Topological structure and filter

Abstract

The embodiment of the invention relates to the technical field of filters, and particularly discloses a topological structure and a filter. Comprising a parallel line, two parallel three lines, four microstrip lines, eight short-circuit branches, an input end and an output end. The first parallel three line and the second parallel three line are symmetrically arranged at two ends of the first parallel line. The first end of the first microstrip line is connected with the first parallel line and the first parallel three-line, the first end of the second microstrip line is connected with the first parallel line and the first parallel three-line, the first microstrip line and the second microstrip line are symmetrically arranged on the two sides of the first parallel line, and the first short-circuit branch knot and the second short-circuit branch knot are both connected with the second end of the first microstrip line. The third short-circuit branch knot and the fourth short-circuit branch knot are connected with the second end of the second microstrip line. The structures of the third microstrip line, the fourth microstrip line, the fifth short-circuit branch knot, the sixth short-circuit branch knot, the seventh short-circuit branch knot and the eighth short-circuit branch knot are similar. Through the structure, the filter is compact, high in selectivity, wide in stop band and high in isolation degree.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of filter technology, and in particular to a topology structure and a filter. Background Art

[0002] Ultra Wide Band (UWB) technology is a wireless carrier communication technology that does not use a sinusoidal carrier but instead uses nanosecond-level non-sinusoidal narrow pulses to transmit data, so it occupies a wide spectrum range.

[0003] With the rapid evolution of modern wireless communication technology, the development of broadband communication systems that can meet people's needs for high-speed data transmission is an inevitable trend. In this context, the research on miniaturization of bandpass filters, one of the key components of communication systems, has extremely high scientific research and commercial value, and has attracted the attention of many scholars and engineers.

[0004] The inventors discovered during the process of implementing the present application that currently, miniaturized broadband filters often have defects such as non-compact structure, poor selectivity, narrow stopband, and low isolation, which seriously affect their use in modern wireless communication systems. Summary of the invention

[0005] The embodiments of the present application provide a topology structure and a filter, which can improve some of the above-mentioned problems.

[0006] In order to solve the above technical problems, a technical solution adopted by the present application is: to provide a topological structure, which is applied to a filter. The topological structure includes: a first parallel line, a first parallel three-line, a second parallel three-line, a first microstrip line, a second microstrip line, a first short-circuit branch, a second short-circuit branch, a third short-circuit branch, a fourth short-circuit branch, a third microstrip line, a fourth microstrip line, a fifth short-circuit branch, a sixth short-circuit branch, a seventh short-circuit branch, an eighth short-circuit branch, and an output end and an input end. The first parallel line, the first parallel three-line, the second parallel three-line, the input end and the output end, the first parallel three-line and the second parallel three-line are symmetrically arranged at the two ends of the first parallel line, the input end is connected to the end of the first parallel three-line away from the first parallel line, and the output end is connected to the end of the second parallel three-line away from the first parallel line. The first microstrip line, the second microstrip line, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch, the first end of the first microstrip line is connected to the first parallel line and the first three parallel lines, the first end of the second microstrip line is connected to the first parallel line and the first three parallel lines, the first microstrip line and the second microstrip line are symmetrically arranged on both sides of the first parallel line, the first short-circuit branch and the second short-circuit branch are both connected to the second end of the first microstrip line, and the third short-circuit branch and the fourth short-circuit branch are both connected to the second end of the second microstrip line. A third microstrip line, a fourth microstrip line, a fifth short-circuit branch, a sixth short-circuit branch, a seventh short-circuit branch and an eighth short-circuit branch, the first end of the third microstrip line is connected to the first parallel line and the second parallel three lines, the first end of the fourth microstrip line is connected to the first parallel line and the second parallel three lines, the third microstrip line and the fourth microstrip line are symmetrically arranged on both sides of the first parallel line, the fifth short-circuit branch and the sixth short-circuit branch are both connected to the second end of the third microstrip line, and the seventh short-circuit branch and the eighth short-circuit branch are both connected to the second end of the fourth microstrip line.

[0007] In some embodiments, the first microstrip line and the third microstrip line are symmetrically arranged at two ends of the first parallel line. The second microstrip line and the fourth microstrip line are symmetrically arranged at two ends of the first parallel line. The first microstrip line and the third microstrip line are both located on the same side of the first parallel line.

[0008] In some embodiments, the first short-circuit branch and the second short-circuit branch are symmetrically arranged on both sides of the first microstrip line. The third short-circuit branch and the fourth short-circuit branch are symmetrically arranged on both sides of the second microstrip line. The fifth short-circuit branch and the sixth short-circuit branch are symmetrically arranged on both sides of the third microstrip line. The seventh short-circuit branch and the eighth short-circuit branch are symmetrically arranged on both sides of the fourth microstrip line.

[0009] In some embodiments, the first parallel line, the first parallel three lines, the second parallel three lines, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch, the fourth short-circuit branch, the fifth short-circuit branch, the sixth short-circuit branch, the seventh short-circuit branch, and the eighth short-circuit branch all extend along a first direction. The first microstrip line, the second microstrip line, the third microstrip line, and the fourth microstrip line all extend along a second direction. The first direction is perpendicular to the second direction.

[0010] In some embodiments, the first short-circuit branch and the third short-circuit branch are symmetrically arranged on both sides of the first three parallel lines. The second short-circuit branch and the fourth short-circuit branch are symmetrically arranged on both sides of the first parallel line. The fifth short-circuit branch and the seventh short-circuit branch are symmetrically arranged on both sides of the first parallel line. The sixth short-circuit branch and the eighth short-circuit branch are symmetrically arranged on both sides of the second three parallel lines.

[0011] In some embodiments, the electrical length of the first parallel line, the electrical length of the first parallel three lines, and the electrical length of the second parallel three lines are equal, and are all equal to a quarter wavelength corresponding to the center frequency of the filter. The electrical length of the first microstrip line, the electrical length of the second microstrip line, the electrical length of the third microstrip line, and the electrical length of the fourth microstrip line are all equal. The electrical length of the first short-circuit branch, the electrical length of the second short-circuit branch, the electrical length of the third short-circuit branch, the electrical length of the fourth short-circuit branch, the electrical length of the fifth short-circuit branch, the electrical length of the sixth short-circuit branch, the electrical length of the seventh short-circuit branch, and the electrical length of the eighth short-circuit branch are all equal.

[0012] In some embodiments, the sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit stub is greater than the electrical length of the first parallel line.

[0013] In some embodiments, the characteristic impedance of the first short-circuit branch, the characteristic impedance of the second short-circuit branch, the characteristic impedance of the third short-circuit branch, the characteristic impedance of the fourth short-circuit branch, the characteristic impedance of the fifth short-circuit branch, the characteristic impedance of the sixth short-circuit branch, the characteristic impedance of the seventh short-circuit branch, and the characteristic impedance of the eighth short-circuit branch are equal.

[0014] In some embodiments, twice the characteristic impedance of the first microstrip line, twice the characteristic impedance of the second microstrip line, twice the characteristic impedance of the third microstrip line, and twice the characteristic impedance of the fourth microstrip line are all equal to the characteristic impedance of the first short-circuit branch.

[0015] In order to solve the above technical problem, another technical solution adopted in the embodiment of the present application is: providing a filter, including a circuit board, and the circuit board is provided with the above topological structure.

[0016] The beneficial effect of the embodiment of the present application is that, different from the prior art, the topological structure provided by the embodiment of the present application includes one parallel line, two parallel three lines, four microstrip lines, eight short-circuit branches, one input end and one output end. The first parallel three lines and the second parallel three lines are symmetrically arranged at the two ends of the first parallel line. The first end of the first microstrip line is connected to the first parallel line and the first parallel three lines, the first end of the second microstrip line is connected to the first parallel line and the first parallel three lines, the first microstrip line and the second microstrip line are symmetrically arranged on both sides of the first parallel line, the first short-circuit branch and the second short-circuit branch are both connected to the second end of the first microstrip line, the third short-circuit branch and the fourth short-circuit branch are both connected to the second end of the second microstrip line; the third microstrip line, the fourth microstrip line, the fifth short-circuit branch, the sixth short-circuit branch, the seventh short-circuit branch and the eighth short-circuit branch have similar arrangement structures. By redesigning the internal structure of the topological structure, it has the advantages of compactness, high selectivity, wide resistance band and high isolation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0018] Figure 1 It is a schematic diagram of the topological structure of an embodiment of the present application.

[0019] Figure 2 This is the layout diagram of the topological structure of the embodiment of the present application on the circuit board.

[0020] Figure 3 It is an S parameter simulation diagram of the filter according to the embodiment of the present application.

[0021] The reference numerals are as follows:

[0022] Topology 100 First short circuit branch 31 The first parallel 11 Second short circuit branch 32 The first three parallel lines 12 The third short circuit branch 33 The second parallel line 13 The fourth short circuit 34 First microstrip line 21 The Fifth Short Circuit 35 Second microstrip line 22 The Sixth Short Circuit 36 The third microstrip line 23 The Seventh Short Circuit 37 Fourth microstrip line 24 The Eighth Short Circuit 38 Input 41 Output 42 DETAILED DESCRIPTION

[0023] In order to facilitate the understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as "fixed to" another element, it can be directly on the other element, or there can be one or more centered elements therebetween. When an element is described as "connected to" another element, it can be directly connected to the other element, or there can be one or more centered elements therebetween. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this specification are for illustrative purposes only.

[0024] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in this specification and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0025] At present, most miniaturized broadband filters often have defects such as non-compact structure, poor selectivity, narrow stopband, and low isolation, which seriously affect their use in modern wireless communication systems. Based on this, the present application provides the following technical solutions.

[0026] See also Figure 1 The present application provides a topological structure 100, including a first parallel line 11, a first parallel three-line 12, a second parallel three-line 13, an input end 41, an output end 42, a first microstrip line 21, a second microstrip line 22, a first short-circuit branch 31, a second short-circuit branch 32, a third short-circuit branch 33, a fourth short-circuit branch 34, a third microstrip line 23, a fourth microstrip line 24, a fifth short-circuit branch 35, a sixth short-circuit branch 36, a seventh short-circuit branch 37, and an eighth short-circuit branch 38. The first parallel three-line 12 and the second parallel three-line 13 are symmetrically arranged at both ends of the first parallel line 11, the input end 41 is connected to the end of the first parallel three-line 12 away from the first parallel line 11, and the output end 42 is connected to the end of the second parallel three-line 13 away from the first parallel line 11. The first end of the first microstrip line 21 is connected to the first parallel line 11 and the first parallel three lines 12, the first end of the second microstrip line 22 is connected to the first parallel line 11 and the first parallel three lines 12, the first microstrip line 21 and the second microstrip line 22 are symmetrically arranged on both sides of the first parallel line 11, the first short-circuit branch 31 and the second short-circuit branch 32 are both connected to the second end of the first microstrip line 21, and the third short-circuit branch 33 and the fourth short-circuit branch 34 are both connected to the second end of the second microstrip line 22. The first end of the third microstrip line 23 is connected to the first parallel line 11 and the second parallel three lines 13, the first end of the fourth microstrip line 24 is connected to the first parallel line 11 and the second parallel three lines 13, the third microstrip line 23 and the fourth microstrip line 24 are symmetrically arranged on both sides of the first parallel line 11, the fifth short-circuit branch 35 and the sixth short-circuit branch 36 are both connected to the second end of the third microstrip line 23, and the seventh short-circuit branch 37 and the eighth short-circuit branch 38 are both connected to the second end of the fourth microstrip line 24.

[0027] In some embodiments, see Figure 1, the first microstrip line 21 and the third microstrip line 23 are symmetrically arranged at the two ends of the first parallel line 11. The second microstrip line 22 and the fourth microstrip line 24 are symmetrically arranged at the two ends of the first parallel line 11. The first microstrip line 21 and the third microstrip line 23 are both located on the same side of the first parallel line 11. Through the above structural design, the first microstrip line 21 and the third microstrip line 23 can make full use of the space at both ends of the first parallel line 11, the second microstrip line 22 and the fourth microstrip line 24 can make full use of the space at both ends of the first parallel line 11, and the first microstrip line 21 and the third microstrip line 23 are located at the different ends of the same side of the first parallel line 11, so as to improve the space utilization rate, improve the compactness of the structure, and facilitate the miniaturization of the equipment.

[0028] In some embodiments, see Figure 1 The first short-circuit branch 31 and the second short-circuit branch 32 are symmetrically arranged on both sides of the first microstrip line 21. The third short-circuit branch 33 and the fourth short-circuit branch 34 are symmetrically arranged on both sides of the second microstrip line 22. The fifth short-circuit branch 35 and the sixth short-circuit branch 36 are symmetrically arranged on both sides of the third microstrip line 23. The seventh short-circuit branch 37 and the eighth short-circuit branch 38 are symmetrically arranged on both sides of the fourth microstrip line 24.

[0029] In some embodiments, see Figure 1 The first parallel line 11, the first parallel three lines 12, the second parallel three lines 13, the first short-circuit branch 31, the second short-circuit branch 32, the third short-circuit branch 33, the fourth short-circuit branch 34, the fifth short-circuit branch 35, the sixth short-circuit branch 36, the seventh short-circuit branch 37 and the eighth short-circuit branch 38 all extend along the first direction. The first microstrip line 21, the second microstrip line 22, the third microstrip line 23 and the fourth microstrip line 24 all extend along the second direction. The first direction is perpendicular to the second direction.

[0030] In some embodiments, the first short-circuit branch 31 and the third short-circuit branch 33 are symmetrically arranged on both sides of the first parallel three lines 12. The second short-circuit branch 32 and the fourth short-circuit branch 34 are symmetrically arranged on both sides of the first parallel line 11. The fifth short-circuit branch 35 and the seventh short-circuit branch 37 are symmetrically arranged on both sides of the first parallel line 11. The sixth short-circuit branch 36 and the eighth short-circuit branch 38 are symmetrically arranged on both sides of the second parallel three lines 13.

[0031] In some embodiments, see Figure 1 and Figure 2, the electrical length of the first parallel line 11, the electrical length of the first parallel three lines 12 and the electrical length of the second parallel three lines 13 are equal, and are all equal to a quarter wavelength corresponding to the center frequency of the filter. The electrical length of the first microstrip line 21, the electrical length of the second microstrip line 22, the electrical length of the third microstrip line 23, and the electrical length of the fourth microstrip line 24 are all equal. The electrical length of the first short-circuit branch 31, the electrical length of the second short-circuit branch 32, the electrical length of the third short-circuit branch 33, the electrical length of the fourth short-circuit branch 34, the electrical length of the fifth short-circuit branch 35, the electrical length of the sixth short-circuit branch 36, the electrical length of the seventh short-circuit branch 37, and the electrical length of the eighth short-circuit branch 38 are all equal.

[0032] In some embodiments, see Figure 1 and Figure 2 , the sum of the electrical length of the first microstrip line 21 and the electrical length of the first short-circuit branch 31 is greater than the electrical length of the first parallel line 11 .

[0033] In some embodiments, the characteristic impedance of the first short-circuit branch 31, the characteristic impedance of the second short-circuit branch 32, the characteristic impedance of the third short-circuit branch 33, the characteristic impedance of the fourth short-circuit branch 34, the characteristic impedance of the fifth short-circuit branch 35, the characteristic impedance of the sixth short-circuit branch 36, the characteristic impedance of the seventh short-circuit branch 37, and the characteristic impedance of the eighth short-circuit branch 38 are equal.

[0034] In some embodiments, twice the characteristic impedance of the first microstrip line 21 , twice the characteristic impedance of the second microstrip line 22 , twice the characteristic impedance of the third microstrip line 23 , and twice the characteristic impedance of the fourth microstrip line 24 are all equal to the characteristic impedance of the first short-circuit branch 31 .

[0035] The present application provides a topological structure 100, including: a first parallel line 11, a first parallel three-line 12, a second parallel three-line 13, a first microstrip line 21, a second microstrip line 22, a first short-circuit branch 31, a second short-circuit branch 32, a third short-circuit branch 33, a fourth short-circuit branch 34, a third microstrip line 23, a fourth microstrip line 24, a fifth short-circuit branch 35, a sixth short-circuit branch 36, a seventh short-circuit branch 37, an eighth short-circuit branch 38, an output terminal 42, and an input terminal 41. The first parallel line 11, the first parallel three-line 12, the second parallel three-line 13, the input terminal 41, and the output terminal 42, the first parallel three-line 12 and the second parallel three-line 13 are symmetrically arranged at both ends of the first parallel line 11, the input terminal is connected to the end of the first parallel three-line 12 away from the first parallel line 11, and the output terminal 42 is connected to the end of the second parallel three-line 13 away from the first parallel line 11. The first microstrip line 21, the second microstrip line 22, the first short-circuit branch 31, the second short-circuit branch 32, the third short-circuit branch 33 and the fourth short-circuit branch 34, the first end of the first microstrip line 21 is connected to the first parallel line 11 and the first parallel three lines 12, the first end of the second microstrip line 22 is connected to the first parallel line 11 and the first parallel three lines 12, the first microstrip line 21 and the second microstrip line 22 are symmetrically arranged on both sides of the first parallel line 11, the first short-circuit branch 31 and the second short-circuit branch 32 are both connected to the second end of the first microstrip line 21, and the third short-circuit branch 33 and the fourth short-circuit branch 34 are both connected to the second end of the second microstrip line 22. The third microstrip line 23, the fourth microstrip line 24, the fifth short-circuit branch 35, the sixth short-circuit branch 36, the seventh short-circuit branch 37 and the eighth short-circuit branch 38, the first end of the third microstrip line 23 is connected to the first parallel line 11 and the second parallel three-line 13, the first end of the fourth microstrip line 24 is connected to the first parallel line 11 and the second parallel three-line 13, the third microstrip line 23 and the fourth microstrip line 24 are symmetrically arranged on both sides of the first parallel line 11, the fifth short-circuit branch 35 and the sixth short-circuit branch 36 are both connected to the second end of the third microstrip line 23, and the seventh short-circuit branch 37 and the eighth short-circuit branch 38 are both connected to the second end of the fourth microstrip line 24. By redesigning the internal structure of the topological structure 100, it has the advantages of compactness, high selectivity, wide resistance band and high isolation.

[0036] Based on the same inventive concept, the present application also provides a filter, the filter includes a circuit board, and the circuit board is provided with a topological structure 100 in any of the above embodiments and combinations thereof. For the specific structure and function of the topological structure 100, please refer to any of the above embodiments, which will not be repeated here.

[0037] This application uses a simulation example to illustrate the characteristics of this topology 100. The filter example is designed on a circuit board with a dielectric constant of 3.38, a dielectric loss of 0.0022, and a thickness of 0.813 mm. Its layout is shown in the following figure. Figure 2The size of the entire layout is only 26.6mm*13.0mm, and the specific size of the filter is:

[0038] l T =7.0mm,s T =0.1mm,w T =0.3mm,l p =7.0mm,s p =0.15mm,w p =0.25mm,l 1 =5.

[0039] 85mm,w 1 =1.0mm,l 2 =3.3mm,w 2 =1.0mm.

[0040] The S parameter simulation results are as follows: Figure 3 As shown. Its passband range with reflection coefficient better than -10dB is 3.32GHz to 9.76GHz, the center frequency is 6.54GHz, the absolute bandwidth is 6.44GHz, and the relative bandwidth is 98.5%. In addition, there are eight transmission poles in the passband, located at 3.46, 3.74, 5.24, 5.83, 7.68, 8.46, 9.08, and 9.56GHz, respectively. These eight transmission poles not only ensure the flatness of the passband, but also directly prove that the ultra-wideband filter designed based on the topology 100 is an eighth-order filter. There are four transmission zeros in the stopband, located at 0, 0.54, 0.68, and 10.64GHz, respectively. These four transmission zeros ensure the high selectivity, wide stopband, and high isolation of the filter.

[0041] It should be noted that the preferred embodiments of the present application are given in the specification and drawings of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described in the specification. These embodiments are not used as additional limitations on the content of the present application. The purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive. In addition, the above-mentioned technical features continue to be combined with each other to form various embodiments not listed above, which are all regarded as the scope of the description of the present application; further, for ordinary technicians in this field, they can be improved or transformed according to the above description, and all these improvements and transformations should belong to the scope of protection of the claims attached to the present application.

Claims

1. A topological structure, applied to a filter, characterized in that: include: A first parallel line, a first parallel three lines, a second parallel three lines, an input end, and an output end, wherein the first parallel three lines and the second parallel three lines are symmetrically arranged at two ends of the first parallel line, the input end is connected to the end of the first parallel three lines away from the first parallel line, and the output end is connected to the end of the second parallel three lines away from the first parallel line; a first microstrip line, a second microstrip line, a first short-circuit branch, a second short-circuit branch, a third short-circuit branch and a fourth short-circuit branch, wherein a first end of the first microstrip line is connected to the first parallel line and the first three parallel lines, a first end of the second microstrip line is connected to the first parallel line and the first three parallel lines, the first microstrip line and the second microstrip line are symmetrically arranged on both sides of the first parallel line, the first short-circuit branch and the second short-circuit branch are both connected to the second end of the first microstrip line, and the third short-circuit branch and the fourth short-circuit branch are both connected to the second end of the second microstrip line; A third microstrip line, a fourth microstrip line, a fifth short-circuit branch, a sixth short-circuit branch, a seventh short-circuit branch and an eighth short-circuit branch, the first end of the third microstrip line is connected to the first parallel line and the second parallel three lines, the first end of the fourth microstrip line is connected to the first parallel line and the second parallel three lines, the third microstrip line and the fourth microstrip line are symmetrically arranged on both sides of the first parallel line, the fifth short-circuit branch and the sixth short-circuit branch are both connected to the second end of the third microstrip line, and the seventh short-circuit branch and the eighth short-circuit branch are both connected to the second end of the fourth microstrip line.

2. The topological structure according to claim 1, characterized in that: The first microstrip line and the third microstrip line are symmetrically arranged at two ends of the first parallel line; The second microstrip line and the fourth microstrip line are symmetrically arranged at two ends of the first parallel line; The first microstrip line and the third microstrip line are both located on the same side of the first parallel line.

3. The topological structure according to claim 2, characterized in that: The first short-circuit branch and the second short-circuit branch are symmetrically arranged on both sides of the first microstrip line; The third short-circuit branch and the fourth short-circuit branch are symmetrically arranged on both sides of the second microstrip line; The fifth short-circuit branch and the sixth short-circuit branch are symmetrically arranged on both sides of the third microstrip line; The seventh short-circuit branch and the eighth short-circuit branch are symmetrically arranged on both sides of the fourth microstrip line.

4. The topological structure according to claim 3, characterized in that: The first parallel line, the first three parallel lines, the second three parallel lines, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch, the fourth short-circuit branch, the fifth short-circuit branch, the sixth short-circuit branch, the seventh short-circuit branch and the eighth short-circuit branch all extend along the first direction; The first microstrip line, the second microstrip line, the third microstrip line and the fourth microstrip line all extend along the second direction; The first direction is perpendicular to the second direction.

5. The topological structure according to claim 3, characterized in that: The first short-circuit branch and the third short-circuit branch are symmetrically arranged on both sides of the first three parallel lines; The second short-circuit branch and the fourth short-circuit branch are symmetrically arranged on both sides of the first parallel line; The fifth short-circuit branch and the seventh short-circuit branch are symmetrically arranged on both sides of the first parallel line; The sixth short-circuit branch and the eighth short-circuit branch are symmetrically arranged on both sides of the second three parallel lines.

6. The topological structure according to any one of claims 1 to 5, characterized in that: The electrical length of the first parallel line, the electrical length of the first three parallel lines, and the electrical length of the second three parallel lines are equal, and are all equal to a quarter wavelength corresponding to the center frequency of the filter; The electrical length of the first microstrip line, the electrical length of the second microstrip line, the electrical length of the third microstrip line, and the electrical length of the fourth microstrip line are all equal; The electrical length of the first short-circuit branch, the electrical length of the second short-circuit branch, the electrical length of the third short-circuit branch, the electrical length of the fourth short-circuit branch, the electrical length of the fifth short-circuit branch, the electrical length of the sixth short-circuit branch, the electrical length of the seventh short-circuit branch and the electrical length of the eighth short-circuit branch are all equal.

7. The topological structure according to claim 6, characterized in that: The sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit branch is greater than the electrical length of the first parallel line.

8. The topological structure according to any one of claims 1 to 5, characterized in that: The characteristic impedance of the first short-circuit branch, the characteristic impedance of the second short-circuit branch, the characteristic impedance of the third short-circuit branch, the characteristic impedance of the fourth short-circuit branch, the characteristic impedance of the fifth short-circuit branch, the characteristic impedance of the sixth short-circuit branch, the characteristic impedance of the seventh short-circuit branch, and the characteristic impedance of the eighth short-circuit branch are equal.

9. The topological structure according to claim 8, characterized in that: Twice the characteristic impedance of the first microstrip line, twice the characteristic impedance of the second microstrip line, twice the characteristic impedance of the third microstrip line, and twice the characteristic impedance of the fourth microstrip line are all equal to the characteristic impedance of the first short-circuit branch.

10. A filter, characterized in that: It comprises a circuit board, wherein the circuit board is provided with a topological structure as claimed in any one of claims 1 to 9.

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