CN221379691U

CN221379691U - Topological structure and wide stop band filter with narrow pass characteristic

Info

Publication number: CN221379691U
Application number: CN202322757840.XU
Authority: CN
Inventors: 毕晓坤; 杨椰楠; 徐雨; 谷媛
Original assignee: Shenzhen Sunway Communication Co Ltd
Current assignee: Shenzhen Sunway Communication Co Ltd
Priority date: 2023-10-12
Filing date: 2023-10-12
Publication date: 2024-07-19
Anticipated expiration: 2033-10-12

Abstract

The utility model discloses a topological structure and a wide stop band filter with narrow pass characteristics, wherein the topological structure comprises a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a first open circuit branch, a second open circuit branch and a third open circuit branch, one end of the first microstrip line is respectively connected with the second microstrip line, the third microstrip line and the fourth microstrip line, and the other end of the first microstrip line is an input end; one end of the second microstrip line far away from the first microstrip line is an output end; one end of the third microstrip line far away from the first microstrip line is connected with the first open-circuit branch; and one end of the fourth microstrip line far away from the first microstrip line is respectively connected with the second open-circuit branch knot and the third open-circuit branch knot. The topological structure is novel in structure, can be used for designing the wide stop band filter, has narrow pass characteristics based on the wide stop band filter designed by the topological structure, is high in selectivity and simple in design process, fills up the market blank, and is easy to popularize and apply.

Description

Topological structure and wide stop band filter with narrow pass characteristic

Technical Field

The utility model relates to the technical field of filters, in particular to a topological structure and a wide stop band filter with narrow pass characteristics.

Background

In order to solve the contradiction between limited spectrum resources and increasing information transmission demands, radio frequency systems operating in different frequency bands and communication modes have been developed. Under the background, the wide stop band filter with high selectivity has extremely high scientific research and commercial value, and attracts attention of vast scholars and engineers.

Compared with a broadband band-pass filter with notch characteristics, a wide stop band filter with narrow pass characteristics in the stop band can effectively inhibit unwanted noise signals and enable useful signals to pass smoothly with low loss. Unfortunately, however, there are few reports of wide stop band filters with narrow pass characteristics, which severely affect the development of modern wireless communication systems.

Disclosure of utility model

The technical problems solved by the utility model are as follows: a topology and a wide stop band filter with narrow pass characteristics designed based on the topology are provided.

In order to solve the technical problems, the first technical scheme adopted by the utility model is as follows: the topological structure comprises a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a first open circuit branch knot, a second open circuit branch knot and a third open circuit branch knot, wherein one end of the first microstrip line is respectively connected with the second microstrip line, the third microstrip line and the fourth microstrip line, and the other end of the first microstrip line is an input end; one end of the second microstrip line far away from the first microstrip line is an output end; one end of the third microstrip line far away from the first microstrip line is connected with the first open-circuit branch; and one end of the fourth microstrip line far away from the first microstrip line is respectively connected with the second open-circuit branch knot and the third open-circuit branch knot.

In an embodiment, the characteristic impedance of the first microstrip line is equal to the characteristic impedance of the second microstrip line; the characteristic impedance of the third microstrip line is equal to the characteristic impedance of the first open circuit branch; the characteristic impedance of the second open circuit branch is equal to the characteristic impedance of the third open circuit branch.

In an embodiment, the electrical length of the first microstrip line, the electrical length of the second microstrip line, the electrical length of the fourth microstrip line, the electrical length of the second open branch and the electrical length of the third open branch are all 0.25λ, where λ is a wavelength corresponding to a center frequency of the band-stop filter; the sum of the electrical length of the third microstrip line and the electrical length of the first open stub is 0.25λ.

In an embodiment, the second open-circuit branch and the third open-circuit branch are symmetrically disposed at two sides of the fourth microstrip line.

In an embodiment, the width of the first microstrip line, the width of the second microstrip line and the width of the third microstrip line are all smaller than the width of the second open branch.

In an embodiment, the length of the third microstrip line is smaller than the length of the first open stub.

In an embodiment, the length direction of the first microstrip line is the same as the length direction of the second microstrip line; the length direction of the fourth microstrip line and the length direction of the third microstrip line are perpendicular to the length direction of the first microstrip line.

In an embodiment, a length direction of the third microstrip line is perpendicular to a length direction of the first open stub.

In an embodiment, the width of the first microstrip line, the width of the second microstrip line and the width of the third microstrip line are smaller than the width of the fourth microstrip line.

In order to solve the technical problems, the second technical scheme adopted by the utility model is as follows: the wide stop band filter with the narrow pass characteristic comprises a circuit board, wherein the circuit board is provided with the topological structure.

The utility model has the beneficial effects that: the topological structure is novel in structure, can be used for designing the wide stop band filter, has narrow pass characteristics based on the wide stop band filter designed by the topological structure, is high in selectivity, compact in structure and simple in design process, fills up the market blank, and is easy to popularize and apply.

Drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present utility model, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a block diagram of a topology according to a first embodiment of the present utility model;

FIG. 2 is a block diagram of a topology of a first embodiment of the utility model in odd mode;

FIG. 3 is a block diagram of a topology in even mode according to a first embodiment of the present utility model;

Fig. 4 is an S-parameter diagram for different Z ₁ in a wide stop band filter with narrow pass characteristics according to a first embodiment of the present utility model;

FIG. 5 is a graph of S parameters for different Z ₂ in a wide stop band filter with narrow pass characteristics according to a first embodiment of the present utility model;

FIG. 6 is a graph of S parameters for different Z ₃ in a wide stop band filter with narrow pass characteristics according to a first embodiment of the present utility model;

FIG. 7 is a graph of S parameters for different Z ₄ in a wide stop band filter with narrow pass characteristics according to one embodiment of the present utility model;

FIG. 8 is a layout of a wide stop band filter with narrow pass characteristics according to a first embodiment of the present utility model;

Fig. 9 is an S-parameter diagram of a wide stop band filter with narrow pass characteristics according to a first embodiment of the present utility model.

Reference numerals illustrate:

1. a first microstrip line;

2. A second microstrip line;

3. A fourth microstrip line;

4. a third microstrip line;

5. An input end;

6. an output end;

7. a second open-circuit stub;

8. third open-circuit branches;

9. A first open-circuit stub;

11. An odd mode microstrip line;

12. A first even mode microstrip line;

13. a second even mode microstrip line;

14. A third even mode microstrip line;

15. Open branches of the first even mode;

16. the second even mode opens the branch.

Detailed Description

The achievement of the objects, functional features and advantages of the present utility model will be further described with reference to the accompanying drawings, in conjunction with the embodiments.

The following description of the embodiments of the present utility model will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the utility model. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

It should be noted that, in the embodiment of the present utility model, directional indications such as up, down, left, right, front, and rear … … are referred to merely for explaining a relative positional relationship, a movement condition, and the like between the components in a specific posture as shown in the drawings, and if the specific posture is changed, the directional indication is changed accordingly.

In addition, if there is a description of "first", "second", etc. in the embodiments of the present utility model, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature.

In addition, if the meaning of "and/or" is presented throughout this document to include three parallel schemes, taking "and/or" as an example, including a scheme, or a scheme that is satisfied simultaneously. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present utility model.

In the present application, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.

Example 1

Referring to fig. 1 to 3, a first embodiment of the present utility model is as follows: as shown in fig. 1, a topology structure includes a first microstrip line 1, a second microstrip line 2, a fourth microstrip line 3, a third microstrip line 4, a second open branch 7, a third open branch 8 and a first open branch 9, wherein one end of the first microstrip line 1 is respectively connected with the second microstrip line 2, the fourth microstrip line 3 and the third microstrip line 4, and the other end of the first microstrip line 1 is an input end 5; one end of the second microstrip line 2, which is far away from the first microstrip line 1, is an output end 6; one end of the fourth microstrip line 3, which is far away from the first microstrip line 1, is respectively connected with the second open-circuit branch 7 and the third open-circuit branch 8; one end of the third microstrip line 4, which is far away from the first microstrip line 1, is connected to the first open branch 9.

The electrical length of the first microstrip line 1, the electrical length of the second microstrip line 2, the electrical length of the fourth microstrip line 3, the electrical length of the second open branch 7 and the electrical length of the third open branch 8 are all 0.25λ, where λ is the wavelength corresponding to the center frequency of the filter; the sum of the electrical length of the third microstrip line 4 and the electrical length of the first open stub 9 is 0.25λ.

The characteristic impedance of the first microstrip line 1 is equal to the characteristic impedance of the second microstrip line 2, and both the characteristic impedance are Z ₁; the characteristic impedance of the third microstrip line 4 is equal to the characteristic impedance of the first open-circuit branch 9, and both the characteristic impedance are Z ₂; the characteristic impedance of the fourth microstrip line 3 is Z ₃; the characteristic impedance of the second open branch 7 is equal to the characteristic impedance of the third open branch 8, both of which are Z ₄. It can be seen that there are only four design parameters of the wide stop band filter based on the topology, Z ₁、Z₂、Z₃ and Z ₄ respectively, that is, the wide stop band filter based on the topology is very simple to design.

Because the topological structure can be equivalent to a bilateral symmetry structure, the transmission poles of the topological structure can be obtained by a parity-check mode analysis method.

FIG. 2 is a block diagram of the structure of the odd mode version of the topology; the impedance of the odd mode microstrip line 11 in fig. 2 is Z ₁ and the electrical length is 0.25 λ. Y _ino = 0, it can be derived that the topology has two odd-mode transmission poles. When f ₀ is the center frequency of the band-stop filter, the frequencies corresponding to the two odd-mode transmission poles are respectively:

f_op1＝0；

f_op2＝2f₀；

FIG. 3 is a block diagram of the structure of the even mode version of the topology; in fig. 3, one end of the first even mode microstrip line 12 is an input end, the other end is respectively connected with the second even mode microstrip line 13 and the third even mode microstrip line 14, one end of the second even mode microstrip line 13 far away from the first even mode microstrip line 12 is connected with the first even mode open branch 15, and one end of the third even mode microstrip line 14 far away from the first even mode microstrip line 12 is connected with the second even mode open branch 16; the characteristic impedance of the first even mode microstrip line 12 is Z ₁, and the electrical length is 0.25λ; the characteristic impedance of the second even mode microstrip line 13 is 2Z ₂, the characteristic impedance of the first even mode open circuit branch 15 is 2Z ₂, and the sum of the electrical length of the second even mode microstrip line 13 and the electrical length of the first even mode open circuit branch 15 is 0.25λ; the characteristic impedance of the third even mode microstrip line 14 is 2Z ₃, and the electrical length of the third even mode microstrip line 14 is 0.25λ; the characteristic impedance of the second even mode open stub 15 is Z ₄, and the electrical length of the second even mode open stub 15 is 0.25λ.

When Y _ine = infinity, it can be obtained that the topology has five even mode transmission poles, and respectively:

Wherein,

Δ₃＝2Z₂Z₃Z₄；

For this topology, its transmission zero can be calculated by: sequentially multiplying the ABCD matrixes of the cascade resonators forming the topological structure to obtain an ABCD matrix corresponding to the topological structure; the ABCD matrix for this topology is converted to a corresponding S matrix. When the |s ₂₁ |=0, it can be obtained that the topology structure has three transmission zeros, and frequencies corresponding to the three transmission zeros are respectively:

f_z2＝f₀；

From the above analysis, the topology structure has two odd-mode transmission poles, five even-mode transmission poles and three transmission zeros. The relative position of these transmission zero poles, f_op1<f_ep1<f_z1<f_ep2<f_z2<f_ep3<f_z3<f_ep4<f_op2<f_ep5,, is unchanged regardless of the value of parameter Z ₁、Z₂、Z₃、Z₄. Therefore, a filter designed based on this topology can only be a wide stop band filter with narrow pass characteristics.

The wide stop band filter with narrow pass characteristic based on the topological structure design has the filtering characteristic only controlled by the parameter Z ₁、Z₂、Z₃、Z₄.

When only the parameter Z ₁ is changed, the S-parameter simulation result of the filter based on the topology is shown in fig. 4. As can be seen from fig. 4, as the parameter Z ₁ becomes larger, the reflection coefficient in the passband becomes larger, the bandwidth of the stopband becomes unchanged, the bandwidths of the two narrow passbands in the stopband become smaller, and the center frequencies of the two narrow passbands in the stopband become unchanged.

When only the parameter Z ₂ is changed, the S-parameter simulation result of the filter based on the topology is shown in fig. 5. As can be seen from fig. 5, as the parameter Z ₂ becomes larger, the reflection coefficient in the passband slightly becomes larger, the bandwidth of the stopband is unchanged, the bandwidths of the two narrow passbands in the stopband are almost unchanged, and the center frequencies of the two narrow passbands in the stopband are close to each other.

When only the parameter Z ₃ is changed, the S-parameter simulation result of the filter based on the topology is shown in fig. 6. As can be seen from fig. 6, as the parameter Z ₃ becomes larger, the reflection coefficient in the passband becomes slightly larger, the bandwidth of the stopband is unchanged, the bandwidths of the two narrow passbands in the stopband become larger, and the center frequencies of the two narrow passbands in the stopband are far away from each other.

When only the parameter Z ₄ is changed, the S-parameter simulation result of the filter based on the topology is shown in fig. 7. As can be seen from fig. 7, as the parameter Z ₄ increases, the reflection coefficient in the passband increases, the bandwidth of the stopband decreases, and the bandwidths of the two narrow passbands in the stopband decrease, and the center frequencies of the two narrow passbands in the stopband approach each other.

From the analysis of fig. 4-7, it can be seen that the reflection coefficient in the passband is mainly affected by the parameter Z ₁、Z₃、Z₄, the bandwidth of the stopband is mainly affected by the parameter Z ₄, the bandwidths of the two narrow passbands in the stopband are mainly affected by the parameter Z ₁、Z₃、Z₄, and the center frequencies of the two narrow passbands in the stopband are mainly affected by the parameter Z ₂、Z₃、Z₄. By optimizing the value of parameter Z ₁、Z₂、Z₃、Z₄, a filter of desired performance can be obtained.

To verify the above topology and analysis, a wide stop band filter example with a dual narrow pass characteristic was designed by simulation.

Simulation instance

Obtaining a circuit board, wherein the length of the circuit board is 24.4mm, the width of the circuit board is 13.0mm, the thickness of the circuit board is 0.813mm, the dielectric constant of the circuit board is 3.38, and the dielectric loss of the circuit board is 0.0022;

the circuit board is provided with a microstrip structure, the microstrip structure is of the topological structure, and the layout of the circuit is shown in figure 8;

The length direction of the first microstrip line 1 is the same as the length direction of the second microstrip line 2, and the length direction of the fourth microstrip line 3 and the length direction of the third microstrip line 4 are perpendicular to the length direction of the first microstrip line 1. The length of the first microstrip line 1 is equal to the length of the second microstrip line 2, and the width of the first microstrip line 1 is equal to the width of the second microstrip line 2, that is, from a certain angle, the first microstrip line 1 and the second microstrip line 2 are symmetrically arranged at two sides of the fourth microstrip line 3.

The second open-circuit branch 7 and the third open-circuit branch 8 are symmetrically disposed at two sides of the fourth microstrip line 3, that is, the length of the second open-circuit branch 7 is equal to the length of the third open-circuit branch 8, and the width of the second open-circuit branch 7 is equal to the width of the third open-circuit branch 8.

The width of the first microstrip line 1, the width of the second microstrip line 2 and the width of the third microstrip line 4 are smaller than the width of the second open branch 7. The width of the first microstrip line 1, the width of the second microstrip line 2 and the width of the third microstrip line 4 are smaller than the width of the fourth microstrip line 3.

Optionally, the length of the third microstrip line 4 is smaller than the length of the first open-circuit branch 9, and the length direction of the third microstrip line 4 is perpendicular to the length direction of the first open-circuit branch 9. The width of the third microstrip line 4 is equal to the width of the first open branch 9.

The physical length of the first microstrip line is noted as i ₁,l₁ = 9.5mm; the physical length of the second microstrip line is also l ₁;

The physical length of the third microstrip line is noted as i ₂,l₂ = 1.7mm;

The physical length of the first open stub is noted as l ₃,l₃ =7.8mm;

the physical length of the fourth microstrip line is noted as i ₄,l₄ = 8.5mm;

The physical length of the second open stub is noted as l ₅,l₅ =9.7mm; the physical length of the third open branch is also l ₅;

The physical width of the first microstrip line is denoted w ₁,w₁ =0.1 mm; the physical width of the second microstrip line is also w ₁;

The physical width of the third microstrip line is denoted w ₂,w₂ =0.1 mm; the physical width of the first open stub is also w ₂,

The physical width of the fourth microstrip line is denoted w ₃,w₃ =1.6 mm;

The physical width of the third open stub is noted as w ₄,w₄ =1.2 mm; the physical width of the second open branch is also w ₄;

It should be noted that, in the simulation example, the reason why the values of l ₁、l₄ and l ₅ are not equal is that: in the schematic diagram of the topological structure, the resonators are connected through points of connection; in the layout, resonators are connected by a transmission line face with a certain width. The difference between points and planes is one of the places that lead to the difference between the theoretical value of the topology and the actual layout design value. In addition, each resonator in the topological structure is mutually independent and in different spaces, and no coupling phenomenon exists; while in layout, all resonators are in one space, and there is a coupling problem. The absence of coupling is two places that cause differences in the theoretical and actual layout design values of the topology.

In general, equal electrical lengths are specified in the topology, and a small difference exists in the physical lengths corresponding to the actual layout to ensure the optimal simulation result of the filter. The exact use of equality relationships in the topology, while achieving basic performance of the topology-based filter, is often not optimal filtering performance. In general, when the filter operating frequency is lower, the size parameter in the actual layout will be smaller than the predicted value of the topological structure.

Fig. 9 is an S-parameter diagram of a wide stop band filter with narrow pass characteristics. As can be seen from fig. 9, the wide stop band filter having the narrow pass characteristic has a stop band range of 1.74GHz to 8.34GHz, a stop band center frequency of 5.04GHz, an absolute bandwidth of 6.60GHz, and a relative bandwidth of 131%. In addition, three transmission zeros are located in the stop band at 2.18GHz, 5.36GHz and 8.08GHz, respectively. Two pass bands are arranged beside the stop band, five transmission poles are arranged in the pass bands and are respectively positioned at 0GHz, 0.91GHz, 8.92GHz, 9.72GHz and 10.78GHz. The three transmission zeroes and the five transmission poles ensure not only the high isolation characteristic of the stop band and the low insertion loss and flatness of the pass band, but also the high selection characteristic of the sidebands of the band-stop filter.

In addition, within the stop band, there are two pass bands with very narrow bandwidths. Wherein, for the first passband, the passband range with the reflection coefficient smaller than-10 dB is 3.94GHz to 4.04GHz, the passband center frequency is 3.99GHz, the absolute bandwidth is 0.10GHz, and the relative bandwidth is 2.5%; for the second passband, the passband range with reflection coefficient less than-10 dB is 6.26GHz to 6.34GHz, passband center frequency is 6.30GHz, absolute bandwidth is 0.08GHz, and relative bandwidth is 1.3%.

The foregoing description is only of the optional embodiments of the present utility model, and is not intended to limit the scope of the utility model, and all the equivalent structural changes made by the description of the present utility model and the accompanying drawings or the direct/indirect application in other related technical fields are included in the scope of the utility model.

Claims

1. A topology characterized by: the micro-strip comprises a first micro-strip line, a second micro-strip line, a third micro-strip line, a fourth micro-strip line, a first open-circuit branch, a second open-circuit branch and a third open-circuit branch, wherein one end of the first micro-strip line is respectively connected with the second micro-strip line, the third micro-strip line and the fourth micro-strip line, and the other end of the first micro-strip line is an input end; one end of the second microstrip line far away from the first microstrip line is an output end; one end of the third microstrip line far away from the first microstrip line is connected with the first open-circuit branch; and one end of the fourth microstrip line far away from the first microstrip line is respectively connected with the second open-circuit branch knot and the third open-circuit branch knot.

2. The topology according to claim 1, wherein: the characteristic impedance of the first microstrip line is equal to the characteristic impedance of the second microstrip line; the characteristic impedance of the third microstrip line is equal to the characteristic impedance of the first open circuit branch; the characteristic impedance of the second open circuit branch is equal to the characteristic impedance of the third open circuit branch.

3. The topology according to claim 1, wherein: the electrical length of the first microstrip line, the electrical length of the second microstrip line, the electrical length of the fourth microstrip line, the electrical length of the second open circuit branch and the electrical length of the third open circuit branch are all 0.25λ, where λ is the wavelength corresponding to the center frequency of the band-stop filter; the sum of the electrical length of the third microstrip line and the electrical length of the first open stub is 0.25λ.

4. A topology according to claim 3, characterized in that: the second open circuit branch knot and the third open circuit branch knot are symmetrically arranged on two sides of the fourth microstrip line.

5. The topology according to claim 4, wherein: the width of the first microstrip line, the width of the second microstrip line and the width of the third microstrip line are smaller than the width of the second open-circuit branch.

6. A topology according to claim 3, characterized in that: the length of the third microstrip line is smaller than the length of the first open-circuit branch.

7. The topology according to claim 1, wherein: the length direction of the first microstrip line is in the same direction as the length direction of the second microstrip line; the length direction of the fourth microstrip line and the length direction of the third microstrip line are perpendicular to the length direction of the first microstrip line.

8. The topology according to claim 1, wherein: the length direction of the third microstrip line is perpendicular to the length direction of the first open-circuit branch.

9. The topology according to claim 1, wherein: the width of the first microstrip line, the width of the second microstrip line and the width of the third microstrip line are smaller than the width of the fourth microstrip line.

10. A wide stop band filter having a narrow pass characteristic, characterized by: comprising a circuit board provided with a topology according to any one of claims 1-9.