Topological structure, band-pass filter and communication equipment
By designing a topological bandpass filter with a varactor diode in the communication system, the problem of complex structure and large volume in the prior art is solved, and the bandwidth is adjustable and the structure is compact.
Patent Information
- Application Number
- CN202420659320.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-29
- Publication Date
- 2025-04-29
- Estimated Expiration
- 2034-03-29
AI Technical Summary
A large number of filters with different indicators are set up in the existing communication systems, resulting in complex structures and large sizes, which is not conducive to the miniaturization of the system.
A bandpass filter with a topological structure is provided, including an input terminal, an output terminal, a parallel three-wire, a microstrip line and an open circuit branch. The capacitor value is adjusted through a varactor diode to achieve bandwidth adjustability.
It realizes adjustable bandwidth, wide bandwidth tuning range, and compact structure, which is suitable for the miniaturization needs of communication systems.
Smart Images
Figure CN222814454U_ABST
Abstract
Description
Technical Field
[0001] The embodiments of the utility model relate to the field of communication technology, and in particular to a topological structure, a bandpass filter and communication equipment. Background Art
[0002] With the rapid development of the fifth generation of mobile communication technology, the multifunctionality and miniaturization of communication systems have become an inevitable development trend, and filters play an important role in communication systems to filter out noise, interference and other unwanted signals. Current filters generally have non-adjustable bandwidth and fixed functions. Therefore, in order to realize the multifunctionality of communication systems, a large number of filters with different indicators need to be set.
[0003] In the process of implementing the embodiments of the present application, the inventors found that: setting a large number of filters with different indicators in the communication system has a complex structure and a large volume, which is not conducive to the miniaturization of the communication system. Utility Model Content
[0004] In view of the above problems, the embodiments of the present utility model provide a topology structure, a 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 three-wire, a second parallel three-wire, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, a seventh microstrip line, a first open-circuit branch, a second open-circuit branch, a third open-circuit branch, a fourth open-circuit branch and a varactor diode; wherein the input end is connected to one end of the first parallel three-wire, the other end of the first parallel three-wire is connected to one end of the second parallel three-wire and one end of the first microstrip line, and the other end of the second parallel three-wire is connected to the output end. The output end is connected, the other end of the first microstrip line is connected to the negative electrode of the varactor diode, the positive electrode of the varactor diode is connected to one end of the second microstrip line and one end of the fifth microstrip line, the other end of the second microstrip line is connected to one end of the third microstrip line and one end of the fourth microstrip line, the other end of the fifth microstrip line is connected to one end of the sixth microstrip line and one end of the seventh microstrip line, the first open branch, the third microstrip line, the fourth microstrip line and the second open branch are connected in sequence, and the third open branch, the sixth microstrip line, the seventh microstrip line and the fourth open branch are connected in sequence.
[0006] Optionally, the second microstrip line and the fifth microstrip line are connected in a straight line, with the straight line where the second microstrip line and the fifth microstrip line are located as the axis of symmetry, and the third microstrip line and the fourth microstrip line, the sixth microstrip line and the seventh microstrip line, the first open branch and the second open branch, the third open branch and the fourth open branch are all symmetrically arranged up and down; the first microstrip line is located on the perpendicular bisector connecting the second microstrip line and the fifth microstrip line, with the perpendicular bisector as the axis of symmetry, the second microstrip line and the fifth microstrip line, the third microstrip line and the sixth microstrip line, the fourth microstrip line and the seventh microstrip line, the first open branch and the third open branch, the second open branch and the fourth open branch, the first parallel three lines and the second parallel three lines are all symmetrically arranged left and right.
[0007] Optionally, the first three parallel lines, the second three parallel lines, the second microstrip line, the fifth microstrip line, the first open branch, the second open branch, the third open branch and the fourth open branch are arranged in parallel and are perpendicular to the first microstrip line, the third microstrip line, the fourth microstrip line, the sixth microstrip line and the seventh microstrip line.
[0008] Optionally, the characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the sixth microstrip line, the characteristic impedance of the seventh 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, and are both twice the characteristic impedance of the second microstrip line; the characteristic impedance of the second microstrip line and the characteristic impedance of the fifth microstrip line are equal, and are both twice the characteristic impedance of the first microstrip line.
[0009] Optionally, the electrical length of the first parallel three lines and the electrical length of the second parallel three lines are both one-quarter wavelength corresponding to the center frequency of the passband, the electrical length of the first microstrip line is one-eighth wavelength corresponding to the center frequency of the passband, the sum of the electrical length of the second microstrip line, the electrical length of the third microstrip line, and the electrical length of the first open branch is three-eighth wavelength corresponding to the center frequency of the passband, the sum of the electrical length of the second microstrip line, the electrical length of the fourth microstrip line, and the electrical length of the second open branch is three-eighth wavelength corresponding to the center frequency of the passband, the sum of the electrical length of the fifth microstrip line, the electrical length of the sixth microstrip line, and the electrical length of the third open branch is three-eighth wavelength corresponding to the center frequency of the passband, and the sum of the electrical length of the fifth microstrip line, the electrical length of the seventh microstrip line, and the electrical length of the fourth open branch is three-eighth wavelength corresponding to the center frequency of the passband.
[0010] Optionally, the first parallel three lines include a first left transmission line, a second left transmission line and a third left transmission line that are arranged in parallel and at equal intervals, the second left transmission line is located between the first left transmission line and the third left transmission line, one end of the first left transmission line and one end of the third left transmission line are both connected to the input end, and one end of the second left transmission line is connected to the first microstrip line; the second parallel three lines include a first right transmission line, a second right transmission line and a third right transmission line that are arranged in parallel and at equal intervals, the second right transmission line is located between the first right transmission line and the third right transmission line, one end of the first right transmission line and one end of the third right transmission line are both connected to the output end, and one end of the second right transmission line is connected to the first microstrip line.
[0011] In order to solve the above technical problem, another technical solution adopted by the present invention is: to provide a bandpass filter including the above topological structure.
[0012] 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 bandpass filter.
[0013] The beneficial effects of the embodiments of the utility model are as follows: different from the prior art, the embodiments of the present application provide a topological structure, including an input end, an output end, a first parallel three wires, a second parallel three wires, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, a seventh microstrip line, a first open-circuit branch node, a second open-circuit branch node, a third open-circuit branch node, a fourth open-circuit branch node and a varactor diode. The input end is connected to one end of the first three parallel lines, the other end of the first three parallel lines is connected to one end of the second three parallel lines and one end of the first microstrip line, the other end of the second three parallel lines is connected to the output end, the other end of the first microstrip line is connected to the negative electrode of the varactor diode, the positive electrode of the varactor diode is connected to one end of the second microstrip line and one end of the fifth microstrip line, the other end of the second microstrip line is connected to one end of the third microstrip line and one end of the fourth microstrip line, the other end of the fifth microstrip line is connected to one end of the sixth microstrip line and one end of the seventh microstrip line, the first open branch, the third microstrip line, the fourth microstrip line and the second open branch are connected in sequence, and the third open branch, the sixth microstrip line, the seventh microstrip line and the fourth open branch are connected in sequence. The bandpass filter based on this topological structure has the characteristics of adjustable bandwidth, wide bandwidth tuning range and compact structure. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.
[0015] Figure 1 It is a schematic diagram of the topological structure of a bandpass filter provided by an embodiment of the utility model;
[0016] Figure 2 It is a layout diagram of a bandpass filter example provided by an embodiment of the utility model;
[0017] Figure 3 It is a diagram of S parameter simulation results of working state 1 (State 1) of a bandpass filter example provided by an embodiment of the utility model;
[0018] Figure 4 It is a diagram of S parameter simulation results of working state 2 (State 2) of a bandpass filter example provided by an embodiment of the utility model;
[0019] Figure 5 IS is a parameter of the working state 1 (State 1) and the working state 2 (State 2) of a bandpass filter example provided by the embodiment of the utility model. 21 I simulation result diagram. DETAILED DESCRIPTION
[0020] 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.
[0021] 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.
[0022] This application provides a topology structure 100, see Figure 1The topological structure 100 includes an input terminal 10, an output terminal 50, a first parallel three-wire 20, a second parallel three-wire 21, a first microstrip line 30, a second microstrip line 31, a third microstrip line 32, a fourth microstrip line 33, a fifth microstrip line 34, a sixth microstrip line 35, a seventh microstrip line 36, a first open-circuit branch 40, a second open-circuit branch 41, a third open-circuit branch 42, a fourth open-circuit branch 43 and a varactor diode D1; wherein the input terminal 10 is connected to one end of the first parallel three-wire 20, the other end of the first parallel three-wire 20 is connected to one end of the second parallel three-wire 21 and one end of the first microstrip line 30, and the other end of the second parallel three-wire 21 is connected to the input terminal 10. The output end 50 is connected, the other end of the first microstrip line 30 is connected to the cathode of the varactor D1, the anode of the varactor D1 is connected to one end of the second microstrip line 31 and one end of the fifth microstrip line 34, the other end of the second microstrip line 31 is connected to one end of the third microstrip line 32 and one end of the fourth microstrip line 33, the other end of the fifth microstrip line 34 is connected to one end of the sixth microstrip line 35 and one end of the seventh microstrip line 36, the first open branch 40, the third microstrip line 32, the fourth microstrip line 33 and the second open branch 41 are connected in sequence, and the third open branch 42, the sixth microstrip line 35, the seventh microstrip line 36 and the fourth open branch 43 are connected in sequence.
[0023] In some embodiments, the second microstrip line 31 and the fifth microstrip line 34 are connected in a straight line, with the straight line where the second microstrip line 31 and the fifth microstrip line 34 are located as the axis of symmetry, and the third microstrip line 32 and the fourth microstrip line 33, the sixth microstrip line 35 and the seventh microstrip line 36, the first open branch 40 and the second open branch 41, the third open branch 42 and the fourth open branch 43 are all symmetrically arranged up and down; the first microstrip line 30 is located on the perpendicular bisector connecting the second microstrip line 31 and the fifth microstrip line 34, with the perpendicular bisector as the axis of symmetry, the second microstrip line 31 and the fifth microstrip line 34, the third microstrip line 32 and the sixth microstrip line 35, the fourth microstrip line 33 and the seventh microstrip line 36, the first open branch 40 and the third open branch 42, the second open branch 41 and the fourth open branch 43, the first parallel three lines 20 and the second parallel three lines 21 are all symmetrically arranged left and right.
[0024] In some embodiments, the first parallel three lines 20, the second parallel three lines 21, the second microstrip line 31, the fifth microstrip line 34, the first open branch 40, the second open branch 41, the third open branch 42 and the fourth open branch 43 are arranged in parallel and are all perpendicular to the first microstrip line 30, the third microstrip line 32, the fourth microstrip line 33, the sixth microstrip line 35 and the seventh microstrip line 36.
[0025] In some embodiments, the characteristic impedance of the third microstrip line 32, the characteristic impedance of the fourth microstrip line 33, the characteristic impedance of the sixth microstrip line 35, the characteristic impedance of the seventh microstrip line 36, the characteristic impedance of the first open branch 40, the characteristic impedance of the second open branch 41, the characteristic impedance of the third open branch 42 and the characteristic impedance of the fourth open branch 43 are equal, and are both twice the characteristic impedance of the second microstrip line 31; the characteristic impedance of the second microstrip line 31 and the characteristic impedance of the fifth microstrip line 34 are equal, and are both twice the characteristic impedance of the first microstrip line 30.
[0026] In some embodiments, the electrical length of the first parallel three lines 20 and the electrical length of the second parallel three lines 21 are both one-quarter wavelength corresponding to the passband center frequency, the electrical length of the first microstrip line 30 is one-eighth wavelength corresponding to the passband center frequency, the sum of the electrical lengths of the second microstrip line 31, the third microstrip line 32, and the first open branch 40 is three-eighth wavelength corresponding to the passband center frequency, the sum of the electrical lengths of the second microstrip line 31, the fourth microstrip line 33, and the second open branch 41 is three-eighth wavelength corresponding to the passband center frequency, the sum of the electrical lengths of the fifth microstrip line 34, the sixth microstrip line 35, and the third open branch 42 is three-eighth wavelength corresponding to the passband center frequency, and the sum of the electrical lengths of the fifth microstrip line 34, the seventh microstrip line 36, and the fourth open branch 43 is three-eighth wavelength corresponding to the passband center frequency.
[0027] In some embodiments, the first parallel three-line 20 includes a first left transmission line 201, a second left transmission line 202, and a third left transmission line 203 arranged in parallel and at equal intervals, the second left transmission line 202 is located between the first left transmission line 201 and the third left transmission line 203, one end of the first left transmission line 201 and one end of the third left transmission line 203 are both connected to the input end 10, and one end of the second left transmission line 202 is connected to the first microstrip line 30; the second parallel three-line 21 includes a first right transmission line 211, a second right transmission line 212, and a third right transmission line 213 arranged in parallel and at equal intervals, the second right transmission line 212 is located between the first right transmission line 211 and the third right transmission line 213, one end of the first right transmission line 211 and one end of the third right transmission line 213 are both connected to the output end 50, and one end of the second right transmission line 212 is connected to the first microstrip line 30.
[0028] For ease of understanding, the present application also provides a simulation experiment embodiment of the topology structure 100 for designing a bandpass filter, see Figure 2The topological structure 100 is arranged on a circuit board (not shown), and a protective resistor R1, a first RF blocking inductor L1, a second RF blocking inductor L2, a first solder pad 60, a second solder pad 70 and a DC ground 80 are also arranged on the circuit board. The second solder pad 70, the protective resistor R1, the first solder pad 60, the first RF blocking inductor L1 and one end of the fifth microstrip line 34 are connected in sequence, and one end of the first microstrip line 30, the second RF blocking inductor L2 and the DC ground 80 are connected in sequence. The second solder pad 70 is used to connect to a DC power supply to provide a DC voltage acting on the varactor diode D1, the first solder pad 60 is used to connect and fix the first RF blocking inductor L1 and the protective resistor R1, and the DC ground 80 is used to form a DC loop.
[0029] The size of the circuit board is 22.0mm*9.1mm, the thickness is 0.813mm, and the dielectric loss is 0.0022. One set of classic parameters is: P =8.9mm,s P =0.15mm,w P =0.2mm, l1=4.6mm, l2=6.7mm, l3=1.75mm, l4=5.85mm, w1=0.6mm, w2=0.3mm, w3=0.15mm, w4=0.15mm.
[0030] Among them, l P 、w P are the physical lengths and physical widths of the first left transmission line 201, the second left transmission line 202, the third left transmission line 203, the first right transmission line 211, the second right transmission line 212, and the third right transmission line 213, respectively. P is the physical spacing between the first left transmission line 201 and the second left transmission line 202, the second left transmission line 202 and the third left transmission line 203, the first right transmission line 211 and the second right transmission line 212, the second right transmission line 212 and the third right transmission line 213, l1 and w1 are the physical length and physical width of the first microstrip line 30, l2 and w2 are the physical length and physical width of the second microstrip line 31 and the fifth microstrip line 34, l3 and w3 are the physical length and physical width of the third microstrip line 32, the fourth microstrip line 33, the sixth microstrip line 35 and the seventh microstrip line 36, l4 and w4 are the physical length and physical width of the first open branch 40, the second open branch 41, the third open branch 42 and the fourth open branch 43, respectively.
[0031] It can be understood that when the DC power supply inputs different DC voltages, the varactor diode D1 changes to different capacitance values, and the filter designed based on the topological structure 100 thus has different operating frequencies. In this simulation experiment embodiment, the DC power supply inputs a first voltage value when in working state 1 (State 1), and the corresponding capacitance value of the varactor diode is 0.6pF; the DC power supply inputs a second voltage value when in working state 2 (State 2), and the corresponding capacitance value of the varactor diode D1 is 48pF.
[0032] For the above simulation examples, please refer to the S parameter simulation results. Figures 3 to 5 , Figure 3 This is the S parameter simulation result diagram in working state 1 (State 1). Figure 4 This is the S parameter simulation result diagram for working state 2 (State 2). Figure 5 IS is the parameter of working state 1 (State 1) and working state 2 (State 2) 21 I simulation result diagram. When in working state 1 (State1), please refer to Figure 3 The S parameter simulation results show that the impedance bandwidth range with reflection coefficient less than -10dB is 5.4377.551GHz, the passband center frequency is 6.494GHz, the absolute bandwidth of the passband is 2.114GHz, and the relative bandwidth of the passband is 32.6%. In the passband, there are two transmission poles, located at 6.02GHz and 7.205GHz respectively. These two transmission poles ensure the flatness in the passband. In the stopband, there are two transmission zeros, located at 3.882GHz and 8.202GHz respectively. These two transmission zeros ensure high selectivity. When in working state 2, please refer to Figure 4 The S parameter simulation results show that the impedance bandwidth range with a reflection coefficient less than -10dB is 3.079 7.531GHz, the passband center frequency is 5.305GHz, the absolute bandwidth of the passband is 4.452GHz, and the relative bandwidth of the passband is 83.9%. In the passband, there are four transmission poles, located at 3.22GHz, 3.876GHz, 5.708GHz and 7.179GHz, respectively. These four transmission poles ensure the flatness in the passband. In the stopband, there are two transmission zeros, located at 2.26GHz and 8.079GHz, respectively. These two transmission zeros ensure high selectivity.
[0033] When changing from working state 1 (State 1) to working state 2 (State 2), the capacitance value of the varactor diode D1 increases from 0.6pF to 48pF, and the relative bandwidth increases from 32.6% to 83.9%, and both working state 1 (State 1) and working state 2 (State 2) have the characteristics of high selectivity. It can be seen that the bandpass filter designed based on topology structure 100 has the characteristics of high selectivity and a wide bandwidth tuning range.
[0034] See also Figure 5 , compare the parameter IS under working state 1 (State 1) and working state 2 (State 2) 21 It can be obtained from the simulation results that, as the capacitance value of the varactor diode D1 increases, the high-frequency sideband of the passband remains unchanged, and the corresponding frequency of the low-frequency sideband decreases. Therefore, the low-frequency sideband of the passband is adjustable.
[0035] It should be noted that, according to common microwave knowledge, the physical length of the first three parallel lines 20 or the physical length of the second three parallel lines 21 can be changed proportionally. P , the physical length l1 of the first microstrip line 30, the physical length l2 of the second microstrip line 31 or the physical length l4 of the fifth microstrip line 34, the physical length l3 of the third microstrip line 32 or the physical length of the fourth microstrip line 34 or the physical length l5 of the sixth microstrip line 36, the physical length l4 of the first open branch 40 or the physical length of the second open branch 41 or the physical length of the third open branch 42 or the physical length of the fourth open branch 43, can change the operating frequency of the bandpass filter in inverse linear proportion.
[0036] The present application provides a topological structure 100, including an input terminal 10, an output terminal 50, a first parallel three-wire 20, a second parallel three-wire 21, a first microstrip line 30, a second microstrip line 31, a third microstrip line 32, a fourth microstrip line 33, a fifth microstrip line 34, a sixth microstrip line 35, a seventh microstrip line 36, a first open-circuit branch 40, a second open-circuit branch 41, a third open-circuit branch 42, a fourth open-circuit branch 43 and a varactor diode D1. The topological structure 100 is symmetrically and compactly arranged, and is used to design a bandpass filter with high selectivity, adjustable bandwidth, and wide bandwidth tuning range, and is conducive to the miniaturization of the filter.
[0037] The present application also provides a bandpass filter embodiment, and the bandpass filter includes the above-mentioned topological structure 100. The structure and function of the topological structure 100 can be referred to the above-mentioned embodiment, and will not be described in detail here.
[0038] The present application also provides a communication device embodiment, the communication device includes the above-mentioned bandpass filter, and the structure and function of the bandpass filter can be referred to the above-mentioned embodiment, which will not be described one by one here.
[0039] 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: It includes an input end, an output end, a first parallel three-wire, a second parallel three-wire, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, a seventh microstrip line, a first open-circuit branch node, a second open-circuit branch node, a third open-circuit branch node, a fourth open-circuit branch node, and a varactor diode; Among them, the input end is connected to one end of the first parallel three lines, the other end of the first parallel three lines is connected to one end of the second parallel three lines and one end of the first microstrip line, the other end of the second parallel three lines is connected to the output end, the other end of the first microstrip line is connected to the negative electrode of the varactor diode, the positive electrode of the varactor diode is connected to one end of the second microstrip line and one end of the fifth microstrip line, the other end of the second microstrip line is connected to one end of the third microstrip line and one end of the fourth microstrip line, the other end of the fifth microstrip line is connected to one end of the sixth microstrip line and one end of the seventh microstrip line, the first open branch, the third microstrip line, the fourth microstrip line and the second open branch are connected in sequence, and the third open branch, the sixth microstrip line, the seventh microstrip line and the fourth open branch are connected in sequence.
2. The topological structure according to claim 1, characterized in that: The second microstrip line and the fifth microstrip line are connected in a straight line, and the straight line where the second microstrip line and the fifth microstrip line are located is used as a symmetry axis, and the third microstrip line and the fourth microstrip line, the sixth microstrip line and the seventh microstrip line, the first open branch node and the second open branch node, and the third open branch node and the fourth open branch node are all symmetrically arranged up and down; The first microstrip line is located on the perpendicular bisector connecting the second microstrip line and the fifth microstrip line. With the perpendicular bisector as the axis of symmetry, the second microstrip line and the fifth microstrip line, the third microstrip line and the sixth microstrip line, the fourth microstrip line and the seventh microstrip line, the first open branch node and the third open branch node, the second open branch node and the fourth open branch node, the first parallel three lines and the second parallel three lines are all arranged symmetrically on the left and right.
3. The topological structure according to claim 1, characterized in that The first three parallel lines, the second three parallel lines, the second microstrip line, the fifth microstrip line, the first open branch, the second open branch, the third open branch and the fourth open branch are arranged in parallel and are perpendicular to the first microstrip line, the third microstrip line, the fourth microstrip line, the sixth microstrip line and the seventh microstrip line.
4. The topological structure according to claim 1, characterized in that , The characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the sixth microstrip line, the characteristic impedance of the seventh 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, and are all twice the characteristic impedance of the second microstrip line; The characteristic impedance of the second microstrip line is equal to the characteristic impedance of the fifth microstrip line, and both are twice the characteristic impedance of the first microstrip line.
5. The topological structure according to claim 1, characterized in that: The electrical length of the first parallel three lines and the electrical length of the second parallel three lines are both one-quarter wavelength corresponding to the center frequency of the passband, the electrical length of the first microstrip line is one-eighth wavelength corresponding to the center frequency of the passband, the sum of the electrical length of the second microstrip line, the electrical length of the third microstrip line, and the electrical length of the first open branch is three-eighth wavelength corresponding to the center frequency of the passband, the sum of the electrical length of the second microstrip line, the electrical length of the fourth microstrip line, and the electrical length of the second open branch is three-eighth wavelength corresponding to the center frequency of the passband, the sum of the electrical length of the fifth microstrip line, the electrical length of the sixth microstrip line, and the electrical length of the third open branch is three-eighth wavelength corresponding to the center frequency of the passband, and the sum of the electrical length of the fifth microstrip line, the electrical length of the seventh microstrip line, and the electrical length of the fourth open branch is three-eighth wavelength corresponding to the center frequency of the passband.
6. The topological structure according to claim 1, characterized in that: The first parallel three lines include a first left transmission line, a second left transmission line and a third left transmission line which are arranged in parallel and at equal intervals, the second left transmission line is located between the first left transmission line and the third left transmission line, one end of the first left transmission line and one end of the third left transmission line are both connected to the input end, and one end of the second left transmission line is connected to the first microstrip line; The second parallel three lines include a first right transmission line, a second right transmission line and a third right transmission line which are arranged in parallel and at equal intervals, the second right transmission line is located between the first right transmission line and the third right transmission line, one end of the first right transmission line and one end of the third right transmission line are both connected to the output end, and one end of the second right transmission line is connected to the first microstrip line.
7. A bandpass filter, characterized in that: Comprising a topological structure as described in any one of claims 1-6.
8. A communication device, characterized in that: Comprising the bandpass filter as claimed in claim 7.