An acoustic wave filter, multiplexer, communication device

Abstract

The embodiment of the present application discloses a kind of acoustic wave filters, at least one series resonator is equipped on the series branch between the input end and the output end of the filter, at least one end in the at least one series resonator is connected with shunt branch, the shunt branch includes at least one parallel resonator and at least one ground inductance, the filter further includes: cross resonator, one end of the cross resonator is connected to the connecting node between the parallel resonator and the ground inductance of one of shunt branch, the other end of the cross resonator is connected to the connecting node of the series branch or the connecting node of other shunt branch;Wherein, the area Ares1 of the cross resonator is less than or equal to 40% of the average equivalent area Aave of the filter.The filter of the present application can improve the out-of-band rejection index at the target frequency without sacrificing insertion loss.

Description

Technical Field

[0001] This invention relates to the field of filter technology, and more specifically, to an acoustic filter, a multiplexer, and a communication device. Background Technology

[0002] A filter is a device used to allow a target frequency signal to pass through while suppressing other frequency signals to a certain extent. Two important performance indicators for filters are in-band insertion loss and out-of-band rejection. In-band insertion loss measures the energy loss of the target frequency signal as it passes through the filter; lower loss is better. Out-of-band rejection measures the suppression performance of the target frequency; higher rejection is better. Generally, insertion loss and rejection are trade-offs for each other in a filter; that is, under the same topology, better insertion loss usually results in worse rejection, and vice versa.

[0003] A typical acoustic filter in the prior art, such as Figure 1 As shown, a series resonator is installed on the series branch between the input and output terminals, and a parallel resonator and a ground inductor are respectively installed on the parallel branch between the connection node of each series resonator and the ground terminal. By adding a mass load layer to each parallel resonator, a frequency difference is created between the parallel and series resonators, thus forming the passband of the filter. However, there is a certain mutual inductive coupling between the ground inductors of this filter, which leads to poor out-of-band rejection. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide an acoustic filter, multiplexer, and communication device that can improve out-of-band rejection performance at a target frequency without sacrificing insertion loss.

[0005] This invention provides an acoustic wave filter, characterized in that at least one series resonator is provided in the series branch between the input and output terminals of the filter, and at least one of the two ends of the at least one series resonator is connected to a parallel branch, the parallel branch including at least one parallel resonator and at least one inductor to ground, and the filter further includes:

[0006] A bridging resonator, one end of which is connected to the connection node between the parallel resonator and the ground inductor in one of the parallel branches, and the other end of which is connected to any connection node of the series branch or the connection node of another parallel branch.

[0007] Wherein, the area Ares1 of the bridging resonator is less than or equal to 40% of the average equivalent area Aave of the filter. The average equivalent area Aave of the filter is the sum of the equivalent areas Aequi of each stage of the filter and divided by the number of resonator stages m of the filter. Aave = (Aequ1 + ... + Aequi + ... + Aequm) / m, i = 1, 2, ..., m, m is greater than or equal to 3.

[0008] As a further improvement of the present invention, for each resonator in the filter,

[0009] When this stage of resonator is constructed using multiple sub-resonators connected in series, the equivalent area Aequ of this stage of resonator is... i Satisfy: 1 / Aequ i = 1 / A1_se + 1 / A2_se + ... + 1 / An / _se, where the areas of the multiple sub-resonators are A1_se, A2_se, ..., An, respectively. / _se,n / n represents the number of sub-resonators connected in series with this stage of resonator. / Greater than or equal to 1;

[0010] When this stage of resonator is constructed using multiple sub-resonators connected in parallel, the equivalent area Aequ of this stage of resonator is... i Satisfy: Aequ i =A1_sh + A2_sh + ... + An / / _sh, where the areas of the multiple sub-resonators are A1_sh, A2_sh, ..., An, respectively. / / _sh, n / / n represents the number of sub-resonators connected in parallel to this stage of the resonator. / / Greater than or equal to 1;

[0011] When this stage of resonator is constructed using multiple sub-resonators connected in series and parallel, the equivalent area Aequ of this stage of resonator is... i It is calculated step by step based on the series and parallel structure of multiple sub-resonators in this stage of the resonator.

[0012] As a further improvement of the present invention, for each stage resonator in the filter, the stage resonator is composed of multiple sub-resonators connected in series and / or in parallel.

[0013] When the structural parameters of each sub-resonator are different, the area of ​​each sub-resonator is normalized to obtain the normalized area of ​​each sub-resonator. Based on the normalized area of ​​each resonator, the equivalent area of ​​the resonator stage is calculated.

[0014] The structural parameters include one or more of the following: layered structure, material, resonant frequency, area, and electromechanical coupling coefficient.

[0015] The normalization process for the area of ​​each sub-resonator, resulting in the normalized area of ​​each sub-resonator, includes:

[0016] The area corresponding to a bridging resonator impedance of 50 ohms is used as the reference area.

[0017] Divide the area of ​​each sub-resonator by the area corresponding to its own impedance of 50 ohms to obtain the processed area of ​​each sub-resonator.

[0018] Multiply the processed area of ​​each sub-resonator by the reference area to obtain the normalized area of ​​each sub-resonator.

[0019] As a further improvement of the present invention, an inductor to ground is provided on another parallel branch, and the other end of the bridging resonator is connected to the connection node between the parallel resonator and the inductor to ground in the other parallel branch.

[0020] As a further improvement of the present invention, two ground inductors are provided on another parallel branch, and the other end of the bridging resonator is connected to the connection node between the two ground inductors of the other parallel branch.

[0021] As a further improvement of the present invention, the one parallel branch and the other parallel branch are two adjacent parallel branches or two non-adjacent parallel branches.

[0022] As a further improvement of the present invention, the bridging resonator is composed of one or more sub-resonators.

[0023] As a further improvement of the present invention, the bridging resonator is composed of multiple sub-resonators, and the structural parameters of each sub-resonator are the same or different. The structural parameters include one or more of the following: stacked structure, material, resonant frequency, area, and electromechanical coupling coefficient.

[0024] As a further improvement of the present invention, when the bridging resonator is composed of multiple series-connected sub-resonators, the area Ares1 of the bridging resonator is equal to the equivalent area Aequ_se of the multiple series-connected sub-resonators, 1 / Aequ_se=1 / A1_se+…+1 / Aj_se+…+1 / An_se, where Aj_se represents the area of ​​each series-connected sub-resonator, j=1,2,…,n, n represents the number of series-connected sub-resonators, n is greater than or equal to 1; or,

[0025] When the bridging resonator is composed of multiple parallel sub-resonators, the area Ares1 of the bridging resonator is equal to the equivalent area Aequ_sh of the multiple parallel sub-resonators, Aequ_sh = A1_sh + ... + Ak_sh + ... + Ap_sh, where Ak_sh represents the area of ​​each parallel sub-resonator, k = 1, 2, ..., p, p represents the number of parallel sub-resonators, and p is greater than or equal to 1; or,

[0026] When the bridging resonator is composed of multiple sub-resonators connected in series and multiple sub-resonators connected in parallel, the area Ares1 of the bridging resonator is calculated step by step according to the series and parallel structure of the multiple sub-resonators in the bridging resonator.

[0027] As a further improvement of the present invention, the area Ares1 of the bridging resonator is less than or equal to 20% of the average equivalent area Aave of the filter.

[0028] This invention also provides a multiplexer, which includes the aforementioned filter.

[0029] This invention also provides a communication device, which includes the aforementioned filter.

[0030] The beneficial effects of this invention are as follows: by adding a bridging resonator and limiting the area of ​​the bridging resonator, the out-of-band rejection index at the target frequency can be improved without sacrificing insertion loss, thereby improving the performance of the acoustic filter. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a typical acoustic filter in the existing technology;

[0033] Figure 2 The topology diagram of an acoustic filter according to a first exemplary embodiment of the present invention is shown below;

[0034] Figure 3 A topology diagram of an acoustic filter according to a second exemplary embodiment of the present invention;

[0035] Figure 4 This is a topology diagram of an acoustic filter according to a third exemplary embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram illustrating a bridging resonator composed of multiple sub-resonators connected in series, as described in an exemplary embodiment of the present invention.

[0037] Figure 6 This is a schematic diagram illustrating that the bridging resonator described in an exemplary embodiment of the present invention is composed of multiple sub-resonators connected in parallel.

[0038] Figure 7 A comparison curve of improved out-of-band suppression of an acoustic filter as described in an exemplary embodiment of the present invention;

[0039] Figure 8 for Figure 7 Enlarged schematic diagram of the 5.0G-5.5G region;

[0040] Figure 9 A comparison curve of insertion loss for an acoustic filter as described in an exemplary embodiment of the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0043] Furthermore, the terminology used in the description of this invention is for illustrative purposes only and is not intended to limit the scope of the invention. The terms "comprising" and / or "including" are used to specify the presence of said elements, steps, operations, and / or components, but do not exclude the presence or addition of one or more other elements, steps, operations, and / or components. The terms "first," "second," etc., may be used to describe various elements, do not represent an order, and do not limit these elements. Moreover, in the description of this invention, unless otherwise stated, "a plurality of" means two or more. These terms are used only to distinguish one element from another. These and / or other aspects become apparent in conjunction with the following drawings, and those skilled in the art will more readily understand the description of the embodiments of the invention. The drawings are used for illustrative purposes only to depict the embodiments of the invention. Those skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods shown in the invention can be employed without departing from the principles of the invention.

[0044] An acoustic wave filter according to an embodiment of the present invention includes at least one series resonator in the series branch between the input and output terminals of the filter. At least one end of the at least one series resonator is connected to a parallel branch, which includes at least one parallel resonator and at least one inductor to ground. The filter further includes:

[0045] A bridging resonator, one end of which is connected to the connection node between the parallel resonator and the ground inductor in one of the parallel branches, and the other end of which is connected to any connection node of the series branch or the connection node of another parallel branch.

[0046] Wherein, the area Ares1 of the bridging resonator is less than or equal to 40% of the average equivalent area Aave of the filter, and the average equivalent area Aave of the filter is the equivalent area Aequ of each stage resonator in the filter. i Add and divide by the number of resonator stages m of the filter, Aave = (Aequ1 + ... + Aequ) i +…+Aequ m ) / m, i = 1, 2, ..., m, m is greater than or equal to 3.

[0047] It is understood that the filter of the present invention includes at least one series resonator and at least two parallel resonators. Each series resonator has a connection node at both ends, and two adjacent series resonators share a connection node. Each parallel resonator is connected to an inductor to ground, and there is a connection node between each parallel resonator and the inductor to ground. The at least two parallel resonators in the filter can be located on the parallel branches connected to the two ends of a series resonator; or they can be located on the parallel branches connected to one end of two series resonators. These two series resonators can be adjacent or non-adjacent. At least one end of the bridging resonator is connected to the connection node between the parallel resonator and the inductor to ground. The other end of the bridging resonator can be at any connection node on the series branch or at a connection node on other parallel branches. Through the above topology, the filter of the present invention simultaneously limits the area of ​​the bridging resonator, ensuring that its area meets certain conditions. Under these conditions, the filter can significantly improve out-of-band rejection at the frequency of interest without sacrificing insertion loss, thereby improving the filter's performance.

[0048] The present invention specifies that the area Ares1 of the bridging resonator satisfies: Ares1 <= 40% * Aave. More preferably, the area Ares1 of the bridging resonator is less than 20% of the average equivalent area of ​​the filter, i.e., Ares1 <= 20% * Aave.

[0049] It should be noted that "each resonator stage" here refers to either each series resonator or each parallel resonator, and the number of resonator stages refers to the number of series and parallel resonators in the filter. It can be understood that regardless of the number of sub-resonators a series resonator is composed of, it is considered to be at stage 1. Similarly, regardless of the number of sub-resonators a parallel resonator is composed of, it is considered to be at stage 1. The filter of this invention includes at least one series resonator and at least two parallel resonators. One series resonator is considered to be at stage 1, and one parallel resonator is considered to be at stage 1. Therefore, the number of resonator stages m of the filter is at least 3, that is, m is greater than or equal to 3.

[0050] Among them, the equivalent area Aequ of each stage resonator i The specific structure of the series / parallel resonator is determined by the number of sub-resonators used and their series or parallel configuration. Here, all sub-resonators are bulk acoustic wave resonators. This invention does not impose specific limitations on the stacked structure used for the series / parallel resonators.

[0051] In one optional implementation, for each stage of the resonator, when the stage (series resonator / parallel resonator) is constructed by connecting multiple sub-resonators in series, the areas of the multiple sub-resonators are A1_se, A2_se, ..., An, respectively. / _se,n / n represents the number of sub-resonators connected in series. / The equivalent area Aequ of this stage of resonator is greater than or equal to 1. i Satisfies the following formula: 1 / Aequ i = 1 / A1_se + 1 / A2_se + ... + 1 / An / _se.

[0052] For each stage of the resonator, when the resonator (series resonator / parallel resonator) is constructed using multiple sub-resonators connected in parallel, the areas of the multiple sub-resonators are A1_sh, A2_sh, ..., An, respectively. / / _sh, n / / n represents the number of sub-resonators connected in parallel. / / The equivalent area Aequ of this stage of resonator is greater than or equal to 1. i Satisfying the following formula: Aequ i =A1_sh + A2_sh + ... + An / / _sh.

[0053] For each stage of the resonator, when the stage (series resonator / parallel resonator) is constructed using multiple sub-resonators connected in series and parallel, the equivalent area Aequ of the stage of the resonator is... i It is calculated step by step based on the series and parallel structure of multiple sub-resonators in this stage of the resonator.

[0054] Understandably, when this stage of resonator is constructed using multiple sub-resonators connected in series and parallel, the final equivalent area, i.e., the equivalent area Aequ of this stage of resonator, needs to be calculated stage by stage based on the specific series and parallel structures. i The step-by-step calculation here refers to calculating the equivalent area based on the series or parallel configuration of the multiple sub-resonators. For example, the equivalent area of ​​the series configuration is calculated first, followed by the equivalent area of ​​the parallel configuration, or vice versa.

[0055] For example, when multiple sub-resonators are connected in series and then in parallel, the first equivalent area of ​​the series connection is obtained first, based on the calculation method for multiple sub-resonators connected in series. Then, based on the first equivalent area, the second equivalent area of ​​the parallel connection is obtained according to the calculation method for multiple sub-resonators connected in parallel. This second equivalent area is used as the equivalent area Aequ of the resonator at this stage. i Correspondingly, when multiple sub-resonators are arranged in parallel and then series, the first equivalent area of ​​the parallel arrangement is obtained first based on the calculation method for the parallel arrangement of multiple sub-resonators. Then, based on the third equivalent area, the fourth equivalent area of ​​the series arrangement is obtained according to the calculation method for the series arrangement of multiple sub-resonators. This fourth equivalent area is taken as the equivalent area Aequ of the resonator at this stage.i .

[0056] In one optional implementation, for each stage resonator in the filter, the stage resonator is composed of multiple sub-resonators connected in series and / or in parallel.

[0057] When the structural parameters of each sub-resonator are different, the area of ​​each sub-resonator is normalized to obtain the normalized area of ​​each sub-resonator. Based on the normalized area of ​​each resonator, the equivalent area of ​​the resonator stage is calculated.

[0058] The structural parameters include one or more of the following: layered structure, material, resonant frequency, area, and electromechanical coupling coefficient.

[0059] The normalization process for the area of ​​each sub-resonator, resulting in the normalized area of ​​each sub-resonator, includes:

[0060] The area corresponding to a bridging resonator impedance of 50 ohms is used as the reference area.

[0061] Divide the area of ​​each sub-resonator by the area corresponding to its own impedance of 50 ohms to obtain the processed area of ​​each sub-resonator.

[0062] Multiply the processed area of ​​each sub-resonator by the reference area to obtain the normalized area of ​​each sub-resonator.

[0063] It should be noted that when calculating the equivalent area of ​​this stage of resonator, if the area corresponding to the impedance value of each sub-resonator is different due to different layer structures, different doping conditions or other methods, it is necessary to normalize the area of ​​each sub-resonator, and then calculate the equivalent area of ​​this stage of resonator based on the normalized area using the above methods (series, parallel, series and parallel methods).

[0064] In one alternative implementation, a ground inductor is provided on another parallel branch, and the other end of the bridging resonator is connected to the connection node between the parallel resonator and the ground inductor of the other parallel branch.

[0065] In one alternative implementation, two ground inductors are provided on another parallel branch, and the other end of the bridging resonator is connected to the connection node between the two ground inductors of the other parallel branch.

[0066] As mentioned above, one end of the bridging resonator is limited to the connection node between the parallel resonator and the ground inductor in one of the parallel branches. The other end of the bridging resonator can be connected to any connection node of the series branch, or to the connection node of other parallel branches other than the parallel branch where one end of the bridging resonator is located.

[0067] Since the filter of this invention includes at least two parallel branches, when it includes two parallel branches (e.g., a first parallel branch and a second parallel branch), one end of the bridging resonator is connected to the connection node between the parallel resonator of one of the parallel branches (e.g., the first parallel branch) and the inductor to ground, and the other end of the bridging resonator is connected to the connection node of the other parallel branch (e.g., the second parallel branch). When it includes three or more parallel branches (e.g., a first parallel branch, a second parallel branch, and a third parallel branch), one end of the bridging resonator is connected to the connection node between the parallel resonator of one of the parallel branches (e.g., the first parallel branch) and the inductor to ground, and the other end of the bridging resonator is connected to the connection node of the other parallel branches (e.g., the second parallel branch or the third parallel branch). The above are illustrative examples of parallel branches, and this invention does not specifically limit the number of parallel branches included in the filter.

[0068] Since each parallel branch is equipped with at least one parallel resonator and at least one ground inductor, when the number of ground inductors is set differently, the other end of the bridging resonator can be connected at the connection node between the parallel resonator and the ground inductor, or it can be connected at the connection node between the ground inductors.

[0069] In one optional implementation, the one parallel branch and the other parallel branch are either two adjacent parallel branches or two non-adjacent parallel branches.

[0070] As mentioned above, the filter includes at least two parallel branches. When there are only two parallel branches (e.g., the first and second parallel branches described above), the two parallel branches (the first and second parallel branches) where the two ends of the bridging resonator are located are adjacent parallel branches. When there are three or more parallel branches (e.g., the first, second, and third parallel branches described above), one end of the bridging resonator is located in one parallel branch (e.g., the first parallel branch), and when the other end of the bridging resonator is located in another parallel branch (e.g., the second parallel branch), the two parallel branches (the first and second parallel branches) where the two ends of the bridging resonator are located are adjacent parallel branches; when the other end of the bridging resonator is located in another parallel branch (e.g., the third parallel branch), the two parallel branches (the first and third parallel branches) where the two ends of the bridging resonator are located are non-adjacent parallel branches.

[0071] It is understood that, in the two parallel branches mentioned above, when the second parallel branch includes at least one parallel resonator and one inductor to ground, the other end of the bridging resonator can be connected to the connection node between the parallel resonator and the inductor to ground in the second parallel branch. When the second parallel branch includes at least one parallel resonator and two inductors to ground, the other end of the bridging resonator can be connected to the connection node between the two inductors to ground in the second parallel branch.

[0072] It is also understood that, in the above three or more parallel branches, when the second or third parallel branch includes at least one parallel resonator and one ground inductor, the other end of the bridging resonator can be connected to the connection node between the parallel resonator and the ground inductor in the second or third parallel branch. When the second or third parallel branch includes at least one parallel resonator and two ground inductors, the other end of the bridging resonator can be connected to the connection node between the two ground inductors in the second or third parallel branch.

[0073] The topology of filters in the prior art is as follows: Figure 1 As shown, the filter comprises multiple series resonators (Se1, Se2, Se3, Se4) and multiple parallel resonators (Sh1, Sh2, Sh3), each parallel resonator being connected to an inductor to ground. The acoustic filter proposed in this invention will be illustrated below with an example.

[0074] For example, such as Figure 2The diagram shows the topology of the acoustic filter according to the first exemplary embodiment of the present invention. Four series resonators Se1, Se2, Se3, and Se4 are connected in series on the series branch between the filter input terminal IN and the output terminal OUT. Each series resonator has a connection node at both ends. The second end of series resonator Se1 and the first end of series resonator Se2 share a connection node. The second end of series resonator Se2 and the first end of series resonator Se3 share a connection node. The second end of series resonator Se3 and the first end of series resonator Se4 share a connection node.

[0075] A first parallel branch is provided between the connection node of the second end of the series resonator Se1 and the grounding terminal G1. The first parallel branch is provided with a parallel resonator Sh1 and a ground inductance L1. A second parallel branch is provided between the connection node of the second end of the series resonator Se2 and the grounding terminal G2. The second parallel branch is provided with a parallel resonator Sh2 and a ground inductance L2. A third parallel branch is provided between the connection node of the second end of the series resonator Se3 and the grounding terminal G3. The third parallel branch is provided with a parallel resonator Sh3 and a ground inductance L3.

[0076] One end of the bridging resonator Res1 is connected to the connection node between the parallel resonator Sh3 and the ground inductor L3 in the third parallel branch, and the other end of the bridging resonator Res1 is connected to the connection node of the first end of the series resonator Se1.

[0077] The filter contains four series resonators and three parallel resonators, i.e., 4 stages in series and 3 stages in parallel, for a total of 7 resonator stages. In this case, the area Ares1 of the bridging resonator is less than or equal to 40% of the filter's average equivalent area Aave. The filter's average equivalent area Aave = (Aequ1 + Aequ2 + ... + Aequ7) / 7, where Aequ1, Aequ2, Aequ3, and Aequ4 are the equivalent areas of the series resonators Se1, Se2, Se3, and Se4, respectively, and Aequ5, Aequ6, and Aequ7 are the equivalent areas of the parallel resonators Sh1, Sh2, and Sh3, respectively.

[0078] For example, such as Figure 3 The diagram shows the topology of the acoustic filter according to the second exemplary embodiment of the present invention. Four series resonators Se1, Se2, Se3, and Se4 are connected in series on the series branch between the filter input terminal IN and the output terminal OUT. Each series resonator has a connection node at both ends. The second end of series resonator Se1 and the first end of series resonator Se2 share a connection node. The second end of series resonator Se2 and the first end of series resonator Se3 share a connection node. The second end of series resonator Se3 and the first end of series resonator Se4 share a connection node.

[0079] A first parallel branch is provided between the connection node of the second end of the series resonator Se1 and the grounding terminal G1. The first parallel branch is provided with a parallel resonator Sh1 and a ground inductance L1. A second parallel branch is provided between the connection node of the second end of the series resonator Se2 and the grounding terminal G2. The second parallel branch is provided with a parallel resonator Sh2 and a ground inductance L2. A third parallel branch is provided between the connection node of the second end of the series resonator Se3 and the grounding terminal G3. The third parallel branch is provided with a parallel resonator Sh3 and a ground inductance L3.

[0080] One end of the bridging resonator Res1 is connected to the connection node between the parallel resonator Sh3 and the ground inductor L3 in the third parallel branch, and the other end of the bridging resonator Res1 is connected to the connection node between the parallel resonator Sh1 and the ground inductor L1 in the first parallel branch.

[0081] The filter contains four series resonators and three parallel resonators, i.e., 4 stages in series and 3 stages in parallel, for a total of 7 resonator stages. In this case, the area Ares1 of the bridging resonator is less than or equal to 40% of the filter's average equivalent area Aave. The filter's average equivalent area Aave = (Aequ1 + Aequ2 + ... + Aequ7) / 7, where Aequ1, Aequ2, Aequ3, and Aequ4 are the equivalent areas of the series resonators Se1, Se2, Se3, and Se4, respectively, and Aequ5, Aequ6, and Aequ7 are the equivalent areas of the parallel resonators Sh1, Sh2, and Sh3, respectively.

[0082] For example, such as Figure 4 The diagram shows the topology of the acoustic filter according to the third exemplary embodiment of the present invention. Four series resonators Se1, Se2, Se3, and Se4 are connected in series on the series branch between the filter input terminal IN and the output terminal OUT. Each series resonator has a connection node at both ends. The second end of series resonator Se1 and the first end of series resonator Se2 share a connection node. The second end of series resonator Se2 and the first end of series resonator Se3 share a connection node. The second end of series resonator Se3 and the first end of series resonator Se4 share a connection node.

[0083] A first parallel branch is provided between the connection node of the second end of the series resonator Se1 and the grounding terminal G1. The first parallel branch is provided with parallel resonators Sh1 and ground inductors L1 and L2. A second parallel branch is provided between the connection node of the second end of the series resonator Se2 and the grounding terminal G2. The second parallel branch is provided with parallel resonators Sh2 and ground inductors L3. A third parallel branch is provided between the connection node of the second end of the series resonator Se3 and the grounding terminal G3. The third parallel branch is provided with parallel resonators Sh3 and ground inductors L4.

[0084] One end of the bridging resonator Res1 is connected to the connection node between the parallel resonator Sh3 and the ground inductor L3 in the third parallel branch, and the other end of the bridging resonator Res1 is connected to the connection node between the ground inductor L1 and the ground inductor L2 in the first parallel branch.

[0085] The filter contains four series resonators and three parallel resonators, i.e., 4 stages in series and 3 stages in parallel, for a total of 7 resonator stages. In this case, the area Ares1 of the bridging resonator is less than or equal to 40% of the filter's average equivalent area Aave. The filter's average equivalent area Aave = (Aequ1 + Aequ2 + ... + Aequ7) / 7, where Aequ1, Aequ2, Aequ3, and Aequ4 are the equivalent areas of the series resonators Se1, Se2, Se3, and Se4, respectively, and Aequ5, Aequ6, and Aequ7 are the equivalent areas of the parallel resonators Sh1, Sh2, and Sh3, respectively.

[0086] In one alternative implementation, the bridging resonator is composed of one or more sub-resonators.

[0087] It should be noted that the bridging resonator described in this invention can be composed of a single resonator, i.e., a sub-resonator, or it can be composed of multiple sub-resonators, for example, it can be... Figure 5 The multiple sub-resonators (Sel1, Sel2, Sel3) shown are connected in series, or they can be... Figure 6 The multiple sub-resonators (Sel1, Sel2, Sel3) shown are connected in parallel, or they can be connected in series and parallel. This invention does not specifically limit the form of the bridging sensor.

[0088] In one optional implementation, the bridging resonator is composed of multiple sub-resonators, each with the same or different structural parameters.

[0089] In another alternative implementation, the structural parameters include one or more of the following: layered structure, material, resonant frequency, area, and electromechanical coupling coefficient.

[0090] As mentioned above, the bridging resonator can be composed of multiple sub-resonators. The structural parameters involved in each sub-resonator include, but are not limited to, the stacked structure, material, resonant frequency, area, and electromechanical coupling coefficient.

[0091] The sub-resonators here are all bulk acoustic wave resonators. The stacked structure refers to the various film layers of the sub-resonator, such as a substrate, an acoustic mirror within the substrate, a bottom electrode on the substrate, a piezoelectric layer on the bottom electrode, a top electrode on the piezoelectric layer, and a passivation layer on the top electrode. It may also include a mass loading layer, which may be deposited on the substrate, deposited on the bottom electrode, sandwiched between the substrate and the bottom electrode, sandwiched between the bottom electrode and the piezoelectric layer, sandwiched between the piezoelectric layer and the top electrode, sandwiched between the top electrode and the passivation layer, or on the passivation layer.

[0092] The materials for the sub-resonators refer to the materials selected for each layer in the stacked structure. For example, substrate materials can include single-crystal silicon (Si), gallium arsenide (GaAs), sapphire (Al2O3), quartz (SiO2), aluminum nitride (ALN), lithium niobate (LiNbO3), TaNbO3, silicon carbide (SiC), gallium nitride (GaN), piezoelectric ceramics (PZT), etc. Piezoelectric layer materials can include aluminum nitride (ALN), zinc oxide (ZnO), piezoelectric ceramics (PZT), etc. Acoustic mirrors can be air cavities or acoustic reflectors formed in the substrate, or other equivalent forms. Bottom electrode materials can include molybdenum (Mo), ruthenium (Ru), gold (Au), aluminum (Al), magnesium (Mg), tungsten (W), copper (Cu), etc. Top electrode 105 materials can include molybdenum (Mo), ruthenium (Ru), gold (Au), aluminum (Al), magnesium (Mg), tungsten (W), copper (Cu), etc. The passivation layer can be made of dielectric materials such as aluminum nitride (ALN), silicon nitride (SiN), quartz (SiO2), and Si3N4, or metallic materials such as gold, silver, copper, and platinum. The mass loading layer can be made of metallic materials such as molybdenum (Mo), ruthenium (Ru), gold (Au), aluminum (Al), magnesium (Mg), tungsten (W), and copper (Cu), or dielectric materials such as aluminum nitride (ALN), silicon nitride (SiN), quartz (SiO2), and Si3N4.

[0093] It is understandable that, for each sub-resonator in the aforementioned bridging resonator, the following situations may occur:

[0094] 1) Each sub-resonator can use the exact same structural parameters, such as the same stacked structure, material, resonant frequency, area, and electromechanical coupling coefficient;

[0095] 2) Some sub-resonators can use the exact same structural parameters, such as stacked structure, material, resonant frequency, area, electromechanical coupling coefficient, etc.

[0096] Some sub-resonators use different structural parameters, such as completely different stacked structures, materials, resonant frequencies, areas, electromechanical coupling coefficients, etc., or they may have one or more different parameters such as stacked structures, materials, resonant frequencies, areas, electromechanical coupling coefficients, etc.

[0097] 3) Each sub-resonator uses different structural parameters, such as completely different stacked structures, materials, resonant frequencies, areas, electromechanical coupling coefficients, etc., or one or more parameters such as stacked structures, materials, resonant frequencies, areas, electromechanical coupling coefficients, etc. may be different.

[0098] In one optional embodiment, the bridging resonator is composed of multiple sub-resonators connected in series, and the area Ares1 of the bridging resonator is equal to the equivalent area Aequ_se of the multiple sub-resonators connected in series, 1 / Aequ_se = 1 / A1_se + ... + 1 / A j _se+…+1 / A n _se, where A j _se represents the area of ​​each series-connected sub-resonator, j = 1, 2, ..., n, where n represents the number of series-connected sub-resonators, and n is greater than or equal to 1; or,

[0099] The bridging resonator is composed of multiple parallel sub-resonators, and the area Ares1 of the bridging resonator is equal to the equivalent area Aequ_sh of the multiple parallel sub-resonators, where Aequ_sh = A1_sh + ... + A k _sh+…+A p _sh, where A k _sh represents the area of ​​each parallel sub-resonator, k = 1, 2, ..., p, where p represents the number of parallel sub-resonators, p is greater than or equal to 1; or,

[0100] When the bridging resonator is composed of multiple sub-resonators connected in series and multiple sub-resonators connected in parallel, the area Ares1 of the bridging resonator is calculated step by step according to the series and parallel structure of the multiple sub-resonators in the bridging resonator.

[0101] It should be noted that when the bridging resonator consists of multiple sub-resonators connected in series and / or in parallel, the area Ares1 of the bridging resonator is calculated using the equivalent area method. That is, the equivalent area of ​​the bridging resonator is less than or equal to 40% of the average equivalent area of ​​the filter. More preferably, it is less than or equal to 20%.

[0102] It is understandable that when the bridging resonator is constructed using multiple parallel sub-resonators, the area Ares1 of the bridging resonator needs to be calculated step-by-step based on the specific series and parallel structures of these sub-resonators. This step-by-step calculation is understood as calculating the area Ares1 of the bridging resonator according to the aforementioned methods for calculating the equivalent area of ​​multiple series / parallel sub-resonators. For example, first calculate the equivalent area of ​​multiple series sub-resonators and then calculate the equivalent area of ​​parallel sub-resonators, or first calculate the equivalent area of ​​multiple parallel sub-resonators and then calculate the equivalent area of ​​series sub-resonators.

[0103] For example, when the bridging resonator adopts a structure of first connecting in series and then in parallel, the fifth equivalent area of ​​the series connection is first obtained according to the calculation method of the equivalent area Aequ_se of the multiple series-connected sub-resonators. Based on the fifth equivalent area, the sixth equivalent area of ​​the parallel connection is then obtained according to the calculation method of the equivalent area Aequ_sh of the multiple parallel-connected sub-resonators, and this is taken as the area Ares1 of the bridging resonator. Correspondingly, when the bridging resonator adopts a structure of first connecting in parallel and then in series, the seventh equivalent area of ​​the parallel connection is first obtained according to the calculation method of the equivalent area Aequ_sh of the multiple parallel-connected sub-resonators. Based on the seventh equivalent area, the eighth equivalent area of ​​the series connection is then obtained according to the calculation method of the equivalent area Aequ_se of the multiple series-connected sub-resonators, and this is taken as the area Ares1 of the bridging resonator.

[0104] Figure 7 The diagram shows a comparison curve of the improved out-of-band rejection of the filter described in this invention under the condition of satisfying a limited area. Figure 8 yes Figure 7 A magnified view of the 5.0G-5.5G region. Figure 7 and Figure 8 In the diagram, the thick solid line represents the curve corresponding to the condition where the area of ​​the bridging resonator satisfies Ares1 <= 20% * Aave; the thin solid line represents the curve corresponding to the condition where the area of ​​the bridging resonator satisfies Ares1 <= 40% * Aave; and the thin dashed line represents the curve corresponding to the condition where there is no bridging resonator in the filter. From... Figure 7 and Figure 8 The comparison curves show that adding a bridging resonator significantly improves out-of-band suppression, and this improvement is even better when the bridging resonator's area is within the specified limit. However, when the area of ​​the bridging resonator is outside the range defined in this invention, the suppression does not improve and may even worsen.

[0105] Figure 9The diagram shows a comparison curve of the insertion loss of the bridging resonator of the filter described in this invention, under the condition of satisfying a limited area. The thick solid line represents the curve corresponding to the condition where Ares1 <= 20% * Aave, the thin solid line represents the curve corresponding to the condition where Ares1 <= 40% * Aave, and the thin dashed line represents the curve corresponding to the condition without a bridging resonator. Figure 9 As can be seen from the comparison curves, the three insertion loss curves basically overlap. Therefore, by adding a bridging resonator to the filter, the out-of-band rejection at the target frequency (frequency of interest) can be significantly improved without deteriorating the insertion loss.

[0106] An embodiment of the present invention provides a multiplexer, which includes the filter described in the foregoing embodiments.

[0107] A communication device according to an embodiment of the present invention includes the filter described in the foregoing embodiments.

[0108] This invention improves the out-of-band rejection at the target frequency without sacrificing insertion loss by incorporating a bridging resonator into the filter and defining its area. This significantly enhances the performance of the acoustic filter. Such filters, when applied to multiplexers (including duplexers) and communication equipment, also contribute to improved device or equipment performance.

[0109] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0110] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0111] Those skilled in the art will understand that although the invention has been described with reference to exemplary embodiments, various changes may be made and its elements may be substituted with equivalents without departing from the scope of the invention. Furthermore, many modifications may be made to adapt particular situations or materials to the teachings of the invention without departing from the essential scope of the invention. Therefore, the invention is not limited to the specific embodiments disclosed, but rather the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. An acoustic wave filter, characterized in that, The filter has at least one series resonator in the series branch between its input and output terminals. At least one end of the series resonator is connected to a parallel branch, which includes at least one parallel resonator and at least one inductor to ground. The filter further includes: A bridging resonator, one end of which is connected to the connection node between the parallel resonator and the ground inductor in one of the parallel branches, and the other end of which is connected to any connection node of the series branch or the connection node of another parallel branch. Wherein, the area Ares1 of the bridging resonator is less than or equal to 40% of the average equivalent area Aave of the filter, and the average equivalent area Aave of the filter is the sum of the equivalent areas Aequi of each stage of the filter divided by the number of resonator stages m of the filter, Aave=(Aequ1+…+Aequi+…+Aequm) / m, i=1,2,…,m, m is greater than or equal to 3; For each stage resonator in the filter, the stage resonator is composed of multiple sub-resonators connected in series and / or in parallel. When the structural parameters of each sub-resonator are different, the area of ​​each sub-resonator is normalized to obtain the normalized area of ​​each sub-resonator. Based on the normalized area of ​​each resonator, the equivalent area of ​​the resonator stage is calculated. The structural parameters include one or more of the following: layered structure, material, resonant frequency, area, and electromechanical coupling coefficient. The normalization process for the area of ​​each sub-resonator, resulting in the normalized area of ​​each sub-resonator, includes: The area corresponding to a bridging resonator impedance of 50 ohms is used as the reference area. Divide the area of ​​each sub-resonator by the area corresponding to its own impedance of 50 ohms to obtain the processed area of ​​each sub-resonator. Multiply the processed area of ​​each sub-resonator by the reference area to obtain the normalized area of ​​each sub-resonator.

2. The filter as described in claim 1, wherein, For each resonator stage in the filter... When the resonator of this stage is composed of multiple sub-resonators connected in series, the equivalent area Aequi of the resonator of this stage satisfies: 1 / Aequi=1 / A1_se+1 / A2_se+…+1 / An / _se, where the areas of the multiple sub-resonators are A1_se, A2_se, …, An / _se, respectively, and n / represents the number of sub-resonators connected in series in this stage, and n / is greater than or equal to 1; When the resonator of this stage is composed of multiple sub-resonators connected in parallel, the equivalent area Aequi of the resonator of this stage satisfies: Aequi = A1_sh + A2_sh + ... + An / / _sh, where the areas of the multiple sub-resonators are A1_sh, A2_sh, ..., An / / _sh, and n / / represents the number of sub-resonators connected in parallel in this stage, and n / / is greater than or equal to 1; When the resonator of this stage is composed of multiple sub-resonators connected in series and in parallel, the equivalent area Aequi of the resonator of this stage is calculated step by step according to the series and parallel structure of the multiple sub-resonators in this stage.

3. The filter as described in claim 1, wherein, Another parallel branch has a ground inductor, and the other end of the bridging resonator is connected to the connection node between the parallel resonator and the ground inductor of the other parallel branch.

4. The filter as described in claim 1, wherein, Two ground inductors are provided on another parallel branch, and the other end of the bridging resonator is connected to the connection node between the two ground inductors of the other parallel branch.

5. The filter as described in claim 3 or 4, wherein, The one parallel branch and the other parallel branch are either two adjacent parallel branches or two non-adjacent parallel branches.

6. The filter as claimed in claim 1, wherein, The bridging resonator consists of one or more sub-resonators.

7. The filter as claimed in claim 6, wherein, The bridging resonator is composed of multiple sub-resonators, each with the same or different structural parameters. The structural parameters include one or more of the following: stacked structure, material, resonant frequency, area, and electromechanical coupling coefficient.

8. The filter as claimed in claim 6 or 7, wherein, When the bridging resonator is composed of multiple sub-resonators connected in series, the area Ares1 of the bridging resonator is equal to the equivalent area Aequ_se of the multiple sub-resonators connected in series, 1 / Aequ_se = 1 / A1_se + ... + 1 / Aj_se + ... + 1 / An_se, where Aj_se represents the area of ​​each sub-resonator connected in series, j = 1, 2, ..., n, and n represents the number of sub-resonators connected in series, n is greater than or equal to 1; or, When the bridging resonator is composed of multiple parallel sub-resonators, the area Ares1 of the bridging resonator is equal to the equivalent area Aequ_sh of the multiple parallel sub-resonators, Aequ_sh = A1_sh + ... + Ak_sh + ... + Ap_sh, where Ak_sh represents the area of ​​each parallel sub-resonator, k = 1, 2, ..., p, p represents the number of parallel sub-resonators, and p is greater than or equal to 1; or, When the bridging resonator is composed of multiple sub-resonators connected in series and multiple sub-resonators connected in parallel, the area Ares1 of the bridging resonator is calculated step by step according to the series and parallel structure of the multiple sub-resonators in the bridging resonator.

9. The filter as claimed in claim 1, wherein, The area Ares1 of the bridging resonator is less than or equal to 20% of the average equivalent area Aave of the filter.

10. A multiplexer, characterized in that, The multiplexer includes the filter described in any one of claims 1-9.

11. A communication device, characterized in that, The communication device includes the filter described in any one of claims 1-9.

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