Filter topology and triple-mode wide dual-band filter

Abstract

The application discloses a filter topology structure and a three-mode wide double-passband filter. The filter topology structure comprises a microstrip line, two parallel five lines and three short-circuit stubs connected with the microstrip line. The two parallel five lines are symmetrically arranged on the two sides of the microstrip line and are connected with the microstrip line respectively. One end of one parallel five line away from the microstrip line is an input end, and one end of the other parallel five line away from the microstrip line is an output end. The length direction of one short-circuit stub is consistent with the length direction of the microstrip line, and the other two short-circuit stubs are symmetrically arranged on the two sides of the microstrip line. The filter topology structure is simple and novel. The double-passband filter designed based on the filter topology structure has the advantages of wide passband, small and flat insertion loss and high isolation, and has high performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of filter, in particular to a filter topology and a three-mode wide dual-passband filter. BACKGROUND

[0002] With the rapid development of modern wireless communication technology, the radio frequency receiving system needs to be compatible with different communication systems to provide more abundant services, so as to meet the increasing demand of people for positioning and communication. Under this background, the dual-passband filter which can work in two different frequency bands emerges as the times require. In addition, the microstrip filter has the advantages of low cost, small size, low profile, light weight and easy integration. Therefore, the research and development of high-performance wide dual-passband filter based on microstrip structure has very high scientific research and commercial value, which attracts the attention of scholars and engineers.

[0003] At present, the dual-passband filter based on microstrip structure reported is mostly single-mode or dual-mode in the passband, which has the problems of narrow passband, large and uneven insertion loss, poor isolation, etc., which seriously affects its use in modern wireless communication systems. SUMMARY

[0004] The technical problem solved by the present application is to provide a high-performance filter topology and a three-mode wide dual-passband filter with the filter topology.

[0005] In order to solve the above technical problems, the technical solution one adopted by the present application is: a filter topology, comprising a microstrip line, two parallel five lines and three short-circuit stubs connected to the microstrip line, the two parallel five lines are symmetrically arranged on both sides of the microstrip line and are respectively connected to the microstrip line, one end of one of the parallel five lines away from the microstrip line is an input end, and one end of the other parallel five line away from the microstrip line is an output end; the length direction of one of the short-circuit stubs is consistent with the length direction of the microstrip line, and the other two short-circuit stubs are symmetrically arranged on both sides of the microstrip line.

[0006] In order to solve the above technical problems, the technical solution two adopted by the present application is: a three-mode wide dual-passband filter, comprising a circuit board, and the filter topology described above is arranged on the circuit board.

[0007] The present application has the advantages that: the filter topology is simple and novel, the dual-passband filter designed based on the filter topology has the advantages of wide passband, small and flat insertion loss, high isolation, and high performance. BRIEF DESCRIPTION OF DRAWINGS

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0009] Figure 1 This is a structural block diagram of the filter topology according to Embodiment 1 of the present invention;

[0010] Figure 2 This is the circuit layout diagram of the three-mode wide dual-passband filter according to Embodiment 1 of the present invention;

[0011] Figure 3 The three-mode wide dual-passband filter of Embodiment 1 of the present invention S Parameters vary with s p Diagram of changes.

[0012] Figure 4 The S-parameters of the three-mode wide dual-passband filter in Embodiment 1 of the present invention vary with w. p Diagram of changes.

[0013] Figure 5 This is a graph showing the relationship between the S-parameters of the three-mode wide dual-passband filter of Embodiment 1 of the present invention and w1.

[0014] Figure 6 This is a graph showing the relationship between the S-parameters of the three-mode wide dual-passband filter of Embodiment 1 of the present invention and w2.

[0015] Figure 7 This is a graph showing the relationship between the S-parameters of the three-mode wide dual-passband filter of Embodiment 1 of the present invention and w3.

[0016] Figure 8 The S-parameter plot of the three-mode wide dual-passband filter is shown in the simulation example.

[0017] Explanation of icon numbers:

[0018] 1. Microstrip line;

[0019] 2. Parallel five lines;

[0020] 3. Short-circuit branch;

[0021] 4. Input terminal;

[0022] 5. Output terminal. Detailed Implementation

[0023] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0024] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort are within the scope of the present application.

[0025] It should be noted that if the embodiments of the present application involve directional indications such as up, down, left, right, front, back, etc., the directional indications are only used to explain the relative positional relationship, movement condition, etc. between components in a certain specific posture, such as shown in the drawings. If the specific posture changes, the directional indications also change accordingly.

[0026] In addition, if the embodiments of the present application involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features.

[0027] In addition, the meaning of "and / or" appearing throughout the text is that it includes three parallel solutions. Taking "and / or" as an example, it includes the solution, or the solution, or the solution that satisfies both. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of a person of ordinary skill in the art. When the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist, and is not within the scope of protection required by the present application.

[0028] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrated; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0029] Embodiment one

[0030] Please refer to Figures 1 to 8 Embodiment one of the present application is: Figure 1As shown, the filter topology comprises a microstrip line 1, two parallel five-line 2 and three short-circuit stubs 3 connected to the microstrip line 1, two parallel five-line 2 are symmetrically arranged on both sides of the microstrip line 1 and are respectively connected to the microstrip line 1, one end of the parallel five-line 2 away from the microstrip line 1 is an input end 4, and the other end of the parallel five-line 2 away from the microstrip line 1 is an output end 5; the length direction of one of the short-circuit stubs 3 is consistent with the length direction of the microstrip line 1, and the other two short-circuit stubs 3 are symmetrically arranged on both sides of the microstrip line 1.

[0031] The electrical length of the parallel five-line 2, the electrical length of the microstrip line 1 and the electrical length of the short-circuit stub 3 are all 0.25λ, λ is the wavelength at the center frequency of the two passbands; the width of the microstrip line 1 is less than half the sum of the widths of the three short-circuit stubs 3.

[0032] One end of the parallel five-line 2 is connected to the microstrip line 1, and the other end of the short-circuit stub 3 is connected to the microstrip line 1, that is, the parallel five-line 2 and the short-circuit stub 3 are arranged away from each other.

[0033] The length direction of the parallel five-line 2 is perpendicular to the length direction of the microstrip line 1; the length direction of the two short-circuit stubs 3 symmetrically arranged on both sides of the microstrip line 1 is respectively perpendicular to the length direction of the microstrip line 1; the short-circuit stub 3 with the length direction consistent with the length direction of the microstrip line 1 and the microstrip line 1 share a common axis. That is, the whole filter topology structure is a left-right symmetric structure.

[0034] One of the parallel five-line 2 is composed of five parallel and equidistant transmission lines, two of which are connected to the microstrip line 1, and the other three are connected to the input end 4, and the two transmission lines connected to the microstrip line 1 and the three transmission lines connected to the input end 4 form a cross-toe structure; the other parallel five-line 2 is also composed of five parallel and equidistant transmission lines, two of which are connected to the microstrip line 1, and the other three are connected to the output end 5, and the two transmission lines connected to the microstrip line 1 and the three transmission lines connected to the output end 5 form a cross-toe structure. The width of each transmission line in the parallel five-line 2 is the same, the length is equal, and the gap spacing between any two adjacent transmission lines is the same.

[0035] The width of the short-circuit stub 3 with the length direction consistent with the length direction of the microstrip line 1 is greater than the width of the other two short-circuit stubs 3.

[0036] The embodiment also provides a three-mode wide dual-passband filter, comprising a circuit board, and the circuit board is provided with the above filter topology structure.

[0037] Simulation example

[0038] A circuit board is obtained, the length of the circuit board is 24.8 mm, the width is 20.0 mm, the thickness is 0.813 mm, the dielectric constant is 3.38, and the dielectric loss is 0.0022;

[0039] The microstrip structure is provided on the circuit board, the microstrip structure is the filter topology structure, and the circuit layout pattern is as shown in Figure 2

[0040] The overall physical length of the single parallel five lines is denoted as l p , l p = 9 mm;

[0041] The physical width of the single transmission line constituting the parallel five lines is denoted as w p , w p = 0.1 mm;

[0042] The gap spacing between the adjacent two transmission lines constituting the parallel five lines is denoted as s p , s p = 0.08 mm;

[0043] The physical width of the microstrip line is denoted as w1, w1 = 2.2 mm;

[0044] The physical length of the microstrip line is denoted as l1, l1 = 9.5 mm;

[0045] The physical width of the horizontal short-circuit stub (that is, the short-circuit stub with the length direction perpendicular to the length direction of the microstrip line) is denoted as w2, w2 = 2 mm;

[0046] The physical length of the horizontal short-circuit stub (that is, the short-circuit stub with the length direction perpendicular to the length direction of the microstrip line) is denoted as l2, l2 = 9.3 mm;

[0047] The physical width of the vertical short-circuit stub (that is, the short-circuit stub with the length direction consistent with the length direction of the microstrip line) is denoted as w3, w3 = 3.8 mm;

[0048] The physical length of the vertical short-circuit stub (that is, the short-circuit stub with the length direction consistent with the length direction of the microstrip line) is denoted as l3, l3 = 9 mm.

[0049] According to the microwave common sense, the values of lp, l1, l2, and l3 are changed synchronously and equally, and the working frequency range of the two passbands can be adjusted linearly in inverse proportion. The parameters affecting the performance of the three-mode wide dual-passband filter are five and only five, which are s p , w p , w1, w2, and w3.

[0050] ​It should be noted that in the simulation example, the reason why the values of lp, li, l2 and l3 are not exactly equal is that in the schematic diagram of the topology, the resonators are connected by points, while in the layout diagram, the resonators are connected by surfaces with a certain width. The difference between points and surfaces is one of the reasons for the difference between the theoretical values of the topology and the actual layout design values. In addition, in the topology, each resonator is independent and in different spaces, and there is no coupling phenomenon. When the layout is designed, all resonators are in the same space, and there will be coupling problems. The existence or non-existence of coupling is the second reason for the difference between the theoretical values of the topology and the actual layout design values.

[0051] Generally speaking, in the topology, the equal electrical length is specified, and in the actual layout, there will be a small difference in the corresponding physical length to ensure the optimal simulation results of the filter. Although the equal relationship in the topology can achieve the basic performance of the filter based on the topology, it is not always the optimal filter performance. Generally, the lower the working frequency of the filter, the smaller the difference between the size parameters in the actual layout and the values predicted by the topology.

[0052] Figure 3 The S parameter of the three-mode wide dual-passband filter changes with s p . As can be seen from Figure 3 , changing only the value of s p not only changes the bandwidth of the three-mode wide dual-passband filter, but also optimizes the reflection coefficient in the passband. As the value of s p becomes smaller, the reflection coefficient in the passband becomes better, and the lower passband edge and the upper passband edge of the first passband move slightly downward, the upper passband edge of the second passband moves slightly upward, and the lower passband edge of the second passband remains unchanged.

[0053] Figure 4 The S parameter of the three-mode wide dual-passband filter changes with w p . As can be seen from Figure 4 , changing only the value of w p not only changes the bandwidth of the three-mode wide dual-passband filter, but also changes the reflection coefficient in the passband. As the value of w p becomes larger, the lower passband edge of the first passband and the lower passband edge of the second passband move downward, and the upper passband edge of the first passband and the upper passband edge of the second passband move upward. In addition, when w p = 0.1 mm, the reflection coefficient in the passband of the mode wide dual-passband filter is the best.

[0054] Figure 5 The S parameter of the three-mode wide dual-passband filter changes with w1. As can be seen from Figure 5It is evident that changing the value of w1 not only alters the bandwidth of the three-mode wide dual-passband filter but also changes its in-band reflection coefficient. As the value of w1 increases, the lower passband edge of the second passband shifts upward, while the upper passband edges of the first and second passbands shift downward, and the lower passband edge of the first passband remains almost unchanged. Furthermore, as the value of w1 increases, the in-band reflection coefficient improves.

[0055] Figure 6 This is a graph showing the relationship between the S-parameters of a three-mode wide dual-passband filter and w2. Figure 6 It is known that simply changing the value of w2 will not change the bandwidth of the tri-mode wide dual-passband filter, but by adjusting the value of w2, the reflection coefficient within the passband can be optimized. As the value of w2 increases, the reflection coefficient within the passband improves.

[0056] Figure 7 This is a graph showing the relationship between the S-parameters of a three-mode wide dual-passband filter and w3. Figure 7 It can be seen that changing the value of w3 not only alters the in-band reflection coefficient but also changes the bandwidth of the three-mode wide dual-passband filter. As the value of w3 increases, the upper passband edge of the first passband shifts slightly upward, the lower passband edge of the second passband and the upper passband edge of the second passband shift slightly downward, while the lower passband edge of the first passband remains almost unchanged. Furthermore, as the value of w3 increases, the in-band reflection coefficient improves.

[0057] Depend on Figures 3 to 7 Analysis shows that the passband bandwidth of the dual-passband filter designed based on this filter topology is affected by parameters w1, w3, and w p s p Controlling and adjusting parameter w2 can independently optimize the passband reflection coefficient and insertion loss flatness without affecting the passband bandwidth. However, regardless of how parameter s is changed... p w p The values ​​of w1, w2, and w3 indicate that the filter designed based on this filter topology can only be a dual-passband filter.

[0058] Figure 8 The S-parameter plots of the three-mode wide-range dual-passband filter used in the simulation example are shown. Figure 8It can be seen that, in the first passband, the impedance bandwidth range with the reflection coefficient less than -10dB is 1.851 to 4.409GHz, the center frequency of the passband is 3.13GHz, the absolute bandwidth of the passband is 2.558GHz, and the relative bandwidth of the passband is 81.7%; in the second passband, the impedance bandwidth range with the reflection coefficient less than -10dB is 6.258 to 9.202GHz, the center frequency of the passband is 7.73GHz, the absolute bandwidth of the passband is 2.944GHz, and the relative bandwidth of the passband is 38.1%. It can be seen that the three-mode wide dual-passband filter has the characteristics of wide passband. In the first passband, the maximum insertion loss is 0.58dB; in the second passband, the maximum insertion loss is 0.73dB. It can be seen that the three-mode wide dual-passband filter has the characteristics of low insertion loss. In addition, in the first passband, there are three transmission poles, respectively located at 1.982GHz, 3.067GHz and 4.108GHz; in the second passband, there are three transmission poles, respectively located at 6.923GHz, 7.481GHz and 8.889GHz, and the six transmission poles can ensure the flatness in the passband. In the stopband between the two passbands, the stopband bandwidth range with the isolation greater than 15dB is 5.024 to 5.606GHz, the center frequency of the stopband is 5.315GHz, the absolute bandwidth of the stopband is 0.582GHz, and the relative bandwidth of the stopband is 11%. There are five transmission zeros in the stopband, respectively located at 0, 5.183GHz, 5.542GHz, 11.128GHz and 11.796GHz, and the five transmission zeros ensure the high selectivity of the passband and the high isolation of the stopband.

[0059] The above are only optional embodiments of the present application, and do not limit the patent scope of the present application. Any equivalent structural transformation, direct / indirect application in other related technical fields, or the like made according to the content of the present application specification and drawings are included in the patent protection scope of the present application.

Claims

1. Filter topology, characterized in that The filter topology comprises a microstrip line, two parallel five-line and three short-circuit branches connecting the microstrip line, two parallel five-line are symmetrically arranged on both sides of the microstrip line and are respectively connected to the microstrip line, one end of one parallel five-line away from the microstrip line is an input end, and one end of the other parallel five-line away from the microstrip line is an output end; the length direction of one short-circuit branch is consistent with the length direction of the microstrip line, and the other two short-circuit branches are symmetrically arranged on both sides of the microstrip line. One end of the parallel five-line is connected to the microstrip line, and the other end of the short-circuit branch is connected to the microstrip line. The length direction of the parallel five-line is perpendicular to the length direction of the microstrip line.

2. The filter topology of claim 1, characterized in that: The length direction of the two short-circuit branches symmetrically arranged on both sides of the microstrip line is respectively perpendicular to the length direction of the microstrip line.

3. The filter topology of claim 1, wherein: The short-circuit branch with the length direction consistent with the length direction of the microstrip line has a common central axis with the microstrip line.

4. The filter topology of claim 1, wherein: The width of the microstrip line is less than half the sum of the widths of the three short-circuit branches.

5. The filter topology of claim 1, wherein: The electrical length of the parallel five-line, the electrical length of the microstrip line and the electrical length of the short-circuit branch are all 0.25λ, and λ is the wavelength at the center frequency of the two passbands.

6. The filter topology of claim 1, wherein: One parallel five-line is composed of five parallel and equidistant transmission lines, two of which are connected to the microstrip line, and the other three are connected to the input end, and the two transmission lines connected to the microstrip line and the three transmission lines connected to the input end form a cross-toe structure.

7. The filter topology of claim 1, wherein: The width of the short-circuit branch with the length direction consistent with the length direction of the microstrip line is greater than the width of the other two short-circuit branches.

8. A triple-mode wide dual-band filter, characterized by: The filter topology comprises a circuit board, and the circuit board is provided with the filter topology of any one of claims 1-7.

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