A miniaturized dual-transmission zero point multi-mode filter
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-08-11
AI Technical Summary
[0003]现有小型化双传输零点多模滤波器多采用微带谐振结构或介质集成谐振结构实现小型化与双传输零点特性，但现有结构往往难以兼顾紧凑尺寸与优异的宽频带传输、高带外抑制性能
1.模型中的开口环结构在特定频率产生谐振，形成通带，开口环谐振器通过环形开口自然形成集中电容，无需额外外接电容元件，大幅简化了谐振单元的结构设计；同时，集中电容与开口环自身的电感特性形成谐振回路，可在更小的物理尺寸下实现目标谐振频率，相较于传统分布式谐振结构，进一步压缩了谐振器的占用面积，助力滤波器整体尺寸控制在毫米级；两个开口环谐振器与中间第二谐振器形成协同谐振体系，其集中电容特性可优化谐振器之间的耦合强度与耦合相位，配合附加调谐结构的作用，进一步稳固通带高低端的传输零点位置，提升带外抑制度；同时，集中电容的存在增强了谐振器对高频信号的选频特性，保障宽通带内信号传输的平坦度。
Smart Images
Figure CN224625873U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of radio frequency communication devices, and in particular to a miniaturized dual-transmission zero-point multimode filter. Background Technology
[0002] With the rapid development of radio frequency (RF) systems towards miniaturization and high performance, stringent requirements have been placed on the miniaturization, wide passband, and high out-of-band rejection characteristics of core components such as filters. Miniaturized dual-transmission zero-point multimode filters, due to their ability to extend the passband width through multimode resonance and improve out-of-band interference suppression capabilities by utilizing transmission zeros, have become one of the key components for adapting to high-frequency RF systems. Their performance directly determines the signal transmission quality and integration compatibility of the RF system.
[0003] Existing miniaturized dual-transmission zero multimode filters mostly employ microstrip resonant structures or dielectric integrated resonant structures to achieve miniaturization and dual-transmission zero characteristics. However, existing structures often struggle to balance compact size with excellent wideband transmission and high out-of-band rejection performance.
[0004] Regarding the aforementioned technologies, the applicant believes that there is a drawback in that miniaturization and wide passband and high out-of-band suppression performance are difficult to achieve simultaneously. Utility Model Content
[0005] To address the aforementioned technical problems, this application provides a miniaturized dual-transmission zero-point multimode filter.
[0006] This application provides a miniaturized dual-transmission zero-point multimode filter, which adopts the following technical solution: A miniaturized dual-transmission zero-point multimode filter includes a dielectric substrate and a microstrip structure disposed on the top layer of the dielectric substrate. An input transmission line is disposed at one end of the dielectric substrate, and an output transmission line is disposed at the other end of the dielectric substrate. A first resonator, a second resonator, and a third resonator are sequentially disposed in the middle of the dielectric substrate. The input transmission line is connected to the first resonator, and the third resonator is connected to the output transmission line. Additional tuning structures are respectively connected to both ends of the conduction band of the second resonator, and two sets of additional tuning structures are symmetrically disposed on both sides of the second resonator.
[0007] By adopting the above technical solution, this filter uses a microstrip structure, which can integrate capacitors and inductors at high density, controlling the overall size to the millimeter level. This effectively solves the problem of traditional filters being too large and difficult to adapt to miniature RF systems. At the same time, its planar structure has excellent integration compatibility, allowing for conformal design with RF front-end modules such as antennas and amplifiers, significantly saving layout space for RF equipment and improving the integration and space utilization of the equipment. Based on the simulation results of the simulation curves, this filter successfully achieves 17 by symmetrically setting additional tuning structures at both ends of the conduction band of the second resonator, combined with the synergistic resonance of the three resonators. With a wide passband coverage of 9GHz-39.4GHz and a relative bandwidth of approximately 75%, it can meet the transmission requirements of multi-band RF signals. At the same time, it forms transmission zeros at both ends of the passband, significantly improving out-of-band rejection and effectively filtering out interference signals outside the passband, ensuring the purity and stability of RF signal transmission. Through optimized resonator structure design and the introduction of additional tuning structures, it achieves the dual performance advantages of wide passband transmission and high out-of-band rejection while maintaining a millimeter-level miniaturized size. This significantly improves the overall performance of the filter and provides key technical support for the development of miniaturized, high-performance RF communication systems.
[0008] Preferably, the microstrip structure is a planar circuit structure made of conductive material.
[0009] By adopting the above technical solutions, conductive materials effectively reduce the ohmic loss of microstrip structures during high-frequency signal transmission, reduce signal attenuation, ensure stable transmission of RF signals over a wide bandwidth, improve the insertion loss performance of filters, and achieve a planar circuit form that is tightly integrated with the dielectric substrate. This not only enables high-density integration of capacitors and inductors but also allows for seamless compatibility with the planar structures of RF modules such as antennas and amplifiers. It facilitates conformal design and integrated layout, further compressing the overall volume of the RF front-end system and improving the space utilization of the equipment.
[0010] Preferably, the input transmission line and the output transmission line are symmetrically distributed along the geometric center line of the dielectric substrate; the first resonator, the second resonator, the third resonator, and the two sets of additional tuning structures are all symmetrically distributed along the geometric center line of the dielectric substrate.
[0011] By adopting the above technical solutions, the symmetrical layout ensures that the signal coupling paths between the input and output transmission lines and the resonators are highly symmetrical, effectively reducing the reflection loss of high-frequency signals at the ports, improving the return loss performance of the filter, and ensuring the matching degree and stability of signal transmission over a wide bandwidth. The symmetrical distribution of the resonators and the additional tuning structure ensures that the electric and magnetic fields of each resonant unit are uniformly and symmetrically distributed, avoiding resonant frequency shifts caused by structural asymmetry. At the same time, it enhances the depth and positional stability of the transmission zeros at both ends of the passband, further improving out-of-band suppression and enhancing the ability to filter out interference signals.
[0012] Preferably, the first resonator and the third resonator are open-loop resonators, and the open-loop resonator has an annular opening.
[0013] By adopting the above technical solution, the open-loop structure in the model resonates at a specific frequency, forming a passband. The open-loop resonator naturally forms a concentrated capacitance through the ring opening, eliminating the need for additional external capacitor components and greatly simplifying the structural design of the resonant unit. At the same time, the concentrated capacitance and the inductive characteristics of the open-loop itself form a resonant circuit, which can achieve the target resonant frequency in a smaller physical size. Compared with the traditional distributed resonant structure, it further reduces the area occupied by the resonator, helping to control the overall size of the filter to the millimeter level. The two open-loop resonators and the middle second resonator form a cooperative resonant system. The concentrated capacitance characteristics can optimize the coupling strength and coupling phase between the resonators. With the help of the additional tuning structure, it further stabilizes the transmission zero position at the high and low ends of the passband and improves the out-of-band rejection. At the same time, the presence of the concentrated capacitance enhances the frequency selectivity of the resonator for high-frequency signals, ensuring the flatness of signal transmission within the wide passband.
[0014] Preferably, the second resonator is a cross-shaped coupled resonator, with one end of the second resonator embedded in the annular opening of the first resonator and the other end of the second resonator embedded in the annular opening of the third resonator.
[0015] By adopting the above technical solutions, the cross-coupled structure allows multiple resonant modes to be superimposed, widening the passband bandwidth. Simultaneously, the coupling strength is adjustable, optimizing in-band flatness. Through asymmetrical coupling between the open loop and the center line, and by loading open-circuit stubs on the sides of the cross-coupled structure, two transmission zeros are introduced, significantly improving the attenuation steepness outside the passband. The two ends of the cross-shaped coupled resonator are embedded with the annular openings of the open-loop resonator, forming an embedded electromagnetic coupling structure. Compared to traditional adjacent coupling, this design significantly improves the coupling strength between resonant units. Furthermore, the multi-directional coupling characteristics of the cross-shaped structure allow for flexible adjustment of the coupling phase and coupling coefficient, precisely matching the wide passband design requirements and ensuring efficient signal transmission within the frequency band. The embedded coupling method enables the three resonators to form a synergistic resonant system. The cross-shaped resonator can interact with the concentrated capacitance and inductance characteristics of the open-loop resonator through its own structural characteristics, further enhancing the depth and positional stability of the transmission zeros at both ends of the passband, effectively improving out-of-band suppression, and achieving more precise and powerful filtering of interference signals outside the passband, ensuring the purity of RF signal transmission.
[0016] Preferably, the additional tuning structure is an open-circuit stub, and the two sets of additional tuning structures are respectively connected to both ends of the conduction band of the cross-shaped coupled resonator. The additional tuning structure and the equivalent distributed capacitance of the conduction band of the cross-shaped coupled resonator are connected in parallel.
[0017] By adopting the above technical solution, the additional parallel capacitor formed by the open-circuit stub can interact with the equivalent distributed parameters of the cross-shaped coupled resonator to achieve precise cancellation of parasitic resonant phase, stably forming attenuation poles at the far-end frequencies of the high and low ends of the passband, thereby constructing dual transmission zeros. This design significantly improves the attenuation amplitude of out-of-band signals, effectively suppresses spurious interference outside the passband, ensures the purity of signal transmission within the wide bandwidth, and solves the technical pain point of insufficient out-of-band suppression of traditional filters. The capacitance value of the additional parallel capacitor can be precisely controlled by adjusting the length and width of the open-circuit stub, thereby flexibly changing the equivalent phase characteristics of the resonator, enabling the coordinated resonant frequency band of the three resonators to accurately cover the target wide passband, while ensuring the flatness of signal transmission within the passband, avoiding signal attenuation fluctuations within the frequency band, and improving the amplitude-frequency response performance of the filter.
[0018] Preferably, the bottom layer of the dielectric substrate is provided with a conductive metal ground plane.
[0019] By adopting the above technical solution, the complete conductive metal ground plane and the top microstrip structure form a standard microstrip transmission line structure, which can effectively constrain the electromagnetic field distribution of high-frequency signals, limit most of the electromagnetic field energy to the area between the dielectric substrate and the ground plane, significantly reduce electromagnetic leakage of high-frequency signals, and avoid electromagnetic interference to surrounding radio frequency modules. At the same time, the grounding structure can reduce radiation loss during signal transmission, ensure the amplitude and phase stability of signal transmission in a wide bandwidth, and optimize the insertion loss and phase consistency index of the filter.
[0020] In summary, this application includes at least one of the following beneficial technical effects: 1. The open-loop structure in the model resonates at a specific frequency, forming a passband. The open-loop resonator naturally forms a concentrated capacitance through the ring opening, eliminating the need for additional external capacitors and significantly simplifying the structural design of the resonant unit. Simultaneously, the concentrated capacitance and the inductive characteristics of the open-loop itself form a resonant circuit, enabling the target resonant frequency to be achieved in a smaller physical size. Compared to traditional distributed resonant structures, this further reduces the resonator's footprint, helping to keep the overall filter size within millimeters. The two open-loop resonators and the second resonator in the middle form a synergistic resonant system. The concentrated capacitance characteristics optimize the coupling strength and coupling phase between the resonators. Combined with the additional tuning structure, this further stabilizes the transmission zero positions at the high and low ends of the passband, improving out-of-band rejection. Furthermore, the presence of the concentrated capacitance enhances the resonator's frequency selectivity for high-frequency signals, ensuring the flatness of signal transmission within the wide passband.
[0021] 2. The cross-shaped coupling structure allows multiple resonant modes to be superimposed, widening the passband bandwidth. Simultaneously, the coupling strength is adjustable, optimizing in-band flatness. Through asymmetrical coupling between the open loop and the center line, and by loading open-circuit stubs on the sides of the cross-shaped coupling, two transmission zeros are introduced, significantly improving the attenuation steepness outside the passband. The two ends of the cross-shaped coupled resonator are embedded with the annular openings of the open-loop resonator, forming an embedded electromagnetic coupling structure. Compared to traditional adjacent coupling, this design significantly improves the coupling strength between resonant units. Furthermore, the multi-directional coupling characteristics of the cross-shaped structure allow for flexible adjustment of the coupling phase and coupling coefficient, precisely matching the wide passband design requirements and ensuring efficient signal transmission within the frequency band. The embedded coupling method enables the three resonators to form a synergistic resonant system. The cross-shaped resonator can interact with the concentrated capacitance and inductance characteristics of the open-loop resonator through its own structural characteristics, further enhancing the depth and positional stability of the transmission zeros at both ends of the passband, effectively improving out-of-band suppression, and achieving more precise and powerful filtering of interference signals outside the passband, ensuring the purity of RF signal transmission. Attached Figure Description
[0022] Figure 1 This is a simulation curve from the embodiment.
[0023] Figure 2 This is a schematic diagram of the overall structure in the embodiment.
[0024] Explanation of reference numerals in the attached figures: 1. Dielectric substrate; 11. Microstrip structure; 2. Input transmission line; 3. Output transmission line; 4. First resonator; 5. Second resonator; 6. Third resonator; 7. Additional tuning structure; 8. Conductive metal ground plane. Detailed Implementation
[0025] The following is in conjunction with the appendix Figure 1-2 This application will be described in further detail.
[0026] This application discloses a miniaturized dual-transmission zero-point multimode filter. (Refer to...) Figure 1 and 2 The filter includes a dielectric substrate 1 and a microstrip structure 11 disposed on the top layer of the dielectric substrate 1. The microstrip structure 11 is a planar circuit structure made of conductive material. A conductive metal ground plane 8 is disposed on the bottom layer of the dielectric substrate 1. An input transmission line 2 is disposed on one end of the dielectric substrate 1, and an output transmission line 3 is disposed on the other end of the dielectric substrate 1. The input transmission line 2 and the output transmission line 3 are symmetrically distributed along the geometric center line of the dielectric substrate 1. A first resonator 4, a second resonator 5, and a third resonator 6 are disposed sequentially in the middle of the dielectric substrate 1. The input transmission line 2 is connected to the first resonator 4, and the third resonator 6 is connected to the output transmission line 3. Additional tuning structures 7 are respectively connected to both ends of the conduction band of the second resonator 5. Two sets of additional tuning structures 7 are symmetrically disposed on both sides of the second resonator 5. The first resonator 4, the second resonator 5, the third resonator 6, and the two sets of additional tuning structures 7 are all symmetrically distributed along the geometric center line of the dielectric substrate 1. Based on the simulation results, the passband of the filter is 17.9GHz-39.4GHz, with a relative bandwidth of about 75%, and transmission zeros at both the high and low ends.
[0027] The first resonator 4 and the third resonator 6 are open-loop resonators, each with an annular opening where a concentrated capacitance is formed. The second resonator 5 is a cross-shaped coupled resonator, with one end embedded in the annular opening of the first resonator 4 and the other end embedded in the annular opening of the third resonator 6, thus achieving electromagnetic coupling between the cross-shaped coupled resonator and the open-loop resonator. The additional tuning structure 7 is an open-circuit stub, with two sets of additional tuning structures 7 connected to both ends of the conduction band of the cross-shaped coupled resonator. The additional tuning structure 7 forms a parallel relationship with the equivalent distributed capacitance of the conduction band of the cross-shaped coupled resonator to introduce additional parallel capacitance. This additional parallel capacitance is used to achieve parasitic resonance phase cancellation and generate attenuation poles at far-end frequencies to introduce transmission zeros.
[0028] The working principle of the miniaturized dual-transmission zero-point multimode filter in this application is as follows: After the input signal is fed in through the input transmission line 2, it is first transmitted to the first resonator 4. The first resonator 4 is an open-loop resonator. A concentrated capacitance is formed at the open loop of the open-loop resonator, which together with the equivalent inductance of the loop conduction band forms a resonant circuit. When the frequency of the input signal falls into the resonant frequency band of the resonator, the first resonator 4 is excited and resonates, transmitting the signal energy to the adjacent second resonator 5 by electromagnetic coupling. The second resonator 5 is a cross-shaped coupled resonator, with one end of the second resonator 5 embedded in... The first resonator 4 has an annular opening, and the other end of the second resonator 5 is embedded in the annular opening of the third resonator 6. This embedded structure achieves strong electromagnetic coupling between the resonators. When the energy of the first resonator 4 is coupled to the second resonator 5, the second resonator 5 is excited to resonate, and at the same time, it couples energy to the third resonator 6, which is an open-loop resonator. Since the resonant frequencies of the three resonators cover a wide range of 17.9 GHz to 39.4 GHz, and the coupling strength between the resonators is optimized and matched, the signal energy in this frequency band can be efficiently transferred from the first resonator 4... The signal is transmitted from the second resonator 5 to the third resonator 6, and finally output through the output transmission line 3, thus forming a wide passband with a relative bandwidth of 75%. The additional tuning structure 7, symmetrically connected to both ends of the conduction band of the second resonator 5, is an open-circuit stub. It forms a parallel relationship with the equivalent distributed capacitance of the conduction band of the cross-shaped coupled resonator, introducing an additional parallel capacitor. At the high and low end frequencies outside the passband, this additional parallel capacitor, together with the equivalent inductance and capacitance of the resonator, induces a parasitic resonance phase cancellation effect: when the signal phase generated by the parasitic resonance is different from the signal phase of the main transmission path... Conversely, the two cancel each other out, and the signal energy cannot pass through the filter, thus forming attenuation poles at the far-end frequencies of high and low ends. The existence of transmission zeros greatly improves the out-of-band attenuation characteristics of the filter and effectively suppresses interference signals outside the passband. The signal in the passband after being filtered by the first resonator 4, the second resonator 5 and the third resonator 6 is transmitted to the output transmission line 3 through the third resonator 6, and finally realizes the filtered output of the broadband signal. The signal outside the passband is either unable to excite the resonator to generate effective coupling, or is greatly attenuated due to the phase cancellation effect of the additional tuning structure 7, thus completing the filtering function.
[0029] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.
Claims
1. A miniaturized dual-transmission zero-point multimode filter, characterized in that: The device includes a dielectric substrate (1) and a microstrip structure (11) disposed on the top layer of the dielectric substrate (1). An input transmission line (2) is disposed at one end of the dielectric substrate (1), and an output transmission line (3) is disposed at the other end of the dielectric substrate (1). A first resonator (4), a second resonator (5), and a third resonator (6) are disposed sequentially in the middle of the dielectric substrate (1). The input transmission line (2) is connected to the first resonator (4), and the third resonator (6) is connected to the output transmission line (3). Additional tuning structures (7) are respectively connected to both ends of the conduction band of the second resonator (5), and two sets of additional tuning structures (7) are symmetrically disposed on both sides of the second resonator (5).
2. The miniaturized dual-transmission zero-point multimode filter according to claim 1, characterized in that: The microstrip structure (11) is a planar circuit structure made of conductive material.
3. A miniaturized dual-transmission zero-point multimode filter according to claim 1, characterized in that: The input transmission line (2) and the output transmission line (3) are symmetrically distributed along the geometric center line of the dielectric substrate (1); the first resonator (4), the second resonator (5), the third resonator (6) and the two sets of additional tuning structures (7) are all symmetrically distributed along the geometric center line of the dielectric substrate (1).
4. A miniaturized dual-transmission zero-point multimode filter according to claim 1, characterized in that: The first resonator (4) and the third resonator (6) are open-loop resonators, and the open-loop resonator has an annular opening.
5. A miniaturized dual-transmission zero-point multimode filter according to claim 4, characterized in that: The second resonator (5) is a cross-shaped coupled resonator. One end of the second resonator (5) is embedded in the annular opening of the first resonator (4), and the other end of the second resonator (5) is embedded in the annular opening of the third resonator (6).
6. A miniaturized dual-transmission zero-point multimode filter according to claim 5, characterized in that: The additional tuning structure (7) is an open-circuit stub. The two sets of additional tuning structures (7) are respectively connected to the two ends of the conduction band of the cross-shaped coupler. The additional tuning structure (7) and the equivalent distributed capacitance of the conduction band of the cross-shaped coupler form a parallel relationship.
7. A miniaturized dual-transmission zero-point multimode filter according to claim 1, characterized in that: The dielectric substrate (1) has a conductive metal ground plane (8) on its bottom layer.