High-selectivity wide-passband filter topological structure and filter
By designing a broad-passband filter topology structure including parallel three-wire, parallel lines and microstrip lines, the problem of poor selectivity of existing filters is solved, and the high selectivity and high isolation of broadband bandpass filters are achieved.
Patent Information
- Application Number
- CN202421602404.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-08
- Publication Date
- 2025-05-20
- Estimated Expiration
- 2034-07-08
AI Technical Summary
The poor selectivity of existing broadband bandpass filters affects their application in modern wireless communication systems.
A highly selective broad-passband filter topology structure is proposed, including a first parallel three lines, a first parallel line and a second parallel three lines connected in sequence along the first direction. Through the combination of the first and second microstrip lines and short-circuit branches, the topology structure has a specific transmission pole and zero point distribution.
High selectivity and high isolation of broadband bandpass filters are achieved, ensuring flatness in the passband and high selectivity in the stopband.
Smart Images
Figure CN222887914U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of filters, in particular to a high-selectivity wide-bandpass filter topology structure and a filter. Background Art
[0002] With the rapid development of modern wireless communication technology, the research and development of broadband communication systems that can meet people's needs for high-speed data transmission is an inevitable trend of development. In this context, as one of the key components of broadband communication systems, the research on the miniaturization of broadband bandpass filters has extremely high scientific research and commercial value, attracting the attention of many scholars and engineers. However, most of the existing miniaturized broadband bandpass filters have the problem of poor selectivity, which seriously affects their use in modern wireless communication systems. Content of the Utility Model
[0003] The main purpose of the utility model is to provide a high-selectivity wide-bandpass filter topology structure and a filter, aiming to solve the problem of poor selectivity of existing wide-bandpass filters.
[0004] To achieve the above object, the utility model provides a high-selectivity wide-bandpass filter topology structure, including a first parallel three-line, a first parallel line, and a second parallel three-line connected in sequence along a first direction. The other end of the first parallel three-line is connected to an input end, and the other end of the second parallel three-line is connected to an output end;
[0005] A first microstrip line is connected between the first parallel three-line and the first parallel line, and the other end of the first microstrip line is connected to a first short-circuit stub; a second microstrip line is connected between the second parallel three-line and the first parallel line, and the other end of the second microstrip line is connected to a second short-circuit stub;
[0006] Both the first microstrip line and the second microstrip line are arranged along a second direction, both the first short-circuit stub and the second short-circuit stub are arranged along the first direction, and the first direction is perpendicular to the second direction.
[0007] Optionally, the first parallel three-line and the second parallel three-line respectively include three mutually parallel transmission lines, and the first parallel line includes two mutually parallel transmission lines.
[0008] Optionally, the first parallel three-line and the second parallel three-line are symmetric about the first parallel line, the first microstrip line and the first short-circuit stub are located on one side of the first parallel line, and the second microstrip line and the second short-circuit stub are located on the other side of the first parallel line.
[0009] Optionally, the electrical lengths of the first parallel line, the first parallel triple line, and the second parallel triple line are equal, and each is equal to a quarter wavelength corresponding to the center frequency of the wideband filter.
[0010] Optionally, the electrical lengths of the first microstrip line and the second microstrip line are equal;
[0011] The electrical lengths of the first short-circuit stub and the second short-circuit stub are equal;
[0012] The sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit stub, and the sum of the electrical length of the second microstrip line and the electrical length of the second short-circuit stub are both greater than the electrical length of the first parallel line.
[0013] Optionally, the odd-mode characteristic impedance of the first parallel triple line is equal to the odd-mode characteristic impedance of the second parallel triple line, and the even-mode characteristic impedance of the first parallel triple line is equal to the even-mode characteristic impedance of the second parallel triple line.
[0014] Optionally, the characteristic impedances of the first microstrip line, the second microstrip line, the first short-circuit stub, and the second short-circuit stub are all equal.
[0015] To achieve the above object, the present invention further provides a filter including any one of the above topological structures.
[0016] Optionally, the filter further includes a circuit board with a dielectric constant of 3.38, a dielectric loss of 0.0022, a thickness of 0.813 mm, and a size of 48.6 mm * 12.5 mm.
[0017] Optionally, the line width of the transmission lines in the first parallel line is set to wp = 0.2 mm, the line spacing is set to sp = 0.1 mm, and the line length is set to lp = 10 mm;
[0018] The line width of the transmission lines in the first parallel triple line and the second parallel triple line is set to w T = 0.2 mm, the line spacing is set to s T = 0.1 mm, and the line length is set to l T = 10 mm;
[0019] The line length of the first microstrip line and the second microstrip line is set to l 1 = 5.2 mm, and the line width is set to w 1 = 2.1 mm;
[0020] The line length of the first short-circuit stub and the second short-circuit stub is set to l 2 = 5.5 mm, and the line width is set to w 2= 2.1 mm.
[0021] The beneficial effects of the present utility model are as follows: It improves the topological structure of the existing wideband filter. The topological structure includes a first parallel three-line, a first parallel line, and a second parallel three-line connected in sequence along a first direction. The other end of the first parallel three-line is connected to an input end, and the other end of the second parallel three-line is connected to an output end; a first microstrip line is connected between the first parallel three-line and the first parallel line, and the other end of the first microstrip line is connected to a first short-circuit stub; a second microstrip line is connected between the second parallel three-line and the first parallel line, and the other end of the second microstrip line is connected to a second short-circuit stub; both the first microstrip line and the second microstrip line are arranged along a second direction, both the first short-circuit stub and the second short-circuit stub are arranged along the first direction, and the first direction is perpendicular to the second direction.
[0022] The filter based on this topological structure has four odd-mode transmission poles, four even-mode transmission poles, and six transmission zeros, and no matter how the characteristic impedance values of its respective stubs are changed, the relative positions of the transmission poles and zeros will not change. Therefore, a broadband band-pass filter can be designed based on this topological structure, with eight transmission poles in the passband to ensure the flatness within the passband and six transmission zeros in the stopband to ensure high selectivity and high isolation. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are only some embodiments of the present utility model, and for those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.
[0024] Figure 1 It is a schematic diagram of the topological structure of the filter of the present utility model;
[0025] Figure 2 It is an odd-mode form diagram of the topological structure of the present utility model;
[0026] Figure 3 It is an even-mode form diagram of the topological structure of the present utility model;
[0027] Figure 4 It is the layout layout diagram of the filter of the present utility model;
[0028] Figure 5 It is the S-parameter simulation result diagram of the filter of the present utility model;
[0029] The realization, functional characteristics, and advantages of the object of the present utility model will be further described in conjunction with the embodiments with reference to the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present utility model in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present utility model.
[0031] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present utility model, then the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.
[0032] In addition, if there are descriptions such as "first", "second", etc. involved in the embodiments of the present utility model, then the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text is that it includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, or solution B, or a solution that satisfies both A and B simultaneously. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present utility model.
[0033] An embodiment of the present utility model provides a high-selectivity wideband filter topology structure. Referring to Figure 1 , it includes a first parallel triple line, a first parallel line, and a second parallel triple line connected in sequence along a first direction. The other end of the first parallel triple line is connected to an input end, and the other end of the second parallel triple line is connected to an output end;
[0034] A first microstrip line is connected between the first parallel triple line and the first parallel line, and the other end of the first microstrip line is connected to a first short-circuit stub; a second microstrip line is connected between the second parallel triple line and the first parallel line, and the other end of the second microstrip line is connected to a second short-circuit stub;
[0035] Both the first microstrip line and the second microstrip line are arranged along a second direction, both the first short-circuit stub and the second short-circuit stub are arranged along the first direction, and the first direction is perpendicular to the second direction.
[0036] This embodiment improves the topological structure of the existing filter. It consists of a parallel line, a pair of parallel triple lines, two microstrip lines, and two short - circuit stubs. Among them, the first parallel triple line and the second parallel triple line are symmetric about the first parallel line. The first microstrip line and the first short - circuit stub are located on one side of the first parallel line, and the second microstrip line and the second short - circuit stub are located on the other side of the first parallel line.
[0037] Further, the first parallel triple line and the second parallel triple line each include three mutually parallel arranged transmission lines, and the first parallel line includes two mutually parallel arranged transmission lines.
[0038] Further, the electrical lengths of the first parallel line, the first parallel triple line, and the second parallel triple line are equal, and each is equal to a quarter - wavelength corresponding to the center frequency of the wide - passband filter.
[0039] Further, the electrical lengths of the first microstrip line and the second microstrip line are equal;
[0040] the electrical lengths of the first short - circuit stub and the second short - circuit stub are equal;
[0041] The sum of the electrical lengths of the first microstrip line and the first short - circuit stub, and the sum of the electrical lengths of the second microstrip line and the second short - circuit stub are both greater than the electrical length of the first parallel line.
[0042] Further, the odd - mode characteristic impedances of the first parallel triple line and the second parallel triple line are equal, and the even - mode characteristic impedances of the first parallel triple line and the second parallel triple line are equal. In this embodiment, the odd - mode characteristic impedances of the first parallel triple line and the second parallel triple line are denoted as Z o1 ; the even - mode characteristic impedances of the first parallel triple line and the second parallel triple line are denoted as Z e1 ; the odd - mode characteristic impedance of the first parallel line is denoted as Z o2 ; the even - mode characteristic impedance of the first parallel line is denoted as Z e2 .
[0043] Further, the characteristic impedances of the first microstrip line, the second microstrip line, the first short - circuit stub, and the second short - circuit stub are all equal. In this embodiment, the characteristic impedances of the first microstrip line, the second microstrip line, the first short - circuit stub, and the second short - circuit stub are denoted as Z m1 .
[0044] Since the topology can be a symmetric structure, its transmission poles can be calculated by the odd - even mode method. To simplify the calculation process, first assume that the sum of the electrical length of the first microstrip line and the electrical length of the first short - circuit stub is equal to a quarter - wavelength corresponding to the center frequency of the broadband band - pass filter. At this time, Figure 2 Figure of the odd - mode form of the simplified topology. Among them, the electrical length of the odd - mode transmission line is the electrical length of the first parallel line; the characteristic impedance of the odd - mode transmission line is the odd - mode characteristic impedance of the first parallel line.
[0045] When Y ino = 0, it can be obtained that the topology has four transmission poles. When f 0 is the center frequency of the band - pass filter, the frequencies corresponding to the four odd - mode transmission poles are:
[0046]
[0047] Where:
[0048] Δ o1 = 2Z o1 (Z e1 - Z o1 )
[0049] Δ o2 = 4Z M1 Z o2 (Z e1 + Z o1 ) + 8Z M1 Z e1 Z o1 + Z o2 (Z e1 - Z o1 ) 2
[0050] Δ o3 = 4Z o2 Z e1 Z o1
[0051] Figure 3 Figure of the even - mode form of the simplified topology. Among them, the electrical length of the even - mode transmission line is the electrical length of the first parallel line; the characteristic impedance of the even - mode transmission line is the even - mode characteristic impedance of the first parallel line.
[0052] When Y ino = 0, it can be obtained that the topology has four transmission poles. When f 0 is the center frequency of the band - pass filter, the frequencies corresponding to the four even - mode transmission poles are:
[0053]
[0054] Where:
[0055] Δ e1 = 2Z e1 (Z e1 - Z o1 )
[0056] Δ e2 = 4Z M1 Z e2 (Z e1 + Z o1 ) + 8Z M1 Z e1 Z o1 + Z e2 (Z e1 - Z o1 ) 2
[0057] Δ e3 = 4Z e2 Z e1 Z o1
[0058] For this topology, its transmission zeros can be calculated by the following method: Multiply the ABCD matrices of the cascaded resonators that make up the topology in sequence to obtain the ABCD matrix corresponding to this topology; convert the ABCD matrix of this topology into the corresponding S matrix. When |S 21 | = 0, it can be obtained that this topology has three transmission zeros, and the frequencies corresponding to the three transmission zeros are respectively:
[0059] f z1 = 0
[0060] f z2 = 2f 0
[0061] From the above analysis, it can be seen that when the sum of the electrical length of the first microstrip line and the electrical length of the first short-circuited stub is equal to a quarter wavelength corresponding to the center frequency of the broadband bandpass filter, this topology has four odd-mode transmission poles, four even-mode transmission poles, and two transmission zeros. Returning to this topology, appropriately increasing the sum of the electrical length of the first microstrip line and the electrical length of the first short-circuited stub will additionally increase four transmission zeros (f z3 , f z4 , f z5 , f z6 ), but the number of original zeros and poles remains unchanged. And no matter how the values of the parameters Z o1 , Z e1 , Z o2 , Z e2 , Z M1 are changed, the relative positions of the transmission zeros and poles, that is, f z1 < f z3<f z4 <f ep1 <f op1 <f op2 <f ep2 <f ep3 <f op3 <f op4 <f ep4 <f z5 <f z6 <f z2 , none of them will change. Therefore, a broadband bandpass filter can be designed based on this topological structure, with eight transmission poles in the passband to ensure the flatness within the band, and six transmission zeros in the stopband to ensure high selectivity and high isolation.
[0062] An embodiment of the present utility model proposes a filter, including the topological structure described in any one of the above. The filter further includes a circuit board, the dielectric constant of the circuit board is 3.38, the dielectric loss is 0.0022, the thickness is 0.813 mm, and the size is 48.6 mm * 12.5 mm.
[0063] Further, referring to Figure 4 , the line width of the transmission lines in the first parallel lines is set to wp = 0.2 mm, the line spacing is set to sp = 0.1 mm, and the line length is set to lp = 10 mm;
[0064] The line width of the transmission lines in the first parallel triple lines and the second parallel triple lines is set to w T = 0.2 mm, the line spacing is set to s T = 0.1 mm, and the line length is set to l T = 10 mm;
[0065] The line length of the first microstrip line and the second microstrip line is set to l 1 = 5.2 mm, and the line width is set to w 1 = 2.1 mm;
[0066] The line length of the first short - circuit stub and the second short - circuit stub is set to l 2 = 5.5 mm, and the line width is set to w 2 = 2.1 mm.
[0067] In this embodiment, the simulation results of the S - parameters of the filter are as Figure 5As shown, the passband range with a reflection coefficient better than -10 dB is from 2.194 GHz to 7.198 GHz, the center frequency is 4.696 Hz, the absolute bandwidth is 5.004 GHz, and the relative bandwidth is 106.6%. In addition, since the microstrip lines in the theoretical model are independent of each other, while the microstrip lines in the simulation model affect each other, there is a transmission pole that merges with the adjacent transmission pole and does not show up in the passband. Only seven transmission poles are shown in the simulation results, located at 2.261, 2.523, 3.079, 4.266, 5.038, 6.573, 7.082 GHz respectively. These seven transmission poles ensure the flatness of the passband. There are six transmission zeros in the stopband, located at 0, 0.402, 1.013, 8.389, 10.602, 10.828 GHz respectively. These six transmission zeros ensure the high selectivity and wide stopband of the filter.
[0068] Therefore, the topological structure of this embodiment can be designed as a broadband bandpass filter, and this filter has the advantages of miniaturization and high selectivity.
[0069] The above are only optional embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or any direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.
Claims
1. A highly selective wide passband filter topology, characterized in that: It includes a first parallel three lines, a first parallel line and a second parallel three lines connected in sequence along a first direction, the other end of the first parallel three lines is connected to the input end, and the other end of the second parallel three lines is connected to the output end; A first microstrip line is connected between the first three parallel lines and the first parallel line, and a first short-circuit branch is connected to the other end of the first microstrip line; A second microstrip line is connected between the second three parallel lines and the first parallel line, and a second short-circuit branch is connected to the other end of the second microstrip line; The first microstrip line and the second microstrip line are both arranged along the second direction, the first short-circuit branch and the second short-circuit branch are both arranged along the first direction, and the first direction is perpendicular to the second direction.
2. The highly selective wide passband filter topology structure according to claim 1, characterized in that: The first parallel three lines and the second parallel three lines respectively include three transmission lines arranged in parallel with each other, and the first parallel lines include two transmission lines arranged in parallel with each other.
3. The highly selective wide passband filter topology structure according to claim 1, characterized in that: The first three parallel lines and the second three parallel lines are symmetrical about the first parallel line, the first microstrip line and the first short-circuit branch are located on one side of the first parallel line, and the second microstrip line and the second short-circuit branch are located on the other side of the first parallel line.
4. The highly selective wide passband filter topology structure according to claim 1, characterized in that: The electrical length of the first parallel line, the electrical length of the first three parallel lines and the electrical length of the second three parallel lines are equal and are all equal to a quarter wavelength corresponding to the center frequency of the wide passband filter.
5. The highly selective wide passband filter topology structure according to claim 4, characterized in that: The electrical length of the first microstrip line is equal to the electrical length of the second microstrip line; The electrical length of the first short-circuit branch is equal to the electrical length of the second short-circuit branch; The sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit stub, the sum of the electrical length of the second microstrip line and the electrical length of the second short-circuit stub are all greater than the electrical length of the first parallel line.
6. The highly selective wide passband filter topology structure according to claim 1, characterized in that: The odd-mode characteristic impedance of the first three parallel wires is equal to the odd-mode characteristic impedance of the second three parallel wires, and the even-mode characteristic impedance of the first three parallel wires is equal to the even-mode characteristic impedance of the second three parallel wires.
7. The highly selective wide passband filter topology structure according to claim 6, characterized in that: The characteristic impedance of the first microstrip line, the characteristic impedance of the second microstrip line, the characteristic impedance of the first short-circuit branch, and the characteristic impedance of the second short-circuit branch are all equal.
8. A filter, characterized in that: It comprises the topological structure described in any one of claims 1 to 7.
9. The filter according to claim 8, characterized in that The filter also includes a circuit board, the dielectric constant of the circuit board is 3.38, the dielectric loss is 0.0022, the thickness is 0.813 mm, and the size is 48.6 mm*12.5 mm.
10. The filter according to claim 9, characterized in that The line width of the transmission lines in the first parallel lines is set to wp=0.2 mm, the line spacing is set to sp=0.1 mm, and the line length is set to lp=10 mm; The line widths of the transmission lines in the first parallel three lines and the second parallel three lines are both set to w T =0.2mm, line spacing is set to s T =0.1mm, the line length is set to l T =10mm; The line lengths of the first microstrip line and the second microstrip line are both set to l1=5.2 mm, and the line widths are both set to w1=2.1 mm; The line lengths of the first short-circuit branch and the second short-circuit branch are both set to l2 = 5.5 mm, and the line widths are both set to w2 = 2.1 mm.