Topological structure and high-selectivity broadband band-pass filter
By optimizing the topological structure design and combining the combination of parallel lines and microstrip lines, the problem of poor selectivity of existing miniaturized broadband bandpass filters is solved, and a high selectivity and miniaturized broadband bandpass filter is achieved.
Patent Information
- Application Number
- CN202422049703.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-22
- Publication Date
- 2025-08-19
- Estimated Expiration
- 2034-08-22
AI Technical Summary
The existing miniaturized broadband bandpass filters have poor selectivity, which affects the use of modern wireless communication systems.
A specific topological structure design is adopted, including the combination of parallel lines, microstrip lines and short-circuit branches, optimize the electrical length and characteristic impedance, and the overall structure is miniaturized.
A wideband bandpass filter with high selectivity and miniaturization is achieved, with good frequency selectivity and compact structure advantages.
Smart Images
Figure CN223246560U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of filters, in particular to a broadband bandpass filter with a topological structure and high selectivity. Background Art
[0002] With the rapid development of modern wireless communication technology, the development of broadband communication systems that can meet the demand for high-speed data transmission is an inevitable trend. In this context, the research on broadband bandpass filters, a key component in broadband communication systems, has attracted the attention of scholars and engineers due to their high selectivity and miniaturization, which holds great scientific and commercial value. However, the miniaturized broadband bandpass filters reported so far often suffer from poor selectivity, which seriously hinders their use in modern wireless communication systems. Utility Model Content
[0003] In view of the above-mentioned deficiencies in the prior art, the main purpose of the present invention is to provide a broadband bandpass filter with a topological structure and high selectivity, aiming to solve the problem of poor selectivity of the existing broadband bandpass filter.
[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:
[0005] A topological structure includes parallel lines, a first parallel three-line, a second parallel three-line, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, a seventh microstrip line, an eighth microstrip line, a ninth microstrip line, a tenth microstrip line, an eleventh microstrip line, a twelfth microstrip line, a first short-circuit branch, a second short-circuit branch, a third short-circuit branch, a fourth short-circuit branch, an input end, and an output end, wherein one end of the parallel lines is respectively connected to one end of the first parallel three-line, one end of the first microstrip line, and one end of the fourth microstrip line, and the other end of the parallel lines is respectively connected to one end of the second parallel three-line, one end of the seventh microstrip line, and one end of the seventh microstrip line. and one end of the tenth microstrip line, the other end of the first microstrip line is connected to the second microstrip line, the third microstrip line and the first short-circuit branch in sequence, the other end of the fourth microstrip line is connected to the fifth microstrip line, the sixth microstrip line and the second short-circuit branch in sequence, the other end of the seventh microstrip line is connected to the eighth microstrip line, the ninth microstrip line and the third short-circuit branch in sequence, the other end of the tenth microstrip line is connected to the eleventh microstrip line, the twelfth microstrip line and the fourth short-circuit branch in sequence, the other end of the first three parallel lines is connected to the input end, and the other end of the second three parallel lines is connected to the output end.
[0006] Optionally, the first parallel three lines and the second parallel three lines are both composed of three parallel and equidistantly arranged transmission lines, the two outer transmission lines of the first parallel three lines are connected to the input end at one end away from the parallel lines, the middle transmission line of the first parallel three lines is connected to the first microstrip line, the fourth microstrip line and the parallel lines at one end close to the parallel lines, the two outer transmission lines of the second parallel three lines are connected to the output end at one end away from the parallel lines, and the middle transmission line of the second parallel three lines is connected to the seventh microstrip line, the tenth microstrip line and the parallel lines at one end close to the parallel lines.
[0007] Optionally, the parallel lines are composed of two parallel transmission lines, the first parallel three lines, the parallel lines and the second parallel three lines are placed in sequence in the horizontal direction, one transmission line of the parallel lines is connected to the first parallel three lines at one end close to the first parallel three lines, and the other transmission line of the parallel lines is connected to the second parallel three lines at one end close to the second parallel three lines.
[0008] Optionally, the first microstrip line and the fourth microstrip line, the seventh microstrip line and the tenth microstrip line are arranged away from the parallel lines, and the third microstrip line, the sixth microstrip line, the ninth microstrip line, the twelfth microstrip line, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are arranged close to the parallel lines.
[0009] Optionally, the first three parallel lines, the second three parallel lines, the parallel lines, the second microstrip line, the fifth microstrip line, the eighth microstrip line, the eleventh microstrip line, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are parallel to each other and are all perpendicular to the first microstrip line, the third microstrip line, the fourth microstrip line, the sixth microstrip line, the seventh microstrip line, the ninth microstrip line, the tenth microstrip line and the twelfth microstrip line.
[0010] Through the position layout between the aforementioned parts, the overall structure is miniaturized.
[0011] Optionally, the electrical length of the parallel lines, 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 broadband bandpass filter based on the topological structure; the electrical length of the first microstrip line is equal to the electrical length of the tenth microstrip line; the electrical length of the second microstrip line, the electrical length of the fifth microstrip line, the electrical length of the eighth microstrip line, and the electrical length of the eleventh microstrip line are equal; the electrical length of the third microstrip line, the electrical length of the sixth microstrip line, the electrical length of the ninth microstrip line, and the electrical length of the twelfth microstrip line are equal; the electrical length of the fourth microstrip line is equal to the electrical length of the sixth microstrip line The electrical length of the strip line is equal to the electrical length of the seventh microstrip line; the electrical length of the first short-circuit branch is equal to the electrical length of the fourth short-circuit branch; the electrical length of the second short-circuit branch is equal to the electrical length of the third short-circuit branch; the sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit branch is equal to the sum of the electrical length of the fourth microstrip line and the electrical length of the second short-circuit branch; the sum of 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 first short-circuit branch is greater than one-quarter wavelength corresponding to the center frequency of the broadband bandpass filter based on the topological structure.
[0012] Optionally, 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 fifth microstrip line, the characteristic impedance of the sixth microstrip line, the characteristic impedance of the seventh microstrip line, the characteristic impedance of the eighth microstrip line, the characteristic impedance of the ninth microstrip line, the characteristic impedance of the tenth microstrip line, the characteristic impedance of the eleventh microstrip line, the characteristic impedance of the twelfth microstrip line, 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 and the characteristic impedance of the fourth short-circuit branch are equal.
[0013] Another technical solution adopted in the present invention is:
[0014] A high-selectivity broadband bandpass filter comprises the above topological structure.
[0015] Optionally, a circuit board is further included, and the topological structure is arranged on the circuit board. The dielectric constant of the circuit board is 3.38, the dielectric loss is 0.0022, the thickness is 0.813 mm, and the size is 34.4 mm*11.7 mm.
[0016] Optionally, the first three parallel lines and the second three parallel lines are each composed of three parallel and equidistant transmission lines, the parallel lines are composed of two parallel transmission lines, and the specific parameters on the circuit board are set as follows:
[0017] The physical length of the first three parallel lines and the physical length of the second three parallel lines are both denoted as l T , l T =9.7mm;
[0018] The spacing between adjacent transmission lines constituting the first three parallel lines and the spacing between adjacent transmission lines constituting the second three parallel lines are both denoted as s. T , s T =0.1mm;
[0019] The physical width of the transmission line constituting the first three parallel lines and the physical width of the transmission line constituting the second three parallel lines are both denoted as w T , w T =0.2mm;
[0020] The physical length of the parallel line is recorded as l p , l p =9.7mm;
[0021] The spacing between the transmission lines that make up the parallel lines is denoted as s. p , s p =0.1mm;
[0022] The physical width of the transmission lines that make up the parallel lines is recorded as w p , w p =0.2mm;
[0023] The physical length of the fourth microstrip line and the physical length of the seventh microstrip line are both denoted as l1, l1=5.4 mm;
[0024] The physical length of the first microstrip line and the physical length of the tenth microstrip line are both recorded as l2, l2=5.1 mm;
[0025] The physical length of the second microstrip line, the physical length of the fifth microstrip line, the physical length of the eighth microstrip line, and the physical length of the eleventh microstrip line are all denoted as l3, where l3=2 mm;
[0026] The physical length of the third microstrip line, the physical length of the sixth microstrip line, the physical length of the ninth microstrip line, and the physical length of the twelfth microstrip line are all denoted as l4, where l4=1.8 mm;
[0027] The physical length of the second short-circuit branch and the physical length of the third short-circuit branch are both recorded as l5, l5=1.8 mm;
[0028] The physical length of the first short-circuit branch and the physical length of the fourth short-circuit branch are both recorded as l6, l6=2.1 mm;
[0029] The physical width of the first microstrip line, the physical width of the second microstrip line, the physical width of the third microstrip line, the physical width of the fourth microstrip line, the physical width of the fifth microstrip line, the physical width of the sixth microstrip line, the physical width of the seventh microstrip line, the physical width of the eighth microstrip line, the physical width of the ninth microstrip line, the physical width of the tenth microstrip line, the physical width of the eleventh microstrip line, the physical width of the twelfth microstrip line, the physical width of the first short-circuit branch, the physical width of the second short-circuit branch, the physical width of the third short-circuit branch and the physical width of the fourth short-circuit branch are all recorded as w1, w1=0.7mm.
[0030] The beneficial effect of the present invention is that a new topological structure is proposed, which can be used to design a high-selectivity broadband bandpass filter. The broadband bandpass filter based on the topological structure has the advantages of high selectivity and miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 Shown is a schematic diagram of the topological structure of an embodiment of the present utility model;
[0032] Figure 2 Shown is a layout diagram of a highly selective broadband bandpass filter according to an embodiment of the present invention;
[0033] Figure 3 Shown are the S-parameter simulation results of the highly selective broadband bandpass filter according to an embodiment of the present invention. DETAILED DESCRIPTION
[0034] In order to more clearly understand the technical content, achieved purposes and effects of the present invention, the present invention is described in detail below in conjunction with specific implementation methods and in conjunction with the accompanying drawings. It should be noted that, in the absence of conflict, the implementation methods of the present invention and the features in the implementation methods can be combined with each other. In the following description, many specific details are elaborated in order to fully understand the present invention. The implementation methods described are only part of the implementation methods of the present invention, not all of the implementation methods. Based on the implementation methods in the present invention, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0035] Please refer to Figure 1 As shown, the first embodiment of the present utility model is:
[0036] A topology structure mainly consists of a parallel line, a pair of parallel three lines, twelve microstrip lines and four short-circuit branches. Figure 1As shown, it includes parallel lines, a first parallel triplet, a second parallel triplet, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, a seventh microstrip line, an eighth microstrip line, a ninth microstrip line, a tenth microstrip line, an eleventh microstrip line, a twelfth microstrip line, a first short-circuit branch, a second short-circuit branch, a third short-circuit branch, a fourth short-circuit branch, an input end and an output end. The parallel lines are composed of two parallel transmission lines with equal length and width. The first parallel triplet and the second parallel triplet are both composed of three parallel transmission lines with equal length and width. The spacing between two adjacent transmission lines is the same.
[0037] The input end, the first three parallel lines, the parallel line, the second three parallel lines and the output end are placed in sequence in the horizontal direction. One end of a transmission line of the parallel line close to the first three parallel lines is connected to one end of the first three parallel lines, one end of the first microstrip line and one end of the fourth microstrip line respectively, and one end of another transmission line of the parallel line close to the second three parallel lines is connected to one end of the second three parallel lines, one end of the seventh microstrip line and one end of the tenth microstrip line respectively, the other end of the first microstrip line is connected to the second microstrip line, the third microstrip line and the first short-circuit branch in sequence, the other end of the fourth microstrip line is connected to the fifth microstrip line, the sixth microstrip line and the second short-circuit branch in sequence, and the other end of the seventh microstrip line is connected to the The eighth microstrip line, the ninth microstrip line and the third short-circuit branch are connected in sequence, the other end of the tenth microstrip line is connected in sequence to the eleventh microstrip line, the twelfth microstrip line and the fourth short-circuit branch, the other end of the first parallel three lines is connected to the input end, and the other end of the second parallel three lines is connected to the output end, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are all grounded, and the ground end of the first short-circuit branch and the ground end of the third short-circuit branch are connected together, and the ground end of the second short-circuit branch and the ground end of the fourth short-circuit branch are connected together. Specifically, the two outer transmission lines of the first three parallel lines are connected to the input end at one end away from the parallel lines, and the middle transmission line of the first three parallel lines is connected to the first microstrip line, the fourth microstrip line and the parallel lines at one end close to the parallel lines, respectively. The two outer transmission lines of the second three parallel lines are connected to the output end at one end away from the parallel lines, and the middle transmission line of the second three parallel lines is connected to the seventh microstrip line, the tenth microstrip line and the parallel lines at one end close to the parallel lines.
[0038] The first three parallel lines, the second three parallel lines, the parallel lines, the second microstrip line, the fifth microstrip line, the eighth microstrip line, the eleventh microstrip line, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are parallel to each other and are perpendicular to the first microstrip line, the third microstrip line, the fourth microstrip line, the sixth microstrip line, the seventh microstrip line, the ninth microstrip line, the tenth microstrip line and the twelfth microstrip line.
[0039] The first microstrip line, the fourth microstrip line, the seventh microstrip line, and the tenth microstrip line are arranged away from the parallel lines, and the third microstrip line, the sixth microstrip line, the ninth microstrip line, the twelfth microstrip line, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch, and the fourth short-circuit branch are arranged close to the parallel lines.
[0040] The electrical length of the 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 broadband bandpass filter based on the topological structure; the electrical length of the first microstrip line and the electrical length of the tenth microstrip line are equal; the electrical length of the second microstrip line, the electrical length of the fifth microstrip line, the electrical length of the eighth microstrip line and the electrical length of the eleventh microstrip line are equal; the electrical length of the third microstrip line, the electrical length of the sixth microstrip line, the electrical length of the ninth microstrip line and the electrical length of the twelfth microstrip line are equal; the electrical length of the fourth microstrip line The electrical length of the first microstrip line is equal to the electrical length of the seventh microstrip line; the electrical length of the first short-circuit branch is equal to the electrical length of the fourth short-circuit branch; the electrical length of the second short-circuit branch is equal to the electrical length of the third short-circuit branch; the sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit branch is equal to the sum of the electrical length of the fourth microstrip line and the electrical length of the second short-circuit branch; the sum of 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 first short-circuit branch is greater than one-quarter wavelength corresponding to the center frequency of the broadband bandpass filter based on the topology structure.
[0041] 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 fifth microstrip line, the characteristic impedance of the sixth microstrip line, the characteristic impedance of the seventh microstrip line, the characteristic impedance of the eighth microstrip line, the characteristic impedance of the ninth microstrip line, the characteristic impedance of the tenth microstrip line, the characteristic impedance of the eleventh microstrip line, the characteristic impedance of the twelfth microstrip line, the characteristic impedance of the first short-circuit stub, the characteristic impedance of the second short-circuit stub, the characteristic impedance of the third short-circuit stub, and the characteristic impedance of the fourth short-circuit stub are equal.
[0042] Please refer to Figure 2 and 3 As shown, the second embodiment of the present utility model is:
[0043] A highly selective broadband bandpass filter comprises a circuit board and the topological structure described in Example 1. The topological structure is arranged on the circuit board, such as Figure 2 The circuit board has a dielectric constant of 3.38, a dielectric loss of 0.0022, a thickness of 0.813 mm, and a size of 34.4 mm*11.7 mm.
[0044] The specific parameters on the circuit board are set as follows:
[0045] The physical length of the first three parallel lines and the physical length of the second three parallel lines are both denoted as l T , l T =9.7mm;
[0046] The spacing between adjacent transmission lines constituting the first three parallel lines and the spacing between adjacent transmission lines constituting the second three parallel lines are both denoted as s. T , s T =0.1mm;
[0047] The physical width of the transmission line constituting the first three parallel lines and the physical width of the transmission line constituting the second three parallel lines are both denoted as w T , w T =0.2mm;
[0048] The physical length of the parallel line is recorded as l p , l p =9.7mm;
[0049] The spacing between the transmission lines that make up the parallel lines is denoted as s. p , s p =0.1mm;
[0050] The physical width of the transmission lines that make up the parallel lines is recorded as w p , w p =0.2mm;
[0051] The physical length of the fourth microstrip line and the physical length of the seventh microstrip line are both denoted as l1, l1=5.4 mm;
[0052] The physical length of the first microstrip line and the physical length of the tenth microstrip line are both recorded as l2, l2=5.1 mm;
[0053] The physical length of the second microstrip line, the physical length of the fifth microstrip line, the physical length of the eighth microstrip line, and the physical length of the eleventh microstrip line are all denoted as l3, where l3=2 mm;
[0054] The physical length of the third microstrip line, the physical length of the sixth microstrip line, the physical length of the ninth microstrip line, and the physical length of the twelfth microstrip line are all denoted as l4, where l4=1.8 mm;
[0055] The physical length of the second short-circuit branch and the physical length of the third short-circuit branch are both recorded as l5, l5=1.8 mm;
[0056] The physical length of the first short-circuit branch and the physical length of the fourth short-circuit branch are both recorded as l6, l6=2.1 mm;
[0057] The physical width of the first microstrip line, the physical width of the second microstrip line, the physical width of the third microstrip line, the physical width of the fourth microstrip line, the physical width of the fifth microstrip line, the physical width of the sixth microstrip line, the physical width of the seventh microstrip line, the physical width of the eighth microstrip line, the physical width of the ninth microstrip line, the physical width of the tenth microstrip line, the physical width of the eleventh microstrip line, the physical width of the twelfth microstrip line, the physical width of the first short-circuit branch, the physical width of the second short-circuit branch, the physical width of the third short-circuit branch and the physical width of the fourth short-circuit branch are all recorded as w1, w1=0.7mm.
[0058] The S parameter simulation results of the above highly selective broadband bandpass filter are as follows: Figure 3 As shown in the figure, the passband with a reflection coefficient better than -10dB ranges from 2.324GHz to 7.198GHz, with a center frequency of 4.861GHz, an absolute bandwidth of 4.874GHz, and a relative bandwidth of 100.3%. Furthermore, there are six transmission poles within the passband, located at 2.438, 2.524, 3.301, 4.148, 4.453, and 6.643GHz, which ensure passband flatness. There are four transmission zeros in the stopband, located at 0, 0.402, 7.55, and 10.631GHz, which ensure high selectivity and isolation.
[0059] In summary, the topology structure proposed in the present invention can be used to design a highly selective broadband bandpass filter. The highly selective broadband bandpass filter designed based on this topology structure has the advantages of high selectivity and compact structure.
[0060] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Therefore, any modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.
Claims
1. A topological structure, characterized in that: The invention comprises a parallel line, a first parallel three-line, a second parallel three-line, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, a seventh microstrip line, an eighth microstrip line, a ninth microstrip line, a tenth microstrip line, an eleventh microstrip line, a twelfth microstrip line, a first short-circuit branch, a second short-circuit branch, a third short-circuit branch, a fourth short-circuit branch, an input end and an output end, wherein one end of the parallel line is respectively connected to one end of the first parallel three-line, one end of the first microstrip line and one end of the fourth microstrip line, and the other end of the parallel line is respectively connected to one end of the second parallel three-line and one end of the seventh microstrip line. and one end of the tenth microstrip line, the other end of the first microstrip line is connected to the second microstrip line, the third microstrip line and the first short-circuit branch in sequence, the other end of the fourth microstrip line is connected to the fifth microstrip line, the sixth microstrip line and the second short-circuit branch in sequence, the other end of the seventh microstrip line is connected to the eighth microstrip line, the ninth microstrip line and the third short-circuit branch in sequence, the other end of the tenth microstrip line is connected to the eleventh microstrip line, the twelfth microstrip line and the fourth short-circuit branch in sequence, the other end of the first parallel three lines is connected to the input end, and the other end of the second parallel three lines is connected to the output end.
2. The topological structure according to claim 1, characterized in that: The first parallel three lines and the second parallel three lines are both composed of three parallel and equidistant transmission lines. The two outer transmission lines of the first parallel three lines are connected to the input end at one end away from the parallel lines, and the middle transmission line of the first parallel three lines is connected to the first microstrip line, the fourth microstrip line and the parallel lines at one end close to the parallel lines. The two outer transmission lines of the second parallel three lines are connected to the output end at one end away from the parallel lines, and the middle transmission line of the second parallel three lines is connected to the seventh microstrip line, the tenth microstrip line and the parallel lines at one end close to the parallel lines.
3. The topological structure according to claim 1, characterized in that: The parallel lines are composed of two parallel transmission lines. The first parallel three lines, the parallel lines and the second parallel three lines are placed in sequence in the horizontal direction. One end of the transmission line of the parallel lines close to the first parallel three lines is connected to the first parallel three lines, and the other end of the transmission line of the parallel lines close to the second parallel three lines is connected to the second parallel three lines.
4. The topological structure according to claim 3, characterized in that: The first microstrip line, the fourth microstrip line, the seventh microstrip line, and the tenth microstrip line are arranged away from the parallel lines, and the third microstrip line, the sixth microstrip line, the ninth microstrip line, the twelfth microstrip line, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch, and the fourth short-circuit branch are arranged close to the parallel lines.
5. The topological structure according to claim 1, characterized in that: The first three parallel lines, the second three parallel lines, the parallel lines, the second microstrip line, the fifth microstrip line, the eighth microstrip line, the eleventh microstrip line, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are parallel to each other and are perpendicular to the first microstrip line, the third microstrip line, the fourth microstrip line, the sixth microstrip line, the seventh microstrip line, the ninth microstrip line, the tenth microstrip line and the twelfth microstrip line.
6. The topological structure according to claim 1, characterized in that: The electrical length of the 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 broadband bandpass filter based on the topological structure; The electrical length of the first microstrip line is equal to the electrical length of the tenth microstrip line; the electrical length of the second microstrip line, the electrical length of the fifth microstrip line, the electrical length of the eighth microstrip line and the electrical length of the eleventh microstrip line are equal; The electrical length of the third microstrip line, the electrical length of the sixth microstrip line, the electrical length of the ninth microstrip line, and the electrical length of the twelfth microstrip line are equal; the electrical length of the fourth microstrip line and the electrical length of the seventh microstrip line are equal; The electrical length of the first short-circuit branch is equal to the electrical length of the fourth short-circuit branch; the electrical length of the second short-circuit branch is equal to the electrical length of the third short-circuit branch; the sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit branch is equal to the sum of the electrical length of the fourth microstrip line and the electrical length of the second short-circuit branch; the sum of 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 first short-circuit branch is greater than one-quarter wavelength corresponding to the center frequency of the broadband bandpass filter based on the topological structure.
7. The topological structure according to claim 1, characterized in that: 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 fifth microstrip line, the characteristic impedance of the sixth microstrip line, the characteristic impedance of the seventh microstrip line, the characteristic impedance of the eighth microstrip line, the characteristic impedance of the ninth microstrip line, the characteristic impedance of the tenth microstrip line, the characteristic impedance of the eleventh microstrip line, the characteristic impedance of the twelfth microstrip line, the characteristic impedance of the first short-circuit stub, the characteristic impedance of the second short-circuit stub, the characteristic impedance of the third short-circuit stub, and the characteristic impedance of the fourth short-circuit stub are equal.
8. A highly selective broadband bandpass filter, characterized in that: The topological structure includes any one of claims 1 to 7.
9. The highly selective broadband bandpass filter according to claim 8, characterized in that: It also includes a circuit board, on which the topological structure is arranged. The circuit board has a dielectric constant of 3.38, a dielectric loss of 0.0022, a thickness of 0.813 mm, and a size of 34.4 mm*11.7 mm.
10. The highly selective broadband bandpass filter according to claim 9, characterized in that: The first three parallel lines and the second three parallel lines are each composed of three parallel and equidistant transmission lines, and the parallel lines are composed of two parallel transmission lines. The specific parameters on the circuit board are set as follows: The physical length of the first three parallel lines and the physical length of the second three parallel lines are both denoted as l T , l T =9.7mm; The spacing between adjacent transmission lines constituting the first three parallel lines and the spacing between adjacent transmission lines constituting the second three parallel lines are both denoted as s. T , s T =0.1mm; The physical width of the transmission line constituting the first three parallel lines and the physical width of the transmission line constituting the second three parallel lines are both denoted as w T , w T =0.2mm; The physical length of the parallel line is recorded as l p , l p =9.7mm; The spacing between the transmission lines that make up the parallel lines is denoted as s. p , s p =0.1mm; The physical width of the transmission lines that make up the parallel lines is recorded as w p , w p =0.2mm; The physical length of the fourth microstrip line and the physical length of the seventh microstrip line are both denoted as l1, l1=5.4 mm; The physical length of the first microstrip line and the physical length of the tenth microstrip line are both recorded as l2, l2=5.1 mm; The physical length of the second microstrip line, the physical length of the fifth microstrip line, the physical length of the eighth microstrip line, and the physical length of the eleventh microstrip line are all denoted as l3, where l3=2 mm; The physical length of the third microstrip line, the physical length of the sixth microstrip line, the physical length of the ninth microstrip line, and the physical length of the twelfth microstrip line are all denoted as l4, where l4=1.8 mm; The physical length of the second short-circuit branch and the physical length of the third short-circuit branch are both recorded as l5, l5=1.8 mm; The physical length of the first short-circuit branch and the physical length of the fourth short-circuit branch are both recorded as l6, l6=2.1 mm; The physical width of the first microstrip line, the physical width of the second microstrip line, the physical width of the third microstrip line, the physical width of the fourth microstrip line, the physical width of the fifth microstrip line, the physical width of the sixth microstrip line, the physical width of the seventh microstrip line, the physical width of the eighth microstrip line, the physical width of the ninth microstrip line, the physical width of the tenth microstrip line, the physical width of the eleventh microstrip line, the physical width of the twelfth microstrip line, the physical width of the first short-circuit branch, the physical width of the second short-circuit branch, the physical width of the third short-circuit branch and the physical width of the fourth short-circuit branch are all recorded as w1, w1=0.7mm.