A coaxial band-stop filter structure and a filtering method

Abstract

The application discloses a coaxial band-stop filtering structure and a filtering method. The filtering structure comprises a coaxial transmission main body and a branch resonant unit. The coaxial transmission main body comprises an outer conductor and an inner conductor. The outer conductor is in a tubular shape and internally provided with a cavity. The inner conductor is arranged in the cavity. A dielectric region is formed between the inner conductor and the outer conductor. The branch resonant unit is a metal piece and is arranged in the dielectric region. The connection mode of the branch resonant unit and the coaxial transmission main body comprises a first connection mode, a second connection mode and a third connection mode. The branch resonant unit is directly integrated in the coaxial transmission main body, so that the filtering structure is more compact. Moreover, different connection modes can be selected for the branch resonant unit according to different target frequencies, so that the adjustment flexibility of the filtering structure is improved.

Description

Technical Field

[0001] This invention relates to the field of radio frequency transmission and filtering technology, and in particular to a coaxial band-stop filter structure and filtering method. Background Technology

[0002] Coaxial transmission structures offer excellent shielding performance, impedance controllability, and wideband transmission capabilities, making them widely used in applications such as RF interconnects, antenna feeding, module adapters, and vertical interconnects of multilayer circuit boards. In practical RF systems, it is often necessary to suppress interference noise, spurious signals, harmonics, or other unwanted signals at specific frequencies; therefore, band-stop filters are crucial functional units in RF links. Traditional band-stop filters are typically implemented using microstrip stubs, open-circuit or short-circuit resonators, lumped LC networks, cavity structures, or off-chip filters.

[0003] However, the aforementioned traditional solutions typically require additional board space, structural space, or packaging space; at the same time, the connection between the external filter and the main link may introduce insertion loss and impedance discontinuities, and increase assembly complexity. Especially for phased array terminals, satellite communication terminals, and high-density RF modules, where system space is limited, traditional external filter structures struggle to balance miniaturization and filtering performance.

[0004] Therefore, it is necessary to propose a band-stop filtering scheme and design method that can be embedded in the coaxial transmission structure itself, so that the coaxial transmission structure can perform the RF interconnection function while also having the target frequency band-stop filtering function, thereby reducing the space occupied by external filters and improving the integration of RF systems. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, this application proposes a coaxial band-stop filter structure that can form a frequency-selective impedance loading in the coaxial transmission body, and realize single-frequency or multi-frequency band-stop filtering without occupying additional external wiring space.

[0006] This application also proposes a filtering method based on the above-mentioned coaxial bandstop filter structure.

[0007] The coaxial bandstop filter structure according to the first aspect of this application includes: A coaxial transmission body includes an outer conductor and an inner conductor. The outer conductor is tubular and has a cavity inside. The inner conductor is disposed in the cavity. The inner conductor and the outer conductor are coaxially arranged, and a dielectric region is formed between the inner conductor and the outer conductor. A stub resonant unit, which is a metal component, is disposed in the dielectric region; The connection methods between the stub resonant unit and the coaxial transmission body include a first connection method, a second connection method, and a third connection method; In the first connection method, one end of the stub resonant unit is connected to the outer conductor, and the other end of the stub resonant unit is a free end; In the second connection method, one end of the stub resonant unit is connected to the inner conductor, and the other end of the stub resonant unit is a free end; In the third connection method, one end of the stub resonant unit is connected to the outer conductor, and the other end of the stub resonant unit is connected to the inner conductor.

[0008] The coaxial band-stop filter structure according to the embodiments of this application has at least the following advantages: the stub resonant unit is directly integrated inside the coaxial transmission body, thereby making the filter structure more compact; and different connection methods can be selected for the stub resonant unit according to different target frequencies, thereby improving the adjustment flexibility of the filter structure.

[0009] According to some embodiments of this application, the stub resonant unit is in the form of a ring or a spiral, and the stub resonant unit is arranged around the inner conductor.

[0010] According to some embodiments of this application, the central axis of the stub resonant unit is coaxial with the outer conductor and the inner conductor.

[0011] According to some embodiments of this application, the end of the stub resonant unit is detachably connected to the outer conductor and / or the inner conductor.

[0012] According to some embodiments of this application, the stub resonant unit is further provided with a capacitor loading structure, which is a plate-like structure and has a rectangular, fan-shaped, circular, or trapezoidal shape.

[0013] According to some embodiments of this application, the electrical length of the stub resonant unit is an integer multiple of one-quarter of the waveguide wavelength corresponding to the target frequency.

[0014] According to some embodiments of this application, an impedance transformation section is provided at the connection between the stub resonant unit and the coaxial transmission body. The impedance transformation section is a linewidth gradient section, a stepped impedance section, a local adjustment section, a local narrowing section, or a transmission line segment with a preset length.

[0015] According to some embodiments of this application, the number of stub resonant units is at least two, and each of the stub resonant units is arranged along the axial direction of the medium region.

[0016] According to some embodiments of this application, each of the stub resonant units is connected to the coaxial transmission body using any of the connection methods described.

[0017] The filtering method according to the second aspect of this application, which is based on the above-described coaxial band-stop filter structure, includes the following steps: Determine the target frequency; The shape and size of the inner conductor and the outer conductor are determined, and the dielectric region is also determined. Determine the initial electrical length of the stub resonant unit; Determine the arrangement position of the stub resonant unit; Select the connection method between the stub resonant unit and the coaxial transmission body; Configure the structural form of the stub resonant unit; Adjust the structural parameters of the stub resonant unit; Perform electromagnetic simulation or testing; Determine whether the current coaxial band-stop filter structure meets the requirements; if yes, output the final structure and perform filtering; if not, perform iterative correction.

[0018] The filtering method according to the embodiments of this application has at least the following beneficial effects: by adjusting the structure, parameters and connection method of the stub resonant unit and conducting corresponding simulation tests, the target frequency can be filtered accurately, thereby improving the filtering accuracy.

[0019] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0020] The accompanying drawings are used to provide a further understanding of the technical solutions disclosed in this application and form part of the specification. They are used together with the embodiments disclosed in this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions disclosed in this application.

[0021] Figure 1 This is a schematic diagram of the first connection method in the coaxial band-stop filter structure according to the first aspect embodiment of this application; Figure 2 This is a top view of the first connection method in the coaxial band-stop filter structure according to the first aspect embodiment of this application; Figure 3 The above are the S-parameter simulation results of the first connection method in the coaxial band-stop filter structure according to the first aspect of this application. Figure 4 This is a schematic diagram of the second connection method in the coaxial band-stop filter structure of the first aspect embodiment of this application; Figure 5 This is a top view of the second connection method in the coaxial band-stop filter structure according to the first aspect embodiment of this application; Figure 6The above are the S-parameter simulation results of the second connection method in the coaxial band-stop filter structure of the first aspect embodiment of this application; Figure 7 This is a schematic diagram of the third connection method in the coaxial band-stop filter structure of the first aspect embodiment of this application; Figure 8 This is a top view of the third connection method in the coaxial band-stop filter structure according to the first aspect embodiment of this application; Figure 9 The above are the S-parameter simulation results of the third connection method in the coaxial band-stop filter structure of the first aspect embodiment of this application; Figure 10 This is a schematic diagram of the structure of the coaxial bandstop filter structure in the first aspect embodiment of this application when multiple stub resonant units are provided; Figure 11 The above are the S-parameter simulation results of the coaxial bandstop filter structure with multiple stub resonant units in the first aspect embodiment of this application. Figure 12 This is a flowchart of a filtering method according to a second aspect embodiment of this application.

[0022] Reference numerals: 100-coaxial transmission body, 110-outer conductor, 120-inner conductor, 130-dielectric region, 200-stub resonant unit, 210-capacitor loading structure. Detailed Implementation

[0023] 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 are only used to explain this application, and should not be construed as limiting this application.

[0024] In the description of this application, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying 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.

[0025] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0026] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0027] In the description of this application, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0028] Coaxial transmission structures offer excellent shielding performance, impedance controllability, and wideband transmission capabilities, making them widely used in applications such as RF interconnects, antenna feeding, module adapters, and vertical interconnects of multilayer circuit boards. In practical RF systems, it is often necessary to suppress interference noise, spurious signals, harmonics, or other unwanted signals at specific frequencies; therefore, band-stop filters are crucial functional units in RF links. Traditional band-stop filters are typically implemented using microstrip stubs, open-circuit or short-circuit resonators, lumped LC networks, cavity structures, or off-chip filters.

[0029] However, the aforementioned traditional solutions typically require additional board space, structural space, or packaging space; at the same time, the connection between the external filter and the main link may introduce insertion loss and impedance discontinuities, and increase assembly complexity. Especially for phased array terminals, satellite communication terminals, and high-density RF modules, where system space is limited, traditional external filter structures struggle to balance miniaturization and filtering performance.

[0030] Therefore, it is necessary to propose a band-stop filtering scheme and design method that can be embedded in the coaxial transmission structure itself, so that the coaxial transmission structure can perform the RF interconnection function while also having the target frequency band-stop filtering function, thereby reducing the space occupied by external filters and improving the integration of RF systems.

[0031] In response, this application proposes a coaxial band-stop filter structure in which the stub resonant unit is directly integrated inside the coaxial transmission body, making the filter structure more compact. Moreover, different connection methods can be selected for the stub resonant unit according to different target frequencies, thereby improving the adjustment flexibility of the filter structure.

[0032] In addition, this application also proposes a filtering method based on the above-mentioned coaxial band-stop filter structure. By adjusting the structure, parameters and connection method of the stub resonant unit and conducting corresponding simulation tests, the target frequency can be accurately filtered, thereby improving the filtering accuracy.

[0033] Reference Figure 1 The coaxial band-stop filter structure in the first aspect embodiment of this application includes a coaxial transmission body 100 and a stub resonant unit 200. The coaxial transmission body 100 is the main structure of the coaxial band-stop filter structure and is used to transmit radio frequency signals; the stub resonant unit 200 is used to filter the signals transmitted in the coaxial transmission body 100.

[0034] Specifically, the coaxial transmission body 100 includes an outer conductor 110 and an inner conductor 120. The outer conductor 110 serves as a grounding or shielding structure, is tubular in shape, and has an internal cavity. The inner conductor 120 is disposed within the cavity. The inner conductor 120 and the outer conductor 110 are coaxially arranged, and a dielectric region 130 is formed between the inner conductor 120 and the outer conductor 110. The dielectric region 130 serves as the main signal transmission path.

[0035] The stub resonant unit 200 is a metal component disposed in the dielectric region 130 to filter the signal in the main signal transmission path. Specifically, the stub resonant unit 200 obtains excitation from the main signal transmission path through electric field coupling. When the signal frequency reaches the target resonant frequency of the stub resonant unit 200, a significant resonance is formed within the stub resonant unit 200, creating a frequency-selective impedance disturbance on the main signal transmission path. This reduces the input impedance of the coaxial transmission body 100 at that frequency, decreasing its transmission capability, thus achieving a band-stop filtering effect.

[0036] The connection methods between the stub resonant unit 200 and the coaxial transmission body 100 include a first connection method, a second connection method, and a third connection method. Different connection methods can produce different filtering effects, so users can choose the appropriate connection method according to their actual filtering needs.

[0037] Reference Figure 1 and Figure 2 In the first connection method, one end of the stub resonant unit 200 is connected to the outer conductor 110, and the other end of the stub resonant unit 200 is a free end. (Refer to...) Figure 3 Simulation results show that, with this connection method, the main signal forms a stopband between 13.87 GHz and 14.30 GHz, with a stopband suppression of 3.00 dB to 13.20 dB.

[0038] Reference Figure 4 and Figure 5In the second connection method, one end of the stub resonant unit 200 is connected to the inner conductor 120, and the other end of the stub resonant unit 200 is a free end. (Refer to...) Figure 6 Simulation results show that, with this connection method, the main signal forms a stopband between 11.60 GHz and 16.10 GHz, with a stopband suppression of 3.00 dB to 32.12 dB.

[0039] Reference Figure 7 and Figure 8 In the third connection method, one end of the stub resonant unit 200 is connected to the outer conductor 110, and the other end of the stub resonant unit 200 is connected to the inner conductor 120. (Refer to...) Figure 9 Simulation results show that, with this connection method, the main signal forms a stopband between 27.05 GHz and 30.45 GHz, with a stopband suppression of 3.00 dB to 24.75 dB.

[0040] Therefore, by selecting different connection methods, the resonant frequency of the stub resonant unit 200 will also differ. Users can choose the appropriate connection method according to actual filtering needs, offering high flexibility. Furthermore, by adjusting the distance between the stub resonant unit 200 and the outer conductor 110 and inner conductor 120, as well as adjusting the thickness and width parameters of the stub resonant unit 200 itself, or adjusting parameters such as the dielectric constant and loss tangent of the dielectric within the dielectric region 130, the coupling strength and impedance depth of the stub resonant unit 200 can be adjusted. By changing the length of the stub resonant unit 200 itself, the resonant frequency of the stub resonant unit 200 can be adjusted.

[0041] Furthermore, regarding the specific shape of the stub resonant unit 200, it is ring-shaped or spiral-shaped, and the stub resonant unit 200 is arranged around the inner conductor 120. More specifically, the stub resonant unit 200 can be locally extended along the circumferential, radial, or axial direction of the coaxial transmission body 100, and the extension path of the stub resonant unit 200 can also be a broken line or a curve, thereby changing the filtering characteristics of the stub resonant unit 200.

[0042] Furthermore, in some embodiments, the central axis of the stub resonant unit 200 is coaxially arranged with the outer conductor 110 and the inner conductor 120.

[0043] Furthermore, regarding the specific connection method of the stub resonant unit 200, the end of the stub resonant unit 200 is detachably connected to the outer conductor 110 and / or the inner conductor 120, so that the user can more freely install, remove and replace the stub resonant unit 200 according to the filtering requirements.

[0044] Furthermore, a capacitor loading structure 210 is also provided on the stub resonant unit 200. The capacitor loading structure 210 is a plate-like structure and its shape can be rectangular, fan-shaped, circular, or trapezoidal. The capacitor loading structure 210 can be placed at any position on the stub resonant unit 200, and it can adjust the impedance of the stub resonant unit 200, as well as the distributed capacitance between the stub resonant unit 200 and the inner conductor 120, the outer conductor 110, and the surrounding metal structure. By adjusting the shape and size of the capacitor loading structure 210, the impedance frequency and impedance depth of the stub resonant unit 200 can be adjusted.

[0045] Furthermore, the electrical length of the stub resonant unit 200 is an integer multiple of one-quarter of the waveguide wavelength corresponding to the target frequency, or an equivalent resonant electrical length can be formed through end loading, bending, dielectric loading, stepped impedance, or slow-wave structure. Thus, the stub resonant unit 200 is not limited to a strict one-quarter wavelength or its integer multiple physical length, but can be equivalently designed according to the spatial constraints and frequency requirements of the actual coaxial transmission body 100.

[0046] Furthermore, an impedance transformation section is provided at the connection between the stub resonant unit 200 and the coaxial transmission body 100. The impedance transformation section can be a linewidth gradient section, a stepped impedance section, a local adjustment section, a local narrowing section, or a transmission line segment with a preset length.

[0047] Furthermore, referring to Figure 10 In some embodiments, there are at least two stub resonator units 200, and the superposition of different stub resonator units 200 can filter signals at multiple target frequencies. Each stub resonator unit 200 is arranged along the axial direction of the dielectric region 130. Each stub resonator unit 200 can employ different electrical lengths, different end-load dimensions, different coupling gaps, different grounding locations, or different spatial orientations to form a band-stop filter response at multiple target frequencies.

[0048] Furthermore, each stub resonant unit 200 is connected to the coaxial transmission body 100 using any of the connection methods. (Refer to...) Figure 11 Simulation results show that using multiple stub resonant units 200 for joint filtering results in a significant band-stop response at three target frequencies, forming a stopband between 13.53 GHz and 14.99 GHz, with stopband suppression ranging from approximately 3.00 dB to 26.75 dB. These simulation results demonstrate that by introducing multiple layers of stub resonant units 200 within the coaxial structure, multi-frequency band-stop filtering can be achieved. The parameters of each stub resonant unit 200 can be independently or collaboratively adjusted to control the stopband position and suppression depth, thus achieving excellent band-stop filtering performance through flexible combination of the stub resonant units 200.

[0049] The filtering method in the second aspect embodiment of this application, which is based on the above-described coaxial band-stop filter structure, includes the following steps: S1. Based on the filtering requirements, determine one or more target frequencies that need to be suppressed; S2. Determine the shape and size of the inner conductor 120 and the outer conductor 110, and at the same time determine the specific shape and size of the dielectric region 130, and place the stub resonant unit 200 in the dielectric region 130; S3. Determine the initial electrical length of the stub resonant unit 200. Specifically, based on the target frequency, the equivalent dielectric constant of the medium, and the waveguide wavelength, set the initial electrical length of the stub resonant unit 200 to one-quarter or an integer multiple of one-quarter of the waveguide wavelength corresponding to the target frequency. S4. Determine the arrangement position of the stub resonant unit 200 and adjust the specific position of the stub resonant unit 200 within the dielectric region 130; S5. Select the connection method between the stub resonant unit 200 and the coaxial transmission body 100, specifically one of the first connection method, the second connection method, and the third connection method; for cases where multiple stub resonant units 200 are provided, the connection methods of each stub resonant unit 200 can be the same or different; S6. Set the structural form of the stub resonant unit 200, such as adjusting the extension direction of the stub resonant unit 200, or replacing the stub resonant unit 200 with a different shape, etc. S7. Adjust the structural parameters of the stub resonant unit 200, including but not limited to: stub length, stub width, size of the capacitor loading structure 210, coupling gap, grounding position, dielectric material parameters, axial position of the stub, and circumferential angle of the stub; S8. Perform electromagnetic simulation or testing, and use at least one of the stopband transmission coefficient, passband insertion loss, input reflection coefficient and target frequency offset as optimization targets to modify the structural parameters of the stub resonant unit 200 so that the coaxial bandstop filter structure meets the requirements of target frequency suppression, low passband loss and input matching. S9. Determine whether the current coaxial band-stop filter structure meets the requirements; if yes, output the final structure and perform filtering; if no, perform iterative correction.

[0050] In some alternative embodiments, the functions / operations mentioned in the block diagrams may not occur in the order shown in the operation diagrams. For example, depending on the functions / operations involved, two consecutively shown blocks may actually be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order. Furthermore, the embodiments presented and described in the flowcharts of this application are provided by way of example to provide a more comprehensive understanding of the technology. The disclosed methods are not limited to the operations and logic flows presented herein. Alternative embodiments are contemplated in which the order of various operations is changed and sub-operations described as part of a larger operation are executed independently.

[0051] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

Claims

1. A coaxial band-stop filter structure, characterized in that, include: A coaxial transmission body includes an outer conductor and an inner conductor. The outer conductor is tubular and has a cavity inside. The inner conductor is disposed in the cavity. The inner conductor and the outer conductor are coaxially arranged, and a dielectric region is formed between the inner conductor and the outer conductor. A stub resonant unit, which is a metal component, is disposed in the dielectric region; The connection methods between the stub resonant unit and the coaxial transmission body include a first connection method, a second connection method, and a third connection method; In the first connection method, one end of the stub resonant unit is connected to the outer conductor, and the other end of the stub resonant unit is a free end; In the second connection method, one end of the stub resonant unit is connected to the inner conductor, and the other end of the stub resonant unit is a free end; In the third connection method, one end of the stub resonant unit is connected to the outer conductor, and the other end of the stub resonant unit is connected to the inner conductor.

2. The coaxial band-stop filter structure according to claim 1, characterized in that: The stub resonant unit is in the form of a ring or a spiral, and the stub resonant unit is arranged around the inner conductor.

3. The coaxial band-stop filter structure according to claim 2, characterized in that: The central axis of the stub resonant unit is coaxial with the outer conductor and the inner conductor.

4. The coaxial band-stop filter structure according to claim 1, characterized in that: The end of the stub resonant unit is detachably connected to the outer conductor and / or the inner conductor.

5. The coaxial band-stop filter structure according to claim 1, characterized in that: The stub resonant unit is also provided with a capacitor loading structure, which is a plate-like structure and has a rectangular, fan-shaped, circular or trapezoidal shape.

6. The coaxial band-stop filter structure according to claim 1, characterized in that: The electrical length of the stub resonant unit is an integer multiple of one-quarter of the waveguide wavelength corresponding to the target frequency.

7. The coaxial band-stop filter structure according to claim 1, characterized in that: An impedance transformation section is provided at the connection between the stub resonant unit and the coaxial transmission body. The impedance transformation section can be a linewidth gradient section, a stepped impedance section, a local adjustment section, a local narrowing section, or a transmission line segment with a preset length.

8. The coaxial band-stop filter structure according to any one of claims 1 to 7, characterized in that: The number of stub resonant units is at least two, and each of the stub resonant units is arranged along the axial direction of the medium region.

9. The coaxial band-stop filter structure according to claim 8, characterized in that: Each of the stub resonant units is connected to the coaxial transmission body using any of the connection methods described.

10. A filtering method, which is based on the coaxial band-stop filter structure according to any one of claims 1 to 9, characterized in that, include: Determine the target frequency; The shape and size of the inner conductor and the outer conductor are determined, and the dielectric region is also determined. Determine the initial electrical length of the stub resonant unit; Determine the arrangement position of the stub resonant unit; Select the connection method between the stub resonant unit and the coaxial transmission body; Configure the structural form of the stub resonant unit; Adjust the structural parameters of the stub resonant unit; Perform electromagnetic simulation or testing; Determine whether the current coaxial band-stop filter structure meets the requirements; if yes, output the final structure and perform filtering; if not, perform iterative correction.

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