Topological structure of broadband double-notch band-pass filter and filter
By optimizing the topological structure, including the design of the third microstrip line and multiple parallel lines, microstrip line and open circuit branches, the problems of poor selectivity and large size of the existing broadband double notch bandpass filter are solved, and the filter is realized The selectivity improvement and miniaturization are suitable for modern wireless communication systems.
Patent Information
- Application Number
- CN202420565550.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-21
- Publication Date
- 2025-01-17
- Estimated Expiration
- 2034-03-21
AI Technical Summary
The existing broadband dual notch bandpass filters have poor selectivity and large size, which limits their application in modern wireless communication systems.
A topological structure including the third microstrip line and a variety of parallel lines, microstrip lines and open branches was designed. By optimizing parameters such as electrical length, characteristic impedance and line width, a symmetric structure is formed to improve the selectivity of the filter and Compactness.
The filter selectivity improvement and miniaturization are achieved, ensuring flatness in the passband and high selectivity in the stopband, and are suitable for modern wireless communication systems.
Smart Images
Figure CN222365710U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of filters, in particular to a topological structure of a broadband dual-notch bandpass filter and a filter. Background Art
[0002] With the rapid development of modern 5G communication technology, broadband bandpass filters, as one of the key components of wireless communication systems, have attracted more and more attention from scholars and engineers. In this context, filters that can suppress in-band interference and transmit signals at high speed, that is, broadband bandpass filters with notch characteristics, have been developed in large quantities.
[0003] Currently, most broadband bandpass filters with dual notch characteristics have the defects of poor selectivity and large size, which greatly limits their use in modern wireless communication systems. Utility Model Content
[0004] The main purpose of the utility model is to provide a topological structure of a broadband dual-notch bandpass filter, aiming to solve the problems of poor selectivity and large size of the existing filter.
[0005] To achieve the above-mentioned purpose, the utility model proposes a topological structure of a broadband dual-notch bandpass filter, comprising a third microstrip line, one end of the third microstrip line is symmetrically connected to one end of a first parallel line and one end of a second parallel line, the other end of the first parallel line is respectively connected to an input end and one end of the first microstrip line, the other end of the second parallel line is respectively connected to an output end and a second open-circuit branch, the other end of the first microstrip line is connected to one end of the second microstrip line, the other end of the second microstrip line is connected to the first open-circuit branch, the other end of the third microstrip line is symmetrically connected to one end of a fourth microstrip line and one end of a sixth microstrip line, the other end of the fourth microstrip line is connected to one end of a fifth microstrip line, the other end of the fifth microstrip line is connected to the third open-circuit branch, the other end of the sixth microstrip line is connected to one end of a seventh microstrip line, and the other end of the seventh microstrip line is connected to the fourth open-circuit branch;
[0006] The first parallel line, the second parallel line, the first microstrip line, the fourth microstrip line, the sixth microstrip line, the first open branch, the second open branch, the third open branch, and the fourth open branch are parallel to each other and are perpendicular to the second microstrip line, the third microstrip line, the fifth microstrip line, and the seventh microstrip line.
[0007] Optionally, the electrical length of the first parallel line and the electrical length of the second parallel line are both a quarter wavelength corresponding to the center frequency of the bandpass filter.
[0008] Optionally, the sum of the electrical length of the third microstrip line, the electrical length of the fourth microstrip line, the electrical length of the fifth microstrip line, and the electrical length of the third open-circuit branch is half the wavelength corresponding to the center frequency of the bandpass filter;
[0009] The sum of the electrical length of the third microstrip line, the electrical length of the sixth microstrip line, the electrical length of the seventh microstrip line, and the electrical length of the fourth open-circuit branch is half the wavelength corresponding to the center frequency of the bandpass filter.
[0010] Optionally, the sum of the electrical lengths of the first microstrip line, the second microstrip line, and the first open-circuit branch is equal to a quarter wavelength corresponding to the first notch center frequency of the bandpass filter, and is greater than a quarter wavelength corresponding to the center frequency of the bandpass filter.
[0011] Optionally, the electrical length of the second open-circuit branch is equal to a quarter wavelength corresponding to the second notch center frequency of the bandpass filter, and is smaller than a quarter wavelength corresponding to the center frequency of the bandpass filter.
[0012] Optionally, the odd-mode characteristic impedance of the first parallel line is equal to the odd-mode characteristic impedance of the second parallel line, and the even-mode characteristic impedance of the first parallel line is equal to the even-mode characteristic impedance of the second parallel line;
[0013] The first parallel lines and the second parallel lines each include two transmission lines that are arranged in parallel and at equal intervals.
[0014] Optionally, the characteristic impedance of the first microstrip line, the characteristic impedance of the second microstrip line, the characteristic impedance of the first open-circuit branch, and the characteristic impedance of the second open-circuit branch are equal;
[0015] 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 third open branch, and the characteristic impedance of the fourth open branch are equal and are all twice the characteristic impedance of the third microstrip line.
[0016] To achieve the above object, the utility model also proposes a filter, including a filter designed with any of the above-mentioned topological structures.
[0017] Optionally, the filter further includes a circuit board, 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 19.2 mm*5.8 mm.
[0018] Optionally, it is characterized in that the length of the first parallel line and the length of the second parallel line are both set to l p=7.6mm, the length of the first microstrip line and the length of the second open branch are both set to l1=6.4mm, the length of the second microstrip line is set to l2=1.0mm, the length of the first open branch is set to l3=3.0mm, the length of the third microstrip line is set to l4=2.6mm, the length of the fourth microstrip line and the length of the sixth microstrip line are both set to l5=6.2mm, the length of the fifth microstrip line and the length of the seventh microstrip line are both set to l6=2.0mm, the length of the third open branch and the length of the fourth open branch are both set to l7=5.7mm, and the spacing between adjacent transmission lines is set to s p =0.1mm, the spacing between the first parallel line and the first microstrip line, and the spacing between the second parallel line and the second open branch are both set to s1=0.3mm, and the line width of the transmission line is set to w p =0.1mm, the line width of the first microstrip line, the line width of the second microstrip line, the line width of the first open branch node, and the line width of the second open branch node are all set to w1=0.1mm, the line width of the third microstrip line is set to w2=0.4mm, the line width of the fourth microstrip line, the line width of the fifth microstrip line, the line width of the sixth microstrip line, the line width of the seventh microstrip line, the third open branch node, and the line width of the fourth open branch node are all set to w3=0.2mm.
[0019] Compared with the prior art, the utility model has the following beneficial effects: the topological structure of the existing filter is improved, including a third microstrip line, one end of the third microstrip line is symmetrically connected to one end of the first parallel line and one end of the second parallel line, the other end of the first parallel line is respectively connected to the input end and one end of the first microstrip line, the other end of the second parallel line is respectively connected to the output end and the second open branch, the other end of the first microstrip line is connected to one end of the second microstrip line, the other end of the second microstrip line is connected to the first open branch, the other end of the third microstrip line is symmetrically connected to one end of the fourth microstrip line and one end of the sixth microstrip line, the other end of the fourth microstrip line is connected to one end of the fifth microstrip line, the other end of the fifth microstrip line is connected to the third open branch, the other end of the sixth microstrip line is connected to one end of the seventh microstrip line, and the other end of the seventh microstrip line is connected to the fourth open branch. The filter designed based on the topological structure of the utility model has the advantages of good selectivity and miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.
[0021] Figure 1 This is a schematic diagram of the topological structure of the filter of the utility model;
[0022] Figure 2 It is an odd-even mode diagram of the simplified topological structure of the utility model;
[0023] Figure 3 It is an even-mode diagram of the simplified topological structure of the utility model;
[0024] Figure 4 This is one of the layout diagrams of the filter of the utility model;
[0025] Figure 5 This is the second layout diagram of the filter of the utility model;
[0026] Figure 6 This is a diagram of the S parameter simulation results of the filter of the utility model.
[0027] Description of Figure Numbers:
[0028] 10. Input terminal; 20. First microstrip line; 21. Second microstrip line; 22. Third microstrip line; 23. Fourth microstrip line; 24. Fifth microstrip line; 25. Sixth microstrip line; 26. Seventh microstrip line; 30. First open-circuit branch; 31. Second open-circuit branch; 32. Third open-circuit branch; 33. Fourth open-circuit branch; 40. First parallel line; 41. Second parallel line; 50. Output terminal; 401. First left transmission line; 402. Second left transmission line; 411. First right transmission line; 412. Second right transmission line.
[0029] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION
[0030] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0031] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.
[0032] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if the meaning of "and / or" appearing in the full text is to include three parallel schemes, taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme that satisfies both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the utility model.
[0033] An embodiment of the present invention provides a topological structure of a broadband dual-notch bandpass filter. Figures 1 to 6 , including a third microstrip line 22, one end of the third microstrip line 22 is symmetrically connected to one end of the first parallel line 40 and one end of the second parallel line 41, the other end of the first parallel line 40 is respectively connected to the input end 10 and one end of the first microstrip line 20, the other end of the second parallel line 41 is respectively connected to the output end 50 and the second open branch 31, the other end of the first microstrip line 20 is connected to one end of the second microstrip line 21, the other end of the second microstrip line 21 is connected to the first open branch 30, the other end of the third microstrip line 22 is symmetrically connected to one end of the fourth microstrip line 23 and one end of the sixth microstrip line 25, the other end of the fourth microstrip line 23 is connected to one end of the fifth microstrip line 24, the other end of the fifth microstrip line 24 is connected to the third open branch 32, the other end of the sixth microstrip line 25 is connected to one end of the seventh microstrip line 26, and the other end of the seventh microstrip line 26 is connected to the fourth open branch 33;
[0034] The first parallel line 40, the second parallel line 41, the first microstrip line 20, the fourth microstrip line 23, the sixth microstrip line 25, the first open branch 30, the second open branch 31, the third open branch 32, and the fourth open branch 33 are parallel to each other and are perpendicular to the second microstrip line 21, the third microstrip line 22, the fifth microstrip line 24, and the seventh microstrip line 26.
[0035] In this embodiment, the topological structure adopts a symmetrical structure setting, and the first parallel line 40 and the second parallel line 41, the fourth microstrip line 23 and the sixth microstrip line 25, the fifth microstrip line 24 and the seventh microstrip line 26, the third open branch 32 and the fourth open branch 33 are all symmetrical about the third microstrip line 22.
[0036] Furthermore, the electrical length of the first parallel line 40 and the electrical length of the second parallel line 41 are both a quarter wavelength corresponding to the center frequency of the bandpass filter.
[0037] Furthermore, the sum of the electrical length of the third microstrip line 22, the electrical length of the fourth microstrip line 23, the electrical length of the fifth microstrip line 24, and the electrical length of the third open branch 32 is one-half wavelength corresponding to the center frequency of the bandpass filter; the sum of the electrical length of the third microstrip line 22, the electrical length of the sixth microstrip line 25, the electrical length of the seventh microstrip line 26, and the electrical length of the fourth open branch 33 is one-half wavelength corresponding to the center frequency of the bandpass filter.
[0038] Furthermore, the sum of the electrical lengths of the first microstrip line 20, the second microstrip line 21, and the first open branch 30 is equal to a quarter wavelength corresponding to the first notch center frequency of the bandpass filter, and is greater than a quarter wavelength corresponding to the center frequency of the bandpass filter.
[0039] Furthermore, the electrical length of the second open-circuit branch 31 is equal to a quarter wavelength corresponding to the second notch center frequency of the bandpass filter, and is smaller than a quarter wavelength corresponding to the center frequency of the bandpass filter.
[0040] Further, the odd-mode characteristic impedance of the first parallel line 40 is equal to the odd-mode characteristic impedance of the second parallel line 41, and the even-mode characteristic impedance of the first parallel line 40 is equal to the even-mode characteristic impedance of the second parallel line 41; the first parallel line 40 and the second parallel line 41 both include two transmission lines that are arranged in parallel and at equal intervals. Specifically, the first parallel line 40 includes a first left transmission line 401 and a second left transmission line 402, and the second parallel line 41 includes a first right transmission line 411 and a second right transmission line 412.
[0041] Furthermore, the characteristic impedance of the first microstrip line 20, the characteristic impedance of the second microstrip line 21, the characteristic impedance of the first open branch 30, and the characteristic impedance of the second open branch 31 are equal; the characteristic impedance of the fourth microstrip line 23, the characteristic impedance of the fifth microstrip line 24, the characteristic impedance of the sixth microstrip line 25, the characteristic impedance of the seventh microstrip line 26, the characteristic impedance of the third open branch 32, and the characteristic impedance of the fourth open branch 33 are equal, and are all twice the characteristic impedance of the third microstrip line 22.
[0042] In this embodiment, the odd-mode characteristic impedance of the first parallel line 40 and the odd-mode characteristic impedance of the second parallel line 41 are both set to Z oo , the even-mode characteristic impedance of the first parallel line 40 and the even-mode characteristic impedance of the second parallel line 41 are both set to Z oe , the characteristic impedance of the first microstrip line 20, the characteristic impedance of the second microstrip line 21, the characteristic impedance of the first open branch 30, and the characteristic impedance of the second open branch 31 are all set to Z1, the characteristic impedance of the third microstrip line 22 is set to Z2, the characteristic impedance of the fourth microstrip line 23, the characteristic impedance of the fifth microstrip line 24, the characteristic impedance of the sixth microstrip line 25, the characteristic impedance of the seventh microstrip line 26, the characteristic impedance of the third open branch 32, and the characteristic impedance of the fourth open branch 33 are all set to 2Z2.
[0043] In order to simplify the analysis of the topological structure, it is first assumed that the electrical length of the first microstrip line 20 and the electrical length of the second open branch 31 are both one-quarter wavelength corresponding to the center frequency of the bandpass filter, and the electrical length of the second microstrip line 21 and the electrical length of the first open branch 30 are both zero. At this time, the simplified topological structure is a left-right symmetrical structure, and its transmission pole can be obtained by odd-even mode analysis. In the odd-mode form of the topological structure, the electrical length of the fifth open branch is one-quarter wavelength corresponding to the center frequency of the bandpass filter, and the characteristic impedance of the fifth open branch is equal to the characteristic impedance of the first microstrip line 20, the characteristic impedance of the second microstrip line 21, the characteristic impedance of the first open branch 30, and the characteristic impedance of the second open branch 31, and they are all Z1.
[0044] When Y ino = 0, it can be concluded that the topology has two transmission poles. When f0 is the center frequency of the bandpass filter, the frequencies corresponding to the two odd-mode transmission poles are:
[0045]
[0046]
[0047] In the even-mode form of the simplified topology structure, the electrical length of the eighth microstrip line is equal to the electrical length of the third microstrip line 22 , and the characteristic impedance of the eighth microstrip line is twice the characteristic impedance of the third microstrip line 22 , which is 2Z2.
[0048] When Y ine = 0, it can be concluded that the topology has three even-mode transmission poles. When f0 is the center frequency of the bandpass filter, the frequencies corresponding to the three even-mode transmission poles are:
[0049]
[0050]
[0051] in,
[0052] α=Z2(Z oe +Z oo )+(Z oe -Z oo ) 2 +2Z1Z2
[0053] β=Z2(Z oe +Z oo +2)+2(2Z oe Z oo +Z1Z oe +Z1Z oo )
[0054] For this simplified topology, its transmission zero point can be calculated by the following method: multiply the ABCD matrices of the cascaded resonators that make up the topology in sequence to obtain the ABCD matrix corresponding to the topology; and convert the ABCD matrix of the topology into the corresponding S matrix. 21 When |=0, it can be concluded that this topology has three transmission zeros, and the frequencies corresponding to the three transmission zeros are:
[0055]
[0056] f z2 =f0
[0057]
[0058] From the above analysis, it can be seen that when the electrical length of the first microstrip line 20 and the electrical length of the second open-circuit branch 31 are both a quarter wavelength corresponding to the center frequency of the bandpass filter, and the electrical length of the second microstrip line 21 and the electrical length of the first open-circuit branch 30 are both zero, the filter based on the simplified topology has two odd-mode transmission poles, three even-mode transmission poles and three transmission zeros. And no matter how the parameter Z is changed oo , Zoe , the values of Z1 and Z2, and the relative positions of the transmission zeros and poles, i.e., f z1 <f ep1 <f op1 <f ep2 =f0=f2 <f op2 <f ep3 <f z3 , nothing will change.
[0059] Returning to this topological structure, when the sum of the electrical lengths of the first microstrip line 20, the second microstrip line 21, and the first open-circuit branch 30 is appropriately greater than a quarter wavelength corresponding to the center frequency of the bandpass filter and the electrical length of the second open-circuit branch 31 is appropriately less than a quarter wavelength corresponding to the center frequency of the bandpass filter, it can be known from the basic microwave theory that the transmission zero f2 of the filter designed based on this topological structure will be split into two transmission zeros f z2L and f z2U , while the number of other zeros and poles remains unchanged. oo , Z oe , the values of Z1 and Z2, and the relative positions of the transmission zeros and poles, i.e., f z1 <f ep1 <f op1 <f z2L <f ep2 <f z2U <f op2 <f ep3 <f z3 , will not change. Therefore, based on this topology, a broadband bandpass filter with double notch characteristics can be designed, and there are five transmission poles in the passband to ensure flatness, two transmission zeros in the stopband to ensure high selectivity, and two transmission zeros in the passband to form the required notch.
[0060] In addition, the center frequency of the first notch of the filter designed based on this topology is f z2L The relationship between the electrical length θ1 of the first microstrip line 20, the electrical length θ2 of the second microstrip line 21, and the electrical length θ3 of the first open branch 30 can be expressed as:
[0061]
[0062] Where λ is the wavelength of the bandpass filter.
[0063] The center frequency of the second notch is f z2U The relationship between the electrical length θ4 of the second open-circuit branch 31 can be expressed as:
[0064]
[0065] To achieve the above object, the utility model also proposes a filter, including a filter designed with any of the above-mentioned topological structures.
[0066] The filter also includes a 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 19.2 mm*5.8 mm.
[0067] The length of the first parallel line 40 and the length of the second parallel line 41 are both set to l p =7.6mm, the length of the first microstrip line and the length of the second open branch 31 are both set to l1=6.4mm, the length of the second microstrip line 21 is set to l2=1.0mm, the length of the first open branch 30 is set to l3=3.0mm, the length of the third microstrip line 22 is set to l4=2.6mm, the length of the fourth microstrip line 23 and the length of the sixth microstrip line 25 are both set to l5=6.2mm, the length of the fifth microstrip line 24 and the length of the seventh microstrip line 26 are both set to l6=2.0mm, the length of the third open branch 32 and the length of the fourth open branch 33 are both set to l7=5.7mm, the spacing between the first left transmission line 401 and the second left transmission line 402, and the spacing between the first right transmission line 411 and the second right transmission line 412 are both set to s p =0.1mm, the spacing between the first parallel line 40 and the first microstrip line 20, and the spacing between the second parallel line 41 and the second open branch 31 are all set to s1=0.3mm, the line width of the first left transmission line 401, the line width of the second left transmission line 402, the line width of the first right transmission line 411, and the line width of the second right transmission line 412 are all set to w p =0.1mm, the line width of the first microstrip line 20, the line width of the second microstrip line 21, the line width of the first open branch node 30, and the line width of the second open branch node 31 are all set to w1=0.1mm, the line width of the third microstrip line 22 is set to w2=0.4mm, the line width of the fourth microstrip line 23, the line width of the fifth microstrip line 24, the line width of the sixth microstrip line 25, the line width of the seventh microstrip line 26, the third open branch node 32, and the line width of the fourth open branch node 33 are all set to w3=0.2mm.
[0068] The S parameter simulation results of the bandpass filter corresponding to the optimized size are as follows: Figure 5As shown in the figure, the impedance bandwidth with a reflection coefficient less than -10dB ranges from 4.031GHz to 8.569GHz, the passband center frequency is 6.3GHz, the absolute bandwidth of the passband is 4.538GHz, and the relative bandwidth of the passband is 72%. In addition, there are five transmission poles in the passband, located at 4.187GHz, 4.962GHz, 6.576GHz, 7.637GHz, and 8.475GHz, respectively. These five transmission poles ensure the flatness of the passband filter in the passband; there are two transmission zeros in the passband to form a notch, with center frequencies of 5.525GHz and 7.225GHz, respectively, and the isolation at the center frequency is 29dB and 26.4dB, respectively, with good isolation; there are two transmission zeros in the stopband, located at 3.275GHz and 9.025GHz, respectively, and these two transmission poles can ensure the high selectivity of the filter.
[0069] It can be seen from the above that the filter with double notch characteristics designed in the topological structure of this embodiment has the advantages of high selectivity and miniaturization.
[0070] The above description is only an optional embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.
Claims
1. A topology structure of a broadband dual notch bandpass filter, characterized in that: The invention comprises a third microstrip line, wherein one end of the third microstrip line is symmetrically connected to one end of the first parallel line and one end of the second parallel line, the other end of the first parallel line is respectively connected to the input end and one end of the first microstrip line, the other end of the second parallel line is respectively connected to the output end and the second open branch node, the other end of the first microstrip line is connected to one end of the second microstrip line, the other end of the second microstrip line is connected to the first open branch node, the other end of the third microstrip line is symmetrically connected to one end of the fourth microstrip line and one end of the sixth microstrip line, the other end of the fourth microstrip line is connected to one end of the fifth microstrip line, the other end of the fifth microstrip line is connected to the third open branch node, the other end of the sixth microstrip line is connected to one end of the seventh microstrip line, and the other end of the seventh microstrip line is connected to the fourth open branch node; The first parallel line, the second parallel line, the first microstrip line, the fourth microstrip line, the sixth microstrip line, the first open branch, the second open branch, the third open branch, and the fourth open branch are parallel to each other and are perpendicular to the second microstrip line, the third microstrip line, the fifth microstrip line, and the seventh microstrip line.
2. The topology of the broadband dual notch bandpass filter according to claim 1, characterized in that: The electrical length of the first parallel line and the electrical length of the second parallel line are both one-quarter wavelength corresponding to the center frequency of the bandpass filter.
3. The topology structure of the broadband dual notch bandpass filter according to claim 1, characterized in that: The sum of the electrical length of the third microstrip line, the electrical length of the fourth microstrip line, the electrical length of the fifth microstrip line, and the electrical length of the third open-circuit branch is half the wavelength corresponding to the center frequency of the bandpass filter; The sum of the electrical length of the third microstrip line, the electrical length of the sixth microstrip line, the electrical length of the seventh microstrip line, and the electrical length of the fourth open-circuit branch is half the wavelength corresponding to the center frequency of the bandpass filter.
4. The topology structure of the broadband dual notch bandpass filter according to claim 1, characterized in that: The sum of the electrical lengths of the first microstrip line, the second microstrip line, and the first open-circuit branch is equal to a quarter wavelength corresponding to the first notch center frequency of the bandpass filter, and is greater than a quarter wavelength corresponding to the center frequency of the bandpass filter.
5. The topology structure of the broadband dual notch bandpass filter according to claim 1, characterized in that: The electrical length of the second open-circuit branch is equal to a quarter wavelength corresponding to the second notch center frequency of the bandpass filter, and is smaller than a quarter wavelength corresponding to the center frequency of the bandpass filter.
6. The topology structure of the broadband dual notch bandpass filter according to claim 1, characterized in that: The odd-mode characteristic impedance of the first parallel line is equal to the odd-mode characteristic impedance of the second parallel line, and the even-mode characteristic impedance of the first parallel line is equal to the even-mode characteristic impedance of the second parallel line; The first parallel lines and the second parallel lines each include two transmission lines that are arranged in parallel and at equal intervals.
7. The topology structure of the broadband dual notch bandpass filter 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 first open-circuit branch, and the characteristic impedance of the second open-circuit branch are equal; 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 third open branch, and the characteristic impedance of the fourth open branch are equal and are all twice the characteristic impedance of the third microstrip line.
8. The topology structure of the broadband dual notch bandpass filter according to claim 1, characterized in that: The filter also includes a 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 19.2 mm*5.8 mm.
9. The topology structure of the broadband dual notch bandpass filter according to claim 6, characterized in that: The length of the first parallel line and the length of the second parallel line are both set to l p =7.6mm, the length of the first microstrip line and the length of the second open branch are both set to l1=6.4mm, the length of the second microstrip line is set to l2=1.0mm, the length of the first open branch is set to l3=3.0mm, the length of the third microstrip line is set to l4=2.6mm, the length of the fourth microstrip line and the length of the sixth microstrip line are both set to l5=6.2mm, the length of the fifth microstrip line and the length of the seventh microstrip line are both set to l6=2.0mm, the length of the third open branch and the length of the fourth open branch are both set to l7=5.7mm, and the spacing between adjacent transmission lines is set to s p =0.1mm, the spacing between the first parallel line and the first microstrip line, and the spacing between the second parallel line and the second open branch are both set to s1=0.3mm, and the line width of the transmission line is set to w p =0.1mm, the line width of the first microstrip line, the line width of the second microstrip line, the line width of the first open branch node, and the line width of the second open branch node are all set to w1=0.1mm, the line width of the third microstrip line is set to w2=0.4mm, the line width of the fourth microstrip line, the line width of the fifth microstrip line, the line width of the sixth microstrip line, the line width of the seventh microstrip line, the third open branch node, and the line width of the fourth open branch node are all set to w3=0.2mm.
10. A filter, characterized in that: A filter comprising a topology structure designed according to any one of claims 1 to 7.