Topological structure, band-pass filter and communication equipment

Abstract

The utility model provides a topological structure, a band-pass filter and communication equipment. The first parallel line is connected between the input end and the first parallel coupling line, and the first microstrip line is connected between the first parallel coupling line and the output end. One end of the second parallel line is connected between the first parallel line and the first parallel coupling line, and one end of the second parallel coupling line is connected between the first parallel coupling line and the first microstrip line. A first rectangular open-circuit branch knot and a first fan-shaped open-circuit branch knot are connected between the first parallel coupling line and the first microstrip line. And a second fan-shaped open-circuit branch knot is connected between the first microstrip line and the output end. The first parallel line and the first parallel coupling line can form a three-mode filter, the second parallel line and the second parallel coupling line can optimize an in-band reflection coefficient, and an additional zero point is introduced to ensure high selectivity and a wide stop band. The first rectangular open-circuit branch knot, the first microstrip line, the first fan-shaped open-circuit branch knot and the second fan-shaped open-circuit branch knot can form a low-pass filter which is used for further widening the stop band.

Description

Technical Field

[0001] The present application relates to the technical field of communication equipment, and in particular to a topology structure, a bandpass filter and a communication device. Background Art

[0002] With the rapid adoption of fifth-generation mobile communication technology (5G), the demand for high-speed data transmission and the development of broadband communication systems that efficiently utilize spectrum resources are inevitable trends in the communications industry. Bandpass filters are key components in communications systems, and research on their wideband and high selectivity is of great scientific and commercial value. However, currently reported broadband filters often suffer from narrow stopbands and large size, which hinders out-of-band noise suppression and miniaturization, seriously limiting their use in modern wireless communication systems. Utility Model Content

[0003] This application proposes a topology structure, a bandpass filter and a communication device, aiming to solve the technical problem that broadband filters have defects such as narrow stopband and large size, which are not conducive to out-of-band noise suppression and miniaturization.

[0004] In a first aspect, an embodiment of the present application proposes a topological structure, including an input end and an output end, wherein a first parallel line, a first parallel coupling line, and a first microstrip line are connected between the input end and the output end. The first parallel line is connected between the input end and the first parallel coupling line, and the first microstrip line is connected between the first parallel coupling line and the output end. A second parallel line and a second parallel coupling line are also included between the first parallel line and the first parallel coupling line; one end of the second parallel line is connected between the first parallel line and the first parallel coupling line, and the other end of the second parallel line is used for grounding. One end of the second parallel coupling line is connected between the first parallel coupling line and the first microstrip line, and the other end of the second parallel coupling line is used for grounding. A first rectangular open branch and a first fan-shaped open branch are also connected between the first parallel coupling line and the first microstrip line. A second fan-shaped open branch is connected between the first microstrip line and the output end.

[0005] In some embodiments, the first parallel lines include a first transmission line and a second transmission line, the first transmission line and the second transmission line being arranged in parallel and spaced apart. The first parallel coupled lines include a third transmission line and a fourth transmission line, the third transmission line and the fourth transmission line being arranged in parallel and spaced apart. The second parallel lines include a fifth transmission line and a sixth transmission line, the fifth transmission line and the sixth transmission line being arranged in parallel and spaced apart. The second parallel coupled lines include a seventh transmission line and an eighth transmission line, the seventh transmission line and the eighth transmission line being arranged in parallel and spaced apart.

[0006] In some embodiments, one end of the first transmission line is connected to the input end, and the other end is open. One end of the second transmission line is connected to one end of the third transmission line, one end of the fifth transmission line, and one end of the seventh transmission line, while the other ends of the second transmission line, the third transmission line, the fifth transmission line, and the seventh transmission line are open. One end of the fourth transmission line is connected to one end of the first rectangular open branch, one end of the first fan-shaped open branch, and one end of the first microstrip line, while the other end of the fourth transmission line is open. One end of the sixth transmission line is open, while the other end is grounded. One end of the eighth transmission line is open, while the other end is grounded.

[0007] In some embodiments, the first transmission line, the second transmission line, the third transmission line, the fourth transmission line, and the first microstrip line are arranged in parallel.

[0008] In some embodiments, the first transmission line, the second transmission line, the third transmission line, the fourth transmission line and the first microstrip line are all perpendicular to the fifth transmission line, the sixth transmission line, the seventh transmission line, the eighth transmission line, the first rectangular open branch, the first fan-shaped open branch and the second fan-shaped open branch.

[0009] In some embodiments, the angle of the first fan-shaped open branch is equal to the angle of the second fan-shaped open branch. The radius of the first fan-shaped open branch is equal to the radius of the second fan-shaped open branch. The equivalent electrical length of the first fan-shaped open branch is equal to the equivalent electrical length of the second fan-shaped open branch. The electrical length of the first rectangular open branch, the electrical length of the first microstrip line, and the equivalent electrical length of the first fan-shaped open branch are all less than the electrical length of the first parallel line, the electrical length of the second parallel line, the electrical length of the first parallel coupled line, and the electrical length of the second parallel coupled line.

[0010] In some embodiments, the electrical length of the first parallel coupled line is equal to the electrical length of the second parallel coupled line, the electrical length of the first parallel line is less than the electrical length of the second parallel coupled line, and the electrical length of the second parallel line is greater than the electrical length of the first parallel coupled line.

[0011] In some embodiments, the characteristic impedance of the first transmission line is equal to the characteristic impedance of the second transmission line, and the electrical length of the first transmission line is equal to the electrical length of the second transmission line. The electrical length of the third transmission line is equal to the electrical length of the fourth transmission line, and the characteristic impedance of the third transmission line is less than the characteristic impedance of the fourth transmission line. The characteristic impedance of the fifth transmission line is equal to the characteristic impedance of the sixth transmission line, and the electrical length of the fifth transmission line is equal to the electrical length of the sixth transmission line. The electrical length of the seventh transmission line is equal to the electrical length of the eighth transmission line, and the characteristic impedance of the seventh transmission line is less than the characteristic impedance of the eighth transmission line.

[0012] In a second aspect, an embodiment of the present application provides a bandpass filter, which is obtained by designing a topology structure as described in any one of the first aspects.

[0013] In a third aspect, an embodiment of the present application provides a communication device comprising the bandpass filter as described in the second aspect.

[0014] Different from the prior art, the present application provides a topological structure, including an input end and an output end, wherein a first parallel line, a first parallel coupling line and a first microstrip line are connected between the input end and the output end. The first parallel line is connected between the input end and the first parallel coupling line, and the first microstrip line is connected between the first parallel coupling line and the output end. A second parallel line and a second parallel coupling line are also included between the first parallel line and the first parallel coupling line, one end of the second parallel line is connected between the first parallel line and the first parallel coupling line, and the other end of the second parallel line is used for grounding. One end of the second parallel coupling line is connected between the first parallel coupling line and the first microstrip line, and the other end of the second parallel coupling line is used for grounding. A first rectangular open branch and a first fan-shaped open branch are also connected between the first parallel coupling line and the first microstrip line. A second fan-shaped open branch is connected between the first microstrip line and the output end. The first parallel lines and the first parallel coupled lines form a three-mode filter. The second parallel lines and the second parallel coupled lines optimize the in-band reflection coefficient and introduce additional zeros to ensure high selectivity and a wide stopband. The second parallel lines and the second parallel coupled lines are bent to miniaturize the broadband filter. The first rectangular open-circuit branch, the first microstrip line, the first fan-shaped open-circuit branch, and the second fan-shaped open-circuit branch form a low-pass filter to further widen the stopband. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 These are some schematic diagrams of topological structures provided in the embodiments of this application;

[0016] Figure 2 Schematic diagram of the layout of some bandpass filters provided in the embodiments of the present application;

[0017] Figure 3 Schematic diagram of the layout of some bandpass filters provided in the embodiments of the present application;

[0018] Figure 4 1 is a diagram of S-parameter simulation and test results of some bandpass filters provided in the embodiments of the present application.

[0019] Description of reference numerals:

[0020] 11. Input end; 12. Output end; 13. First parallel line; 131. First transmission line; 132. Second transmission line; 14. Second parallel line; 141. Fifth transmission line; 142. Sixth transmission line; 15. First parallel coupled line; 151. Third transmission line; 152. Fourth transmission line; 16. Second parallel coupled line; 161. Seventh transmission line; 162. Eighth transmission line; 17. First microstrip line; 18. First rectangular open branch; 19. First fan-shaped open branch; 21. Second fan-shaped open branch. DETAILED DESCRIPTION

[0021] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0022] In the description of the embodiments of this application, the technical terms "first," "second," etc. are used only to distinguish different objects and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "several" means more than one, unless otherwise specifically defined.

[0023] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0024] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of such a phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive with other embodiments. Furthermore, the technical features described below in the different embodiments of the present application may be combined with one another as long as they do not conflict with each other.

[0025] First, please refer to Figure 1 , Figure 1This is a schematic diagram of some topological structures provided in an embodiment of the present application, which topological structure includes an input end 11, an output end 12, a first parallel line 13, a second parallel line 14, a first parallel coupling line 15, a second parallel coupling line 16, a first rectangular open branch 18, a first fan-shaped open branch 19, a second fan-shaped open branch 21 and a first microstrip line 17.

[0026] Specifically, a first parallel line 13, a first parallel coupling line 15, and a first microstrip line 17 are connected between the input end 11 and the output end 12. The first parallel line 13 is connected between the input end 11 and the first parallel coupling line 15, and the first microstrip line 17 is connected between the first parallel coupling line 15 and the output end 12. A second parallel line 14 and a second parallel coupling line 16 are also included between the first parallel line 13 and the first parallel coupling line 15; one end of the second parallel line 14 is connected between the first parallel line 13 and the first parallel coupling line 15, and the other end of the second parallel line 14 is used for grounding. One end of the second parallel coupling line 16 is connected between the first parallel coupling line 15 and the first microstrip line 17, and the other end of the second parallel coupling line 16 is used for grounding. A first rectangular open branch 18 and a first fan-shaped open branch 19 are also connected between the first parallel coupling line 15 and the first microstrip line 17. A second fan-shaped open branch 21 is connected between the first microstrip line 17 and the output end 12.

[0027] In some embodiments, please refer to Figure 1 The first parallel line 13 includes a first transmission line 131 and a second transmission line 132, which are arranged in parallel and spaced apart. The first parallel coupled line 15 includes a third transmission line 151 and a fourth transmission line 152, which are arranged in parallel and spaced apart. The second parallel line 14 includes a fifth transmission line 141 and a sixth transmission line 142, which are arranged in parallel and spaced apart. The second parallel coupled line 16 includes a seventh transmission line 161 and an eighth transmission line 162, which are arranged in parallel and spaced apart.

[0028] Furthermore, one end of the first transmission line 131 is connected to the input terminal 11, and the other end is open-circuited. One end of the second transmission line 132 is connected to one end of the third transmission line 151, one end of the fifth transmission line 141, and one end of the seventh transmission line 161, while the other ends of the second transmission line 132, the third transmission line 151, the fifth transmission line 141, and the seventh transmission line 161 are open-circuited. One end of the fourth transmission line 152 is connected to one end of the first rectangular open branch 18, one end of the first fan-shaped open branch 19, and one end of the first microstrip line 17, while the other end of the fourth transmission line 152 is open-circuited. One end of the sixth transmission line 142 is open-circuited, and the other end is grounded. One end of the eighth transmission line 162 is open-circuited, and the other end is grounded.

[0029] In some embodiments, the characteristic impedance of the first transmission line 131 is equal to the characteristic impedance of the second transmission line 132, and the electrical length of the first transmission line 131 is equal to the electrical length of the second transmission line 132. The electrical length of the third transmission line 151 is equal to the electrical length of the fourth transmission line 152, and the characteristic impedance of the third transmission line 151 is less than the characteristic impedance of the fourth transmission line 152. The characteristic impedance of the fifth transmission line 141 is equal to the characteristic impedance of the sixth transmission line 142, and the electrical length of the fifth transmission line 141 is equal to the electrical length of the sixth transmission line 142. The electrical length of the seventh transmission line 161 is equal to the electrical length of the eighth transmission line 162, and the characteristic impedance of the seventh transmission line 161 is less than the characteristic impedance of the eighth transmission line 162. The characteristic impedance of the third transmission line 151 is unequal to the characteristic impedance of the fourth transmission line 152, and the characteristic impedance of the seventh transmission line 161 is unequal to the characteristic impedance of the eighth transmission line 162. This is done to make the designed bandpass filter more flexible, reduce return loss, and eliminate glitches in the circuit. The electrical length refers to the ratio of the physical length of the transmission line to the wavelength of the transmitted electromagnetic wave. When the wavelengths are equal, the physical lengths are equal, which means that the electrical lengths are equal.

[0030] In some embodiments, the first transmission line 131 , the second transmission line 132 , the third transmission line 151 , the fourth transmission line 152 , and the first microstrip line 17 are arranged in parallel.

[0031] In some embodiments, the first transmission line 131, the second transmission line 132, the third transmission line 151, the fourth transmission line 152 and the first microstrip line 17 are all perpendicular to the fifth transmission line 141, the sixth transmission line 142, the seventh transmission line 161, the eighth transmission line 162, the first rectangular open branch 18, the first fan-shaped open branch 19 and the second fan-shaped open branch 21.

[0032] In some embodiments, the angle of the first fan-shaped open branch 19 is equal to the angle of the second fan-shaped open branch 21. For example, the error between the angle of the first fan-shaped open branch 19 and the angle of the second fan-shaped open branch 21 can be considered equal within the range of 0 to 3°. The radius of the first fan-shaped open branch 19 is equal to the radius of the second fan-shaped open branch 21. For example, the error between the radius of the first fan-shaped open branch 19 and the radius of the second fan-shaped open branch 21 can be considered equal within the range of 0 to 0.3 mm. The equivalent electrical length of the first fan-shaped open branch 19 is equal to the equivalent electrical length of the second fan-shaped open branch 21. For example, the error between the equivalent electrical length of the first fan-shaped open branch 19 and the equivalent electrical length of the second fan-shaped open branch 21 can be considered equal within the range of 0.95 to 1.05. The electrical length of the first rectangular open stub 18, the electrical length of the first microstrip line 17, and the equivalent electrical length of the first fan-shaped open stub 19 are all shorter than the electrical length of the first parallel line 13, the electrical length of the second parallel line 14, the electrical length of the first parallel coupled line 15, and the electrical length of the second parallel coupled line 16. The electrical length of the first rectangular open stub 18, the electrical length of the first microstrip line 17, and the equivalent electrical length of the first fan-shaped open stub 19 are similar in the range of 0.9 to 1.1.

[0033] In some embodiments, the electrical lengths of the first parallel coupling lines 15 and the second parallel coupling lines 16 are equal. The electrical lengths of the first parallel lines 13 and 14 are less than the electrical lengths of the second parallel coupling lines 16. The electrical lengths of the second parallel lines 14 and 15 are greater than the electrical lengths of the first parallel coupling lines 15.

[0034] The present application provides a topological structure including an input terminal 11 and an output terminal 12, with a first parallel line 13, a first parallel coupling line 15, and a first microstrip line 17 connected between the input terminal 11 and the output terminal 12. The first parallel line 13 is connected between the input terminal 11 and the first parallel coupling line 15, and the first microstrip line 17 is connected between the first parallel coupling line 15 and the output terminal 12. A second parallel line 14 and a second parallel coupling line 16 are also included between the first parallel line 13 and the first parallel coupling line 15; one end of the second parallel line 14 is connected between the first parallel line 13 and the first parallel coupling line 15, and the other end of the second parallel line 14 is grounded. One end of the second parallel coupling line 16 is connected between the first parallel coupling line 15 and the first microstrip line 17, and the other end of the second parallel coupling line 16 is grounded. A first rectangular open branch 18 and a first fan-shaped open branch 19 are also connected between the first parallel coupling line 15 and the first microstrip line 17. A second fan-shaped open branch 21 is connected between the first microstrip line 17 and the output terminal 12. The first parallel lines 13 and first parallel coupled lines 15 form a three-mode filter. The second parallel lines 14 and second parallel coupled lines 16 optimize the in-band reflection coefficient and introduce additional zeros to ensure high selectivity and a wide stopband. The second parallel lines 14 and second parallel coupled lines 16 are bent to miniaturize the broadband filter. The first rectangular open-circuit branch 18, first microstrip line 17, first fan-shaped open-circuit branch 19, and second fan-shaped open-circuit branch 21 form a low-pass filter to further widen the stopband.

[0035] In a second aspect, an embodiment of the present application provides a bandpass filter, which is obtained by designing a topological structure according to any one of the first aspects.

[0036] To facilitate understanding of the concepts of this application, the following simulation experiment uses a real-world bandpass filter, which can be placed on a circuit board. The overall dimensions of the circuit board are 11.03mm × 44.63mm, with a thickness of 0.508mm. The circuit board has a dielectric constant of 3.38 and a dielectric loss of 0.0027. The second parallel line and the second parallel coupling line are bent to achieve miniaturization of the broadband filter.

[0037] Please refer to Figures 1 to 3 The size parameters of the bandpass filter include: L1 is the physical length of the first parallel line, L1 = 18.27 mm; L2 is the physical length of the first parallel coupling line, L2 = 21.425 mm; L3 is the physical length of the second parallel coupling line, the second parallel coupling line is as follows Figure 3 The bending setting shown is as follows: L3 = 21.1 mm; L4 is the physical length of the second parallel line. Figure 3The bending arrangement shown is as follows: L4 = 24.1 mm; W1 is the physical width of the first transmission line, W1 = 0.075 mm; W2 is the physical width of the second transmission line, W2 = 0.075 mm; W3 is the physical width of the third transmission line, W3 = 0.45 mm; W4 is the physical width of the fourth transmission line, W4 = 0.25 mm; W5 is the physical width of the fifth transmission line, W5 = 0.075 mm; W6 is the physical width of the sixth transmission line, W6 = 0.075 mm; W7 is the physical width of the seventh transmission line, W7 = 0.375 mm; W8 is the physical width of the eighth transmission line The physical width of the first transmission line is W8 = 0.125 mm; g1 is the distance between the first transmission line and the second transmission line, g1 = 0.2 mm; g2 is the distance between the fifth transmission line and the sixth transmission line, g2 = 0.1 mm; g3 is the distance between the seventh transmission line and the eighth transmission line, g3 = 0.1 mm; g4 is the distance between the third transmission line and the sixth transmission line, g4 = 0.1 mm; L5 is the length of the first rectangular open branch, L5 = 2.075 mm; L6 is the length of the first microstrip line, L6 = 0.8 mm; W9 is the width of the first rectangular open branch, W9 = 1.025 mm; W 10 is the width of the first microstrip line, W 10 =0.1mm; R1 is the radius length of the first fan-shaped open branch, R1=3.64mm; R2 is the radius length of the second fan-shaped open branch, R2=3.64mm; θ1 is the fan angle of the first fan-shaped open branch, θ1=30°; θ2 is the fan angle of the second fan-shaped open branch, θ2=30°.

[0038] Figure 4 Figure 1 is a diagram of S-parameter simulation and test results of some bandpass filters provided in the embodiments of this application. Figure 4 It can be seen that the passband range of the filter with a reflection coefficient better than -22dB is 1.8GHz to 3.1GHz, the center frequency is 2.4GHz, the absolute bandwidth is 1.3GHz, the relative bandwidth is 54.1%, and the insertion loss in the passband is less than 0.9dB. There are three transmission poles in the passband, located at 2.08GHz, 2.53GHz and 2.91GHz, which can ensure the flatness of the passband; there are twenty-two transmission zeros in the stopband, located at 0GHz, 1.59GHz, 3.31GHz, 4.84GHz, 5.42GHz, 6.03GHz, 6.87GHz, 7.21GHz, 7.59GHz, 8.04GHz, 9.21GHz, 11.38GHz, 12.31GHz, 15.42GHz, 16.83GHz, 18.32GHz, 19.33GHz, 20.22GHz, 21.54GHz, 22.82GHz, 23.24GHz and 25.23GHz. These transmission zeros not only ensure the high selectivity of the filter, but also ensure a wide stopband and high isolation.

[0039] In a third aspect, the present application also provides a communication device including the bandpass filter according to the second aspect. The structure and function of the bandpass filter can be found in the above embodiments and will not be described in detail here.

[0040] It should be noted that the preferred embodiments of the present invention are given in the specification and drawings of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments do not serve as additional limitations on the content of the present invention. The purpose of providing these embodiments is to make the understanding of the disclosure of the present invention 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 considered to be within the scope of the description of the present invention; further, it is obvious to those skilled in the art that improvements or changes can be made based on the above description, and all such improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A topological structure, characterized in that: It includes an input end and an output end, wherein a first parallel line, a first parallel coupling line and a first microstrip line are connected between the input end and the output end; The first parallel line is connected between the input end and the first parallel coupling line, and the first microstrip line is connected between the first parallel coupling line and the output end; A second parallel line and a second parallel coupling line are further included between the first parallel line and the first parallel coupling line; one end of the second parallel line is connected between the first parallel line and the first parallel coupling line, and the other end of the second parallel line is grounded; One end of the second parallel coupling line is connected between the first parallel coupling line and the first microstrip line, and the other end of the second parallel coupling line is grounded; A first rectangular open branch and a first fan-shaped open branch are further connected between the first parallel coupling line and the first microstrip line; A second fan-shaped open-circuit branch is connected between the first microstrip line and the output end.

2. The topological structure according to claim 1, characterized in that: The first parallel lines include a first transmission line and a second transmission line, and the first transmission line and the second transmission line are arranged in parallel and spaced apart; The first parallel coupling line includes a third transmission line and a fourth transmission line, and the third transmission line and the fourth transmission line are arranged in parallel and spaced apart; The second parallel lines include a fifth transmission line and a sixth transmission line, and the fifth transmission line and the sixth transmission line are arranged in parallel and spaced apart; The second parallel coupling line includes a seventh transmission line and an eighth transmission line, and the seventh transmission line and the eighth transmission line are arranged in parallel and spaced apart.

3. The topological structure according to claim 2, characterized in that: One end of the first transmission line is connected to the input end, and the other end is open; One end of the second transmission line is connected to one end of the third transmission line, one end of the fifth transmission line, and one end of the seventh transmission line, and the other ends of the second transmission line, the third transmission line, the fifth transmission line, and the seventh transmission line are open; One end of the fourth transmission line is connected to one end of the first rectangular open branch, one end of the first fan-shaped open branch, and one end of the first microstrip line, and the other end of the fourth transmission line is open; One end of the sixth transmission line is open, and the other end is grounded; one end of the eighth transmission line is open, and the other end is grounded.

4. The topological structure according to claim 2, characterized in that: The first transmission line, the second transmission line, the third transmission line, the fourth transmission line and the first microstrip line are arranged in parallel.

5. The topological structure according to claim 2, characterized in that: The first transmission line, the second transmission line, the third transmission line, the fourth transmission line and the first microstrip line are all perpendicular to the fifth transmission line, the sixth transmission line, the seventh transmission line, the eighth transmission line, the first rectangular open branch, the first fan-shaped open branch and the second fan-shaped open branch.

6. The topological structure according to any one of claims 1 to 5, characterized in that: The angle of the first fan-shaped open branch is equal to the angle of the second fan-shaped open branch; The radius of the first fan-shaped open branch is equal to the radius of the second fan-shaped open branch; The equivalent electrical length of the first fan-shaped open-circuit branch is equal to the equivalent electrical length of the second fan-shaped open-circuit branch; The electrical length of the first rectangular open branch, the electrical length of the first microstrip line, and the equivalent electrical length of the first fan-shaped open branch are all smaller than the electrical length of the first parallel line, the electrical length of the second parallel line, the electrical length of the first parallel coupled line, and the electrical length of the second parallel coupled line.

7. The topological structure according to any one of claims 1 to 5, characterized in that: The electrical length of the first parallel coupling line is equal to the electrical length of the second parallel coupling line; The electrical length of the first parallel lines is less than the electrical length of the second parallel coupling lines; The electrical length of the second parallel lines is greater than the electrical length of the first parallel coupling lines.

8. The topological structure according to claim 2, characterized in that: The characteristic impedance of the first transmission line is equal to the characteristic impedance of the second transmission line, and the electrical length of the first transmission line is equal to the electrical length of the second transmission line; The electrical length of the third transmission line is equal to the electrical length of the fourth transmission line, and the characteristic impedance of the third transmission line is smaller than the characteristic impedance of the fourth transmission line; The characteristic impedance of the fifth transmission line is equal to the characteristic impedance of the sixth transmission line, and the electrical length of the fifth transmission line is equal to the electrical length of the sixth transmission line; The electrical length of the seventh transmission line is equal to the electrical length of the eighth transmission line, and the characteristic impedance of the seventh transmission line is smaller than the characteristic impedance of the eighth transmission line.

9. A bandpass filter, characterized in that: The method is obtained by designing the topological structure according to any one of claims 1 to 8.

10. A communication device comprising the bandpass filter according to claim 9.

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