Topological structure and filter
By employing a topology of parallel transmission lines and microstrip lines in the filter, the contradiction between stopband width, design complexity, and performance stability of second-order broadband bandpass filters is resolved, achieving a filter design with wide stopband, high selectivity, and compactness.
Patent Information
- Application Number
- CN202520489933.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-19
- Publication Date
- 2026-03-06
- Estimated Expiration
- 2035-03-19
AI Technical Summary
Existing second-order broadband bandpass filters suffer from a trade-off between stopband width, design complexity, and performance stability, especially in high-frequency, wide-bandwidth scenarios where stopband suppression capability is insufficient.
A topology is adopted, including parallel transmission lines and microstrip lines and open stubs, to form periodic impedance mismatch to reflect signals in specific frequency bands, reduce signal crosstalk, and form a multi-transmission zero and compact structure.
It improves the trade-off between stopband width, design complexity, and performance stability in second-order broadband bandpass filters, achieving a design with wide stopband, high selectivity, and compact structure.
Smart Images
Figure CN223978072U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of filter technology, and in particular to a topology and filter. Background Technology
[0002] Against the backdrop of rapid development in wireless communication and radio frequency systems, broadband bandpass filters, as core components of signal processing, directly affect the system's anti-interference capability and communication quality. While traditional second-order bandpass filters offer advantages such as simple structure and low cost, they generally suffer from insufficient stopband suppression, particularly in terms of stopband width and attenuation depth, making them unsuitable for high-frequency, wide-bandwidth applications.
[0003] In existing technologies, methods such as cascaded low-pass responses or defective ground structures (DGS) are often used to widen the stopband, but these solutions have significant limitations. The aforementioned problems indicate that existing second-order broadband bandpass filters suffer from significant contradictions in stopband width, design complexity, and performance stability, necessitating an innovative design that balances wide stopband, high selectivity, and compact structure. Utility Model Content
[0004] This application provides a topology and filter that can improve the current situation where there are significant contradictions between the stopband width, design complexity and performance stability of second-order broadband bandpass filters.
[0005] To solve the above-mentioned technical problems, this application adopts the following technical solution: providing a topology. The topology includes a first parallel line, a first microstrip line, a fourth microstrip line, an input terminal, an output terminal, a second microstrip line, a third microstrip line, a first open-circuit stub, and a second open-circuit stub. The first parallel line includes a first transmission line and a second transmission line, which are placed parallel to each other. One end of the first microstrip line is connected to one end of the first transmission line, and the input terminal is connected to the other end of the first microstrip line. One end of the fourth microstrip line is connected to one end of the second transmission line, and the output terminal is connected to the other end of the fourth microstrip line. One end of the second microstrip line is connected to the other end of the first transmission line, and the other end of the second microstrip line is connected to the first open-circuit stub. One end of the third microstrip line is connected to the other end of the second transmission line, and the other end of the third microstrip line is connected to the second open-circuit stub.
[0006] Optionally, both the first and second transmission lines extend along a first direction, and are placed close to each other parallel to each other along a second direction. The first and fourth microstrip lines are disposed on either side of the first parallel line along the first direction. The second and third microstrip lines are disposed on either side of the first parallel line along the second direction. The first direction is perpendicular to the second direction.
[0007] Optionally, the second microstrip line is perpendicular to the first transmission line, the first open-circuit stub is perpendicular to the second microstrip line, and the first open-circuit stub is parallel to the first transmission line. The third microstrip line is perpendicular to the second transmission line, the second open-circuit stub is perpendicular to the third microstrip line, and the second open-circuit stub is parallel to the second transmission line.
[0008] Optionally, the first open-circuit stub extends from the output terminal toward the input terminal along the first direction. The second open-circuit stub extends from the input terminal toward the output terminal along the second direction.
[0009] Optionally, the input terminal, the first microstrip line, and the first transmission line are collinear, and the second transmission line, the fourth microstrip line, and the output terminal are collinear.
[0010] Optionally, the input terminal, the first microstrip line, the first transmission line, the second microstrip line, and the first open-circuit stub are rotationally symmetrical with the output terminal, the fourth microstrip line, the second transmission line, the third microstrip line, and the second open-circuit stub.
[0011] Optionally, the electrical length of the first transmission line is equal to the electrical length of the second transmission line. The electrical length of the first microstrip line is equal to the electrical length of the fourth microstrip line. The electrical length of the second microstrip line is equal to the electrical length of the third microstrip line. The electrical length of the first open-circuit stub is equal to the electrical length of the second open-circuit stub.
[0012] Optionally, the sum of the electrical length of the first microstrip line, the electrical length of the first transmission line, the electrical length of the second microstrip line, and the electrical length of the first open stub is a quarter wavelength corresponding to the center frequency of the bandpass filter.
[0013] Optionally, the characteristic impedances of the first transmission line, the second transmission line, the first microstrip line, the second microstrip line, the third microstrip line, the fourth microstrip line, the first open-circuit stub, and the second open-circuit stub are equal.
[0014] To address the aforementioned technical problems, another technical solution adopted in this application is to provide a filter. The filter includes the aforementioned topology.
[0015] The beneficial effects of this application embodiment are as follows: Unlike the prior art, this application embodiment provides a topology including a first parallel line, a first microstrip line, a fourth microstrip line, an input terminal, an output terminal, a second microstrip line, a third microstrip line, a first open-circuit stub, and a second open-circuit stub. The first parallel line includes a first transmission line and a second transmission line, which are placed parallel to each other. One end of the first microstrip line is connected to one end of the first transmission line, and the input terminal is connected to the other end of the first microstrip line. One end of the fourth microstrip line is connected to one end of the second transmission line, and the output terminal is connected to the other end of the fourth microstrip line. One end of the second microstrip line is connected to the other end of the first transmission line, and the other end of the second microstrip line is connected to the first open-circuit stub. One end of the third microstrip line is connected to the other end of the second transmission line, and the other end of the third microstrip line is connected to the second open-circuit stub. With the above structure, the parallel first and second transmission lines constitute the first parallel line. Coupling between the parallel lines may cause periodic disturbances in the transmission line impedance. This periodic impedance mismatch reflects signals in specific frequency bands, creating a wide stopband. Specifically, the first microstrip line is connected only to the first transmission line, the second microstrip line is connected only to the first transmission line, the third microstrip line is connected only to the second transmission line, and the fourth microstrip line is connected only to the second transmission line. That is, when a single microstrip line is connected to only one of the parallel transmission lines, the other transmission line can act as a shield, reducing crosstalk between signals. This results in a multi-transmission zero, compact structure, and high-frequency topology, resolving the trade-off between stopband width, design complexity, and performance stability in second-order broadband bandpass filters. Attached Figure Description
[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application 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 the drawings without creative effort.
[0017] Figure 1 This is a schematic diagram of the topology provided in one embodiment of this application;
[0018] Figure 2 This is a layout diagram of a filter provided in one embodiment of this application;
[0019] Figure 3This is a graph showing the variation of the S-parameter simulation results of a bandpass filter provided in one embodiment of this application with different s1 values;
[0020] Figure 4 This is a graph showing the variation of the S-parameter simulation results of a bandpass filter provided in one embodiment of this application with different w1 values;
[0021] Figure 5 This is a simulation result diagram of the S-parameters of a broadband bandpass filter provided in one embodiment of this application.
[0022] The attached figures are labeled as follows:
[0023] Topology 100 Third microstrip line 22 First parallel line 10 Fourth microstrip line 23 First transmission line 11 First branch of the road 30 Second transmission line 12 Second branch 31 First microstrip line 20 Input end 40 Second microstrip line 21 Output 50 Detailed Implementation
[0024] To facilitate understanding of this application, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as being "connected" to another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this specification are for illustrative purposes only.
[0025] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.
[0026] Please see Figure 1This application provides a topology 100, which includes a first parallel line 10, a first microstrip line 20, a fourth microstrip line 23, an input terminal 40, an output terminal 50, a second microstrip line 21, a third microstrip line 22, a first open-circuit stub 30, and a second open-circuit stub 31. The first parallel line 10 includes a first transmission line 11 and a second transmission line 12, which are placed parallel to each other. One end of the first microstrip line 20 is connected to one end of the first transmission line 11, and the input terminal 40 is connected to the other end of the first microstrip line 20. One end of the fourth microstrip line 23 is connected to one end of the second transmission line 12, and the output terminal 50 is connected to the other end of the fourth microstrip line 23. One end of the second microstrip line 21 is connected to the other end of the first transmission line 11, and the other end of the second microstrip line 21 is connected to the first open-circuit stub 30. One end of the third microstrip line 22 is connected to the other end of the second transmission line 12, and the other end of the third microstrip line 22 is connected to the second open-circuit stub 31. With the above structure, the first transmission line 11 and the second transmission line 12, placed in parallel, constitute the first parallel line 10. The coupling between the parallel lines may cause periodic disturbances in the transmission line impedance. This periodic impedance mismatch will reflect signals in a specific frequency band, forming a wide stopband. Specifically, the first microstrip line 20 is connected only to the first transmission line 11, the second microstrip line 21 is connected only to the first transmission line 11, the third microstrip line 22 is connected only to the second transmission line 12, and the fourth microstrip line 23 is connected only to the second transmission line 12. That is, when a single microstrip line is connected to only one of the parallel transmission lines, the other transmission line can act as a shield, reducing crosstalk between signals. This forms a multi-transmission zero, compact structure, and high-frequency topology 100, improving the trade-off between stopband width, design complexity, and performance stability in a second-order broadband bandpass filter.
[0027] In some embodiments, both the first transmission line 11 and the second transmission line 12 extend along a first direction, and are placed close to each other along a second direction. "The first transmission line 11 and the second transmission line 12 are placed close to each other along the second direction" means that in the second direction, the first transmission line 11 and the second transmission line 12 are parallel and close together. This structure creates controllable electromagnetic coupling, improves the compactness of the layout, makes the topology 100 multifunctional, and reduces costs. The first microstrip line 20 and the fourth microstrip line 23 are disposed on both sides of the first parallel line 10 along the first direction. The second microstrip line 21 and the third microstrip line 22 are disposed on both sides of the first parallel line 10 along the second direction. The first direction is perpendicular to the second direction. This structure gives the topology 100 symmetry, thereby balancing electrical characteristics, suppressing interference, simplifying design, and improving reliability.
[0028] In some embodiments, the second microstrip line 21 is perpendicular to the first transmission line 11, and the first open-circuit stub 30 is perpendicular to and parallel to the first transmission line 11. The third microstrip line 22 is perpendicular to the second transmission line 12, and the second open-circuit stub 31 is perpendicular to the third microstrip line 22 and parallel to the second transmission line 12. This optimizes the distribution of the topology 100, facilitating miniaturized and integrated design.
[0029] Furthermore, the first open-circuit stub 30 extends from the output end 50 toward the input end 40 along a first direction. The second open-circuit stub 31 extends from the input end 40 toward the output end 50 along a second direction. This causes the first open-circuit stub 30 and the second open-circuit stub 31 to extend inward, thereby reducing the overall volume and improving compactness.
[0030] In some embodiments, the input terminal 40, the first microstrip line 20, and the first transmission line 11 are collinear, and the second transmission line 12, the fourth microstrip line 23, and the output terminal 50 are collinear. This structure reduces path corners or structural abrupt changes, thereby reducing reflection losses and parasitic parameters caused by impedance discontinuities, improving signal transmission efficiency, facilitating precise phase control, and reducing crosstalk.
[0031] In some embodiments, the input terminal 40, the first microstrip line 20, the first transmission line 11, the second microstrip line 21, and the first open-circuit stub 30 are rotationally symmetrical with the output terminal 50, the fourth microstrip line 23, the second transmission line 12, the third microstrip line 22, and the second open-circuit stub 31. This rotationally symmetrical structure homogenizes the physical field distribution of the topology 100, simplifies the filter manufacturing process, and enhances overall robustness.
[0032] In some embodiments, the electrical lengths of the first transmission line 11 and the second transmission line 12 are equal. The electrical lengths of the first microstrip line 20 and the fourth microstrip line 23 are equal. The electrical lengths of the second microstrip line 21 and the third microstrip line 22 are equal. The electrical lengths of the first open stub 30 and the second open stub 31 are equal.
[0033] In some embodiments, the sum of the electrical length of the first microstrip line 20, the electrical length of the first transmission line 11, the electrical length of the second microstrip line 21, and the electrical length of the first open stub 30 is a quarter wavelength corresponding to the center frequency of the bandpass filter.
[0034] In some embodiments, the characteristic impedances of the first transmission line 11, the second transmission line 12, the first microstrip line 20, the second microstrip line 21, the third microstrip line 22, the fourth microstrip line 23, the first open stub 30, and the second open stub 31 are equal.
[0035] The broadband bandpass filter designed based on this topology 100 has six design parameters: the physical length l1 of the first microstrip line 20 or the fourth microstrip line 23, the physical length l2 of the first transmission line 11 or the second transmission line 12, the physical length l3 of the second microstrip line 21 or the third microstrip line 22, the physical length l4 of the first open stub 30 or the second open stub 31, the spacing s1 between the first transmission line 11 and the second transmission line 12, and the physical widths w1 of the first transmission line 11, the second transmission line 12, the first microstrip line 20, the second microstrip line 21, the third microstrip line 22, the fourth microstrip line 23, the first open stub 30, and the second open stub 31. According to fundamental microwave theory, l1, l2, l3, and l4 determine the center frequency of the bandpass filter. Changing the values of l1, l2, l3, and l4 proportionally changes the center frequency of the bandpass filter inversely. s1 and w1 determine the performance of the filter.
[0036] One example of a bandpass filter based on this topology 100 was designed on a circuit board with a dielectric loss of 0.0022 and a thickness of 0.813 mm, and the circuit board dimensions were 13 mm * 4.8 mm. Figure 2 As shown. One set of typical dimensional parameters is: l1 = 0.9 mm, l2 = 7.6 mm, l3 = 1.2 mm, l4 = 2.2 mm, s1 = 0.1 mm, w1 = 0.15 mm.
[0037] Figure 3 The effect of changing only s1 on filter performance is shown. Figure 3 It can be seen that as the value of parameter s1 increases, the operating bandwidth of the bandpass filter decreases, the reflection coefficient in the passband improves, the isolation of the lower stopband improves, the isolation of the low-frequency part of the upper stopband improves, and the high-frequency part of the upper stopband first deteriorates and then improves.
[0038] Figure 4 The effect of changing only w1 on filter performance is shown. Figure 4 It can be seen that as the value of parameter w1 increases, the operating bandwidth of the bandpass filter decreases, the reflection coefficient in the passband improves, and the isolation in the stopband deteriorates.
[0039] Combination Figure 3 and Figure 4 Analysis shows that, regardless of how the parameters s1 and w1 are changed, the filter designed based on this topology 100 can only be a bandpass filter.
[0040] The simulation results of the S-parameters of the broadband bandpass filters corresponding to the above typical dimensions are as follows: Figure 5 As shown in the figure, the impedance bandwidth with a reflection coefficient less than -10dB ranges from 3.18 to 5.62 GHz, the passband center frequency is 4.4 GHz, the absolute passband bandwidth is 2.44 GHz, and the relative passband bandwidth is 55.5%. Furthermore, within the passband, there are two transmission poles located at 3.6 GHz and 5.1 GHz, respectively. These two transmission poles not only ensure the flatness of the passband filter but also directly prove that the filter designed based on this topology is a second-order bandpass filter. In the stopband, there are five transmission zeros located at 0, 9.53, 12.5, 15.77, and 17.9 GHz; the lower stopband bandwidth with isolation greater than 10dB ranges from 0 to 1.84 GHz, and the upper stopband bandwidth with isolation greater than 10dB ranges from 8.32 to 17.96 GHz, exhibiting wide stopband characteristics.
[0041] This application aims to provide a topology 100, which includes a first parallel line 10, a first microstrip line 20, a fourth microstrip line 23, an input terminal 40, an output terminal 50, a second microstrip line 21, a third microstrip line 22, a first open-circuit stub 30, and a second open-circuit stub 31. The first parallel line 10 includes a first transmission line 11 and a second transmission line 12, which are placed parallel to each other. One end of the first microstrip line 20 is connected to one end of the first transmission line 11, and the input terminal 40 is connected to the other end of the first microstrip line 20. One end of the fourth microstrip line 23 is connected to one end of the second transmission line 12, and the output terminal 50 is connected to the other end of the fourth microstrip line 23. One end of the second microstrip line 21 is connected to the other end of the first transmission line 11, and the other end of the second microstrip line 21 is connected to the first open-circuit stub 30. One end of the third microstrip line 22 is connected to the other end of the second transmission line 12, and the other end of the third microstrip line 22 is connected to the second open-circuit stub 31. With the above structure, the first transmission line 11 and the second transmission line 12, placed in parallel, constitute the first parallel line 10. The coupling between the parallel lines may cause periodic disturbances in the transmission line impedance. This periodic impedance mismatch will reflect signals in a specific frequency band, forming a wide stopband. Specifically, the first microstrip line 20 is connected only to the first transmission line 11, the second microstrip line 21 is connected only to the first transmission line 11, the third microstrip line 22 is connected only to the second transmission line 12, and the fourth microstrip line 23 is connected only to the second transmission line 12. That is, when a single microstrip line is connected to only one of the parallel transmission lines, the other transmission line can act as a shield, reducing crosstalk between signals. This forms a multi-transmission zero, compact structure, and high-frequency topology 100, improving the trade-off between stopband width, design complexity, and performance stability in a second-order broadband bandpass filter.
[0042] Based on the same inventive concept, this application also provides a filter, which includes a topology 100. This topology 100 has the same structure and function as the topology 100 described above, and will not be repeated here. Therefore, this filter can also improve the contradiction between stopband width, design complexity, and performance stability in current second-order broadband bandpass filters.
[0043] It should be noted that while preferred embodiments of this application are provided in the specification and accompanying drawings, this application can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are not intended to impose additional limitations on the content of this application; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of this application. Furthermore, the above-described technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of this application's specification. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.
Claims
1. A topology applied to a filter, characterized in that, The topology structure comprises: a first parallel line, a first microstrip line, a fourth microstrip line, an input terminal and an output terminal, the first parallel line comprises a first transmission line and a second transmission line, the first transmission line and the second transmission line are placed in parallel, one end of the first microstrip line is connected to one end of the first transmission line, the input terminal is connected to the other end of the first microstrip line, one end of the fourth microstrip line is connected to one end of the second transmission line, and the output terminal is connected to the other end of the fourth microstrip line; a second microstrip line, a third microstrip line, a first open stub and a second open stub, one end of the second microstrip line is connected to the other end of the first transmission line, the other end of the second microstrip line is connected to the first open stub, one end of the third microstrip line is connected to the other end of the second transmission line, and the other end of the third microstrip line is connected to the second open stub.
2. The topology of claim 1, wherein, The first transmission line and the second transmission line extend along a first direction, and the first transmission line and the second transmission line are placed in close proximity in parallel along a second direction; The first microstrip line and the fourth microstrip line are arranged on two sides of the first parallel line along the first direction; The second microstrip line and the third microstrip line are arranged on two sides of the first parallel line along the second direction; The first direction is perpendicular to the second direction.
3. The topology structure according to claim 2, wherein: The second microstrip line is perpendicular to the first transmission line, the first open stub is perpendicular to the second microstrip line, and the first open stub is parallel to the first transmission line; The third microstrip line is perpendicular to the second transmission line, the second open stub is perpendicular to the third microstrip line, and the second open stub is parallel to the second transmission line.
4. The topology of claim 3, wherein, The first open stub extends along the first direction from the output terminal towards the input terminal; The second open stub extends along the second direction from the input terminal towards the output terminal.
5. The topology of claim 3, wherein, The input terminal, the first microstrip line and the first transmission line are collinear, and the second transmission line, the fourth microstrip line and the output terminal are collinear.
6. The topology of claim 4, wherein, The input terminal, the first microstrip line, the first transmission line, the second microstrip line and the first open stub, and The output terminal, the fourth microstrip line, the second transmission line, the third microstrip line and the second open stub are rotationally symmetrical.
7. The topology of claim 6, wherein, The electrical length of the first transmission line is equal to the electrical length of the second transmission line; The electrical length of the first microstrip line is equal to the electrical length of the fourth microstrip line; The electrical length of the second microstrip line is equal to the electrical length of the third microstrip line; The electrical length of the first open stub is equal to the electrical length of the second open stub.
8. The topology of claim 7, wherein, The sum of the electrical length of the first microstrip line, the electrical length of the first transmission line, the electrical length of the second microstrip line and the electrical length of the first open stub is equal to one quarter of the wavelength corresponding to the center frequency of the band-pass filter.
9. The topology of any of claims 1-7, wherein, impedance of the first transmission line, the characteristic impedance of the second transmission line, the characteristic impedance of the first microstrip line, the characteristic impedance of the second microstrip line, the characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the first open-circuit stub, and the characteristic impedance of the second open-circuit stub are equal.
10. A filter, characterized by, comprising a topology as claimed in any of claims 1-9.