Filter and method for adjusting coupling polarity

Abstract

The application relates to the communication technical field, and provides a filter and a coupling polarity adjusting method.The filter comprises a first component, a second component, a first resonator, a second resonator and a coupling piece, the first resonator and the second resonator are located in a first resonant cavity and a second resonant cavity formed between the first component and the second component; one end of the coupling piece is located in the first resonant cavity and connected to the first resonator or the first component to form a short-circuit end, and the other end of the coupling piece is suspended in the second resonant cavity and located on one side of the second resonator to form an open-circuit end; and the coupling piece is used for capacitive coupling or inductive coupling between the first resonator and the second resonator.The filter provided by the application can realize capacitive coupling or inductive coupling between the first resonator and the second resonator by setting the coupling piece with the same structure and only setting different lengths, and the structure can be effectively simplified.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to a filter and a method for adjusting coupling polarity. Background Technology

[0002] The two adjacent resonators of a filter generally need to be capacitively or inductively coupled. When capacitive coupling is required, a flybar is usually placed between the two resonators; when inductive coupling is required, a coupling window or connecting rod is usually placed between the two resonators.

[0003] Therefore, in order to achieve capacitive or inductive coupling, different structural forms need to be set between the two resonators, resulting in a more complex structure and affecting the performance of the filter. Summary of the Invention

[0004] This application provides a filter and a coupling polarity adjustment method, which can improve the technical problem of needing to set different structural forms between two resonators to achieve capacitive coupling or inductive coupling.

[0005] In a first aspect, embodiments of this application provide a filter, the filter comprising:

[0006] First component;

[0007] The second component engages with the first component to form a first resonant cavity and a second resonant cavity that are connected between the second component and the first component;

[0008] The first resonator is located inside the first resonant cavity and is disposed on the first component;

[0009] A second resonator, located within the second resonant cavity, and disposed on the first component or the second component; and

[0010] A coupling element is located between the first resonator and the second resonator; one end of the coupling element is located inside the first resonant cavity and connected to the first resonator or the first component to form a short-circuit end, and the other end of the coupling element is suspended inside the second resonant cavity and located on one side of the second resonator to form an open-circuit end; the coupling element is used to enable capacitive coupling or inductive coupling between the first resonator and the second resonator.

[0011] The technical solutions described in this application have at least the following technical effects or advantages:

[0012] The filter provided in this application embodiment uses a coupling element between a first resonator and a second resonator. One end of the coupling element is located inside the first resonant cavity and connected to the first resonator or a first component to form a short-circuit end, while the other end of the coupling element is suspended inside the second resonant cavity and located on one side of the second resonator to form an open-circuit end. This coupling element forms a signal transmission structure with one end short-circuited and the other open, exhibiting different properties (capacitive or inductive) at different lengths, enabling capacitive or inductive coupling between the first and second resonators. Therefore, by using a coupling element with the same structural form, only different lengths are needed to achieve capacitive or inductive coupling between the first and second resonators, eliminating the need for different structural forms to achieve capacitive and inductive coupling separately. This effectively simplifies the structure, reduces production costs, and reduces the possibility of filter performance being affected by structural elements such as booms and connecting ribs.

[0013] In some embodiments, the resonant frequency of the coupling element is higher than the center frequency of the filter, so that capacitive coupling is achieved between the first resonator and the second resonator; or

[0014] The resonant frequency of the coupling element is lower than the center frequency of the filter, so that the first resonator and the second resonator are inductively coupled.

[0015] In some embodiments, the resonant frequency of the coupler is higher than the center frequency of the filter, so that the first resonator and the second resonator are inductively coupled; or

[0016] The resonant frequency of the coupling element is lower than the center frequency of the filter, so that capacitive coupling is achieved between the first resonator and the second resonator.

[0017] In some embodiments, the electrical length of the coupler is less than one-quarter of the wavelength corresponding to the center frequency of the filter, so that the resonant frequency of the coupler is higher than the center frequency of the filter; or

[0018] The electrical length of the coupler is greater than one-quarter of the wavelength corresponding to the center frequency of the filter, so that the resonant frequency of the coupler is lower than the center frequency of the filter.

[0019] In some embodiments, the short-circuit terminal is detachably connected to the first resonator or the first component.

[0020] In some embodiments, the coupling element includes:

[0021] A first coupling segment, one end of which is the short-circuit end; and

[0022] The second coupling segment is bent and connected to the first coupling segment, and the end of the second coupling segment away from the first coupling segment is located on one side of the second resonator.

[0023] In some embodiments, the first coupling segment is a non-linear structure; and / or, the second coupling segment is a non-linear structure.

[0024] In some embodiments, the first coupling segment includes a plurality of first sub-coupling segments connected end-to-end, with adjacent first sub-coupling segments bent and connected; and / or

[0025] The second coupling segment includes multiple second sub-coupling segments connected end to end in sequence, with adjacent second sub-coupling segments bent and connected.

[0026] In some embodiments, at least two adjacent first sub-coupled segments are detachably connected; and / or, at least two adjacent second sub-coupled segments are detachably connected.

[0027] In some embodiments, the second coupling segment is detachably connected to the first coupling segment.

[0028] In some embodiments, the end of the second coupling segment furthest from the first coupling segment is the open circuit end.

[0029] In some embodiments, the coupling element further includes a third coupling segment, which is bent and connected to the second coupling segment; the end of the third coupling segment away from the second coupling segment is the open circuit end.

[0030] In some embodiments, the third coupling segment is a non-linear structure; and / or, the third coupling segment is detachably connected to the second coupling segment.

[0031] Secondly, embodiments of this application provide a coupling polarity adjustment method applicable to the filters described in any of the above embodiments, the coupling polarity adjustment method comprising:

[0032] Replace the current coupling element to change the capacitive coupling between the first resonator and the second resonator into inductive coupling or vice versa; or

[0033] The length of the coupling element is adjusted so that the coupling between the first resonator and the second resonator changes from capacitive coupling to inductive coupling or from inductive coupling to capacitive coupling.

[0034] The technical solutions described in this application have at least the following technical effects or advantages:

[0035] The coupling polarity adjustment method provided in this application embodiment can change the coupling polarity between the first resonator and the second resonator from capacitive coupling to inductive coupling or vice versa by replacing or adjusting the coupling component of the same structural form. That is, it changes the coupling polarity between the first resonator and the second resonator without having to change different structural forms to achieve capacitive and inductive coupling respectively. This can effectively simplify the structure, reduce production costs, and reduce the possibility that the filter performance will be affected by the setting of structural forms such as fly rods and connecting ribs.

[0036] In some embodiments, replacing the current coupling element includes:

[0037] If the resonant frequency of the current coupler is higher than the center frequency of the filter, then the resonant frequency of the replaced coupler should be lower than the center frequency of the filter; or

[0038] If the resonant frequency of the current coupler is lower than the center frequency of the filter, then the resonant frequency of the replaced coupler is made higher than the center frequency of the filter.

[0039] In some embodiments, adjusting the length of the coupling member includes:

[0040] If the electrical length of the coupling element is less than one-quarter of the wavelength corresponding to the center frequency of the filter, then the electrical length of the coupling element is adjusted to be greater than one-quarter of the wavelength corresponding to the center frequency of the filter; or

[0041] If the electrical length of the coupling element is greater than one-quarter of the wavelength corresponding to the center frequency of the filter, then the electrical length of the coupling element is adjusted to be less than one-quarter of the wavelength corresponding to the center frequency of the filter. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the structure of the first type of filter provided in the embodiments of this application;

[0044] Figure 2 for Figure 1 A schematic diagram of the cross-section of the filter shown;

[0045] Figure 3 This is a schematic diagram of the structure of a second type of filter provided in an embodiment of this application;

[0046] Figure 4 for Figure 3 A schematic diagram of the cross-section of the filter shown;

[0047] Figure 5 A cross-sectional schematic diagram of the third type of filter provided in the embodiments of this application;

[0048] Figure 6 This is a schematic diagram of the structure of the fourth type of filter provided in the embodiments of this application;

[0049] Figure 7 This is a schematic diagram of the structure of the fifth type of filter provided in the embodiments of this application;

[0050] Figure 8 for Figure 7 A schematic diagram of the cross-section of the filter shown;

[0051] Figure 9 This is a schematic diagram of the structure of the sixth type of filter provided in the embodiments of this application;

[0052] Figure 10 for Figure 9 A schematic diagram of the cross-section of the filter shown;

[0053] Figure 11 This is a cross-sectional schematic diagram of the seventh type of filter provided in the embodiments of this application.

[0054] The following are the labeling elements in the figure:

[0055] 100. Filter; 10. First component; 20. Second component; 101. First resonant cavity; 102. Second resonant cavity; 30. First resonator; 40. Second resonator; 50. Coupler; 501. Short-circuit terminal; 502. Open-circuit terminal; 51. First coupling section; 52. Second coupling section; 521. Second sub-coupling section; 53. Third coupling section; 60. Rib; 70. Coupling adjustment structure. Detailed Implementation

[0056] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0058] In the description of the embodiments of this application, the terms "inner", "outer", "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0059] The terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, "first resonator" and "second resonator" are merely used to distinguish different resonators and do not limit their order or number. A first resonator may also be named a second resonator, and a second resonator may also be named a first resonator, without departing from the scope of the various described embodiments. Furthermore, the terms "first," "second," etc., do not imply that the indicated features must be different.

[0060] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the terms "connected," "linked," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. "Multiple" means at least two, that is, two or more; "multiple" means at least two, that is, two or more.

[0061] In this application, "and / or" is merely a way of describing the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0062] It should be noted that in this application, the words "in some embodiments," "exemplarily," and "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described in this application as "in some embodiments," "exemplarily," or "for example" should not be construed as being more preferred or advantageous than other embodiments or design solutions. Specifically, the use of words such as "in some embodiments," "exemplarily," and "for example" is intended to present related concepts in a specific manner, meaning that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of this application. The appearance of the above words in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0063] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments.

[0064] As a frequency selective device, filters are widely used in the field of communications to select communication signals and filter out noise or interference signals outside the communication signal frequency. In other words, they allow useful signals to pass through with minimal attenuation while attenuating unwanted signals to the greatest extent possible. Filters typically contain multiple resonators. Adjacent resonators generally require capacitive or inductive coupling. For capacitive coupling, a flybar is usually placed between the two resonators, and the flybar needs to be fixed to the cavity's ribs using an insulating bracket. For inductive coupling, a coupling window or connecting rib is usually placed between the two resonators. The connecting rib is typically protruding from the inner bottom wall of the cavity and integrally formed with the cavity.

[0065] Therefore, in order to achieve capacitive or inductive coupling, different structural forms need to be set between the two resonators (i.e., setting a flying rod structure, or setting a coupling window or connecting rib structure), which makes the structure more complex and affects the performance of the filter.

[0066] Based on this, in order to improve the technical problem of needing to set different structural forms between two resonators to achieve capacitive coupling or inductive coupling, the inventors proposed the following solution.

[0067] Please see Figures 1 to 4 This application provides a filter 100, which includes a first component 10, a second component 20, a first resonator 30, a second resonator 40, and a coupling element 50, wherein:

[0068] The second component 20 engages with the first component 10 to form a connected first resonant cavity 101 and a second resonant cavity 102 between the second component 20 and the first component 10. It can be understood that the first component 10 and the second component 20 are structural components capable of cooperating to form a closed resonant cavity. For example, the first component 10 can be a cavity body and the second component 20 a cover plate, or the first component 10 can be a cover plate and the second component 20 a cavity body, with the cover plate covering the opening of the cavity body to form the resonant cavity. Alternatively, both the first component 10 and the second component 20 can be cavities, with the openings of the two cavities engaging to form the resonant cavity.

[0069] The first resonator 30 is located within the first resonant cavity 101 and is disposed on the first component 10. It is understood that the first resonator 30 can be various types of resonators, such as a metal coaxial resonator, a ceramic dielectric resonator, a metal coaxial resonator loaded with a ceramic dielectric, a sheet stripline resonator, a resonator loaded with a ceramic dielectric and a sheet stripline, etc., but is not limited to these. Figure 1 The example shown is a case where the first resonator 30 is a metal coaxial resonator.

[0070] The second resonator 40 is located within the second resonant cavity 102 and is disposed on the first component 10 or the second component 20. It is understood that the second resonator 40 can be a variety of types of resonators, such as a metal coaxial resonator, a ceramic dielectric resonator, a metal coaxial resonator loaded with a ceramic dielectric, a sheet stripline resonator, a resonator loaded with a ceramic dielectric and a sheet stripline, etc., but is not limited to these. Figure 1 The example shown illustrates the case where the second resonator 40 is a metal coaxial resonator. The structure of the second resonator 40 may be the same as or different from the structure of the first resonator 30.

[0071] The coupling element 50 is located between the first resonator 30 and the second resonator 40. One end of the coupling element 50 is located inside the first resonant cavity 101 and connected to the first resonator 30 or the first component 10 to form a short-circuit terminal 501; the other end of the coupling element 50 is suspended inside the second resonant cavity 102 and located on one side of the second resonator 40 to form an open-circuit terminal 502. The coupling element 50 is used to enable capacitive or inductive coupling between the first resonator 30 and the second resonator 40.

[0072] It can be understood that the coupling element 50 refers to a structural component that can influence the coupling polarity between the first resonator 30 and the second resonator 40. Specifically, the coupling polarity between the first resonator 30 and the second resonator 40 during capacitive coupling is opposite to that during inductive coupling; capacitive coupling, also known as electric coupling or electric field coupling, can be considered negative coupling; inductive coupling, also known as magnetic coupling or magnetic field coupling, can be considered positive coupling. The coupling element 50 can be a structural component of various regular or irregular shapes, and can be a linear or non-linear structure, a line structure, or a sheet structure. The coupling element 50 can be made entirely of metallic materials, or it can be formed by depositing metallic materials on the surface of insulating materials (e.g., electroplating, spraying, or attaching metal to the surface of insulating materials). The short-circuit end 501 of the coupling element 50 can be connected to the first resonator 30 or the first component 10 in various ways, intended to be short-circuited to the first resonator 30; the open-circuit end 502 of the coupling element 50, suspended in the second resonant cavity 102, means that the open-circuit end 502 does not contact any other components.

[0073] As can be seen from the above, the filter 100 provided in this application embodiment, by providing a coupling member 50 between the first resonator 30 and the second resonator 40, with one end of the coupling member 50 located in the first resonant cavity 101 and connected to the first resonator 30 or the first component 10 to form a short-circuit end 501, and the other end of the coupling member 50 suspended in the second resonant cavity 102 and located on one side of the second resonator 40 to form an open-circuit end 502; the coupling member 50 can form a signal transmission structure with one end short-circuited and the other end open, and has the characteristic of exhibiting different properties (capacitive or inductive) at different lengths, enabling capacitive or inductive coupling between the first resonator 30 and the second resonator 40; specifically, the coupling member 50 can generate resonance near the center frequency of the filter 100, and the resonant frequency of the coupling member 50 affects the coupling polarity between the first resonator 30 and the second resonator 40. By changing the length of the coupling member 50, its resonant frequency can be changed, thereby changing the coupling polarity between the first resonator 30 and the second resonator 40. Therefore, by setting the coupling element 50 with the same structural form, capacitive or inductive coupling between the first resonator 30 and the second resonator 40 can be achieved simply by setting different lengths, without the need to set different structural forms to achieve capacitive and inductive coupling respectively. This effectively simplifies the structure (while the existing technology uses a structure with a flying rod and insulating bracket, which involves many types of materials and has low assembly efficiency), reduces production costs, and reduces the possibility that the setting of flying rods and connecting ribs will affect the performance of the filter 100. At the same time, since the coupling polarity between the first resonator 30 and the second resonator 40 can be changed by setting the coupling element 50 with different lengths, the position of the transmission zero point generated when the first resonator 30 and the second resonator 40 are cross-coupled can be adjusted (in addition to the first resonator 30 and the second resonator 40, there can also be other resonant cavities and resonators to facilitate cross-coupling between at least three resonant cavities), making the position of the transmission zero point controllable and effectively improving the out-of-band rejection performance of the filter 100.

[0074] Furthermore, existing technologies employ a flybar structure for capacitive coupling, where the coupling strength depends heavily on the flybar's dimensions and the distance between it and the resonator, exhibiting high sensitivity. This necessitates high precision in the flybar's manufacturing process, otherwise, filter performance will be affected. In contrast, the coupling element 50 provided in this embodiment, with one end being a short-circuit terminal 501 and the other an open-circuit terminal 502, results in a coupling strength that is less sensitive to its size, exhibiting better tolerance and requiring lower manufacturing precision. This reduces production costs and improves reliability. Moreover, existing technologies use connecting ribs for inductive coupling, which are integrally formed with the filter cavity. This not only occupies a large volume, increasing the filter's weight, but also negatively impacts the filter's frequency, temperature drift, and power performance. The coupling element 50 provided in this embodiment, however, does not require integral forming with the filter cavity, reducing volume and weight, facilitating filter miniaturization and weight reduction, and minimizing the impact on the filter's frequency and other performance characteristics, resulting in high reliability.

[0075] It should be noted that the coupler 50 can resonate near the center frequency of the filter 100 (the resonant frequency of the coupler 50 is within the passband of the filter 100). The coupler 50 itself acts as a resonator. Therefore, the signal from the first resonator 30 is transmitted to the second resonator 40 after passing through the coupler 50, and the phase of the signal changes by 90° when passing through the coupler 50 (for example, the phase changes by +90° when the resonant frequency of the coupler 50 is higher than the center frequency of the filter 100, and the phase changes by -90° when the resonant frequency of the coupler 50 is lower than the center frequency of the filter 100). Specifically, the signal undergoes a 90° phase change when it is transmitted from the first resonator 30 to the coupler 50, a 90° phase change when it passes through the coupler 50, and a 90° phase change when it is transmitted from the coupler 50 to the second resonator 40. Therefore, at least three phase changes occur, and the final inductive or capacitive coupling is the property formed by the first resonator 30, the coupler 50, and the second resonator 40 as a whole. In contrast, existing coupling devices only serve to couple two resonators and do not function as resonators themselves. Therefore, when a signal propagates between the two resonators, only a single 90° phase change occurs. Consequently, existing coupling devices are typically used for cross-coupling between resonators in two non-cascaded resonant cavities. However, the coupling device 50 provided in this embodiment functions as a resonator itself, making it suitable not only for cross-coupling between resonators in two non-cascaded resonant cavities but also for coupling between resonators in two cascaded resonant cavities.

[0076] In some embodiments, the resonant frequency of the coupler 50 is higher than the center frequency of the filter 100, so that the first resonator 30 and the second resonator 40 are capacitively coupled. Alternatively, the resonant frequency of the coupler 50 is lower than the center frequency of the filter 100, so that the first resonator 30 and the second resonator 40 are inductively coupled.

[0077] It can be understood that the resonant frequency of the coupler 50 refers to the frequency at which the coupler 50 resonates within the filter 100. The center frequency of the filter 100 refers to the center frequency of the passband of the filter 100. Both the resonant frequency of the coupler 50 and the center frequency of the filter 100 can be obtained by measurement and analysis using equipment such as a network analyzer.

[0078] With this configuration, capacitive or inductive coupling can be performed between the first resonator 30 and the second resonator 40 as needed, and the coupling element 50 is correspondingly configured to make its resonant frequency higher or lower than the center frequency.

[0079] For example, please refer to Figure 1 and Figure 2 The first component 10 is a cavity, and the first resonator 30 and the second resonator 40 are both disposed on the inner bottom wall of the first component 10. The short-circuit terminal 501 is connected to the inner bottom wall of the first component 10. The resonant frequency of the coupling element 50 is higher than the center frequency of the filter 100, so that the first resonator 30 and the second resonator 40 are capacitively coupled.

[0080] Through the Figure 1 The filter was measured, and the intrinsic mode resonant frequency of the first resonator 30 was found to be 3.51738 GHz, the intrinsic mode resonant frequency of the second resonator 40 was found to be 3.45642 GHz, and the resonant frequency of the coupler 50 was found to be 5.63135 GHz. Therefore, the resonant frequency of the coupler 50 is higher than the resonant frequency of the first resonator 30 and the resonant frequency of the second resonator 40, so that the first resonator 30 and the second resonator 40 are capacitively coupled.

[0081] For example, please refer to Figure 3 and Figure 4 The first component 10 is a cavity, and the first resonator 30 and the second resonator 40 are both disposed on the inner bottom wall of the first component 10. The short-circuit terminal 501 is connected to the inner bottom wall of the first component 10. The resonant frequency of the coupling element 50 is lower than the center frequency of the filter 100, so that the first resonator 30 and the second resonator 40 are inductively coupled.

[0082] Through the Figure 3The filter was measured, and the intrinsic mode resonant frequency of the first resonator 30 was found to be 3.8138 GHz, the intrinsic mode resonant frequency of the second resonator 40 was found to be 3.52488 GHz, and the resonant frequency of the coupler 50 was found to be 3.17115 GHz. Therefore, the resonant frequency of the coupler 50 is lower than the resonant frequency of the first resonator 30 and the resonant frequency of the second resonator 40, so that the first resonator 30 and the second resonator 40 are inductively coupled.

[0083] It should be noted that when the resonant frequency of the coupler 50 is higher than the center frequency of the filter 100, the first resonator 30 and the second resonator 40 are not necessarily capacitively coupled; similarly, when the resonant frequency of the coupler 50 is lower than the center frequency of the filter 100, the first resonator 30 and the second resonator 40 are not necessarily inductively coupled. The main function of the coupler 50 is that, under the condition that other factors remain unchanged, by changing the resonant frequency of the coupler 50 (even if its resonant frequency is higher or lower than the center frequency of the filter 100), the coupling polarity between the first resonator 30 and the second resonator 40 can be changed (i.e., from capacitive coupling to inductive coupling or from inductive coupling to capacitive coupling).

[0084] In other embodiments, the resonant frequency of the coupler 50 is higher than the center frequency of the filter 100, so that the first resonator 30 and the second resonator 40 are inductively coupled. Alternatively, the resonant frequency of the coupler 50 is lower than the center frequency of the filter 100, so that the first resonator 30 and the second resonator 40 are capacitively coupled.

[0085] With this configuration, the first resonator 30 and the second resonator 40 can be inductively or capacitively coupled as needed, and the coupling element 50 is correspondingly configured so that its resonant frequency is higher or lower than the center frequency.

[0086] For example, please refer to Figure 5 The first component 10 is a cavity, the second component 20 is a cover plate, the first resonator 30 is disposed on the inner bottom wall of the first component 10, and the second resonator 40 is disposed on the second component 20; the short-circuit terminal 501 is connected to the inner bottom wall of the first component 10. The resonant frequency of the coupling element 50 is higher than the center frequency of the filter 100, so that the first resonator 30 and the second resonator 40 are inductively coupled. Figure 5 The filter shown is Figure 2 The main difference of the filter 100 shown is that the position of the second resonator 40 is changed, which reverses the coupling polarity between the first resonator 30 and the second resonator 40.

[0087] For example, please refer to Figure 6The first component 10 is a cavity, the second component 20 is a cover plate, the first resonator 30 is disposed on the inner bottom wall of the first component 10, and the second resonator 40 is disposed on the second component 20; the short-circuit terminal 501 is connected to the inner bottom wall of the first component 10. The resonant frequency of the coupling element 50 is lower than the center frequency of the filter 100, so that the first resonator 30 and the second resonator 40 are capacitively coupled. Figure 6 The filter shown is Figure 4 The main difference of the filter 100 shown is that the position of the second resonator 40 is changed, which reverses the coupling polarity between the first resonator 30 and the second resonator 40.

[0088] Optionally, in some embodiments, please refer to Figure 2 and Figure 5 The electrical length of the coupler 50 is less than one-quarter of the wavelength corresponding to the center frequency of the filter 100, so that the resonant frequency of the coupler 50 is higher than the center frequency of the filter 100. Alternatively, please refer to... Figure 4 and Figure 6 The electrical length of the coupling element 50 is greater than one-quarter of the wavelength corresponding to the center frequency, so that the resonant frequency of the coupling element 50 is lower than the center frequency of the filter 100.

[0089] It is understood that the electrical length of the coupler 50 is a definition in the field of communication technology, rather than a physical length. It can be determined through measurement and analysis using equipment such as network analyzers. The concept of electrical length is well-known to those skilled in the art. The electrical length of the coupler 50 reflects the characteristics exhibited by the coupler 50 for a specific frequency signal within a unit physical length. The physical length (i.e., mechanical length or geometric length) of the coupler 50 is positively correlated with its electrical length; that is, the longer the physical length of the coupler 50, the longer its electrical length. The physical length of the coupler 50 can be considered as the length of the path between the short-circuited end 501 and the open-circuited end 502 of the coupler 50.

[0090] With this configuration, by adjusting the physical length of the coupling element 50, the electrical length of the coupling element 50 can be adjusted, thereby adjusting the resonant frequency of the coupling element 50 to be higher or lower than the center frequency of the filter 100, so that capacitive or inductive coupling can be achieved between the first resonator 30 and the second resonator 40.

[0091] In some embodiments, the short-circuit terminal 501 is detachably connected to the first resonator 30 or the first component 10. It is understood that the short-circuit terminal 501 can be connected to the first resonator 30 or the first component 10 by various detachable connection methods, such as threaded connection, plug-in connection, snap-fit ​​connection, fastener (screw, bolt, pin, etc.) connection, adhesive connection, etc., but is not limited thereto.

[0092] This configuration allows the coupling element 50 to be detached from the first resonator 30 or the first component 10, so as to replace different coupling elements 50 or adjust the length of the coupling element 50, thereby changing the resonant frequency of the coupling element 50 and thus changing the coupling polarity between the first resonator 30 and the second resonator 40.

[0093] Optionally, in one possible implementation, the outer surface of the short-circuit end 501 is provided with an external thread, and the first resonator 30 or the first component 10 is provided with a threaded hole. The short-circuit end 501 is threadedly connected to the threaded hole to realize the detachable connection of the coupling member 50.

[0094] Optionally, in one possible implementation, the first resonator 30 or the first component 10 is provided with a plug-in hole, and the short-circuit end 501 is inserted into the plug-in hole to realize the detachable connection of the coupling member 50. The short-circuit end 501 and the plug-in hole can be interference fit or transition fit.

[0095] Optionally, in one possible implementation, the short-circuit end 501 is provided with a locking structure, and the first resonator 30 or the first component 10 is provided with a locking engagement structure. The locking structure engages with the locking engagement structure to achieve a detachable connection of the coupling member 50.

[0096] Alternatively, in one possible implementation, the short-circuit end 501 is connected to the first resonator 30 or the first component 10 by screws or bolts to achieve a detachable connection of the coupling element 50.

[0097] Alternatively, in one possible implementation, the short-circuit end 501 is connected to the first resonator 30 or the first component 10 by removable adhesive to achieve a detachable connection of the coupling member 50.

[0098] It should be noted that in some other embodiments, the short-circuit terminal 501 can also be fixed to the first resonator 30 or the first component 10 by means of welding, riveting or other fixed connections.

[0099] In some embodiments, please refer to Figure 2 , Figure 3 , Figure 7 and Figure 8 The coupling element 50 includes a first coupling segment 51 and a second coupling segment 52. One end of the first coupling segment 51 is a short-circuit end 501. The second coupling segment 52 is bent and connected to the first coupling segment 51. The end of the second coupling segment 52 away from the first coupling segment 51 is located on one side of the second resonator 40.

[0100] It can be understood that both the first coupling segment 51 and the second coupling segment 52 are part of the coupling element 50, and can be various regular or irregular structures. The bending connection between the second coupling segment 52 and the first coupling segment 51 means that the structure formed after the second coupling segment 52 and the first coupling segment 51 are connected is a non-linear structure, that is, not on the same straight line.

[0101] With this configuration, since the coupling element 50 includes a bent first coupling segment 51 and a second coupling segment 52, compared to a straight structure, it is advantageous to increase the physical length of the coupling element 50, thereby increasing the electrical length of the coupling element 50, which is beneficial for adjusting the resonant frequency of the coupling element 50. Moreover, with the same physical length, the bent structure can make better use of the space in the height direction of the filter than the straight structure, which is beneficial for reducing the distance between the first resonator 30 and the second resonator 40.

[0102] Optionally, in some embodiments, please refer to Figure 8 The short-circuit end 501 can be connected to the inner bottom wall of the first component 10, the first coupling section 51 is approximately perpendicular to the inner bottom wall of the first component 10, and the second coupling section 52 is approximately parallel to the inner bottom wall of the first component 10.

[0103] Of course, in some other embodiments, the short-circuit end 501 may be connected to the first resonator 30, the first coupling section 51 may be approximately parallel to the inner bottom wall of the first component 10, and the second coupling section 52 may be approximately perpendicular to the inner bottom wall of the first component 10. In some other embodiments, the first coupling section 51 may be inclined to the inner bottom wall of the first component 10, that is, the angle formed between the first coupling section 51 and the inner bottom wall of the first component 10 may be an acute angle; the second coupling section 52 may be parallel to or inclined to the inner bottom wall of the first component 10.

[0104] Optionally, in some embodiments, please refer to Figure 9 and Figure 10 The second coupling segment 52 is a non-linear structure, that is, a structure of any shape other than a linear structure.

[0105] This configuration, compared to a linear structure, allows for an increase in the physical length of the second coupling segment 52, thereby increasing the electrical length of the coupling element 50, which facilitates the adjustment of the resonant frequency of the coupling element 50.

[0106] Similarly, the first coupling segment 51 can also be a non-linear structure, which can further increase the physical length of the coupling element 50, thereby increasing the electrical length.

[0107] Optionally, please refer to Figure 10 The second coupling segment 52 includes multiple second sub-coupling segments 521 connected end to end, with adjacent second sub-coupling segments 521 bent and connected. Figure 10The example shown is the case where the number of second sub-coupled segments 521 is five.

[0108] It can be understood that the second sub-coupling segment 521 is a part of the second coupling segment 52, and can be a structure of various regular or irregular shapes. Adjacent second sub-coupling segments 521 can form any angle. The shapes of each second sub-coupling segment 521 can be the same or different.

[0109] This configuration allows for a further increase in the physical length of the second coupling segment 52, which in turn increases the electrical length of the coupling element 50, making it easier to adjust the resonant frequency of the coupling element 50.

[0110] Optionally, please refer to Figure 10 A second sub-coupled segment 521 located at the end is connected to the first coupled segment 51.

[0111] Optionally, please refer to Figure 9 and Figure 10 The second sub-coupling segment 521 has a linear structure, which makes the structure more regular and easier to manufacture. Of course, in some other embodiments, the second sub-coupling segment 521 may also be a non-linear structure.

[0112] Optionally, please refer to Figure 10 The two adjacent second sub-coupling segments 521 can be arranged approximately perpendicularly, making the overall shape of the second coupling segment 52 more regular and facilitating manufacturing or assembly. Of course, in some other embodiments, the included angle between two adjacent second sub-coupling segments 521 can also be an acute angle or an obtuse angle.

[0113] Optionally, at least two adjacent second sub-coupling segments 521 are detachably connected; that is, any two adjacent second sub-coupling segments 521 can be detachably connected, or at least two adjacent second sub-coupling segments 521 can be detachably connected, while other adjacent second sub-coupling segments 521 can be fixedly connected.

[0114] It is understood that the two second sub-coupling segments 521 can be connected in various detachable ways, such as threaded connection, plug-in, snap-fit, fastener (screw, bolt, pin, etc.) connection, but not limited to these.

[0115] This configuration allows for increasing the number of second sub-coupling segments 521 to increase the length of the second coupling segment 52, thereby increasing the overall length of the coupling element 50. This makes the electrical length of the coupling element 50 greater than one-quarter of the wavelength corresponding to the center frequency of the filter 100, ensuring that the resonant frequency of the coupling element 50 is lower than the center frequency of the filter 100. Alternatively, the number of second sub-coupling segments 521 can be reduced to shorten the length of the second coupling segment 52, thereby shortening the overall length of the coupling element 50. This makes the electrical length of the coupling element 50 less than one-quarter of the wavelength corresponding to the center frequency of the filter 100, ensuring that the resonant frequency of the coupling element 50 is higher than the center frequency of the filter 100.

[0116] Optionally, in one possible implementation, one end of the second sub-coupling segment 521 is provided with a threaded hole, and the other end is provided with an external thread; in two adjacent second sub-coupling segments 521, one end of the second sub-coupling segment 521 is threadedly connected to the threaded hole of the other second sub-coupling segment 521 through the external thread, so as to realize the detachable connection between the two second sub-coupling segments 521.

[0117] Optionally, in one possible implementation, one end of the second sub-coupling segment 521 is provided with a plug hole, and the other end is provided with a plug portion; in two adjacent second sub-coupling segments 521, the plug portion at one end of one second sub-coupling segment 521 is plugged into the plug hole of the other second sub-coupling segment 521 to realize a detachable connection between the two second sub-coupling segments 521.

[0118] Optionally, in one possible implementation, one end of the second sub-coupling segment 521 is provided with a locking structure, and the other end is provided with a locking engagement structure; in two adjacent second sub-coupling segments 521, the locking structure at one end of one second sub-coupling segment 521 engages with the locking engagement structure of the other second sub-coupling segment 521 to achieve a detachable connection between the two second sub-coupling segments 521.

[0119] Alternatively, in one possible implementation, two adjacent second sub-coupled segments 521 are connected by screws or bolts to achieve a detachable connection between the two second sub-coupled segments 521.

[0120] Alternatively, in one possible implementation, two adjacent second sub-coupled segments 521 are connected by removable adhesive to achieve a detachable connection between the two second sub-coupled segments 521.

[0121] Similarly, the first coupling segment 51 may also include multiple first sub-coupling segments connected end to end, with adjacent first sub-coupling segments bent and connected, which can further increase the physical length of the first coupling segment 51, and thus increase the electrical length of the coupling member 50, so as to facilitate the adjustment of the resonant frequency of the coupling member 50. Optionally, at least two adjacent first sub-coupling segments may be detachably connected, so as to increase or decrease the number of first sub-coupling segments as needed to increase or shorten the length of the first coupling segment, and thus increase or shorten the overall length of the coupling member 50.

[0122] Optionally, in some embodiments, the second coupling segment 52 and the first coupling segment 51 are detachably connected. They can be connected by various detachable connection methods, such as threaded connection, plug-in connection, snap-fit ​​connection, fastener (screw, bolt, pin, etc.) connection, etc., but are not limited to these. Any method of detachable connection between the two second sub-coupling segments 521 in the above embodiments can be adopted, which will not be described in detail here.

[0123] With this configuration, the second coupling segment 52 or the first coupling segment 51 of different lengths or shapes can be replaced as needed to adjust the overall length of the coupling element 50, which is beneficial to make the electrical length of the coupling element 50 greater than or less than one-quarter of the wavelength corresponding to the center frequency of the filter 100.

[0124] Of course, in some other embodiments, the second coupling segment 52 and the first coupling segment 51 may also be fixedly connected.

[0125] Optionally, in some embodiments, please refer to Figure 7 and Figure 8 The end of the second coupling segment 52 that is far from the first coupling segment 51 is an open circuit end 502. The coupling element 50 is composed of two segments, the first coupling segment 51 and the second coupling segment 52. Compared with multiple segments of three or more, the structure is relatively simple and easy to manufacture.

[0126] Alternatively, in some other embodiments, please refer to Figure 3 and Figure 4 The coupling element 50 also includes a third coupling segment 53, which is bent and connected to the second coupling segment 52; the end of the third coupling segment 53 away from the second coupling segment 52 is an open circuit end 502.

[0127] This configuration allows for a further increase in the physical length of the coupling element 50, which in turn increases the electrical length of the coupling element 50, thus facilitating the adjustment of the resonant frequency of the coupling element 50.

[0128] Optionally, the third coupling segment 53 may be substantially perpendicular to the inner bottom wall of the first component 10. Of course, in some other embodiments, it may also be parallel to or inclined to the inner bottom wall of the first component 10.

[0129] Optionally, the third coupling segment 53 can be a non-linear structure to increase the physical length of the third coupling segment 53, thereby further increasing the electrical length of the coupling element 50, so as to adjust the resonant frequency of the coupling element 50.

[0130] Of course, in some other embodiments, the third coupling segment 53 may also be a linear structure.

[0131] Optionally, the third coupling segment 53 and the second coupling segment 52 are detachably connected. They can be connected in various detachable ways, such as threaded connection, plug-in connection, snap-fit ​​connection, fastener (screw, bolt, pin, etc.) connection, etc., but are not limited to these. They can be connected in any way that is detachably connected to the two second sub-coupling segments 521 in the above embodiment, which will not be described in detail here.

[0132] With this configuration, the third coupling segment 53 of different lengths or shapes can be replaced as needed to adjust the overall length of the coupling element 50, which is beneficial to make the electrical length of the coupling element 50 greater than or less than one-quarter of the wavelength corresponding to the center frequency of the filter 100.

[0133] In some embodiments, please refer to Figure 11 A rib 60 is provided between the first resonant cavity 101 and the second resonant cavity 102, and the coupling member 50 spans the rib 60. The rib 60 is provided to facilitate the adjustment of the coupling strength between the first resonator 30 and the second resonator 40.

[0134] In some embodiments, please refer to Figure 11 The filter 100 also includes a coupling adjustment structure 70, which is disposed on the first component 10 or the second component 20 and located between the first resonator 30 and the second resonator 40, for adjusting the coupling strength between the first resonator 30 and the second resonator 40.

[0135] It is understood that the coupling adjustment structure 70 can be a structure of various structural forms used to adjust the coupling strength, such as a coupling screw, a coupling plate, etc., but is not limited to these.

[0136] This application embodiment also provides a coupling polarity adjustment method, applicable to the filter 100 of any of the above embodiments, the coupling polarity adjustment method includes:

[0137] Replace the current coupling element 50 to change the capacitive coupling between the first resonator 30 and the second resonator 40 to either inductive coupling or capacitive coupling.

[0138] Adjust the length of the coupling element 50 so that the coupling between the first resonator 30 and the second resonator 40 changes from capacitive coupling to inductive coupling or from inductive coupling to capacitive coupling.

[0139] It can be understood that replacing the current coupling element 50 means replacing the current coupling element 50 with another coupling element 50, so that the coupling polarity between the first resonator 30 and the second resonator 40 is reversed compared to the previous coupling polarity, that is, changing from capacitive coupling to inductive coupling or from inductive coupling to capacitive coupling. Adjusting the length of the coupling element 50 means adjusting it based on the current coupling element 50, to decrease or increase the length of the coupling element 50, so that the coupling polarity between the first resonator 30 and the second resonator 40 is reversed compared to the previous coupling polarity, that is, changing from capacitive coupling to inductive coupling or from inductive coupling to capacitive coupling.

[0140] The coupling polarity adjustment method provided in this application embodiment can change the coupling polarity between the first resonator 30 and the second resonator 40 from capacitive coupling to inductive coupling or vice versa by replacing or adjusting the coupling element 50 of the same structural form. This means changing the coupling polarity between the first resonator 30 and the second resonator 40 without needing to change different structural forms to achieve capacitive and inductive coupling separately. This effectively simplifies the structure, reduces production costs, and reduces the possibility of the filter 100's performance being affected by the configuration of structural forms such as fly rods and connecting ribs. Furthermore, since the coupling polarity between the first resonator 30 and the second resonator 40 can be changed by replacing or adjusting the coupling element 50, the position of the transmission zero point generated when the first resonator 30 and the second resonator 40 are cross-coupled can be adjusted (in addition to the first resonator 30 and the second resonator 40, other resonant cavities and resonators can be included to facilitate cross-coupling between at least three resonant cavities). This makes the position of the transmission zero point controllable and effectively improves the out-of-band rejection performance of the filter 100.

[0141] In some embodiments, replacing the current coupling element 50 includes:

[0142] If the resonant frequency of the current coupler 50 is higher than the center frequency of the filter 100, then the resonant frequency of the replaced coupler 50 will be lower than the center frequency of the filter 100. Alternatively,

[0143] If the resonant frequency of the current coupler 50 is lower than the center frequency of the filter 100, then the resonant frequency of the replaced coupler 50 is made higher than the center frequency of the filter 100.

[0144] With this configuration, by changing the resonant frequency of the current coupler 50, the coupling polarity between the first resonator 30 and the second resonator 40 can be reversed.

[0145] Optionally, in some embodiments, if the resonant frequency of the current coupler 50 is higher than the center frequency of the filter 100, it means that the electrical length of the current coupler 50 is less than one-quarter of the wavelength corresponding to the center frequency of the filter 100. By making the electrical length of the replaced coupler 50 greater than one-quarter of the wavelength corresponding to the center frequency of the filter 100, the resonant frequency of the coupler 50 can be lower than the center frequency of the filter 100, thereby reversing the coupling polarity between the first resonator 30 and the second resonator 40.

[0146] Optionally, in some embodiments, if the resonant frequency of the current coupler 50 is lower than the center frequency of the filter 100, it means that the electrical length of the current coupler 50 is greater than one-quarter of the wavelength corresponding to the center frequency of the filter 100. By making the electrical length of the replaced coupler 50 less than one-quarter of the wavelength corresponding to the center frequency of the filter 100, the resonant frequency of the coupler 50 can be made higher than the center frequency of the filter 100, thereby reversing the coupling polarity between the first resonator 30 and the second resonator 40.

[0147] In some embodiments, adjusting the length of the coupling member 50 includes:

[0148] If the electrical length of the coupling element 50 is less than one-quarter of the wavelength corresponding to the center frequency of the filter 100, then adjust the electrical length of the coupling element 50 to be greater than one-quarter of the wavelength corresponding to the center frequency of the filter 100. Or,

[0149] If the electrical length of the coupling element 50 is greater than one-quarter of the wavelength corresponding to the center frequency of the filter 100, then the electrical length of the coupling element 50 is adjusted to be less than one-quarter of the wavelength corresponding to the center frequency of the filter 100.

[0150] With this configuration, by adjusting the electrical length of the coupling element 50 (the electrical length of the coupling element 50 is positively correlated with its physical length, and the electrical length of the coupling element 50 can be adjusted by adjusting its physical length), the coupling polarity between the first resonator 30 and the second resonator 40 can be reversed.

[0151] Optionally, in some embodiments, the length of the second coupling segment 52 can be adjusted by increasing or decreasing the number of the second sub-coupling segments 521, thereby adjusting the overall length of the coupling member 50. This is to make the electrical length of the coupling member 50 greater than or less than one-quarter of the wavelength corresponding to the center frequency of the filter 100, so that the resonant frequency of the coupling member 50 is lower than or higher than the center frequency of the filter 100, thereby reversing the coupling polarity between the first resonator 30 and the second resonator 40.

[0152] Optionally, in some embodiments, the length of the first coupling segment can be adjusted by increasing or decreasing the number of the first sub-coupling segments, thereby adjusting the overall length of the coupling member 50. This is to make the electrical length of the coupling member 50 greater than or less than one-quarter of the wavelength corresponding to the center frequency of the filter 100, so that the resonant frequency of the coupling member 50 is lower than or higher than the center frequency of the filter 100, thereby reversing the coupling polarity between the first resonator 30 and the second resonator 40.

[0153] Optionally, in some embodiments, the overall length of the coupling member 50 can be adjusted by disassembling the second coupling segment 52 and the first coupling segment 51, and replacing the second coupling segment 52 or the first coupling segment 51 with different lengths or shapes as needed. This is to make the electrical length of the coupling member 50 greater than or less than one-quarter of the wavelength corresponding to the center frequency of the filter 100, so that the resonant frequency of the coupling member 50 is lower than or higher than the center frequency of the filter 100, thereby reversing the coupling polarity between the first resonator 30 and the second resonator 40.

[0154] Optionally, in some embodiments, the overall length of the coupling member 50 can be adjusted by removing or adding the third coupling segment 53, or by replacing the third coupling segment 53 with one of different lengths as needed, so that the electrical length of the coupling member 50 is greater than or less than one-quarter of the wavelength corresponding to the center frequency of the filter 100, so that the resonant frequency of the coupling member 50 is lower than or higher than the center frequency of the filter 100, thereby reversing the coupling polarity between the first resonator 30 and the second resonator 40.

[0155] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A filter, characterized in that, The filter includes: First component; The second component is engaged with the first component to form a first resonant cavity and a second resonant cavity that are connected between the second component and the first component; The first resonator is located inside the first resonant cavity and is disposed on the first component; A second resonator, located within the second resonant cavity, and disposed on the first component or the second component; and A coupling element is located between the first resonator and the second resonator, and the resonant frequency of the coupling element is within the passband of the filter. One end of the coupling element is located in the first resonant cavity and connected to the first resonator or the first component to form a short-circuit terminal, and the other end of the coupling element is suspended in the second resonant cavity and located on one side of the second resonator to form an open-circuit terminal. The coupling element is used to enable capacitive or inductive coupling between the first resonator and the second resonator. The coupling element includes a first coupling segment and a second coupling segment, one end of the first coupling segment being the short-circuit end; the second coupling segment is bent and connected to the first coupling segment, and the end of the second coupling segment away from the first coupling segment is located on one side of the second resonator. The first coupling segment includes multiple first sub-coupling segments connected end-to-end, adjacent first sub-coupling segments are bent and connected, and at least two adjacent first sub-coupling segments are detachably connected; and / or The second coupling segment includes multiple second sub-coupling segments connected end to end in sequence, with adjacent second sub-coupling segments bent and connected, and at least two adjacent second sub-coupling segments being detachably connected.

2. The filter according to claim 1, characterized in that, The resonant frequency of the coupling element is higher than the center frequency of the filter, so that capacitive coupling is achieved between the first resonator and the second resonator; or The resonant frequency of the coupling element is lower than the center frequency of the filter, so that the first resonator and the second resonator are inductively coupled.

3. The filter according to claim 1, characterized in that, The resonant frequency of the coupling element is higher than the center frequency of the filter, so that inductive coupling is achieved between the first resonator and the second resonator; or The resonant frequency of the coupling element is lower than the center frequency of the filter, so that capacitive coupling is achieved between the first resonator and the second resonator.

4. The filter according to claim 2 or 3, characterized in that, The electrical length of the coupler is less than one-quarter of the wavelength corresponding to the center frequency of the filter, so that the resonant frequency of the coupler is higher than the center frequency of the filter; or The electrical length of the coupler is greater than one-quarter of the wavelength corresponding to the center frequency of the filter, so that the resonant frequency of the coupler is lower than the center frequency of the filter.

5. The filter according to any one of claims 1 to 3, characterized in that, The short-circuit terminal is detachably connected to the first resonator or the first component.

6. The filter according to claim 1, characterized in that, The second coupling segment is detachably connected to the first coupling segment; and / or The end of the second coupling segment furthest from the first coupling segment is the open circuit end.

7. The filter according to claim 1, characterized in that, The coupling element further includes a third coupling segment, which is bent and connected to the second coupling segment; the end of the third coupling segment away from the second coupling segment is the open circuit end.

8. A method for adjusting coupling polarity, characterized in that, The coupling polarity adjustment method, applicable to any one of claims 1 to 7, comprises: The length of the coupling element is adjusted so that the coupling between the first resonator and the second resonator changes from capacitive coupling to inductive coupling or from inductive coupling to capacitive coupling.

9. The coupling polarity adjustment method according to claim 8, characterized in that, Adjusting the length of the coupling element includes: If the electrical length of the coupling element is less than one-quarter of the wavelength corresponding to the center frequency of the filter, then the electrical length of the coupling element is adjusted to be greater than one-quarter of the wavelength corresponding to the center frequency of the filter; or If the electrical length of the coupling element is greater than one-quarter of the wavelength corresponding to the center frequency of the filter, then the electrical length of the coupling element is adjusted to be less than one-quarter of the wavelength corresponding to the center frequency of the filter.

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