A topological structure, broadband bandpass filter and communication equipment
By adopting a new topological design of a broadband bandpass filter, the existing filters have solved the problems of narrow stopband and poor selectivity, and the characteristics of high selectivity, high isolation and wide stopband are achieved, which improves its performance in modern wireless communication systems.
Patent Information
- Application Number
- CN202421522279.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-28
- Publication Date
- 2025-04-08
- Estimated Expiration
- 2034-06-28
AI Technical Summary
Due to the defects in structural design, the existing broadband bandpass filters have narrow stopbands and poor selectivity, which affects their use in modern wireless communication systems.
A broadband bandpass filter designed with a new topological structure, which includes components such as input, output, parallel and microstrip lines. Through specific connection methods and electrical length settings, the filter has two transmission poles in the passband and four transmission zeros in the stopband.
The design achieves high selectivity and high isolation of broadband bandpass filters, ensuring the characteristics of wide stopbands and improving its performance in modern wireless communication systems.
Smart Images
Figure CN222735327U_ABST
Abstract
Description
Technical Field
[0001] The embodiments of the utility model relate to the technical field of communication equipment, and in particular to a topological structure, a broadband bandpass filter and communication equipment. Background Art
[0002] With the rapid development of modern wireless communication technology, the research and development of high-performance broadband communication systems that can meet people's needs for high-speed data transmission is an inevitable trend. In this context, the research on broadband bandpass filters, one of the key components of broadband communication systems, has extremely high scientific and commercial value, attracting the attention of many scholars and engineers due to its wide stopband and high selectivity.
[0003] The inventor of the present invention found in the process of realizing the present invention that: currently, the existing broadband bandpass filter is subject to defects in its structural design, which makes the broadband bandpass filter narrow in stopband and poor in selectivity, seriously affecting its use in modern wireless communication systems. Utility Model Content
[0004] The main technical problem solved by the embodiments of the utility model is to provide a topology structure, a broadband bandpass filter and a communication device, which overcome the above problems or at least partially solve the above problems.
[0005] In order to solve the above technical problems, a technical solution adopted by the utility model is: to provide a topological structure, including: an input end, an output end, a first parallel line, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a first short-circuit branch, a second short-circuit branch, a third short-circuit branch and a fourth short-circuit branch; wherein, one end of the first parallel line is connected to one end of the third microstrip line and the input end respectively, the other end of the third microstrip line is connected to one end of the fourth microstrip line, the other end of the fourth microstrip line is connected to one end of the fourth short-circuit branch and one end of the third short-circuit branch, the other end of the fourth short-circuit branch and the other end of the third short-circuit branch are grounded respectively, the other end of the first parallel line is connected to one end of the first microstrip line and the output end respectively, 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 one end of the second short-circuit branch and one end of the first short-circuit branch, and the other end of the first short-circuit branch and the other end of the second short-circuit branch are grounded respectively.
[0006] Optionally, the first short-circuit branch and the second short-circuit branch are symmetrically arranged up and down with respect to the second microstrip line, and the third short-circuit branch and the fourth short-circuit branch are symmetrically arranged up and down with respect to the fourth microstrip line.
[0007] Optionally, the first parallel line, the fourth microstrip line and the second microstrip line are arranged in parallel.
[0008] Optionally, the first microstrip line, the third microstrip line, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are all perpendicular to the first parallel line, the fourth microstrip line and the second microstrip line.
[0009] Optionally, the electrical length of the first microstrip line is equal to the electrical length of the third microstrip line; the electrical length of the second microstrip line is equal to the electrical length of the fourth microstrip line; the electrical length of the first short-circuit branch, the electrical length of the second short-circuit branch, the electrical length of the third short-circuit branch and the electrical length of the fourth short-circuit branch are all equal.
[0010] 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 short-circuit branch is one quarter of the wavelength corresponding to the center frequency of the bandpass filter.
[0011] Optionally, the electrical length of the first parallel line is one quarter of the wavelength corresponding to the center frequency of the bandpass filter.
[0012] Optionally, the odd-mode characteristic impedance of the first parallel line is Zoo, and the even-mode characteristic impedance of the first parallel line is Zoe; the characteristic impedance of the first microstrip line, the characteristic impedance of the second microstrip line, the characteristic impedance of the third microstrip line and the characteristic impedance of the fourth microstrip line are all equal; 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 all equal and are both twice the characteristic impedance of the first microstrip line.
[0013] In order to solve the above technical problem, another technical solution adopted by the utility model is: to provide a broadband bandpass filter, which is obtained by the above topological structure design.
[0014] In order to solve the above technical problem, another technical solution adopted by the present invention is: to provide a communication device, including the above broadband bandpass filter.
[0015] The beneficial effects of the embodiments of the utility model are as follows: Different from the prior art, the embodiments of the utility model provide a topological structure, characterized in that it includes an input end, an output end, a first parallel line, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a first short-circuit branch, a second short-circuit branch, a third short-circuit branch and a fourth short-circuit branch; wherein one end of the first parallel line is connected to one end of the third microstrip line and the input end respectively, the other end of the third microstrip line is connected to one end of the fourth microstrip line, the other end of the fourth microstrip line is connected to one end of the fourth short-circuit branch and one end of the third short-circuit branch, the other end of the fourth short-circuit branch and the other end of the third short-circuit branch are grounded respectively, the other end of the first parallel line is connected to one end of the first microstrip line and the output end respectively, 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 one end of the second short-circuit branch and one end of the first short-circuit branch, and the other end of the first short-circuit branch and the other end of the second short-circuit branch are grounded respectively. The broadband bandpass filter designed based on the above topological structure has two transmission poles in its passband, which ensure the flatness of the broadband bandpass filter, and four transmission zeros in its stopband, which ensure the high isolation and high selectivity of the broadband bandpass filter. Its high isolation makes the broadband bandpass filter exhibit the characteristics of a wide stopband. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the embodiments of the utility model 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 drawings without creative work.
[0017] Figure 1 It is a schematic diagram of a topological structure provided by an embodiment of the utility model;
[0018] Figure 2 It is a schematic diagram of a topological structure of an odd-mode form provided by an embodiment of the utility model;
[0019] Figure 3 This is a schematic diagram of a topological structure of an even mode provided by an embodiment of the utility model;
[0020] Figure 4 It is a schematic diagram of a layout of a broadband bandpass filter provided by an embodiment of the utility model;
[0021] Figure 5 It is another schematic diagram of a layout of a low-pass filter provided by an embodiment of the utility model;
[0022] Figure 6 This is a diagram of S-parameter simulation results of a low-pass filter provided in an embodiment of the utility model. DETAILED DESCRIPTION
[0023] In order to facilitate the understanding of the utility model, the utility model is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as "fixed to" another element, it can be directly on the other element, or there can be one or more centered elements therebetween. When an element is described as "connected to" another element, it can be directly connected to the other element, or there can be one or more centered elements therebetween. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this specification are for illustrative purposes only.
[0024] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by technicians in the technical field of the present invention. The terms used in this specification are only for the purpose of describing specific embodiments and are not used to limit the present invention. The term "and / or" used in this specification includes any and all combinations of one or more related listed items.
[0025] See also Figure 1 The topological structure 1000 includes an input terminal 10, a first parallel line 20, a first microstrip line 30, a second microstrip line 31, a third microstrip line 32, a fourth microstrip line 33, a first short-circuit branch 40, a second short-circuit branch 41, a third short-circuit branch 42, a fourth short-circuit branch 43 and an output terminal 50; wherein one end of the first parallel line 20 is connected to one end of the third microstrip line 32 and the input terminal 10 respectively, the other end of the third microstrip line 32 is connected to one end of the fourth microstrip line 33, and the other end of the fourth microstrip line 33 is connected to one end of the fourth short-circuit branch 43 The first short-circuit branch 41 is connected to one end of the first microstrip line 30 and the output end 50, and the other end of the first microstrip line 30 is connected to one end of the second microstrip line 31. The other end of the second microstrip line 31 is connected to one end of the second short-circuit branch 41 and one end of the first short-circuit branch 40. The other end of the first short-circuit branch 40 and the other end of the second short-circuit branch 41 are grounded respectively.
[0026] In some embodiments, Figure 4As shown, the first parallel line 20 is composed of two mutually parallel first transmission lines 201 and second transmission lines 202, one end of the first transmission line 201 is connected to the input end, the other end of the first transmission line 201 is connected to one end of the first microstrip line 30, one end of the second transmission line 202 is connected to the output end 50, and the other end of the second transmission line 202 is connected to one end of the third microstrip line 32.
[0027] Specifically, one end of the first transmission line 201 is connected to the input end 10, the other end of the first transmission line 201 is connected to one end of the first microstrip line 30, the other end of the first microstrip line 30 is connected to one end of the second microstrip line 31, the other end of the second microstrip line 31 is connected to one end of the first short-circuit branch 40 and one end of the second short-circuit branch 41, the other end of the first short-circuit branch 40 and the other end of the second short-circuit branch 41 are grounded respectively, one end of the second transmission line 202 is connected to the output end 50, the other end of the second transmission line 202 is connected to one end of the third microstrip line 32, the other end of the third microstrip line 32 is connected to one end of the fourth microstrip line 33, the other end of the fourth microstrip line 33 is connected to one end of the third short-circuit branch 42 and one end of the fourth short-circuit branch 43, the other end of the third short-circuit branch 42 and the other end of the fourth short-circuit branch 43 are grounded respectively.
[0028] In some embodiments, the first short-circuit branch 40 and the second short-circuit branch 41 are symmetrically arranged about the second microstrip line 31 , and the third short-circuit branch 42 and the fourth short-circuit branch 43 are symmetrically arranged about the fourth microstrip line 33 .
[0029] In some embodiments, the first parallel line 20 , the fourth microstrip line 33 and the second microstrip line 31 are arranged in parallel.
[0030] In some embodiments, the first microstrip line 30 , the third microstrip line 32 , the first short-circuit branch 40 , the second short-circuit branch 41 , the third short-circuit branch 42 and the fourth short-circuit branch 43 are all perpendicular to the first parallel line 20 , the fourth microstrip line 33 and the second microstrip line 31 .
[0031] In some embodiments, the electrical length of the first microstrip line 30 is equal to the electrical length of the third microstrip line 32; the electrical length of the second microstrip line 31 is equal to the electrical length of the fourth microstrip line 33; the electrical length of the first short-circuit branch 40, the electrical length of the second short-circuit branch 41, the electrical length of the third short-circuit branch 42 and the electrical length of the fourth short-circuit branch 43 are all equal.
[0032] In some embodiments, the sum of the electrical length of the first microstrip line 30 , the electrical length of the second microstrip line 31 and the electrical length of the first short-circuit stub 40 is a quarter wavelength corresponding to the center frequency of the bandpass filter.
[0033] In some embodiments, the electrical length of the first parallel line 20 is a quarter wavelength corresponding to the center frequency of the bandpass filter.
[0034] In some embodiments, the odd-mode characteristic impedance of the first parallel line 20 is Z oo , the even-mode characteristic impedance of the first parallel line 20 is Z oe ; The characteristic impedance of the first microstrip line 30, the characteristic impedance of the second microstrip line 31, the characteristic impedance of the third microstrip line 32 and the characteristic impedance of the fourth microstrip line 33 are all equal and can be set to Z1; the characteristic impedance of the first short-circuit branch 40, the characteristic impedance of the second short-circuit branch 41, the characteristic impedance of the third short-circuit branch 42 and the characteristic impedance of the fourth short-circuit branch 43 are all equal and are twice the characteristic impedance of the first microstrip line 30, and can be set to 2Z1.
[0035] Based on the above analysis of the topological structure 1000, it can be known that the topological structure 1000 of the present invention is a symmetrical structure, and therefore, its transmission poles can be obtained by odd-even mode analysis, as follows:
[0036] like Figure 2 The odd-mode version of the symmetrical topology 1000 is shown, including the input terminal Y ino , a first microstrip line 30, a second microstrip line 31, a fifth microstrip line, a first short-circuit branch 40, a second short-circuit branch 41 and a ground terminal. ino The fifth microstrip line is connected to one end of the fifth microstrip line, the other end of the fifth microstrip line is connected to one end of the first microstrip line 30, the other end of the first microstrip line 30 is connected to one end of the second microstrip line 31, the other end of the second microstrip line 31 is connected to one end of the first short-circuit branch 40 and one end of the second short-circuit branch 41, the other end of the first short-circuit branch 40 and the other end of the second short-circuit branch 41 are grounded respectively, wherein the fifth microstrip line and the second microstrip line 31 are arranged in parallel, and the fifth microstrip line and the second microstrip line 31 are perpendicular to the first microstrip line 30, the first short-circuit branch 40 and the second short-circuit branch 41, and the electrical length of the fifth microstrip line in the odd-mode form of the symmetrical topological structure 1000 is equal to the electrical length of the first parallel line 20, and the characteristic impedance of the fifth microstrip line is equal to the odd-mode characteristic impedance of the first parallel line 20, that is, the characteristic impedance of the fifth microstrip line is Z oo When Y ino=∞, it can be concluded that the topology 1000 has two odd-mode transmission poles, and their corresponding frequencies are:
[0037]
[0038] Where f0 is the center frequency of the bandpass filter.
[0039] like Figure 3 The even-mode version of topology 1000 is shown, including the input terminal Y ine , a first microstrip line 30, a second microstrip line 31, a sixth microstrip line, a first short-circuit branch 40 and a second short-circuit branch 41, the input terminal Y ine The second microstrip line 31 is connected to one end of the sixth microstrip line, the other end of the sixth microstrip line is connected to one end of the first microstrip line 30, the other end of the first microstrip line 30 is connected to one end of the second microstrip line 31, the other end of the second microstrip line 31 is connected to one end of the first short-circuit branch 40 and one end of the second short-circuit branch 41, and the other end of the first short-circuit branch 40 and the other end of the second short-circuit branch 41 are grounded respectively. The second microstrip line 31 and the sixth microstrip line are arranged in parallel, and the second microstrip line 31 and the sixth microstrip line are perpendicular to the first microstrip line 30, the first short-circuit branch 40 and the second short-circuit branch 41, and in the even-mode form of the symmetrical topological structure 1000, the electrical length of the sixth microstrip line is equal to the electrical length of the first parallel line 20, and the characteristic impedance of the sixth microstrip line is equal to the even-mode characteristic impedance of the first parallel line 20, that is, the characteristic impedance of the sixth microstrip line is Z oe When Y ine =∞, it can be concluded that the topology 1000 has two even-mode transmission poles, and the frequencies corresponding to the two even-mode transmission poles are:
[0040]
[0041] Where f0 is the center frequency of the bandpass filter.
[0042] For this topology 1000, the transmission zero point can be calculated by the following formula:
[0043]
[0044] From the above calculation results, it can be seen that the topology structure 1000 has four transmission zeros, and the frequencies corresponding to the four transmission zeros are:
[0045] f z1 =0
[0046]
[0047] f z4 =2f0
[0048] From the above analysis, it can be seen that the broadband bandpass filter 2000 based on the topological structure 1000 has two odd-mode transmission poles, two even-mode transmission poles and four transmission zeros. When the coupling between the parallel lines is weak and the characteristic impedance of the first microstrip line 30 is greater than the odd-mode characteristic impedance and the even-mode characteristic impedance of the parallel lines, that is, Z1>Z oo ≈Z oe , the relative position of the transmission zero pole, that is, f z1 <f2<f op1 ≈f ep1 <f ep2 ≈f op2 <f3<f z4 Therefore, a bandpass filter can be designed based on this topology 1000, and there are two transmission poles in the passband to ensure its flatness within the band, and there are four transmission zeros in the stopband to ensure high isolation and wide stopband.
[0049] In order to verify the concept of the present invention, the present invention also provides a broadband bandpass filter 2000 embodiment and performs simulation experiments on it. Figure 4 and Figure 5 As shown, the broadband bandpass filter 2000 includes a circuit board and the above-mentioned topological structure 1000. The structure and function of the topological structure 1000 can be found in the above-mentioned embodiment, which will not be described in detail here.
[0050] See also Figure 4 The dielectric loss of the circuit board is 0.0022, the thickness is 0.813 mm, the length is 13.0 mm, and the width is 12.6 mm. The design size of the broadband bandpass filter 2000 is l P =9.2mm,s P =0.1mm,w P =0.25mm, l1=4.1mm, l2=5.1mm, l3=3.4mm, w1=w2=2w3=0.6mm. P is the length of the two first parallel lines 20, s P is the distance between the two first parallel lines 20, w Pis the width of the two first parallel lines 20, l1 is the length of the third microstrip line 32 and the length of the first microstrip line 30, l2 is the length of the second microstrip line 31 and the length of the fourth microstrip line 33, l3 is the sum of the lengths of the fourth short-circuit branch 43 and the third short-circuit branch 42 and the sum of the lengths of the first short-circuit branch 40 and the second short-circuit branch 41, w1 is the width of the first microstrip line 30 and the width of the third microstrip line 32, w2 is the width of the fourth microstrip line 33 and the width of the second microstrip line 3 1, w3 is the width of the first short-circuit branch 40, the width of the second short-circuit branch 41, the width of the third short-circuit branch 42 and the width of the fourth short-circuit branch 43, and the width of the first microstrip line 30, the width of the third microstrip line 32, the width of the fourth microstrip line 33 and the width of the second microstrip line 31 are all twice the width of the first short-circuit branch 40, the width of the second short-circuit branch 41, the width of the third short-circuit branch 42 and the width of the fourth short-circuit branch 43.
[0051] The simulation results of the broadband bandpass filter 2000 under the above-mentioned limited conditions are as follows: Figure 6 As shown. Figure 6 It can be seen that the impedance bandwidth of the broadband bandpass filter 2000 with a reflection coefficient less than -10dB ranges from 4.22GHz to 5.84GHz, the passband center frequency is 5.03GHz, the passband absolute bandwidth is 1.62GHz, and the passband relative bandwidth is 32.2%, showing broadband characteristics. In addition, there are two transmission poles in the passband, located at 4.54GHz and 5.56GHz respectively. These two transmission poles ensure the flatness of the bandpass filter in the passband; there are four transmission zeros in the stopband, located at 0GHz, 1.84GHz, 8.15GHz, and 10.62GHz respectively. These four transmission zeros not only ensure high selectivity, but also ensure high isolation of the stopband; the lower stopband bandwidth with isolation greater than 10dB ranges from 0GHz to 2.98GHz, and the upper stopband bandwidth with isolation greater than 10dB ranges from 6.79GHz to 12GHz, showing the characteristics of a wide stopband.
[0052] In the embodiment of the utility model, the topological structure 1000 includes an input terminal 10, an output terminal 50, a first parallel line 20, a first microstrip line 30, a second microstrip line 31, a third microstrip line 32, a fourth microstrip line 33, a first short-circuit branch 40, a second short-circuit branch 41, a third short-circuit branch 42 and a fourth short-circuit branch 43; wherein one end of the first parallel line 20 is connected to one end of the third microstrip line 32 and the input terminal 10 respectively, the other end of the third microstrip line 32 is connected to one end of the fourth microstrip line 33, and the other end of the fourth microstrip line 33 is connected to the fourth short-circuit branch One end of the node 43 is connected to one end of the third short-circuit branch 42, the other end of the fourth short-circuit branch 43 and the other end of the third short-circuit branch 42 are grounded respectively, the other end of the first parallel line 20 is connected to one end of the first microstrip line 30 and the output end 50 respectively, the other end of the first microstrip line 30 is connected to one end of the second microstrip line 31, the other end of the second microstrip line 31 is connected to one end of the second short-circuit branch 41 and one end of the first short-circuit branch 40, and the other end of the first short-circuit branch 40 and the other end of the second short-circuit branch 41 are grounded respectively. The broadband bandpass filter 2000 designed based on the above-mentioned topological structure 1000 has two transmission poles in the passband to ensure the flatness in the passband, and four transmission zeros in the stopband to ensure high selectivity and high isolation of the stopband, and its high isolation makes the broadband bandpass filter 2000 show the characteristics of wide stopband.
[0053] The present invention also provides a communication device embodiment, wherein the communication device includes the above-mentioned broadband bandpass filter 2000. The structure and function of the broadband bandpass filter 2000 can be referred to the above-mentioned embodiment, which will not be described in detail here.
[0054] It should be noted that the preferred embodiments of the utility model are given in the specification and drawings of the utility model, but the utility model can be implemented in many different forms and is not limited to the embodiments described in the specification. These embodiments are not used as additional restrictions on the content of the utility model. The purpose of providing these embodiments is to make the understanding of the disclosure of the utility model more thorough and comprehensive. In addition, the above-mentioned technical features continue to be combined with each other to form various embodiments not listed above, which are all regarded as the scope of the description of the utility model; further, for ordinary technicians in this field, they can be improved or transformed according to the above description, and all these improvements and transformations should belong to the scope of protection of the claims attached to the utility model.
Claims
1. A topological structure, characterized in that: include An input end, an output end, a first parallel line, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a first short-circuit branch, a second short-circuit branch, a third short-circuit branch, and a fourth short-circuit branch; Among them, one end of the first parallel line is connected to one end of the third microstrip line and the input end respectively, the other end of the third microstrip line is connected to one end of the fourth microstrip line, the other end of the fourth microstrip line is connected to one end of the fourth short-circuit branch and one end of the third short-circuit branch, the other end of the fourth short-circuit branch and the other end of the third short-circuit branch are grounded respectively, the other end of the first parallel line is connected to one end of the first microstrip line and the output end respectively, 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 one end of the second short-circuit branch and one end of the first short-circuit branch, the other end of the first short-circuit branch and the other end of the second short-circuit branch are grounded respectively.
2. The topological structure according to claim 1, characterized in that: The first short-circuit branch and the second short-circuit branch are symmetrically arranged up and down with respect to the second microstrip line, and the third short-circuit branch and the fourth short-circuit branch are symmetrically arranged up and down with respect to the fourth microstrip line.
3. The topological structure according to claim 1, characterized in that: The first parallel line, the fourth microstrip line and the second microstrip line are arranged in parallel.
4. The topological structure according to claim 1, characterized in that: The first microstrip line, the third microstrip line, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are all perpendicular to the first parallel line, the fourth microstrip line and the second microstrip line.
5. The topological structure according to claim 1, characterized in that: The electrical length of the first microstrip line is equal to the electrical length of the third microstrip line; The electrical length of the second microstrip line is equal to the electrical length of the fourth microstrip line; The electrical length of the first short-circuit branch, the electrical length of the second short-circuit branch, the electrical length of the third short-circuit branch, and the electrical length of the fourth short-circuit branch are all equal.
6. The topological structure 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 short-circuit branch is a quarter wavelength corresponding to the center frequency of the bandpass filter.
7. The topological structure according to claim 1, characterized in that The electrical length of the first parallel line is a quarter wavelength corresponding to the center frequency of the bandpass filter.
8. The topological structure according to any one of claims 1 to 7, characterized in that: The odd-mode characteristic impedance of the first parallel line is Zoo, and the even-mode characteristic impedance of the first parallel line is Zoe; The characteristic impedance of the first microstrip line, the characteristic impedance of the second microstrip line, the characteristic impedance of the third microstrip line and the characteristic impedance of the fourth microstrip line are all equal; 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 all equal, and are all twice the characteristic impedance of the first microstrip line.
9. A broadband bandpass filter, characterized in that: The method is obtained by designing the topological structure as described in any one of claims 1 to 8.
10. A communication device comprising the broadband bandpass filter according to claim 9.