A bulk acoustic wave resonator with adjustable electromechanical coupling coefficient and a method for adjusting the same

Abstract

This invention provides a bulk acoustic wave resonator with adjustable electromechanical coupling coefficient and its adjustment method. The bulk acoustic wave resonator includes a piezoelectric functional layer and i electrical port groups. The piezoelectric functional layer has open sides. The i electrical port groups are arranged sequentially and at intervals along a preset direction, with equal distance between any two adjacent electrical port groups. Each electrical port group includes a first electrical port and a second electrical port. The first electrical port is located on the upper surface of the piezoelectric functional layer, and the second electrical port is located on the lower surface of the piezoelectric functional layer, directly opposite the first electrical port. This invention's bulk acoustic wave resonator with adjustable electromechanical coupling coefficient achieves dynamic adjustment of the anti-resonance frequency while maintaining a constant resonant frequency by changing the electrical connection between the first and second electrical ports located opposite each other on both sides of the piezoelectric functional layer. This allows for dynamic adjustment of the electromechanical coupling coefficient of the bulk acoustic wave resonator.

Description

Technical Field

[0001] This invention belongs to the field of resonator technology and relates to a bulk acoustic resonator with adjustable electromechanical coupling coefficient and its adjustment method. Background Technology

[0002] With the continuous development of modern wireless communication technology, electronic devices need to support more and more frequency bands and communication standards. The traditional approach of equipping each frequency band with an independent filter makes the entire RF front-end system more complex, requires a larger design size, and increases design costs. Therefore, using a single frequency-tunable filter instead of multiple filters can achieve device miniaturization and keep equipment costs within a certain range.

[0003] Typically, filter design is based on resonator design. Therefore, designing a frequency-tunable resonator first is an effective path to designing a frequency-tunable filter.

[0004] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a bulk acoustic resonator with adjustable electromechanical coupling coefficient and its adjustment method, so as to solve the problem that the frequency of the resonator-based filter is not adjustable, which makes the entire radio frequency front-end system more complicated.

[0006] To achieve the above and other related objectives, in one aspect, the present invention provides a bulk acoustic resonator with adjustable electromechanical coupling coefficient, comprising:

[0007] A piezoelectric functional layer, wherein the two sides of the piezoelectric functional layer are hollowed out to allow the piezoelectric functional layer to be in a free boundary condition;

[0008] There are i electrical port groups, where i is an integer greater than 2. The i electrical port groups are arranged sequentially and at intervals along a preset direction. The distance between any two adjacent electrical port groups is equal. Each electrical port group includes a first electrical port and a second electrical port. The first electrical port is disposed on the upper surface of the electrical functional layer, and the second electrical port is disposed on the lower surface of the piezoelectric functional layer and directly opposite the first electrical port. All first electrical ports and all second electrical ports have the same width, the same length, the same thickness, and the same material.

[0009] Optionally, the material of the piezoelectric functional layer includes at least one of lithium niobate and lithium tantalate; the thickness range of the piezoelectric functional layer is 10 - nanometers.

[0010] Optionally, the number range of the electrical port groups is 2 - ; the materials of the first electrical port and the second electrical port include at least one of aluminum, silver, molybdenum, nickel, chromium, gold, copper, tungsten, platinum, and titanium; the thickness range of the first electrical port and the second electrical port is 10 - nanometers, the width range of the first electrical port and the second electrical port is 10 - nanometers, the length range of the first electrical port and the second electrical port is 100 - nanometers; the distance range between any two adjacent electrical port groups is 10 - nanometers.

[0011] On the other hand, the present invention also provides a method for adjusting the electromechanical coupling coefficient, which is applied to the above-mentioned bulk acoustic wave resonator with adjustable electromechanical coupling coefficient. The method for adjusting the electromechanical coupling coefficient includes the following steps:

[0012] Select n electrical port groups from multiple electrical port groups to determine the resonance frequency of the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient. The n electrical port groups are symmetrically arranged with respect to a first plane, and the first plane is perpendicular to the preset direction, 2 < n ≤ i;

[0013] Connect all the first electrical ports in the selected n electrical port groups to a first potential, and connect all the second electrical ports in the selected n electrical port groups to a second potential different from the first potential, so that the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient is in a first open - circuit condition, and a first anti - resonance frequency is obtained;

[0014] Select m electrical port groups that are symmetrically arranged with respect to the first plane from the n electrical port groups, 0 < m < n. Connect all the first electrical ports in the n - m unselected electrical port groups and all the second electrical ports in the selected m electrical port groups to the first potential, and connect all the second electrical ports in the n - m unselected electrical port groups and all the first electrical ports in the selected m electrical port groups to the second potential, so that the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient is in a second open - circuit condition, and a second anti - resonance frequency is obtained.

[0015] Optionally, the first potential is a termination voltage and the second potential is a ground voltage; or, the first potential is a ground voltage and the second potential is a termination voltage.

[0016] Optionally, the second anti-resonant frequency is less than the first anti-resonant frequency.

[0017] Optionally, the selected n electrical port groups are sequentially adjacent; or, among the selected n electrical port groups, at least two electrical port groups are separated by an unselected electrical port group.

[0018] Optionally, the selected m electrical port groups are sequentially adjacent; or, among the selected m electrical port groups, at least two electrical port groups are separated by an unselected electrical port group.

[0019] Alternatively, different resonant frequencies can be obtained by adjusting the value of n and / or adjusting the positions of the selected n electrical port groups.

[0020] Optionally, when n is a fixed value and the positions of the selected n electrical port groups are fixed, the value of the second anti-resonant frequency can be adjusted by adjusting the value of m and / or adjusting the position of the selected m electrical port groups in the selected n electrical port groups.

[0021] Optionally, when n is odd, When the number is odd, the number of second anti-resonant frequencies with different values ​​is:

[0022]

[0023] Or, when n is even and When the number is odd, the number of second anti-resonant frequencies with different values ​​is:

[0024]

[0025] Or, when n is odd and When the number is even, the number of second anti-resonant frequencies with different values ​​is:

[0026]

[0027] Or, when n is even and When the number is even, the number of second anti-resonant frequencies with different values ​​is:

[0028]

[0029] Optionally, when m is less than a preset value, the larger m is, the smaller the second anti-resonant frequency is.

[0030] Optionally, when m is a fixed value and the selected m electrical port groups are not located at the center of the selected n electrical port groups, the closer the position of the m electrical port groups is to the center of the n electrical port groups, the smaller the second anti-resonant frequency.

[0031] On the other hand, the present invention also provides a filter comprising at least one of the above-described electromechanical coupling coefficient adjustable bulk acoustic resonators.

[0032] As described above, the electromechanical coupling coefficient adjustable bulk acoustic resonator of the present invention includes a piezoelectric functional layer and i electrical port groups. The piezoelectric functional layer is hollowed out on both sides to allow it to be in a free boundary condition. i is an integer greater than 2. The i electrical port groups are arranged sequentially and at intervals along a preset direction. The distance between any two adjacent electrical port groups is equal. Each electrical port group includes a first electrical port and a second electrical port. The first electrical port is disposed on the upper surface of the piezoelectric functional layer, and the second electrical port is disposed on the lower surface of the piezoelectric functional layer and directly opposite the first electrical port. All first electrical ports and all second electrical ports have the same width, the same length, the same thickness, and the same material. The electromechanical coupling coefficient-tunable bulk acoustic wave resonator of the present invention achieves dynamic adjustment of the anti-resonance frequency while maintaining a constant resonant frequency by changing the electrical connection method of the first electrical port and the second electrical port arranged opposite to each other on both sides of the piezoelectric functional layer. This allows for dynamic adjustment of the electromechanical coupling coefficient of the resonator. Furthermore, the resonator also enables bandwidth compression, thereby improving the quality factor and reducing energy loss, which is beneficial for constructing high-precision filters. Attached Figure Description

[0033] Figure 1 The image shown is a top view of an embodiment of the electromechanical coupling coefficient adjustable bulk acoustic resonator of the present invention.

[0034] Figure 2 Shown is a front view of an embodiment of the electromechanical coupling coefficient adjustable bulk acoustic resonator of the present invention.

[0035] Figure 3 The diagram shown is a schematic representation of the admittance response curve of the bulk acoustic resonator with adjustable electromechanical coupling coefficient according to an embodiment of the present invention.

[0036] Figure 4The diagram shown illustrates an embodiment of the electromechanical coupling coefficient adjustable bulk acoustic resonator of the present invention participating in electrical connection under short-circuit conditions.

[0037] Figure 5 The diagram shown illustrates an embodiment of the electromechanical coupling coefficient adjustable bulk acoustic resonator of the present invention participating in electrical connection under open-circuit conditions.

[0038] Figure 6 The diagram shown is a flowchart of an embodiment of the electromechanical coupling coefficient adjustment method of the present invention.

[0039] Figure 7 The diagram shown is a schematic representation of the first embodiment of the electromechanical coupling coefficient adjustment method of the present invention after selecting n electrical port groups.

[0040] Figure 8 This is a schematic diagram of the second embodiment of the electromechanical coupling coefficient adjustment method of the present invention after selecting n electrical port groups.

[0041] Figure 9 This is a schematic diagram of the third embodiment of the electromechanical coupling coefficient adjustment method of the present invention after selecting n electrical port groups.

[0042] Figure 10 The diagram shows a schematic of the structure obtained after obtaining the first anti-resonance frequency in the electromechanical coupling coefficient adjustment method of the present invention, which involves electrically connecting the electrical port group in a bulk acoustic resonator with adjustable electromechanical coupling coefficient.

[0043] Figure 11 This is a schematic diagram in the first embodiment of the electromechanical coupling coefficient adjustment method of the present invention, after selecting m electrical port groups from n electrical port groups.

[0044] Figure 12 The diagram shown is a schematic diagram in the second embodiment of the electromechanical coupling coefficient adjustment method of the present invention after selecting m electrical port groups from n electrical port groups.

[0045] Figure 13 The diagram shows a schematic of the structure obtained after electrically connecting the electrical port group in a bulk acoustic resonator with adjustable electromechanical coupling coefficient to obtain a second anti-resonance frequency in the electromechanical coupling coefficient adjustment method of the present invention.

[0046] Figure 14 This is a schematic diagram in the third embodiment of the electromechanical coupling coefficient adjustment method of the present invention, after selecting m electrical port groups from n electrical port groups.

[0047] Figure 15 The diagram shown is a structural schematic of an embodiment of the electromechanical coupling coefficient adjustable bulk acoustic resonator of the present invention.

[0048] Figure 16 The diagram shown is a schematic representation of the admittance response curve of the electromechanical coupling coefficient adjustable bulk acoustic resonator of the present invention in the second embodiment.

[0049] Figures 17a-17d The diagram shown illustrates different embodiments of the electromechanical coupling coefficient adjustment method of the present invention after selecting m electrical port groups from n electrical port groups.

[0050] Figure 18 The diagram shown is a schematic representation of the admittance response curve of the bulk acoustic resonator with adjustable electromechanical coupling coefficient according to the present invention in the third embodiment.

[0051] Figure 19 This is a schematic diagram in the fourth embodiment of the electromechanical coupling coefficient adjustment method of the present invention, after selecting m electrical port groups from n electrical port groups.

[0052] Figure 20 The diagram shown is a schematic representation of the admittance response curve of the bulk acoustic resonator with adjustable electromechanical coupling coefficient according to the present invention in the fourth embodiment.

[0053] Explanation of reference numerals in the attached figures

[0054] 1 piezoelectric functional layer 2 Electrical port group 21 First electrical port 22 Second electrical port S601~S603 step Detailed Implementation

[0055] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0056] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components.

[0057] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0058] In the detailed description of embodiments of the present invention, for ease of explanation, the schematic diagrams illustrating the device structure may be partially enlarged without adhering to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0059] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.

[0060] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0061] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0062] Please see Figure 1 and Figure 2 The diagram shows a structural schematic of the electromechanical coupling coefficient adjustable bulk acoustic resonator of the present invention in one embodiment, wherein... Figure 1 This is a top view of the bulk acoustic resonator with adjustable electromechanical coupling coefficient. Figure 2 This is a front view of the electromechanically coupled bulk acoustic resonator. The electromechanically coupled bulk acoustic resonator includes a piezoelectric functional layer 1 and i electrical port groups 2 (…). Figure 1 and Figure 2 Each has 6 electrical port groups 2, with the label 2 indicating one of them, and i is an integer greater than 2. The two sides of the piezoelectric functional layer 1 are hollowed out to allow the piezoelectric functional layer 1 to be in a free boundary condition. The i electrical port groups 2 are arranged along a preset direction (the preset direction is parallel to...). Figure 2 The electrical ports 2 are arranged sequentially and at intervals, with the direction indicated by the dashed line AA' in the middle, and the distance between any two adjacent electrical port groups 2 is equal.

[0063] In this invention, the electrical port group 1 includes a first electrical port 21 and a second electrical port 22. The first electrical port 21 is disposed on the upper surface of the electrical functional layer 1, and the second electrical port 22 is disposed on the lower surface of the electrical functional layer 1 and directly opposite the first electrical port 21. The first electrical port 21 and the second electrical port 22 in each electrical port group 2 are related to... Figure 2The dashed line AA' indicates a planar symmetrical arrangement, meaning that the first electrical port 21 and the second electrical port 22 in the electrical port group 2 are vertically aligned.

[0064] In this invention, all the first electrical ports 21 and all the second electrical ports 22 have the same thickness, the same width, the same length and the same material.

[0065] In some embodiments, the material of all the first electrical ports 21 and all the second electrical ports 22 includes at least one selected from aluminum, silver, molybdenum, nickel, chromium, gold, copper, tungsten, platinum, and titanium. All the first electrical ports 21 and all the second electrical ports 22 can be a single-layer material or a multi-layer material. A multi-layer material is composed of multiple stacked single-layer materials, and the thickness and / or material composition of each single-layer material in the multi-layer material can be exactly the same, partially the same, or completely different. The single-layer material can be formed from a single metal or an alloy of multiple metals. For example, all the first electrical ports 21 and all the second electrical ports 22 can be formed by a combination of a 5-nanometer-thick titanium metal layer and a 30-nanometer-thick aluminum metal layer located on top of the titanium metal layer.

[0066] In some embodiments, the thickness range of all the first electrical ports 21 and all the second electrical ports 22 is 10- Nanometers, preferably 30 nanometers, 50 nanometers, 100 nanometers, 500 nanometers, 600 nanometers and 1 micrometer.

[0067] In some embodiments, the width range of all the first electrical ports 21 and all the second electrical ports 22 is 10- Nanometers, preferably 30 nanometers, 50 nanometers, 100 nanometers, 500 nanometers, 600 nanometers and Micrometer.

[0068] In some embodiments, the length range of all the first electrical ports 21 and all the second electrical ports 22 is 100- Nanometers, preferably 100 nanometers, 500 nanometers, 600 nanometers, 10 micrometers, 20 micrometers, 50 micrometers and 200 micrometers.

[0069] In some embodiments, the number of electrical port groups 2 ranges from 2 to... One, with priority given to 20, 50 and 100.

[0070] In some embodiments, the distance between any two adjacent electrical port groups is in the range of 10- Nanometers, preferably 50 nanometers and 100 nanometers.

[0071] In some embodiments, the material of the piezoelectric functional layer 1 includes at least one of lithium niobate and lithium tantalate.

[0072] In some embodiments, the thickness of the piezoelectric functional layer 1 is in the range of 10- Nanometers, preferably 50 nanometers, 100 nanometers, 200 nanometers, 500 nanometers, 1 micrometer and 2 micrometers.

[0073] Generally, each resonator has its inherent resonant frequency and anti-resonant frequency. The resonant frequency and anti-resonant frequency are the core parameters describing the resonator's operating characteristics, and together they determine the resonator's frequency response. The resonant frequency is the frequency at which the resonator responds strongest to external excitation (at its minimum impedance or maximum amplitude), at which point the system's energy exchange efficiency is highest. The anti-resonant frequency is the frequency at which the resonator responds weakest to external excitation (at its maximum impedance or minimum amplitude), at which point the system has almost no response to external excitation.

[0074] Please see Figure 3 The diagram shows the admittance response curve of the electromechanical coupling coefficient adjustable bulk acoustic resonator of the present invention in one embodiment. Figure 3 As shown, the vertical axis represents admittance, and the horizontal axis represents frequency. The frequency corresponding to the peak value of the admittance response curve is the resonant frequency, and the frequency corresponding to the valley value is the anti-resonant frequency. By using different electrical connection methods to electrically connect the first electrical port 21 and the second electrical port 22 in the resonator, the resonant frequency and anti-resonant frequency of the resonator can be obtained.

[0075] Please see Figure 4 The diagram shows a schematic representation of the electromechanical coupling coefficient adjustable bulk acoustic resonator of the present invention participating in electrical connection under short-circuit conditions in one embodiment. All the first electrical ports 21 and all the second electrical ports 22 are connected to the same voltage, at which point the frequency of the entire system under short-circuit conditions, i.e., the resonant frequency, can be obtained.

[0076] Please see Figure 5 The diagram shows a schematic representation of the electromechanical coupling coefficient adjustable bulk acoustic resonator of the present invention participating in electrical connection under open-circuit conditions in one embodiment. All the first electrical ports 21 are connected to the terminal voltage as terminal ports, and all the second electrical ports 22 are connected to the ground voltage, which is different from the terminal voltage, as grounding ports. At this time, the frequency of the entire system under open-circuit conditions, i.e., the anti-resonant frequency, can be obtained.

[0077] In the present invention, when the number and positions of the electrical port groups 2 participating in electrical connection in the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient do not change, without changing the structure of the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient, only changing the voltage connection mode of the first electrical port 21 and the second electrical port 22 in the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient will not change the resonance frequency of the resonator, but can change the anti-resonance frequency of the resonator, and finally achieve dynamic adjustment of the electromechanical coupling coefficient of the resonator.

[0078] In this regard, the present invention also provides a method for adjusting the electromechanical coupling coefficient. By changing the voltage connection mode of the first electrical port 21 and the second electrical port 22 in the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient, when the number and positions of the electrical port groups 2 participating in electrical connection remain unchanged, it is possible to make the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient achieve continuous dynamic adjustment of the anti-resonance frequency while maintaining the resonance frequency unchanged, so as to achieve dynamic adjustment of the electromechanical coupling coefficient of the resonator.

[0079] Please refer to Figure 6 , which shows a schematic flowchart of the method for adjusting the electromechanical coupling coefficient of the present invention in an embodiment, and includes the following steps:

[0080] S601: Select n electrical port groups from multiple electrical port groups to determine the resonance frequency of the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient. The n electrical port groups are symmetrically arranged with respect to a first plane, and the first plane is perpendicular to the preset direction, where 2 < n ≤ i.

[0081] S602: Connect all the first electrical ports in the selected n electrical port groups to a first potential, and connect all the second electrical ports in the selected n electrical port groups to a second potential different from the first potential, so that the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient is in a first open-circuit condition, and a first anti-resonance frequency is obtained.

[0082] S603: Select m electrical port groups that are symmetrically arranged with respect to the first plane from the n electrical port groups, where 0 < m < n. Connect all the first electrical ports in the n - m unselected electrical port groups and all the second electrical ports in the selected m electrical port groups to the first potential, and connect all the second electrical ports in the n - m unselected electrical port groups and all the first electrical ports in the selected m electrical port groups to the second potential, so that the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient is in a second open-circuit condition, and a second anti-resonance frequency is obtained.

[0083] The above steps will be described in detail below with reference to examples.

[0084] In step S601, n electrical port groups 2 are selected from the i electrical port groups 2. By selecting a certain number and certain positions of the electrical port groups 2 to participate in the electrical connection, the resonance frequency of the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient can be determined. The overall structure formed by the selected n electrical port groups 2 is symmetrically arranged with respect to a first plane perpendicular to the preset direction (such as the direction indicated by the dotted line AA' shown in Figure 2 ), and the first plane may change due to the change of the overall structure formed by the selected n electrical port groups 2. It is required to select more than 2 electrical port groups 2. The selected electrical port groups 2 can be all the electrical port groups 2 in the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient (in this case, n = i), or can be some of the electrical port groups 2 in the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient (in this case, 2 < n < i). The number of the selected electrical port groups 2 can be odd or even.

[0085] In some possible embodiments, the selected n electrical port groups 2 are adjacent to each other in sequence. Please refer to Figure 7 , there are a total of 8 electrical port groups 2 in the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient, and 6 adjacent electrical port groups 2 located in the dotted box are selected to participate in the electrical connection to determine the resonance frequency of the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient. The selected 6 electrical port groups 2 are symmetric with respect to the plane indicated by the dotted line BB' in the figure.

[0086] In some possible embodiments, among the selected n electrical port groups 2, there are at least two electrical port groups 2 with unselected electrical port groups spaced therebetween. For example, please refer to Figure 8 , there are a total of 8 electrical port groups 2 in the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient. There is 1 unselected electrical port group 2 between the 2 adjacent electrical port groups 2 located in the left dotted box and the 2 adjacent electrical port groups 2 located in the right dotted box that are selected. The selected 4 electrical port groups 2 are symmetric with respect to the plane indicated by the dotted line BB' in the figure. For example, please refer to Figure 9The electromechanical coupling coefficient adjustable bulk acoustic resonator has a total of 8 electrical port groups 2. There is one unselected electrical port group 2 between the two adjacent electrical port groups 2 located in the left dashed box and the two adjacent electrical port groups 2 located in the middle dashed box. There is one unselected electrical port group 2 between the two adjacent electrical port groups 2 located in the right dashed box and the two adjacent electrical port groups 2 located in the middle dashed box. The five selected electrical port groups 2 are symmetrical about the plane indicated by the dashed line BB' in the figure.

[0087] In step S602, all the first electrical ports 21 in the selected n electrical port groups 2 are connected to a first potential, and all the second electrical ports 22 in the selected n electrical port groups are connected to a second potential different from the first potential, so that the electromechanical coupling coefficient adjustable bulk acoustic resonator is in a first open circuit condition, and a first anti-resonance frequency is obtained.

[0088] In some possible embodiments, the first potential is a termination voltage and the second potential is a ground voltage; or, the first potential is a ground voltage and the second potential is a termination voltage.

[0089] For ease of explanation, the first potential is defined as the terminal voltage, and the second potential as the ground voltage. Since the electrical port connected to the terminal voltage is typically named the terminal port, and the electrical port connected to the ground voltage is typically named the ground port, for ease of illustration, the electrical port connected to the first potential (i.e., the terminal voltage) (first electrical port 21 or second electrical port 22) in the following figures is labeled T, and the electrical port connected to the second potential (i.e., the ground voltage) (first electrical port 21 or second electrical port 22) in the following figures is labeled G.

[0090] For example, please refer to Figure 10 The six selected electrical port groups 2 are numbered sequentially from left to right. The first electrical ports 21 located on the upper side of the piezoelectric functional layer 1 are numbered 1T, 2T, 3T, 4T, 5T, and 6T from left to right, and the second electrical ports 22 located on the lower side of the piezoelectric functional layer 1 are numbered 1G, 2G, 3G, 4G, 5G, and 6G from left to right. All the first electrical ports 21 are connected to the first potential, and all the second electrical ports 22 in the six selected electrical port groups are connected to the second potential. This electrical connection method yields the first anti-resonant frequency.

[0091] In step S603, m electrical port groups 2 are selected from the n electrical port groups 2. All the first electrical ports 21 in the unselected nm electrical port groups 2 and all the second electrical ports 22 in the selected m electrical port groups 2 are connected to the first potential. All the second electrical ports 22 in the unselected nm electrical port groups 2 and all the first electrical ports 21 in the selected m electrical port groups 2 are connected to the second potential, so that the electromechanical coupling coefficient adjustable bulk acoustic resonator is in the second open-circuit condition, and the second anti-resonance frequency is obtained.

[0092] In this invention, the value of m is required to be less than n, that is, a portion of the electrical port groups 2 are selected from the selected n electrical port groups 2. When selecting m electrical port groups 2 again from the n electrical port groups 2 selected in step S601 (defined as the first selection operation), in the second selection operation, each selected electrical port group 2 can have two sides that are selected in both selection operations, or both sides that are selected in the first selection operation but not in the second selection operation, or one side that is selected in both selection operations and the other side that is selected in the first selection operation but not in the second selection operation. The overall structure formed by the selected m electrical port groups 2 is perpendicular to the preset direction (e.g., Figure 2 The first plane (indicated by the direction shown by the dashed line AA') is symmetrically arranged, wherein the first plane may change due to changes in the overall structure of the selected m electrical port groups 2.

[0093] In some possible embodiments, the selected m electrical port groups 2 are sequentially adjacent. See also... Figure 11 The six electrical port groups 2 located within the outer frame are selected by the first selection operation, while the four sequentially adjacent electrical port groups 2 located within the inner frame are selected by the second selection operation. The four sequentially adjacent electrical port groups 2 located within the inner frame are symmetrical about the plane indicated by the dashed line BB' in the figure.

[0094] In some possible embodiments, among the selected m electrical port groups 2, at least two electrical port groups 2 are separated by an unselected electrical port group 2. For example, please refer to... Figure 12The six electrical port groups 2 located within the outer frame are selected by the first selection operation, and the two electrical port groups 2 located within the two inner frame lines are selected by the second selection operation. Between the two electrical port groups 2 located within the inner frame lines, there are electrical port groups 2 that were selected in the first selection operation but not in the second selection operation. The two electrical port groups 2 located within the inner frame lines are symmetrical about the plane indicated by the dashed line BB' in the figure.

[0095] In this invention, after the second selection operation, the n electrical port groups 2 selected in the first selection operation are electrically reconnected to adjust the value of the anti-resonance frequency, thereby obtaining a second anti-resonance frequency different from the first anti-resonance frequency. During the reconnection, all the first electrical ports 21 in the nm electrical port groups 2 that were not selected in the second selection operation are connected to the first potential; all the first electrical ports 21 in the m electrical port groups 2 that were selected in the second selection operation are changed from being connected to the first potential to being connected to the second potential; all the second electrical ports 22 in the nm electrical port groups 2 that were not selected in the second selection operation are connected to the second potential; and all the second electrical ports 22 in the m electrical port groups 2 that were selected in the second selection operation are changed from being connected to the second potential to being connected to the first potential. This operation yields the second anti-resonance frequency. By comparing the new electrical connection method with the original electrical connection method, it can be found that by selecting m electrical port groups 2 from the n electrical port groups 2 and swapping the voltages connected to the first electrical port 21 and the second electrical port 22 in the m electrical port groups 2, the second anti-resonant frequency can be obtained.

[0096] For example, please refer to Figure 13 Two more electrical port groups 2 are selected from the six electrical port groups 2 selected in the first selection operation (the second electrical port group 2 in the left dashed box and the fifth electrical port group 2 in the right dashed box). The first electrical port 21 is labeled 1T, 2G, 3T, 4T, 5G, and 6T from left to right, and the second electrical port 22 is labeled 1G, 2T, 3G, 4G, 5T, and 6G from left to right. When reconnecting the six electrical port groups 2 selected in the first selection operation, the voltages connected to the first electrical port 21 and the second electrical port 22 in the two electrical port groups 2 selected in the second selection operation are swapped. The voltages connected to the first electrical port 21 and the second electrical port 22 in the four electrical port groups 2 that were not selected in the second selection operation remain unchanged. The second anti-resonant frequency can be obtained through this electrical connection method.

[0097] In this invention, certain electrical port groups 2 are selected for electrical connection. All first electrical ports 21 located on the piezoelectric functional layer 1 are connected to the first potential, and all second electrical ports 22 located below the piezoelectric functional layer 1 are connected to the second potential. This allows the first anti-resonance frequency of the resonator under open-circuit conditions to be obtained. By swapping the voltage connection methods of the first electrical ports 21 and the second electrical ports 22 in certain electrical port groups 2, and then reconnecting them electrically under open-circuit conditions, the second anti-resonance frequency of the electromechanically coupled bulk acoustic wave resonator can be obtained. Because the electrical ports connected to the first potential and the electrical ports connected to the second potential change (equivalent to a change in the distribution of the terminal port and the ground port), the frequency of the intrinsic mode corresponding to the electromechanically coupled bulk acoustic wave resonator changes, thereby altering the anti-resonance frequency of the electromechanically coupled bulk acoustic wave resonator. Furthermore, the second anti-resonance frequency is lower than the first anti-resonance frequency.

[0098] In this invention, when n is a fixed value in step S601 and the positions of the n electrical port groups 2 are fixed, by adjusting the value of m in step S603 or adjusting the position of the m electrical port groups 2 in the n electrical port groups 2, a second anti-resonant frequency with different values ​​can be obtained.

[0099] In some embodiments, when n is a fixed value and the positions of the n electrical port groups 2 are fixed, adjusting only the value of m can yield a second anti-resonant frequency that is different from the value of the first anti-resonant frequency.

[0100] In some embodiments, when n and m are constants and the positions of the n electrical port groups 2 are fixed, adjusting only the positions of the m electrical port groups 2 within the n electrical port groups 2 can yield a second anti-resonant frequency that is different from the first anti-resonant frequency.

[0101] In some embodiments, when n is a fixed value and the positions of the n electrical port groups 2 are fixed, by simultaneously adjusting the value of m and the positions of the m electrical port groups 2 in the n electrical port groups 2, a second anti-resonant frequency different from the value of the first anti-resonant frequency can be obtained.

[0102] In this invention, assuming the positions and number of the electrical port groups 2 involved in the electrical connection are fixed, the number of second anti-resonant frequencies with different values ​​is investigated. Since the operation in step S603 causes a change in the positions and number of electrical ports connected to the first voltage and the second voltage on each side of the piezoelectric functional layer 1, and further causes a change in the second anti-resonant frequency obtained in step S603, determining all possible switching methods in the n electrical port groups 2 and excluding equivalent switching methods can determine the types of changes in the terminal port and ground port, thereby determining the number of second anti-resonant frequencies with different values. All possible switching methods in the n electrical port groups 2 are the same as the number of second anti-resonant frequencies with different values.

[0103] In this invention, when n electrical port groups 2 are involved in the connection, since the n electrical port groups 2 are symmetrical about the first plane, and the m electrical port groups 2 to be swapped are also symmetrical about the first plane, it is only necessary to consider all possible swapping methods of the left or right half of the electrical port groups 2 (e.g., ...). Figure 7 The first three or the last three of the six electrical port groups 2. The number of all possible swapping arrangements in the n electrical port groups is:

[0104] (n is an odd number)

[0105] (n is an even number)

[0106] in, This represents the number of combinations of choosing M elements from N elements. Since the terminal ports and ground ports are reciprocal, swapping the terminal ports and ground ports as a whole has the same effect. Therefore, swapping x groups of electrical port group 2 is essentially equivalent to swapping Nx groups of electrical port group 2, and should be excluded. For example, please refer to... Figure 14 By swapping the 1st, 3rd, 4th, and 6th electrical port groups 2 in the 6 electrical port groups 2, and electrically connecting them under open-circuit conditions, the second anti-resonant frequency obtained is... Figure 13 The structures shown have the same value for the second anti-resonant frequency.

[0107] In some possible implementations, when n is odd and When the number is odd, the number of second anti-resonant frequencies with different values ​​is:

[0108]

[0109] In some possible embodiments, when n is even and When the number is odd, the number of second anti-resonant frequencies with different values ​​is:

[0110]

[0111] In some possible implementations, when n is odd and When the number is even, the number of second anti-resonant frequencies with different values ​​is:

[0112]

[0113] In some possible embodiments, when n is even and When the number is even, the number of second anti-resonant frequencies with different values ​​is:

[0114]

[0115] In this invention, when the number n of the electrical port groups 2 involved in the electrical connection is constant, the larger the number m of the electrical port groups 2 selected in the second selection operation is below a certain value, the smaller the second anti-resonant frequency becomes. When m is small, the second anti-resonant frequency continuously decreases as m increases. When m increases to a certain value, the second anti-resonant frequency gradually increases with further increases in m. Since the voltage connection method of swapping the first electrical port 21 and the second electrical port 22 in x groups of electrical port groups 2 is substantially equivalent to the voltage connection method of swapping the first electrical port 21 and the second electrical port 22 in Nx groups of electrical port groups 2, when m increases to a certain value, the excitation method after the swap plays a major role, and the part of the electrical port groups 2 that has not been swapped is equivalent to a disturbance. Therefore, as the number of swapped electrical port groups 2 increases, the second anti-resonant frequency actually increases.

[0116] In some embodiments, when m is less than half of n, the larger m is, the smaller the second anti-resonant frequency is.

[0117] Please see Figure 15The diagram shows a schematic representation of an embodiment of the electromechanically coupled bulk acoustic wave resonator of the present invention. The electromechanically coupled bulk acoustic wave resonator includes a piezoelectric functional layer 1 and 20 electrical port groups 2. The piezoelectric functional layer 1 is made of lithium niobate, with a thickness of 200 nm and a length of 300 nm. All the first electrical ports 21 and all the second electrical ports 22 are made of aluminum, with a thickness of 50 nm and a width of 14 nm. Starting from both ends of the electromechanically coupled bulk acoustic wave resonator, the voltage connection of the first electrical ports 21 and the second electrical ports 22 in the electrical port groups 2 is swapped, and the number of swapped electrical port groups 2 is gradually increased from the outside to the inside (increasing by two each time, i.e., one additional port on each side of the electromechanically coupled bulk acoustic wave resonator). After each swap, the first voltage and the second voltage are electrically connected respectively to obtain the second anti-resonance frequency corresponding to each swap, thus obtaining... Figure 16 The admittance response curves are shown. When all first electrical ports 21 are connected to the first voltage and all second electrical ports 22 are connected to the second voltage, the admittance response curve corresponding to the number 0 can be obtained after the electrical connection. By swapping the voltage connection methods of the first electrical ports 21 and the second electrical ports 22 in the 1st and 20th electrical port groups 2, the admittance response curve corresponding to the number 2 can be obtained after the electrical connection. By swapping the voltage connection methods of the first electrical ports 21 and the second electrical ports 22 in the 1st, 2nd, 19th, and 20th electrical port groups 2, the admittance response curve corresponding to the number 4 can be obtained after the electrical connection. Similarly, by swapping the voltage connection methods of the first electrical ports 21 and the second electrical ports 22 in all electrical port groups 2, the admittance response curve corresponding to the number 20 can be obtained after the electrical connection.

[0118] like Figure 16 As shown, when m is less than 18, the value of the second anti-resonant frequency gradually decreases as m increases. When m is greater than 16, the value of the second anti-resonant frequency gradually increases as m increases.

[0119] In this invention, when n and m are constants, the positions of the n electrical port groups 2 are fixed, and the m electrical port groups 2 are not located at the center of the n electrical port groups 2, the closer the positions of the m electrical port groups 2 are to the center of the n electrical port groups 2, the smaller the second anti-resonant frequency.

[0120] In some possible embodiments, n and m are constants, and the positions of the n electrical port groups 2 are fixed. The closer the position of the m electrical port groups 2 is to the center of the n electrical port groups 2, the smaller the second anti-resonant frequency.

[0121] Please see Figures 17a-17d The electromechanically adjustable bulk acoustic resonator includes a piezoelectric functional layer 1 and six electrical port groups 2. The piezoelectric functional layer 1 is made of lithium niobate, with a thickness of 500 nm and a length of 900 nm. All the first electrical ports 21 are made of aluminum, with a thickness of 70 nm and a width of 127.5 nm. Starting from both ends of the electromechanically adjustable bulk acoustic resonator, the electrical port groups 2 whose voltage connection methods of the first electrical ports 21 and the second electrical ports 22 are to be swapped are selected, and the selected electrical port groups 2 are gradually changed from the outside to the inside. After each selection, electrical connection is performed under open-circuit conditions to obtain the corresponding second anti-resonance frequency, as shown below. Figure 18 The admittance response curve is shown. Wherein, Figure 17a When all the first electrical ports 21 are connected to the first potential and all the second electrical ports 22 are connected to the second potential, the admittance response curve corresponding to the commutation form a can be obtained after the electrical connection. Figure 17b By swapping the voltage connection of the first electrical port 21 and the second electrical port 22 in the first and sixth electrical port groups 2, the admittance response curve corresponding to the swapped form b can be obtained after the electrical connection is made. Figure 17c By swapping the voltage connection of the first electrical port 21 and the second electrical port 22 in the second and fifth electrical port groups 2, the admittance response curve corresponding to the swapped form c can be obtained after the electrical connection is made. Figure 17d By swapping the voltage connection of the first electrical port 21 and the second electrical port 22 in the third and fourth electrical port groups 2, the admittance response curve corresponding to the swapped configuration d can be obtained. For example... Figure 18 As shown, when n is 6, m is 2, and the positions of the n electrical port groups 2 are fixed, the closer the positions of the two electrical port groups 2 are to the center position of the six electrical port groups 2, the smaller the second anti-resonant frequency.

[0122] In some possible embodiments, n and m are constants, and the positions of the n electrical port groups 2 are fixed. When the m electrical port groups 2 are not located at the center of the n electrical port groups 2, the closer the m electrical port groups 2 are to the center of the n electrical port groups 2, the smaller the second anti-resonant frequency; when the m electrical port groups 2 are located at the center of the n electrical port groups 2, the second anti-resonant frequency actually increases.

[0123] As an example, such as Figure 19 As shown, starting from both ends of the electromechanically adjustable bulk acoustic resonator, the electrical port group 2 to be swapped (the voltage connection mode of the first electrical port 21 and the second electrical port 22) is selected, and the selected electrical port group 2 is gradually changed from the outside to the inside (two electrical port groups 2 are selected each time). After each selection, electrical connections are made under open-circuit conditions to obtain the second anti-resonant frequency corresponding to each swap, thus obtaining the following... Figure 20 The admittance response curve is shown. Wherein, Figure 20 The transposition forms shown from top to bottom correspond to the following order: Figure 19 The admittance response curves are shown from top to bottom. Figure 20 As shown, when n is 6, m is 2, and the positions of the n electrical port groups 2 are fixed, except for swapping the voltage connection of the first electrical port 21 and the second electrical port 22 in the electrical port group 2 at the center position, the closer the positions of the two electrical port groups 2 are to the center position of the 20 electrical port groups 2, the smaller the second anti-resonant frequency; however, when the voltage connection of the first electrical port 21 and the second electrical port 22 in the electrical port group 2 at the center position is swapped, the second anti-resonant frequency shows a numerical increase.

[0124] In this invention, when the value of n is constant and the positions of the n electrical port groups 2 are constant, if adjusting the value of m in step S603 or adjusting the positions of the m electrical port groups 2 within the n electrical port groups 2 still fails to obtain the desired second anti-resonant frequency, the value of the second anti-resonant frequency can be adjusted by increasing or decreasing the value of n, i.e., by increasing or decreasing the number of electrical port groups 2 involved in the electrical connection, or by changing the positions of the n electrical port groups 2. At this time, because the number of electrical port groups 2 involved in the electrical connection changes, the resonant frequency of the electromechanical coupling coefficient adjustable bulk acoustic resonator will also change.

[0125] The electromechanical coupling coefficient adjustable bulk acoustic wave resonator of the present invention, with a fixed structure, achieves dynamic adjustment of the anti-resonance frequency while maintaining a constant resonant frequency by changing the electrical connection method of the first electrical port 21 and the second electrical port 22 disposed opposite to each other on both sides of the piezoelectric functional layer 1. This allows for dynamic adjustment of the electromechanical coupling coefficient of the resonator. Frequency adjustment of the resonator can be achieved simply by changing the voltage-carrying connection method of the electrical ports in the resonator.

[0126] In this invention, the electromechanical coupling coefficient adjustment method applied to the adjustable bulk acoustic wave resonator (BAW) changes the voltage connection of the first electrical port 21 and the second electrical port 22 in the electrical port group 2 of the BAW. This allows the admittance response of the BAW to be continuously and dynamically adjustable at the anti-resonance point while maintaining the resonant point, thereby achieving dynamic adjustment of the electromechanical coupling coefficient. The method reduces the anti-resonance frequency without changing the resonant frequency and also compresses the bandwidth of the BAW, contributing to the construction of high-precision filters. Since the quality factor is defined as the ratio of the center frequency to the bandwidth, the method also helps improve the quality factor of the BAW, thereby reducing its energy loss and enhancing the interaction between the electromagnetic field and matter, thus aiding in the study of acoustic nonlinear effects.

[0127] The present invention also provides a filter comprising at least one of the aforementioned electromechanically tunable bulk acoustic resonators. The filter is fabricated based on a single electromechanically tunable bulk acoustic resonator system, enabling adjustable electromechanical coupling. Replacing multiple filters with this electromechanically tunable filter allows for device miniaturization and cost control, simplifying the entire RF front-end system.

[0128] In summary, the electromechanical coupling coefficient adjustable bulk acoustic resonator of the present invention includes a piezoelectric functional layer and i electrical port groups. The piezoelectric functional layer is hollowed out on both sides to allow it to be in a free boundary condition. i is an integer greater than 2. The i electrical port groups are arranged sequentially and at intervals along a preset direction. The distance between any two adjacent electrical port groups is equal. Each electrical port group includes a first electrical port and a second electrical port. The first electrical port is disposed on the upper surface of the piezoelectric functional layer, and the second electrical port is disposed on the lower surface of the piezoelectric functional layer and directly opposite the first electrical port. All first electrical ports and all second electrical ports have the same width, the same length, the same thickness, and the same material. The electromechanical coupling coefficient-tunable bulk acoustic wave resonator of the present invention achieves dynamic adjustment of the anti-resonance frequency while maintaining a constant resonant frequency by changing the electrical connection method of the first electrical port and the second electrical port arranged opposite to each other on both sides of the piezoelectric functional layer. This allows for dynamic adjustment of the electromechanical coupling coefficient of the resonator. Furthermore, the resonator also enables bandwidth compression, thereby improving the quality factor and reducing energy loss, which is beneficial for constructing high-precision filters. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial applicability.

[0129] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A bulk acoustic resonator with adjustable electromechanical coupling coefficient, characterized in that, Comprising: A piezoelectric functional layer, with both sides of the piezoelectric functional layer hollowed out so that the piezoelectric functional layer is under free boundary conditions; i electrical port groups, where i is an integer greater than 2. The i electrical port groups are arranged in sequence and at intervals along a preset direction, and the distance between any two adjacent electrical port groups is equal. The electrical port group includes a first electrical port and a second electrical port. The first electrical port is arranged on the upper surface of the electrical functional layer, and the second electrical port is arranged on the lower surface of the piezoelectric functional layer and is directly opposite to the first electrical port. All the first electrical ports and all the second electrical ports have the same width, the same length, the same thickness, and the same material.

2. The bulk acoustic resonator with adjustable electromechanical coupling coefficient according to claim 1, characterized in that: The material of the piezoelectric functional layer includes at least one of lithium niobate and lithium tantalate; the thickness of the piezoelectric functional layer is in the range of 10- nanometer.

3. The bulk acoustic resonator with adjustable electromechanical coupling coefficient according to claim 1, characterized in that: The number of electrical port groups ranges from 2 to... The first and second electrical ports are made of at least one of aluminum, silver, molybdenum, nickel, chromium, gold, copper, tungsten, platinum, and titanium; the thickness of the first and second electrical ports is 10- The width range of the first electrical port and the second electrical port is 10- nanometers. Nanometers, the length range of the first electrical port and the second electrical port is 100- Nanometers; the distance between any two adjacent electrical port groups is in the range of 10- nanometer.

4. A method for adjusting the electromechanical coupling coefficient, characterized in that, Applied to the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient as described in any one of claims 1 - 3, the method for adjusting the electromechanical coupling coefficient of the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient includes the following steps: Select n electrical port groups from the multiple electrical port groups to determine the resonant frequency of the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient. The n electrical port groups are symmetrically arranged with respect to a first plane, and the first plane is perpendicular to the preset direction, where 2 < n ≤ i; Connect all the first electrical ports in the selected n electrical port groups to a first potential, and connect all the second electrical ports in the selected n electrical port groups to a second potential different from the first potential, so that the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient is under a first open - circuit condition, and a first anti - resonant frequency is obtained; Select m electrical port groups that are symmetrically arranged with respect to the first plane from the n electrical port groups, where 0 < m < n. Connect all the first electrical ports in the n - m non - selected electrical port groups in the n electrical port groups and all the second electrical ports in the selected m electrical port groups to the first potential, and connect all the second electrical ports in the n - m non - selected electrical port groups in the n electrical port groups and all the first electrical ports in the selected m electrical port groups to the second potential, so that the bulk acoustic wave resonator with adjustable electromechanical coupling coefficient is under a second open - circuit condition, and a second anti - resonant frequency is obtained.

5. The electromechanical coupling coefficient adjustment method according to claim 4, characterized in that: The first potential is the terminal voltage, and the second potential is the ground voltage; or, the first potential is the ground voltage, and the second potential is the terminal voltage.

6. The electromechanical coupling coefficient adjustment method according to claim 4, characterized in that: The second anti - resonant frequency is less than the first anti - resonant frequency.

7. The electromechanical coupling coefficient adjustment method according to claim 4, characterized in that: The selected n electrical port groups are adjacent in sequence; or, among the selected n electrical port groups, there is at least one unselected electrical port group between at least two electrical port groups.

8. The electromechanical coupling coefficient adjustment method according to claim 4, characterized in that: The selected m electrical port groups are adjacent in sequence; or, among the selected m electrical port groups, there is at least one unselected electrical port group between at least two electrical port groups.

9. The electromechanical coupling coefficient adjustment method according to claim 4, characterized in that: Obtain different resonant frequencies by adjusting the value of n and / or adjusting the positions of the selected n electrical port groups.

10. The electromechanical coupling coefficient adjustment method according to claim 4 or 9, characterized in that: When n is a fixed value and the positions of the selected n electrical port groups are fixed, the value of the second anti-resonant frequency is adjusted by adjusting the value of m and / or adjusting the position of the selected m electrical port groups in the selected n electrical port groups.

11. The electromechanical coupling coefficient adjustment method according to claim 10, characterized in that: When n is odd, When the number is odd, the number of second anti-resonant frequencies with different values ​​is: Or, when n is even and When the number is odd, the number of second anti-resonant frequencies with different values ​​is: Or, when n is odd and When the number is even, the number of second anti-resonant frequencies with different values ​​is: Or, when n is even and When the number is even, the number of second anti-resonant frequencies with different values ​​is:

12. The electromechanical coupling coefficient adjustment method according to claim 10, characterized in that: When m is less than the preset value, the larger m is, the smaller the second anti-resonant frequency is.

13. The electromechanical coupling coefficient adjustment method according to claim 10, characterized in that: When m is a constant and the selected m electrical port groups are not located at the center of the selected n electrical port groups, the closer the position of the m electrical port groups is to the center of the n electrical port groups, the smaller the second anti-resonant frequency.

14. A filter, characterized in that, It includes at least one bulk acoustic resonator with an adjustable electromechanical coupling coefficient as described in any one of claims 1-3.

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