Filter and method for solving transmission zero series cavity
By incorporating a CT structure and a coupling adjustment structure into the filter, the problem of transmission zero-point cross-cavity was solved, improving the accuracy of the design and production efficiency, and ensuring the accuracy of the simulation model and the performance consistency of the actual product.
Patent Information
- Application Number
- CN202511651762.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-12
- Publication Date
- 2026-01-13
AI Technical Summary
In existing technologies, transmission zeros are prone to cross-cavity in filter design, leading to discrepancies between simulation results and actual performance, affecting production efficiency and product throughput. It is also difficult to precisely adjust all zeros to the target frequency using traditional tuning screws.
By setting multiple CT structures in the filter, each CT structure includes three resonant cavities, sharing at least one resonant cavity to generate a transmission zero, and setting coupling adjustment structures between non-adjacent resonant cavities to increase the physical spacing or set electrical coupling to reduce or eliminate the coupling between resonant cavities.
It achieves high-precision prediction of simulation models, significantly shortens the R&D cycle, reduces the complexity and time consumption of production debugging, and ensures that there is almost no mutual influence between zero points, meeting the design requirements.
Smart Images
Figure CN121332136A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of filter, in particular to a filter and method for solving transmission zero point series cavity. BACKGROUND
[0002] 5G communication is a communication technology that is being built comprehensively at present, and the large-scale construction of base stations puts forward very high performance, cost and size requirements for passive devices such as filters and duplexers. These high-power filters and duplexers are mainly cavity structures. In order to reduce cost and size, many filters will set as many transmission zeros as possible. Transmission zero can greatly improve the out-of-band signal suppression capability of the filter, thereby allowing fewer resonant cavities to be used to achieve the same suppression index, or achieving better performance without increasing the number of cavities, which directly leads to cost reduction and size reduction. In the prior art, the CT (cross-coupling) structure is the most commonly used method to generate transmission zeros. By introducing inductive or capacitive coupling in a three-cavity structure, a transmission zero can be generated at the high end or low end of the passband; however, although multiple CT structures are used in the same filter to increase the number of transmission zeros, complex coupling topologies are formed between the corresponding transmission zeros, which easily link between the zeros, commonly known as series cavities, especially between inductive zeros. Once the filter zeros appear in series, since the zeros are related to each other, adjusting one zero will affect the position of the other zero, making it difficult for technicians to accurately adjust all zeros to the target frequency through traditional tuning screws, which seriously affects production efficiency and product pass rate; during the design stage based on electromagnetic simulation software, the series cavity phenomenon will cause the simulation results to be seriously inconsistent with the actual product performance. This makes the simulation model lose its guiding significance, and the design cycle is forced to be extended.
[0003] Therefore, there is an urgent need in the art for a technical solution that can foresee and eliminate the risk of zero point series cavity from the design source, thereby improving the accuracy, manufacturability and production efficiency of filter design. SUMMARY
[0004] The purpose of the present application is to solve the problems in the background art, and to provide a filter and method for solving transmission zero point series cavity.
[0005] The technical solution of the present application, the first aspect of the present application provides a filter for solving transmission zero point series cavity, comprising a plurality of resonant cavities; the plurality of resonant cavities are connected by a coupling structure to form a filter passageway, The plurality of resonant cavities are configured as a plurality of CT structures, each CT structure comprising three resonant cavities, wherein the first resonant cavity and the third resonant cavity are connected by an inductive or capacitive coupling structure, and the second resonant cavity is a zero point cavity for generating a transmission zero point outside the filter passband; the three resonant cavities of each CT structure generate an inductive zero point or a capacitive zero point; a plurality of CT structures share at least one resonant cavity to set a plurality of transmission zeros; a coupling adjustment structure is arranged between at least one pair of non-adjacent resonant cavities to reduce or eliminate the coupling between the pair of resonant cavities to prevent the inter-cavity of the transmission zeros.
[0006] Preferably, the coupling adjustment structure increases the physical distance between the pair of resonant cavities to make the coupling between the pair of resonant cavities below a preset threshold.
[0007] Preferably, the coupling adjustment structure sets an electric coupling between the pair of resonant cavities to neutralize the positive coupling between the pair of resonant cavities due to the magnetic coupling.
[0008] Preferably, the transmission zeros include at least one of an inductive zero and a capacitive zero, wherein the inductive zero is located at the high end of the passband and the capacitive zero is located at the low end of the passband.
[0009] Preferably, when the inductive coupling structure is arranged between the first resonant cavity and the third resonant cavity, the transmission zero of the filter is an inductive zero.
[0010] Preferably, when the capacitive coupling structure is arranged between the first resonant cavity and the third resonant cavity, the transmission zero of the filter is a capacitive zero.
[0011] Preferably, the intensity of the plurality of transmission zeros is set in a preset order. Preferably, the strongest transmission zero is set in the zero cavity of the first CT structure, the second strongest transmission zero is set in the zero cavity of the second CT structure, and the subsequent transmission zeros are set in the zero cavities of other CT structures in order of decreasing intensity.
[0012] Preferably, the number of resonant cavities is 14, including 5 CT structures, specifically: resonant cavities 1-2-3, resonant cavities 3-4-5, resonant cavities 6-7-8, resonant cavities 10-11-12, and resonant cavities 12-13-14. The strongest transmission zero is set in the resonant cavity 7, the second strongest transmission zero is set in the resonant cavity 13, the third strongest transmission zero is set in the resonant cavity 2, the fourth strongest transmission zero is set in the resonant cavity 11, and the fifth strongest transmission zero is set in the resonant cavity 4.
[0013] The second aspect of the present application provides a design method of a filter solving the inter-cavity of transmission zeros, comprising the following specific steps: S1, establishing a filter model in electromagnetic simulation software, the model comprising a plurality of resonant cavities; the plurality of resonant cavities are configured as a plurality of CT structures, each CT structure comprising three resonant cavities for generating transmission zeros; S2, setting a plurality of transmission zeros, wherein the plurality of CT structures share at least one resonant cavity; S3, identifying a resonant cavity pair in the plurality of resonant cavities that can cause cross-cavity; S4, applying a coupling adjustment measure to the resonant cavity pair to reduce or eliminate the coupling between the resonant cavity pair.
[0014] Preferably, the coupling adjustment measure includes increasing the physical distance between the resonant cavity pair or setting an electrical coupling between the resonant cavity pair to neutralize the magnetic coupling between the resonant cavity pair. According to the physical constraints of the filter, one of the measures of increasing the physical distance of the resonant cavity or setting the electrical coupling is selected and implemented.
[0015] Compared with the prior art, the present application has the following beneficial technical effects: The present application fundamentally overcomes the difficult-to-avoid "cross-cavity" problem in the design of a multi-transmission zero point filter by pre-identifying potential parasitic coupling points caused by resonant cavity sharing in electromagnetic simulation and using the measures of increasing the distance or setting an electrical coupling for neutralization. This makes the simulation model be able to accurately predict the performance of the real product, significantly shortens the research and development cycle, and greatly reduces the complexity and time consumption of production debugging. According to the present application, the existing CT structure is improved, and the actual product and simulation are compared. The results show that there is almost no mutual influence between these zero points, which meets the design requirements. BRIEF DESCRIPTION OF DRAWINGS
[0016] Figure 1 It is a schematic diagram of the CT topology structure in the prior art; Figure 2 It is a schematic diagram of the topology structure of the filter in the prior art; Figure 3 It is a schematic diagram of the topology structure of the filter after using the increased distance scheme in the embodiment of the present application; Figure 4 It is a schematic diagram of the topology structure of the filter after using the electrical coupling neutralization scheme in the embodiment of the present application; Figure 5 It is a layout diagram of the actual product in the embodiment of the present application; Figure 6 It is a simulation diagram of the CT topology structure with the cross-cavity problem in the prior art; Figure 7 It is a simulation diagram of the improved CT topology structure using the increased distance scheme in the embodiment of the present application; Figure 8 It is a simulation diagram of the improved CT topology structure using the electrical coupling neutralization scheme in the embodiment of the present application; Figure 9 It is a simulation diagram of the actual product in the embodiment of the present application; Figure 10 It is a simulation diagram of the filter optimization S parameter in the embodiment of the present application. DETAILED DESCRIPTION Embodiment 1
[0017] As Figure 1 shown, the embodiment proposes a filter for solving the problem of transmission zero point stringing cavities, which includes a plurality of resonant cavities; the plurality of resonant cavities are connected through a coupling structure to form a filter passband, In actual filter requirements, multiple zero points need to be set to meet performance requirements, and in the CT structure, resonant cavity 1 or resonant cavity 3 needs to share multiple resonant cavities, which will appear as Figure 5 shown; it is configured as several CT structures, each of which includes three resonant cavities, wherein the first resonant cavity and the third resonant cavity are connected through an inductive coupling or a capacitive coupling structure, and the second resonant cavity is a zero point cavity for generating a transmission zero point outside the filter passband; the three resonant cavities of each CT structure generate an inductive zero point or a capacitive zero point; Several CT structures share at least one resonant cavity to set multiple transmission zero points; A coupling adjustment structure is provided between at least one pair of non-adjacent resonant cavities to reduce or eliminate the coupling between the pair of resonant cavities to prevent the stringing of transmission zero points.
[0018] The transmission zero point includes at least one of an inductive zero point and a capacitive zero point, wherein the inductive zero point is located at the high end of the passband, and the capacitive zero point is located at the low end of the passband. When the inductive coupling structure is provided between the first resonant cavity and the third resonant cavity, the transmission zero point of the filter is an inductive zero point. When the capacitive coupling structure is provided between the first resonant cavity and the third resonant cavity, the transmission zero point of the filter is a capacitive zero point.
[0019] The following uses an actual case to introduce the scheme of the embodiment in detail: The embodiment provides a filter topology structure, as Figure 2 shown, which is composed of 14 resonant cavities, sets 5 inductive transmission zero points, and needs to share resonant cavities with CT structures. Modeling and analysis in electromagnetic simulation software, as Figure 6 shown, there is coupling between resonant cavity 2 and resonant cavity 4, and the zero point is easy to string cavities, and similarly, there is coupling between resonant cavity 11 and resonant cavity 13, and the zero point is easy to string cavities. Then in order to make the coupling between resonant cavity 2 and resonant cavity 4 almost zero, and similarly, the coupling between resonant cavity 11 and resonant cavity 13 almost zero, the solution of the scheme is two: 1. The coupling adjustment structure increases the physical distance between a pair of resonant cavities, so that the coupling between the pair of resonant cavities is lower than a preset threshold. Figure 2 Adjust the original filter topology structure of Figure 3the topology shown; and Figure 3 The simulation results of the topology in Figure 7 After increasing the distance, there is almost no coupling and no cavity coupling phenomenon.
[0020] 2. The coupling adjustment structure neutralizes the magnetic coupling (positive coupling) between a pair of resonant cavities by setting an electric coupling (negative coupling) between the pair of resonant cavities. The topology result is shown in Figure 4 As shown in Figure 8 After the electric coupling of the capacitor structure between the two resonant cavities is neutralized, there is almost no coupling between the two cavities.
[0021] As a preferred scheme of the embodiment, the strengths of the multiple transmission zeros are set in a preset order; Among them, the strongest transmission zero is set in the zero point cavity of the first CT structure, the second strongest transmission zero is set in the zero point cavity of the second CT structure, and the subsequent transmission zeros are set in the zero point cavities of other CT structures in order of decreasing strength.
[0022] As a preferred scheme of the embodiment, the number of resonant cavities is 14, including 5 CT structures, specifically: resonant cavities 1-2-3, resonant cavities 3-4-5, resonant cavities 6-7-8, resonant cavities 10-11-12, and resonant cavities 12-13-14; The strongest transmission zero is set in the resonant cavity 7, which is the zero point cavity in the CT of resonant cavities 6-7-8; the second strongest transmission zero is set in the resonant cavity 13, which is the zero point cavity in the CT of resonant cavities 12-13-14; the third strongest transmission zero is set in the resonant cavity 2, which is the zero point cavity in the CT of resonant cavities 1-2-3; the fourth strongest transmission zero is set in the resonant cavity 11, which is the zero point cavity in the CT of resonant cavities 10-11-12; and the fifth strongest transmission zero is set in the resonant cavity 4, which is the zero point cavity in the CT of resonant cavities 3-4-5. In this embodiment, the strongest zero point is placed in the middle cavity first, the second strongest zero point is placed at the beginning and end of the filter, and the weakest two zero points are placed between the strongest and second strongest zero points, forming an alternating layout of strong and weak, making the zero point more stable and less likely to be coupled. Because the zero point of the middle resonant cavity in the filter is easier to strengthen, in the cross-coupled filter, the middle resonant cavity has the most coupling paths, it has coupling with the left and right adjacent cavities, as well as the non-adjacent cavities for generating zero points; inserting weak zero points between the strongest and second strongest zero points makes the energy and coupling strength more evenly distributed throughout the filter link, reducing the mutual dependence and restraint between each resonant cavity. When the frequency of a cavity drifts slightly due to some reason, this layout can better suppress the propagation of such disturbance to other cavities, thereby being less likely to be coupled. The required coupling coefficients do not appear to be extremely strong or extremely weak in some cases, which also reduces the difficulty of processing and debugging. Embodiment 2
[0023] The embodiment provides a design method of a filter with transmission zero point series cavities, and comprises the following specific steps: S1, establishing a filter model in electromagnetic simulation software, wherein the model comprises a plurality of resonant cavities; the plurality of resonant cavities are configured as a plurality of CT structures, each CT structure comprising three resonant cavities for generating transmission zero points; S2, setting a plurality of transmission zero points, wherein the plurality of CT structures share at least one resonant cavity; S3, identifying a resonant cavity pair in the plurality of resonant cavities that may cause series cavities; S4, applying a coupling adjustment measure to the resonant cavity pair to reduce or eliminate the coupling between the resonant cavity pair.
[0024] The coupling adjustment measure comprises increasing the physical distance between the resonant cavity pair or setting an electric coupling between the resonant cavity pair to neutralize the magnetic coupling between the resonant cavity pair; and one of the measures of increasing the physical distance of the resonant cavity or setting the electric coupling is selected and implemented according to the physical constraints of the filter. In the same filter, one of the two schemes is usually used, that is, the physical distance between the resonant cavities is increased to reduce the mutual influence, or the electric coupling is set to neutralize the magnetic coupling on both sides because the distance cannot be increased due to various conditions. In product design, if the conditions permit, the distance is preferably increased, which is the preferred layout, and if the size cannot be achieved, the electric coupling must be set in the vicinity.
[0025] In the embodiment, the topology structure as shown in Figure 2 is adjusted, the physical distance between the resonant cavity pair is selected to be increased because the space size meets the needs; the adjusted filter topology diagram is as shown in Figure 3 , the actual product diagram is as shown in Figure 5 , the number of resonant cavities is 14, including five CT structures, specifically: resonant cavities 1-2-3, resonant cavities 3-4-5, resonant cavities 6-7-8, resonant cavities 10-11-12, and resonant cavities 12-13-14; The strongest transmission zero point is set in the resonant cavity 7, the resonant cavity 7 is the zero point cavity in the CT of the resonant cavities 6-7-8; the second strongest transmission zero point is set in the resonant cavity 13, the resonant cavity 13 is the zero point cavity in the CT of the resonant cavities 12-13-14; the third strongest transmission zero point is set in the resonant cavity 2, the resonant cavity 2 is the zero point cavity in the CT of the resonant cavities 1-2-3; the fourth strongest transmission zero point is set in the resonant cavity 11, the resonant cavity 11 is the zero point cavity in the CT of the resonant cavities 10-11-12; and the fifth strongest transmission zero point is set in the resonant cavity 4, the resonant cavity 4 is the zero point cavity in the CT of the resonant cavities 3-4-5; Figure 5The middle blue dot is a debugging screw, and the hollow circle is a cylindrical cavity; the space in the middle of the cavity is designed to meet the design requirements of the filter, so as to achieve the purpose of adjusting the coupling. In this embodiment, the space in the middle of the cavity functions to enable the resonant cavities to achieve the coupling required by the filter performance, and the cavities that need to be coupled need to achieve the coupling bandwidth required by the filter performance, and the cavities that do not need to be coupled need to be in an isolated state. The design of the window size is determined according to the filter performance and the different coupling bandwidths between the resonant cavities. For example Figure 5 In this embodiment, the spacing between the resonant cavities 2-9 and 6-13 is relatively small, and the remaining parts are connected by hollow cylinders to form a hollow cylinder, which is designed because the resonant cavities 2-9 and 6-13 are in an isolated state, and in order to maximize the application of the cavity space, the screw is processed into a resonant cavity. The remaining parts are connected by hollow cylinders, which are mainly used to adjust the coupling between the resonant cavities of the filter, and ultimately to meet the overall performance indicators of the filter. Through simulation experiments on the actual product as shown in Figure 5 As shown in Figure 9 As shown in Figure 10 As shown in
[0026] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited thereto, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present application.
Claims
1. A filter for solving the problem of transmission zero-point crosstalk, characterized in that, It includes multiple resonant cavities; these cavities are connected through a coupling structure to form a filter path. Multiple resonant cavities are configured into several CT structures, each CT structure including three resonant cavities, wherein the first and third resonant cavities are connected by an inductive or capacitive coupling structure, and the second resonant cavity is a zero-point cavity used to generate transmission zeros outside the filter passband; each of the three resonant cavities of each CT structure generates an inductive zero or a capacitive zero. Several CT structures share at least one resonant cavity to set multiple transmission zeros; A coupling adjustment structure is provided between at least one pair of non-adjacent resonant cavities to reduce or eliminate the coupling between the pair of resonant cavities, so as to prevent crosstalk between transmission zeros.
2. The filter for solving the problem of transmission zero-point crosstalk according to claim 1, characterized in that, The coupling adjustment structure increases the physical spacing between a pair of resonant cavities, making the coupling between the pair of resonant cavities lower than a preset threshold.
3. The filter for solving the problem of transmission zero-point crosstalk according to claim 1, characterized in that, The coupling adjustment structure neutralizes the positive coupling caused by magnetic coupling between a pair of resonant cavities by setting an electrical coupling between them.
4. The filter for solving transmission zero-point crosstalk according to claim 2 or 3, characterized in that, The transmission zero includes at least one of an inductive zero and a capacitive zero, wherein the inductive zero is located at the high end of the passband and the capacitive zero is located at the low end of the passband.
5. The filter for solving transmission zero-point crosstalk according to claim 4, characterized in that, When an inductive coupling structure is set between the first resonant cavity and the third resonant cavity, the transmission zero of the filter is an inductive zero.
6. The filter for solving the problem of transmission zero-point crosstalk according to claim 4, characterized in that, When a capacitive coupling structure is set between the first resonant cavity and the third resonant cavity, the transmission zero of the filter is a capacitive zero.
7. The filter for solving the problem of transmission zero-point crosstalk according to claim 4, characterized in that, The strengths of multiple transmission zeros are set according to a preset order; The strongest transmission zero point is set in the zero-point cavity of the first CT structure, the second strongest transmission zero point is set in the zero-point cavity of the second CT structure, and subsequent transmission zero points are set in the zero-point cavities of other CT structures in descending order of intensity.
8. The filter for solving the problem of transmission zero-point crosstalk according to claim 1, characterized in that, There are 14 resonant cavities, including 5 CT structures, specifically: resonant cavity 1-2-3, resonant cavity 3-4-5, resonant cavity 6-7-8, resonant cavity 10-11-12 and resonant cavity 12-13-14; The strongest transmission zero is set in resonant cavity 7, the second strongest transmission zero is set in resonant cavity 13, the third strongest transmission zero is set in resonant cavity 2, the fourth strongest transmission zero is set in resonant cavity 11, and the fifth strongest transmission zero is set in resonant cavity 4.
9. A design method for a filter to solve the problem of transmission zero-point crosstalk, characterized in that, The specific steps include the following: S1. Establish a filter model in electromagnetic simulation software. The model includes multiple resonant cavities. The multiple resonant cavities are configured as multiple CT structures. Each CT structure includes three resonant cavities for generating transmission zeros. S2. Set multiple transmission zeros, wherein the multiple CT structures share at least one resonant cavity; S3. Identify resonant cavity pairs among the plurality of resonant cavities that may cause crosstalk; S4. Apply coupling adjustment measures to the resonant cavity pair to reduce or eliminate the coupling between the resonant cavity pair.
10. The filter design method for solving the problem of transmission zero-point crosstalk as described in claim 9, characterized in that, The coupling adjustment measures include increasing the physical spacing between the resonant cavity pairs or setting electrical coupling between the resonant cavity pairs to neutralize the magnetic coupling between the resonant cavity pairs; Based on the physical constraints of the filter, a measure is selected and implemented between increasing the physical distance of the resonant cavity and setting up electrical coupling.