also be formed by cascading a plurality of reference interdigital transducers to withstand a large power. Among them, the cascading method between the reference interdigital transducers can be a lateral coupling method, that is, a cascaded resonator formed by arranging a plurality of reference interdigital transducers along the extending direction of the reference interdigital electrodes.

[0049] In some embodiments, the reference cascaded resonator can also be obtained by equivalently converting a single interdigital transducer into a form of cascading two or more reference interdigital transducers.

[0050] In this embodiment, the extending direction of the reference interdigital electrode can be the direction in which the reference interdigital electrode extends from one side bus bar connected thereto to the other side bus bar, or it can be understood as the length direction of the reference interdigital electrode.

[0051] Specifically, refer to Figure 4, the reference cascaded resonator 10 may include a first reference interdigital transducer 11, a second reference interdigital transducer 12, and a reference reflection grating 13. Among them, the first reference interdigital transducer 11 and the second reference interdigital transducer 12 are cascaded in a lateral coupling manner. Specifically, the first reference interdigital transducer 11 and the second reference interdigital transducer 12 are connected through a shared bus bar. Of course, in some embodiments, the reference cascaded resonator may also include multiple reference interdigital transducers cascaded in a lateral coupling manner with other quantities, such as 4, 5, etc.

[0052] In this embodiment, the reference specification data may reflect the size information and structural design information of the reference cascaded resonator. Specifically, the reference specification data may include a first reference data for representing the aperture size of the reference interdigital transducer, and a second reference data for representing the number of reference interdigital electrodes in the reference interdigital transducer. For example, continuing with Figure 4 as a reference, Figure 4 the first reference data of the first reference interdigital transducer 11 shown in is W1, and the second reference data is 12 (it is shown in the figure that there are a total of 12 interdigital electrodes).

[0053] In this embodiment, among the multiple reference interdigital transducers, the reference specification data of each reference interdigital transducer may be the same. As shown in Figure 4 , the first reference data of the second reference interdigital transducer 12 is also W1, and the second reference data is also 12.

[0054] In this embodiment, the multiple reference interdigital transducers may correspond one by one to the multiple interdigital transducers in the cascaded resonator to be fabricated.

[0055] In some embodiments, among the multiple reference interdigital transducers, the reference specification data of each reference interdigital transducer may also be different. For example, in some embodiments, Figure 4 the first reference data of the second reference interdigital transducer 12 may also be W2, and the second reference data may also be 10. The reference specification data of each reference interdigital transducer may be set separately according to actual requirements.

[0056] S120: Determine the specification data of the target cascaded resonator according to the first reference data and the second reference data; the specification data includes a first target data for representing the aperture size of the interdigital transducer in the target cascaded resonator, and a second target data for representing the number of interdigital electrodes in the interdigital transducer; the first target data is greater than the first reference data, and the second target data is less than the second reference data; wherein, the product of the first target data and the second target data is equal to the product of the first reference data and the second reference data.

[0057] In this embodiment, based on the acquired first reference data and second reference data, the first reference data can be increased and the second reference data can be decreased while keeping the product of the first reference data and the second reference data unchanged. In this way, when the impedance of the target cascaded resonator remains unchanged relative to the impedance of the reference surface acoustic wave, by increasing the aperture of the interdigital transducer, more acoustic wave energy can be concentrated in the central region between the bus bars. Furthermore, the acoustic wave energy propagating laterally will be relatively weakened at the ends of the fingers of the interdigital electrodes. At the same time, since the number of interdigital electrodes in the interdigital transducer is reduced, the source of the acoustic wave energy propagating laterally becomes less, and the excitation of the transverse wave mode at the ends of the fingers can also be weakened.

[0058] In this embodiment, specifically, for the multiple reference interdigital transducers in the reference cascaded resonator, based on the first reference data and the second reference data of each reference interdigital transducer, the first target data and the second target data of the corresponding interdigital transducers in the target cascaded resonator to be fabricated are determined respectively.

[0059] In some embodiments, the first target data is a specified integer multiple of the first reference data, and the second reference data is a specified integer multiple of the second target data.

[0060] Specifically, referring to Figure 4 and Figure 5 , Figure 5 the target cascaded resonator 20 shown in can include a first interdigital transducer 21, a second interdigital transducer 22, and a reflection grating 23. The first bus bar 211 in the first interdigital transducer 21 and the second bus bar 222 in the second interdigital transducer 22 are electrically connected to each other through a common finger 24.

[0061] Among them, the aperture of the first interdigital transducer 21 is 2*W1, which is 2 times that of the first reference interdigital transducer 11, and the aperture of the second interdigital transducer 22 is also 2*W1, which is 2 times that of the second reference interdigital transducer 12. At the same time, the number of interdigital electrodes in the first interdigital transducer 21 is 6, which is half of the number of reference interdigital electrodes in the first reference interdigital transducer 11, and the number of interdigital electrodes in the second interdigital transducer 22 is also 6, which is half of the number of reference interdigital electrodes in the second reference interdigital transducer 12. Therefore, in Figure 5 the target cascaded resonator 20 shown, relative to Figure 4 the reference cascaded resonator 10 shown, the first target data is 2 times the first reference data, and the second reference data is 2 times the second target data.

[0062] Of course, in some embodiments, a plurality of different reference interdigital transducers may be included in the reference cascaded resonator, and the first reference data and the second reference data corresponding to each reference interdigital transducer are different. Then, in the target cascaded resonator, for each reference interdigital transducer, the first target data and the second target data of the interdigital transducer can be determined respectively.

[0063] In some embodiments, the specified integer is greater than or equal to 2. For example, the specified integer can be 2, or other integers such as 3, 5, etc.

[0064] In some embodiments, when determining the second target data, the second reference data needs to be divided by the specified integer. If there is a situation where it cannot be divided evenly, the result of dividing the second reference data by the specified integer can be rounded to obtain the second target data. For example, if the second reference data is 7 and the specified integer is 3, then the second target data can be 2.

[0065] S130: Based on the specification data, a target cascaded resonator with the corresponding specification is prepared.

[0066] In this embodiment, except for the first target data and the second target data, other data in the specification data of the target cascaded resonator can be kept consistent with the reference specification data to ensure that the main performance of the cascaded resonator remains basically unchanged. For example, the pitch of the interdigital transducer can be kept consistent with the pitch of the reference interdigital transducer.

[0067] In this embodiment, a target cascaded resonator with acoustic cascading is formed by the longitudinal coupling method of multiple interdigital transducers. And compared with the reference cascaded resonator with transverse coupling, on the premise that the product of the aperture of the interdigital transducer and the number of interdigital electrodes remains unchanged, by setting a larger aperture of the interdigital transducer and a smaller number of interdigital electrodes, the transverse wave mode in the end region of the interdigital electrode is weakened, and the excitation of non-linear second harmonic and non-linear third harmonic is suppressed, so as to improve the linearity of the prepared target cascaded resonator to a certain extent while the occupied area and the main performance remain basically unchanged.

[0068] In this embodiment, since the aperture of the interdigital transducer is increased and the number of interdigital electrodes is reduced compared with the reference cascaded resonator, the aperture and the number of interdigital electrodes of the prepared target cascaded resonator are different from those of the cascaded resonator in the conventional cascading method along the surface acoustic wave direction. Optionally, in the prepared cascaded resonator, the length value range of the aperture of the interdigital transducer in the extending direction of the interdigital electrode is 20um - 150um, and the value range of the number of interdigital electrodes in the interdigital transducer is 100 - 600.

[0069] The target cascaded resonator prepared according to the above specifications and dimensions can suppress the excitation of non-linear second harmonics and non-linear third harmonics, and improve the linearity of the cascaded resonator.

[0070] In some embodiments, among the plurality of interdigital transducers, two adjacent interdigital transducers are connected by a common finger bar; wherein, the bus bar connecting the common finger bar is used to access the intermediate potential point between the signal bus bar and the ground bus bar of the target cascaded resonator.

[0071] Specifically, as Figure 5 shown, there is a common finger bar 24 between the adjacent first interdigital transducer 21 and the second interdigital transducer 22, and both ends of the common finger bar 24 are respectively connected to the bus bars of the first interdigital transducer and the second interdigital transducer. Among them, the two bus bars connecting the common finger bar are in different positions in the extending direction of the interdigital electrode. The bus bars of the first interdigital transducer and the second interdigital transducer that are not connected to the common finger bar can be used as the signal bus bar and the ground bus bar respectively.

[0072] In some embodiments, by connecting the bus bar connecting the common finger bar to the intermediate potential point, the voltage stress on a single interdigital transducer can be reduced. Under high-power working conditions, it helps to reduce the non-linear distortion of the target cascaded resonator and improve the reliability of the target cascaded resonator.

[0073] Optionally, as Figure 6 shown, the number of the common finger bars 24 can be multiple to form a reflection grating between two adjacent interdigital transducers.

[0074] In some embodiments, among the plurality of interdigital transducers, at least two interdigital transducers have different finger pitches and duty cycles. The finger pitch and duty cycle of each interdigital transducer in the target cascaded resonator can be set separately, so as to improve the flexibility of the design and preparation of the cascaded resonator.

[0075] In some embodiments, among the plurality of interdigital transducers, the connection manner of the plurality of interdigital transducers can be: the first bus bar and the second bus bar in adjacent interdigital transducers are electrically connected to each other through a common finger bar.

[0076] Another embodiment of the present application provides a coupled resonator, and the cascaded resonator can be the target cascaded resonator described in the foregoing embodiments. The cascaded resonator can be prepared according to the preparation method in the foregoing embodiments.

[0077] The cascaded resonator includes a plurality of interdigital transducers arranged along the surface acoustic wave propagation direction; wherein, the aperture length of the interdigital transducer in the extending direction of the interdigital electrode ranges from 20 um to 150 um, and the number of interdigital electrodes in the interdigital transducer ranges from 100 to 600.

[0078] In some embodiments, the cascaded resonator corresponds to a reference cascaded resonator; the reference cascaded resonator includes a plurality of reference interdigital transducers, and the plurality of reference interdigital transducers are arranged along the extending direction of the reference interdigital electrode in the reference interdigital transducer; wherein, the aperture of the interdigital transducer in the cascaded resonator is larger than the aperture of the reference interdigital transducer in the reference cascaded resonator; the number of interdigital electrodes in the interdigital transducer is greater than the number of reference interdigital electrodes in the reference interdigital transducer; the product of the aperture value of the interdigital transducer and the number value of the interdigital electrode is equal to the product of the aperture value of the reference interdigital transducer and the number value of the reference interdigital electrode.

[0079] In some embodiments, the interdigital transducer and the reference interdigital transducer have the same impedance.

[0080] In some embodiments, the aperture of the interdigital transducer is a specified integer multiple of the aperture of the reference interdigital transducer; and, the number of interdigital electrodes is a specified integer multiple of the number of reference interdigital electrodes; wherein, the specified integer is greater than or equal to 2.

[0081] In some embodiments, among the plurality of interdigital transducers, two adjacent interdigital transducers are connected by a common finger bar; wherein, the bus bar connecting the common finger bar is used to access the intermediate potential point between the signal bus bar and the ground bus bar of the cascaded resonator.

[0082] In some embodiments, the number of the common finger bars is multiple to form a reflection grating between two adjacent interdigital transducers.

[0083] In some embodiments, among the plurality of interdigital transducers, at least two interdigital transducers have different finger spacings and duty cycles.

[0084] Regarding the specific functions and effects of the cascaded resonator and its structure, reference can be made to other embodiments of this application for explanation, which will not be elaborated here.

[0085] Please refer to Figure 7 Another embodiment of this application provides a filter, and the filter includes the target cascaded resonator as described in the foregoing embodiments.

[0086] In this embodiment, the filter may be composed of the target cascaded resonator described in the foregoing embodiment, or may be designed by combining the target cascaded resonator described in the foregoing embodiment with other resonators. In some embodiments, the target cascaded resonator may also be connected in series and / or in parallel with other resonators.

[0087] Regarding the specific functions and effects of the target cascaded resonator in the filter, reference may be made to other embodiments of the present application for explanation, which will not be elaborated here.

[0088] Specifically, taking Figure 7 the filter topology shown in Figure 7 as an example, ANT in Figure 7 represents the antenna input end, B1TX and B3TX respectively represent signal paths of different frequency bands, and load represents the absorption load path. When two signals with frequencies F1 and F2 and a power of 14 dbm are input at the ANT end, the non-linear second harmonic signal with a frequency of 2*F1 generated in the absorption load path can be non-linearly intermodulated with the signal with a frequency of F2 again to generate an intermodulation product signal with a frequency of 2*F1 - F2. This signal will be reflected back to the B3TX path, interfering with the filter signal and affecting the performance of the filter. By using the target cascaded resonator provided in the present application in the filter topology shown in

[0089] Figure 7 Figure 7 In some embodiments, the filter includes multiple paths connected in parallel to the antenna end. Specifically, as shown in Figure 7 Figure 7 Figure 7 Figure 7

[0090] In this embodiment, in at least one path, the cascaded resonator with one end connected to the antenna end is provided. Specifically, as shown in Figure 7 Figure 7

[0091] Of course, in some embodiments, the target cascaded resonator may also include all the interdigital transducers in any one path of the filter, and can be specifically designed flexibly according to needs.

[0092] In some embodiments, the filter is composed of paths of different frequency bands and an absorption load path; the target cascaded resonator is disposed in the absorption load path.

[0093] To illustrate the above effects, the technician conducted tests on the filter topology shown in Figure 7 , and the results of the measured intermodulation product signals are shown in Table 1, Table 2 and Figure 8 . Among them, Table 1 is a comparative example, and Table 2 is an embodiment. In the comparative example, the target cascaded resonator provided in the present application is not adopted in the filter topology, and the comparative example adopts the Figure 4 structure. In the embodiment, the target cascaded resonator provided in the present application is used in each path. Figure 8 is the data comparison curve between Table 1 and Table 2. In Table 1, Table 2 and Figure 8 , PIM represents the intermodulation product signal. It can be seen from the test results that the use of the target cascaded resonator provided in the present application weakens the intermodulation product signal in the filter.

[0094]

[0095] Table 1

[0096]

[0097] Table 2

[0098] In some embodiments, the filter may further include a reference cascaded resonator corresponding to the target cascaded resonator as described in the foregoing embodiments. Among them, the product of the aperture value of the interdigital transducer and the number value of the interdigital electrodes in the target cascaded resonator is equal to the product of the aperture value of the reference interdigital transducer and the number value of the reference interdigital electrodes in the reference cascaded resonator. And, the aperture of the interdigital transducer in the target cascaded resonator is greater than the aperture of the reference interdigital transducer in the reference cascaded resonator; the number of interdigital electrodes of the interdigital transducer in the target cascaded resonator is less than the number of reference interdigital electrodes of the reference interdigital transducer.

[0099] Specifically, the target cascaded resonator and the reference cascaded resonator can be respectively disposed in different paths, or in different positions in the same path. For example, as Figure 7As shown, the target cascaded resonator and the reference cascaded resonator can both be arranged in the B3TX path, and can be cascaded with each other or cascaded through other interdigital transducers. Of course, the target cascaded resonator and the reference cascaded resonator can also be arranged in the B1TX and load paths respectively.

[0100] It can be understood that the specific examples in this article are only for helping those skilled in the art to better understand the embodiments of the present application, rather than limiting the scope of the present invention.

[0101] It can be understood that in various embodiments of the present application, the magnitudes of the serial numbers of the various processes do not mean the order of execution. The order of execution of the various processes should be determined according to their functions and internal logics, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0102] It can be understood that the various embodiments described in the present application can be implemented separately or in combination, and the embodiments of the present application do not limit this.

[0103] Unless otherwise specified, all technical and scientific terms used in the embodiments of the present application have the same meaning as commonly understood by those skilled in the technical field of the present application. The terms used in the present application are only for the purpose of describing specific embodiments, and are not intended to limit the scope of the present application. The term "and / or" used in the embodiments of the present application and the appended claims includes any and all combinations of one or more of the related listed items. The singular forms "a", "above-mentioned" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0104] As described above, the above are only specific embodiments of the present application, but the protection scope of the present invention is not limited thereto. Any person skilled in the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, and all of them should be covered by the protection scope of the present application. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A cascade resonator, characterized in that: The cascade resonator includes a plurality of interdigital transducers arranged along the propagation direction of surface acoustic waves; wherein any of the interdigital transducers is divided into a first bus bar, an interdigital electrode and a second bus bar along a specified direction; the specified direction is parallel to the extension direction of the interdigital electrodes; among the plurality of interdigital transducers, the first bus bar and the second bus bar of any two adjacent interdigital transducers are electrically connected to each other.

2. The cascade resonator according to claim 1, characterized in that Among the multiple IDTs, the first bus bar and the second bus bar of any two adjacent IDTs are electrically connected to each other through one or more common fingers; when the mutual connection is achieved through multiple common fingers, the multiple common fingers form a reflection grating located between the two adjacent IDTs.

3. The cascade resonator according to claim 2, characterized in that: The bus bar connecting the common fingers is used to access the middle potential point between the signal bus bar and the ground bus bar of the cascade resonator.

4. The cascade resonator according to claim 1, characterized in that: In any of the IDTs, the length of the aperture in the extension direction of the interdigital electrodes ranges from 20 um to 150 um, and the number of the interdigital electrodes in the IDT ranges from 100 to 600.

5. The cascade resonator according to claim 1, characterized in that: Among the multiple IDTs of the cascade resonator, there are at least two IDTs with different finger spacings and duty cycles.

6. A method for preparing a target cascade resonator, wherein the target cascade resonator is: the cascade resonator according to any one of claims 1 to 5; characterized in that: The preparation method comprises: Acquire reference specification data of a reference cascade resonator corresponding to the target cascade resonator; wherein the reference cascade resonator comprises a plurality of reference interdigital transducers, and the plurality of reference interdigital transducers are arranged along an extension direction of reference interdigital electrodes in the reference interdigital transducer; the reference specification data comprises first reference data indicating an aperture size of the reference interdigital transducer, and second reference data indicating the number of reference interdigital electrodes in the reference interdigital transducer; Determine specification data of the target cascade resonator according to the first reference data and the second reference data; the specification data includes: first target data indicating the aperture size of the IDT in the target cascade resonator, and second target data indicating the number of IDT electrodes in the IDT; the first target data is greater than the first reference data, and the second target data is less than the second reference data; wherein the product of the first target data and the second target data is equal to the product of the first reference data and the second reference data; Based on the specification data, a target cascade resonator with corresponding specifications is prepared.

7. The preparation method according to claim 6, characterized in that: The first target data is a specified integer multiple of the first reference data; and the second reference data is a specified integer multiple of the second target data; wherein the specified integer is greater than or equal to 2.

8. The preparation method according to claim 6, characterized in that: The IDT in the target cascade resonator and the reference IDT have the same impedance.

9. A filter, characterized in that: The filter comprises the cascade resonator according to any one of claims 1 to 5.

10. The filter according to claim 9, characterized in that The filter comprises a plurality of paths connected in parallel at the antenna end; wherein, at least one of the paths is provided with the cascade resonator having one end connected to the antenna end.

11. The filter according to claim 10, characterized in that The multiple paths include paths of different frequency bands and an absorption load path; the cascade resonator is arranged in the absorption load path.

12. An electronic device, characterized in that: It comprises the cascade resonator as claimed in any one of claims 1 to 5, or the filter as claimed in any one of claims 9 to 11.

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