Broadband band-pass filter topological structure with double-notch characteristic and filter

Abstract

The utility model discloses a broadband band-pass filter topological structure with a double-notch characteristic and a filter, the topological structure comprises a first parallel line and a second parallel line which are connected in sequence, the other end of the first parallel line is connected with an input end, and the other end of the second parallel line is connected with an output end; a first microstrip line and a second open-circuit branch are connected between the first parallel line and the input end, and the other end of the first microstrip line is sequentially connected with a second microstrip line and a first open-circuit branch; a third microstrip line and a fourth open-circuit branch are connected between the second parallel line and the output end, and the other end of the third microstrip line is sequentially connected with a fourth microstrip line and a third open-circuit branch; a fifth microstrip line is connected between the first parallel line and the second parallel line, and the other end of the fifth microstrip line is symmetrically connected with a fifth open-circuit branch knot and a sixth open-circuit branch knot; the broadband band-pass filter solves the problem that an existing broadband band-pass filter with the double-notch characteristic is poor in selectivity.

Description

Technical Field

[0001] The utility model relates to the technical field of filters, in particular to a broadband bandpass filter topology structure and a filter with double notch characteristics. Background Art

[0002] With the rapid development of modern 5G communication technology, wideband bandpass filters, as a key component in wireless communication systems, have attracted increasing attention from scholars and engineers. In this context, filters that can suppress in-band interference while enabling high-speed signal transmission—that is, wideband bandpass filters with notch characteristics—have been extensively developed. However, most current wideband bandpass filters with dual-notch characteristics suffer from poor selectivity, significantly limiting their use in modern wireless communication systems. Utility Model Content

[0003] The main purpose of the utility model is to provide a broadband bandpass filter topology structure and filter with double notch characteristics, aiming to solve the problem of poor selectivity of existing broadband bandpass filters with double notch characteristics.

[0004] To achieve the above object, the present invention proposes a broadband bandpass filter topology with dual notch characteristics, comprising a first parallel line and a second parallel line connected in sequence, wherein the other end of the first parallel line is connected to an input end, and the other end of the second parallel line is connected to an output end;

[0005] A first microstrip line and a second open branch are connected between the first parallel line and the input end, and the other end of the first microstrip line is connected to the second microstrip line and the first open branch in sequence;

[0006] A third microstrip line and a fourth open branch node that are parallel to each other are connected between the second parallel line and the output end, and the other end of the third microstrip line is connected to the fourth microstrip line and the third open branch node in sequence;

[0007] The first parallel line, the second parallel line, the first microstrip line, the third microstrip line, the second open branch, the fourth open branch, the first open branch, and the third open branch are all arranged along a first direction, the second microstrip line and the fourth microstrip line are all arranged along a second direction, and the first direction is perpendicular to the second direction;

[0008] A fifth microstrip line is connected between the first parallel line and the second parallel line, and the other end of the fifth microstrip line is symmetrically connected to a fifth open branch node and a sixth open branch node;

[0009] The fifth microstrip line is arranged along the second direction, and the fifth open branch node and the sixth open branch node are both arranged along the first direction;

[0010] The first and second parallel lines, the first and third microstrip lines, the second and fourth open branches, the second and fourth microstrip lines, the first and third open branches, the fifth and sixth open branches are all symmetrical about the fifth microstrip line.

[0011] Optionally, the odd-mode characteristic impedances of the first parallel line and the second parallel line are equal, and the even-mode characteristic impedances of the first parallel line and the second parallel line are equal.

[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 first open branch, the characteristic impedance of the second open branch, the characteristic impedance of the third open branch and the characteristic impedance of the fourth open branch are equal.

[0013] Optionally, the characteristic impedance of the fifth open-circuit branch is equal to the characteristic impedance of the sixth open-circuit branch.

[0014] Optionally, the electrical length of the first parallel line, the electrical length of the second parallel line, the electrical length of the fifth microstrip line, the electrical length of the fifth open branch and the electrical length of the sixth open branch are all equal and are all one-quarter wavelength corresponding to the center frequency of the bandpass filter.

[0015] Optionally, the sum of the electrical length of the first microstrip line, the electrical length of the second microstrip line and the electrical length of the first open branch is equal to the sum of the electrical length of the third microstrip line, the electrical length of the fourth microstrip line and the electrical length of the third open branch, and both are greater than one-quarter wavelength corresponding to the center frequency of the bandpass filter.

[0016] Optionally, the electrical length of the second open-circuit branch is equal to the electrical length of the fourth open-circuit branch, and both are smaller than a quarter wavelength corresponding to the center frequency of the bandpass filter.

[0017] To achieve the above objectives, the present invention further provides a filter comprising any of the above-mentioned topological structures.

[0018] 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 19.6 mm*9.5 mm.

[0019] Optionally, the line width of the transmission line in the first parallel line and the second parallel line is set to w p =0.15mm, line spacing is set to s p =0.1mm, line length is set to l p =7.0mm;

[0020] The line lengths of the first microstrip line, the third microstrip line, the second open branch, and the fourth open branch are all set to l1 = 5.9 mm, the line lengths of the second microstrip line and the fourth microstrip line are all set to l2 = 0.9 mm, and the line lengths of the first open branch and the third open branch are all set to l3 = 2.0 mm;

[0021] The line widths of the first microstrip line, the third microstrip line, the second open branch, the fourth open branch, the second microstrip line, the fourth microstrip line, the first open branch, and the third open branch are all set to w1 = 0.1 mm;

[0022] The spacing between the first microstrip line and the first parallel line, the spacing between the second open branch and the first parallel line, the spacing between the third microstrip line and the second parallel line, and the spacing between the fourth open branch and the second parallel line are all set to s1 = 0.45 mm;

[0023] The line length of the fifth microstrip line is set to l4=7.7mm, and the line width is set to w2=2.0mm;

[0024] The line lengths of the fifth open branch and the sixth open branch are both set to l5 = 7.0 mm, and the line widths are both set to w3 = 0.7 mm.

[0025] The beneficial effects of the utility model are: improving the topological structure of the existing dual-notch broadband bandpass filter, the topological structure includes a first parallel line and a second parallel line connected in sequence, the other end of the first parallel line is connected to the input end, and the other end of the second parallel line is connected to the output end; a first microstrip line and a second open-circuit branch are connected between the first parallel line and the input end, and the other end of the first microstrip line is connected to the second microstrip line and the first open-circuit branch in sequence; a third microstrip line and a fourth open-circuit branch are connected between the second parallel line and the output end, and the other end of the third microstrip line is connected to the fourth microstrip line and the third open-circuit branch in sequence; the first A fifth microstrip line is connected between the parallel line and the second parallel line, and the other end of the fifth microstrip line is symmetrically connected to a fifth open-circuit branch and a sixth open-circuit branch. The filter based on this topology has two odd-mode transmission poles, three even-mode transmission poles, and four transmission zeros. Regardless of how the characteristic impedance of each branch is changed, the relative positions of the transmission zeros and poles remain unchanged. Therefore, based on this topology, a broadband bandpass filter with dual-notch characteristics can be designed. The five transmission poles ensure the flatness of the bandpass filter in the passband, and the four transmission zeros ensure high selectivity and in-band notching. Compared with existing dual-notch broadband bandpass filters, this one has the advantage of good selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0027] Figure 1 This is a schematic diagram of the topological structure of the filter of the utility model;

[0028] Figure 2 It is an odd-mode diagram of the topological structure of the utility model;

[0029] Figure 3 It is an even-mode diagram of the topological structure of the utility model;

[0030] Figure 4 This is a layout diagram of the filter of the utility model;

[0031] Figure 5 This is the S parameter simulation result diagram of the utility model filter;

[0032] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0035] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such 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 in which A and B are satisfied at the same time. 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 mutually 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 present invention.

[0036] An embodiment of the present invention provides a broadband bandpass filter topology with dual notch characteristics, referring to Figure 1 , comprising a first parallel line and a second parallel line connected in sequence, wherein the other end of the first parallel line is connected to the input end, and the other end of the second parallel line is connected to the output end;

[0037] A first microstrip line and a second open branch are connected between the first parallel line and the input end, and the other end of the first microstrip line is connected to the second microstrip line and the first open branch in sequence;

[0038] A third microstrip line and a fourth open branch node that are parallel to each other are connected between the second parallel line and the output end, and the other end of the third microstrip line is connected to the fourth microstrip line and the third open branch node in sequence;

[0039] The first parallel line, the second parallel line, the first microstrip line, the third microstrip line, the second open branch, the fourth open branch, the first open branch, and the third open branch are all arranged along a first direction, the second microstrip line and the fourth microstrip line are all arranged along a second direction, and the first direction is perpendicular to the second direction;

[0040] A fifth microstrip line is connected between the first parallel line and the second parallel line, and the other end of the fifth microstrip line is symmetrically connected to a fifth open branch node and a sixth open branch node;

[0041] The fifth microstrip line is arranged along the second direction, and the fifth open branch node and the sixth open branch node are both arranged along the first direction;

[0042] The first and second parallel lines, the first and third microstrip lines, the second and fourth open branches, the second and fourth microstrip lines, the first and third open branches, the fifth and sixth open branches are all symmetrical about the fifth microstrip line.

[0043] This embodiment improves the topology of the existing filter, which consists of five microstrip lines, two parallel lines, and six open branches. The first and second parallel lines, the first and third microstrip lines, the second and fourth microstrip lines, the first and third open branches, the second and fourth open branches, and the fifth and sixth open branches are all symmetrical about the fifth microstrip line.

[0044] The first parallel line, the second parallel line, the first microstrip line, the third microstrip line, the first open branch, the second open branch, the third open branch, the fourth open branch, the fifth open branch and the sixth open branch are parallel to each other and perpendicular to the second microstrip line, the fourth microstrip line and the fifth microstrip line.

[0045] Furthermore, the first parallel line and the second parallel line respectively include two parallel first transmission lines and second transmission lines, the first transmission line is connected to the input end or the output end, and the second transmission line is connected to the fifth microstrip line.

[0046] Furthermore, the odd-mode characteristic impedance of the first parallel line and the second parallel line is equal, and the even-mode characteristic impedance of the first parallel line and the second parallel line is equal. In this embodiment, the odd-mode characteristic impedance of the first parallel line and the second parallel line is Z oo , the even-mode characteristic impedance is Z oe .

[0047] Furthermore, the characteristic impedance of the first microstrip line, the characteristic impedance of the second microstrip line, the characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the first open stub, the characteristic impedance of the second open stub, the characteristic impedance of the third open stub, and the characteristic impedance of the fourth open stub are equal. In this embodiment, the characteristic impedance of the first microstrip line, the characteristic impedance of the second microstrip line, the characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the first open stub, the characteristic impedance of the second open stub, the characteristic impedance of the third open stub, and the characteristic impedance of the fourth open stub are all set to Z1.

[0048] Furthermore, the characteristic impedance of the fifth open branch is equal to the characteristic impedance of the sixth open branch. In this embodiment, the characteristic impedance of the fifth microstrip line is Z2; the characteristic impedance of the fifth open branch is equal to the characteristic impedance of the sixth open branch, both being Z3.

[0049] Furthermore, the electrical length of the first parallel line, the electrical length of the second parallel line, the electrical length of the fifth microstrip line, the electrical length of the fifth open branch and the electrical length of the sixth open branch are all equal and are all one quarter wavelength corresponding to the center frequency of the bandpass filter.

[0050] Furthermore, the sum of the electrical length of the first microstrip line, the electrical length of the second microstrip line and the electrical length of the first open branch is equal to the sum of the electrical length of the third microstrip line, the electrical length of the fourth microstrip line and the electrical length of the third open branch, and both are greater than one-quarter wavelength corresponding to the center frequency of the bandpass filter. In this embodiment, it corresponds to one-quarter wavelength corresponding to the center frequency of the first notch.

[0051] Furthermore, the electrical length of the second open branch is equal to the electrical length of the fourth open branch, and both are smaller than a quarter wavelength corresponding to the center frequency of the bandpass filter. In this embodiment, they correspond to a quarter wavelength corresponding to the second notch center frequency.

[0052] The following analysis of this topology simplifies its performance analysis by assuming that the electrical lengths of the first microstrip line, the third microstrip line, the second open-circuit stub, and the fourth open-circuit stub are each a quarter wavelength at the bandpass filter's center frequency, and that the electrical lengths of the second microstrip line, the fourth microstrip line, the first open-circuit stub, and the third open-circuit stub are all zero. In this case, the topology is bilaterally symmetrical, and its transmission poles can be derived using even-odds-mode analysis.

[0053] The odd-mode form of this topology is as follows Figure 2 Here, the electrical length of the seventh open branch and the electrical length of the eighth open branch are a quarter wavelength corresponding to the center frequency of the bandpass filter, and the characteristic impedance of the seventh open branch and the characteristic impedance of the eighth open branch are equal to the characteristic impedance of the first microstrip line, the characteristic impedance of the second microstrip line, the characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the first open branch, the characteristic impedance of the second open branch, the characteristic impedance of the third open branch, and the characteristic impedance of the fourth open branch, that is, Z1.

[0054] 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:

[0055]

[0056] The even mode form of this topology is as follows Figure 3 As shown, here, the electrical length of the sixth microstrip line is equal to the electrical length of the fifth microstrip line, and the characteristic impedance of the sixth microstrip line is twice the characteristic impedance of the fifth microstrip line.

[0057] 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:

[0058]

[0059] f ep2 =f0

[0060]

[0061] in:

[0062]

[0063] β=2Z2Z3(Z oe +Z oo +2)+(4Z oe Z oo +Z1Z oe +Z1Z oo )(2Z2+Z3)

[0064] For this topology, its transmission zero 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:

[0065]

[0066] f z2 =f0

[0067]

[0068] From the above analysis, it can be seen that when the electrical length of the first microstrip line, the electrical length of the third microstrip line, the electrical length of the second open branch, and the electrical length of the fourth open branch are all one-quarter wavelength corresponding to the center frequency of the bandpass filter, and the electrical length of the second microstrip line, the electrical length of the fourth microstrip line, the electrical length of the first open branch, and the electrical length of the third open branch are all zero, the filter based on this 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 、Z oe , the values ​​of Z1, Z2, and Z3, and the relative positions of the transmission poles and zeros, i.e., f z1 <f ep1 <f op1 <f ep2 =f2 <f op2 <f ep3 <f z3 , nothing will change.

[0069] Obviously, in the topology structure provided by the present invention, the sum of the electrical length of the first microstrip line, the electrical length of the second microstrip line, and the electrical length of the first open branch is not equal to the electrical length of the second open branch, and the sum of the electrical length of the third microstrip line, the electrical length of the fourth microstrip line, and the electrical length of the third open branch is also not equal to the electrical length of the fourth open branch. It can be known from the basic microwave theory that the transmission zero f2 of the filter designed based on this topology structure will be split into two transmission zeros f z2L and f z2U , while the number of other zero poles remains unchanged. When the sum of the electrical length of the first microstrip line, the electrical length of the second microstrip line, and the electrical length of the first open branch is appropriately greater than a quarter wavelength corresponding to the center frequency of the bandpass filter, and the electrical length of the second open branch is appropriately less than a quarter wavelength corresponding to the center frequency of the bandpass filter, no matter how the parameter Z is changed oo 、Z oe , the values ​​of Z1, Z2, and Z3, and the relative positions of the transmission poles and zeros, i.e., f z1 <f ep1 <f op1 <f z2L <f ep2 <f z2U <f op2 <f ep3 <f z3 , will not change. Therefore, a broadband bandpass filter with dual notch characteristics can be designed based on this topology. When the electrical length of the first microstrip line is equal to the electrical length of the third microstrip line, it is set to θ1; the electrical length of the second microstrip line is equal to the electrical length of the fourth microstrip line, it is set to θ2; the electrical length of the first open branch is equal to the electrical length of the third open branch, it is set to θ3; the electrical length of the second open branch is equal to the electrical length of the fourth open branch, it is set to θ4.

[0070] At this time, the center frequency of the first notch is f z2L The relationship between θ1, θ2, and θ3 can be expressed as

[0071]

[0072] Where λ is the wavelength of the bandpass filter;

[0073] The center frequency of the second notch f z2U The relationship between and θ4 can be expressed as

[0074]

[0075] An embodiment of the present invention provides a filter including any of the above-mentioned topological structures.

[0076] Furthermore, 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 19.6 mm*9.5 mm.

[0077] Further, refer to Figure 4 , the line width of the transmission line in the first parallel line and the second parallel line is set to w p =0.15mm, line spacing is set to s p =0.1mm, line length is set to l p =7.0mm;

[0078] The line lengths of the first microstrip line, the third microstrip line, the second open branch, and the fourth open branch are all set to l1 = 5.9 mm, the line lengths of the second microstrip line and the fourth microstrip line are all set to l2 = 0.9 mm, and the line lengths of the first open branch and the third open branch are all set to l3 = 2.0 mm;

[0079] The line widths of the first microstrip line, the third microstrip line, the second open branch, the fourth open branch, the second microstrip line, the fourth microstrip line, the first open branch, and the third open branch are all set to w1 = 0.1 mm;

[0080] The spacing between the first microstrip line and the first parallel line, the spacing between the second open branch and the first parallel line, the spacing between the third microstrip line and the second parallel line, and the spacing between the fourth open branch and the second parallel line are all set to s1 = 0.45 mm;

[0081] The line length of the fifth microstrip line is set to l4=7.7mm, and the line width is set to w2=2.0mm;

[0082] The line lengths of the fifth open branch and the sixth open branch are both set to l5 = 7.0 mm, and the line widths are both set to w3 = 0.7 mm.

[0083] 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 4.346 to 9.152GHz, the passband center frequency is 6.749GHz, the absolute passband bandwidth is 4.806GHz, and the relative passband bandwidth is 71.2%. In addition, there are five transmission poles within the passband, located at 4.453, 5.301, 7.049, 8.202, and 8.951GHz, respectively. These five transmission poles ensure the flatness of the bandpass filter in the passband. There are also two transmission zeros in the passband, forming notches, with center frequencies of 6.049 and 7.801GHz, respectively. The isolation at the center frequencies is 52.7 and 57.4dB, respectively, demonstrating excellent isolation. There are two transmission zeros in the stopband, located at 3.351GHz and 10.449GHz, respectively. These two transmission zeros ensure the high selectivity of the filter.

[0084] As can be seen from the above, the broadband bandpass filter with notch characteristics designed in the topology of this embodiment has the advantage of good selectivity.

[0085] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by utilizing the contents of the present invention specification and drawings under the utility model concept, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A broadband bandpass filter topology with dual notch characteristics, characterized in that: It includes a first parallel line and a second parallel line connected in sequence, wherein the other end of the first parallel line is connected to the input end, and the other end of the second parallel line is connected to the output end; A first microstrip line and a second open branch are connected between the first parallel line and the input end, and the other end of the first microstrip line is connected to the second microstrip line and the first open branch in sequence; A third microstrip line and a fourth open branch node that are parallel to each other are connected between the second parallel line and the output end, and the other end of the third microstrip line is connected to the fourth microstrip line and the third open branch node in sequence; The first parallel line, the second parallel line, the first microstrip line, the third microstrip line, the second open branch, the fourth open branch, the first open branch, and the third open branch are all arranged along a first direction, the second microstrip line and the fourth microstrip line are all arranged along a second direction, and the first direction is perpendicular to the second direction; A fifth microstrip line is connected between the first parallel line and the second parallel line, and the other end of the fifth microstrip line is symmetrically connected to a fifth open branch node and a sixth open branch node; The fifth microstrip line is arranged along the second direction, and the fifth open branch node and the sixth open branch node are both arranged along the first direction; The first and second parallel lines, the first and third microstrip lines, the second and fourth open branches, the second and fourth microstrip lines, the first and third open branches, the fifth and sixth open branches are all symmetrical about the fifth microstrip line.

2. The broadband bandpass filter topology structure with dual notch characteristics according to claim 1, characterized in that: The odd-mode characteristic impedances of the first parallel line and the second parallel line are equal, and the even-mode characteristic impedances of the first parallel line and the second parallel line are equal.

3. The broadband bandpass filter topology structure with dual notch characteristics according to claim 2, 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 first open branch, the characteristic impedance of the second open branch, the characteristic impedance of the third open branch and the characteristic impedance of the fourth open branch are equal.

4. The broadband bandpass filter topology structure with dual notch characteristics according to claim 3, characterized in that: The characteristic impedance of the fifth open-circuit branch is equal to the characteristic impedance of the sixth open-circuit branch.

5. The broadband bandpass filter topology structure with dual notch characteristics according to claim 1, characterized in that: The electrical length of the first parallel line, the electrical length of the second parallel line, the electrical length of the fifth microstrip line, the electrical length of the fifth open branch and the electrical length of the sixth open branch are all equal and are all a quarter wavelength corresponding to the center frequency of the bandpass filter.

6. The broadband bandpass filter topology structure with dual notch characteristics according to claim 5, characterized in that: The sum of the electrical length of the first microstrip line, the electrical length of the second microstrip line and the electrical length of the first open branch is equal to the sum of the electrical length of the third microstrip line, the electrical length of the fourth microstrip line and the electrical length of the third open branch, and both are greater than one-quarter wavelength corresponding to the center frequency of the bandpass filter.

7. The broadband bandpass filter topology structure with dual notch characteristics according to claim 6, characterized in that: The electrical length of the second open-circuit branch is equal to the electrical length of the fourth open-circuit branch, and both are smaller than a quarter wavelength corresponding to the center frequency of the bandpass filter.

8. A filter, characterized in that: The topological structure includes any one of claims 1 to 7.

9. The filter according to claim 8, characterized in that The filter further includes a circuit board having a dielectric constant of 3.38, a dielectric loss of 0.0022, a thickness of 0.813 mm, and a size of 19.6 mm*9.5 mm.

10. The filter according to claim 9, characterized in that The line width of the transmission line in the first parallel line and the second parallel line is set to w p =0.15mm, line spacing is set to s p =0.1mm, line length is set to l p =7.0mm; The line lengths of the first microstrip line, the third microstrip line, the second open branch, and the fourth open branch are all set to l1 = 5.9 mm, the line lengths of the second microstrip line and the fourth microstrip line are all set to l2 = 0.9 mm, and the line lengths of the first open branch and the third open branch are all set to l3 = 2.0 mm; The line widths of the first microstrip line, the third microstrip line, the second open branch, the fourth open branch, the second microstrip line, the fourth microstrip line, the first open branch, and the third open branch are all set to w1 = 0.1 mm; The spacing between the first microstrip line and the first parallel line, the spacing between the second open branch and the first parallel line, the spacing between the third microstrip line and the second parallel line, and the spacing between the fourth open branch and the second parallel line are all set to s1 = 0.45 mm; The line length of the fifth microstrip line is set to l4=7.7mm, and the line width is set to w2=2.0mm; The line lengths of the fifth open branch and the sixth open branch are both set to l5 = 7.0 mm, and the line widths are both set to w3 = 0.7 mm.

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