CN222106987U - Compact wide-stopband filter topology and filter with narrow-pass characteristics - Google Patents

Abstract

The utility model discloses a compact wide stop band filter topological structure with narrow pass characteristics and a filter, wherein the topological structure comprises a first microstrip line and an eighth microstrip line which are sequentially connected, the other end of the first microstrip line is connected with an input end, the other end of the eighth microstrip line is connected with an output end, a second microstrip line and a seventh microstrip line are symmetrically connected between the first microstrip line and the eighth microstrip line, the other end of the second microstrip line is sequentially connected with a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line and a first open circuit branch, and the other end of the seventh microstrip line is symmetrically connected with a second open circuit branch and a third open circuit branch.

Description

Compact wide stop band filter topological structure with narrow pass characteristic and filter

Technical Field

The utility model relates to the technical field of filters, in particular to a microstrip double-notch band-pass filter topological structure and a filter.

Background

In order to solve the contradiction between limited spectrum resources and increasing information transmission demands, high-selectivity 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 wide pass band filter with notch characteristics, a wide stop band filter with narrow pass characteristics in the stop band can effectively inhibit unwanted noise and enable useful signals to pass smoothly with low loss. However, there are few reports of wide stop band filters with narrow pass characteristics, which seriously affect the development of modern wireless communication systems.

Disclosure of utility model

The utility model mainly aims to provide a compact wide stop band filter topological structure with narrow pass characteristics and a filter, and aims to solve the problem that the conventional wide stop band filter does not have the narrow pass characteristics.

In order to achieve the above objective, the present utility model provides a compact wide stop band filter topology structure with narrow pass characteristics, which comprises a first microstrip line and an eighth microstrip line connected in sequence, wherein the other end of the first microstrip line is connected with an input end, and the other end of the eighth microstrip line is connected with an output end;

a second microstrip line and a seventh microstrip line are symmetrically connected between the first microstrip line and the eighth microstrip line;

The other end of the second microstrip line is sequentially connected with a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line and a first open circuit branch knot, and the other end of the seventh microstrip line is symmetrically connected with a second open circuit branch knot and a third open circuit branch knot;

The first microstrip line, the eighth microstrip line, the third microstrip line, the fifth microstrip line, the first open circuit branch, the second open circuit branch and the third open circuit branch are all arranged along a first direction, the second microstrip line, the seventh microstrip line, the fourth microstrip line and the sixth microstrip line are all arranged along a second direction, and the second direction is perpendicular to the first direction;

The first microstrip line and the eighth microstrip line, the second open-circuit branch and the third open-circuit branch are symmetrical about the second microstrip line and the seventh microstrip line.

Optionally, the characteristic impedance of the first microstrip line is equal to the characteristic impedance of the eighth microstrip line.

Optionally, the characteristic impedance of the second microstrip line, the characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the fifth microstrip line, the characteristic impedance of the sixth microstrip line, and the characteristic impedance of the first open circuit branch are equal.

Optionally, the characteristic impedance of the second open branch and the characteristic impedance of the third open branch are equal and are each twice the characteristic impedance of the seventh microstrip line.

Optionally, the electrical length of the first microstrip line is equal to the electrical length of the eighth microstrip line, and the electrical lengths are all quarter wavelengths corresponding to the center frequency of the stop band filter.

Optionally, the sum of the electrical length of the second microstrip line, the electrical length of the third microstrip line, the electrical length of the fourth microstrip line, the electrical length of the fifth microstrip line, the electrical length of the sixth microstrip line, and the electrical length of the first open circuit branch is one half wavelength corresponding to the center frequency of the stop band filter.

Optionally, the sum of the electrical length of the seventh microstrip line and the electrical length of the second open circuit branch is a quarter wavelength corresponding to the center frequency of the stop band filter, and the sum of the electrical length of the seventh microstrip line and the electrical length of the third open circuit branch is a quarter wavelength corresponding to the center frequency of the stop band filter.

To achieve the above object, the present utility model further provides a filter, including a filter designed based on any one of the above topologies.

Optionally, the dielectric constant of the circuit board is 3.38, the dielectric loss is 0.0022, the thickness is 0.813mm, and the size is 23.0mm x 10.6mm.

Optionally, the line lengths of the first microstrip line and the eighth microstrip line are both l ₁ =9.3 mm, and the line widths are both w ₁ =0.1 mm;

The second microstrip line has a line length of l ₂ =4.55mm, the third microstrip line has a line length of l ₃ =5.4mm, the fourth microstrip line has a line length of l ₄ =2.5mm, the fifth microstrip line has a line length of l ₅ =12 mm, the sixth microstrip line has a line length of l ₆ =2.5mm, and the first open branch has a line length of l ₇ =3.4mm;

The line widths of the second microstrip line, the third microstrip line, the fourth microstrip line, the fifth microstrip line, the sixth microstrip line and the first open-circuit branch are all set to be w ₂ =0.8 mm;

The line length of the seventh microstrip line is set to be l ₈ =1.7 mm, and the line width is set to be w ₃ =0.2 mm;

The line length of the second open branch and the line length of the third open branch are respectively set to be l ₉ =7.6 mm, and the line width is respectively set to be w ₄ =0.1 mm.

The wide stop band filter has the advantages that the topology structure of the existing wide stop band filter is improved, the wide stop band filter comprises a first microstrip line and an eighth microstrip line which are sequentially connected, the other end of the first microstrip line is connected with an input end, the other end of the eighth microstrip line is connected with an output end, a second microstrip line and a seventh microstrip line are symmetrically connected between the first microstrip line and the eighth microstrip line, the other end of the second microstrip line is sequentially connected with a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line and a first open circuit branch, the other end of the seventh microstrip line is symmetrically connected with a second open circuit branch and a third open circuit branch, the first microstrip line, the eighth microstrip line, the third microstrip line, the fifth microstrip line, the first open circuit branch, the second open circuit branch and the third open circuit branch are all arranged along a first direction, the second microstrip line, the seventh microstrip line, the fourth microstrip line and the sixth microstrip line are all arranged along a second direction, the second direction is perpendicular to the first direction, and the first microstrip line, the third microstrip line and the third microstrip line are all arranged symmetrically about the first microstrip line and the third microstrip line.

The filter based on the topological structure is provided with two odd-mode transmission poles, five even-mode transmission poles and three transmission zeroes, and the relative positions of the transmission zeroes are not changed no matter how the values of the characteristic impedance of each branch are changed. Therefore, based on the topological structure, the wide stop band filter with narrow pass characteristic can be designed, and the wide stop band filter has the advantages of compact structure and high selectivity.

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 schematic diagram of the topology of a filter of the present utility model;

FIG. 2 is a diagram of an odd mode version of the topology of the present utility model;

FIG. 3 is a diagram of an even mode version of the topology of the present utility model;

FIG. 4 is a layout of a filter of the present utility model;

FIG. 5 is a diagram of S-parameter simulation results of the filter of the present utility model;

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.

Detailed Description

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, if directional indications (such as up, down, left, right, front, and rear are referred to in the embodiments of the present utility model), the directional indications are merely used to explain the relative positional relationship, movement conditions, and the like between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indications are correspondingly changed.

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, it is intended to include three schemes in parallel, taking "a and/or B" as an example, including a scheme, or B scheme, or a scheme where a and B meet 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.

An embodiment of the present utility model proposes a compact wide stop band filter topology structure with narrow pass characteristics, referring to fig. 1, the topology structure includes a first microstrip line and an eighth microstrip line connected in sequence, wherein the other end of the first microstrip line is connected with an input end, and the other end of the eighth microstrip line is connected with an output end;

a second microstrip line and a seventh microstrip line are symmetrically connected between the first microstrip line and the eighth microstrip line;

The other end of the second microstrip line is sequentially connected with a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line and a first open circuit branch knot, and the other end of the seventh microstrip line is symmetrically connected with a second open circuit branch knot and a third open circuit branch knot;

The first microstrip line, the eighth microstrip line, the third microstrip line, the fifth microstrip line, the first open circuit branch, the second open circuit branch and the third open circuit branch are all arranged along a first direction, the second microstrip line, the seventh microstrip line, the fourth microstrip line and the sixth microstrip line are all arranged along a second direction, and the second direction is perpendicular to the first direction;

The first microstrip line and the eighth microstrip line, the second open-circuit branch and the third open-circuit branch are symmetrical about the second microstrip line and the seventh microstrip line.

The embodiment improves the topology of the existing filter, which consists of three open branches and eight microstrip lines. The first microstrip line, the eighth microstrip line, the second open-circuit branch and the third open-circuit branch are symmetrical about the perpendicular bisector of the second microstrip line or the perpendicular bisector of the seventh microstrip line;

The first microstrip line, the third microstrip line, the fifth microstrip line, the eighth microstrip line, the first open circuit branch, the second open circuit branch and the third open circuit branch are parallel to each other and are perpendicular to the second microstrip line, the fourth microstrip line, the sixth microstrip line and the seventh microstrip line;

Further, the characteristic impedance of the first microstrip line is equal to the characteristic impedance of the eighth microstrip line, and in this embodiment, the characteristic impedance of the first microstrip line and the characteristic impedance of the eighth microstrip line are both set to Z ₁.

Further, the characteristic impedance of the second microstrip line, the characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the fifth microstrip line, the characteristic impedance of the sixth microstrip line, and the characteristic impedance of the first open circuit branch are equal, and in this embodiment, the characteristic impedance of the second microstrip line, the characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the fifth microstrip line, the characteristic impedance of the sixth microstrip line, and the characteristic impedance of the first open circuit branch are all set to Z ₂.

Further, the characteristic impedance of the second open branch and the characteristic impedance of the third open branch are equal and are twice the characteristic impedance of the seventh microstrip line, in this embodiment, the characteristic impedance of the seventh microstrip line is set to Z ₃, and the characteristic impedance of the second open branch and the characteristic impedance of the third open branch are both set to 2Z ₃.

Further, the electrical length of the first microstrip line is equal to the electrical length of the eighth microstrip line, and the electrical lengths are quarter wavelengths corresponding to the center frequency of the stop band filter.

The sum of the electrical length of the second microstrip line, the electrical length of the third microstrip line, the electrical length of the fourth microstrip line, the electrical length of the fifth microstrip line, the electrical length of the sixth microstrip line and the electrical length of the first open circuit branch is one half wavelength corresponding to the center frequency of the stop band filter.

The sum of the electric length of the seventh microstrip line and the electric length of the second open circuit branch is a quarter wavelength corresponding to the center frequency of the stop band filter, and the sum of the electric length of the seventh microstrip line and the electric length of the third open circuit branch is a quarter wavelength corresponding to the center frequency of the stop band filter.

The topology structure is analyzed, and the transmission poles of the topology structure can be obtained by a parity-check mode analysis method due to the equivalent bilateral symmetry structure of the topology structure.

Fig. 2 is an odd-mode version of the topology, and referring to fig. 2, when 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 an even mode form of the topology, referring to fig. 3, where the electrical length of the ninth microstrip line is equal to the electrical length of the second microstrip line, the electrical length of the tenth microstrip line is equal to the electrical length of the third microstrip line, the electrical length of the eleventh microstrip line is equal to the electrical length of the fourth microstrip line, the electrical length of the twelfth microstrip line is equal to the electrical length of the fifth microstrip line, the electrical length of the thirteenth microstrip line is equal to the electrical length of the sixth microstrip line, the electrical length of the fourteenth microstrip line is equal to the electrical length of the seventh microstrip line, the electrical length of the fourth circuit branch is equal to the electrical length of the first open circuit branch, the characteristic impedance of the ninth microstrip line, the characteristic impedance of the tenth microstrip line, the characteristic impedance of the eleventh microstrip line, the characteristic impedance of the thirteenth microstrip line, and the characteristic impedance of the fourth circuit branch are equal, all 2Z ₂, and the characteristic impedance of the fourteenth microstrip line is 2Z ₃. When Y _ino = infinity, it can be obtained that the topology has five even mode transmission poles, and respectively:

Wherein:

For the topological structure, the transmission zero point of the topological structure can be calculated by multiplying the ABCD matrixes of the cascade resonators forming the topological structure in sequence to obtain the corresponding ABCD matrix of the topological structure, and converting the ABCD matrix of the topological structure into the corresponding S matrix. when-S ₂₁ - (0), it can be obtained that the topology has three transmission zeros, and the 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. Therefore, a wide stop band filter with narrow pass characteristics can be designed based on this topology.

An embodiment of the utility model provides a filter comprising a filter designed based on any of the above topologies.

Further, the dielectric constant of the circuit board is 3.38, the dielectric loss is 0.0022, the thickness is 0.813mm, and the size is 23.0mm x 10.6mm.

Referring to fig. 4, the first microstrip line and the eighth microstrip line are each set to l ₁ =9.3 mm in length and w ₁ =0.1 mm in line width;

The second microstrip line has a line length of l ₂ =4.55mm, the third microstrip line has a line length of l ₃ =5.4mm, the fourth microstrip line has a line length of l ₄ =2.5mm, the fifth microstrip line has a line length of l ₅ =12 mm, the sixth microstrip line has a line length of l ₆ =2.5mm, and the first open branch has a line length of l ₇ =3.4mm;

The line widths of the second microstrip line, the third microstrip line, the fourth microstrip line, the fifth microstrip line, the sixth microstrip line and the first open-circuit branch are all set to be w ₂ =0.8 mm;

The line length of the seventh microstrip line is set to be l ₈ =1.7 mm, and the line width is set to be w ₃ =0.2 mm;

The line length of the second open branch and the line length of the third open branch are respectively set to be l ₉ =7.6 mm, and the line width is respectively set to be w ₄ =0.1 mm.

The S-parameter simulation result is shown in fig. 5. The isolation is larger than 20dB, the stop band range is 1.621 to 8.713GHz, the stop band center frequency is 5.167GHz, the absolute bandwidth is 7.092GHz, and the relative bandwidth is 137.3%. In addition, three transmission zero points are arranged in the stop band and are respectively positioned at 1.74,5.3 and 8.599GHz, two pass bands are arranged beside the stop band, and five transmission poles are arranged in the pass bands and are respectively positioned at 0,0.94,9.375,10.038 and 10.721GHz. 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 less than-10 dB is 2.887GHz to 3.025GHz, the passband center frequency is 2.956GHz, the absolute bandwidth is 0.138GHz, the relative bandwidth is 4.67%, and for the second passband, the passband range with the reflection coefficient less than-10 dB is 7.174GHz to 7.298GHz, the passband center frequency is 7.236GHz, the absolute bandwidth is 0.124GHz, and the relative bandwidth is 1.71%.

Therefore, the topological structure of the embodiment can design a wide stop band filter with narrow pass characteristics, and the filter has the advantages of compact structure and high selectivity.

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 (10)

1. The topological structure of the compact wide stop band filter with the narrow pass characteristic is characterized by comprising a first microstrip line and an eighth microstrip line which are sequentially connected, wherein the other end of the first microstrip line is connected with an input end, and the other end of the eighth microstrip line is connected with an output end;

a second microstrip line and a seventh microstrip line are symmetrically connected between the first microstrip line and the eighth microstrip line;

The other end of the second microstrip line is sequentially connected with a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line and a first open circuit branch knot, and the other end of the seventh microstrip line is symmetrically connected with a second open circuit branch knot and a third open circuit branch knot;

The first microstrip line, the eighth microstrip line, the third microstrip line, the fifth microstrip line, the first open circuit branch, the second open circuit branch and the third open circuit branch are all arranged along a first direction, the second microstrip line, the seventh microstrip line, the fourth microstrip line and the sixth microstrip line are all arranged along a second direction, and the second direction is perpendicular to the first direction;

The first microstrip line and the eighth microstrip line, the second open-circuit branch and the third open-circuit branch are symmetrical about the second microstrip line and the seventh microstrip line.

2. The compact, wide stop band filter topology with narrow pass characteristics of claim 1, wherein the characteristic impedance of the first microstrip line is equal to the characteristic impedance of the eighth microstrip line.

3. The compact, wide stop band filter topology with narrow pass characteristics of claim 2, wherein the characteristic impedance of the second microstrip line, the characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the fifth microstrip line, the characteristic impedance of the sixth microstrip line, and the characteristic impedance of the first open circuit branch are equal.

4. A compact, wide stop band filter topology with narrow pass characteristics according to claim 3, characterized in that the characteristic impedance of the second open branch and the characteristic impedance of the third open branch are equal and are each twice the characteristic impedance of the seventh microstrip line.

5. The compact, wide stop band filter topology with narrow pass characteristics of claim 1, wherein the electrical length of the first microstrip line and the electrical length of the eighth microstrip line are equal and are each a quarter wavelength corresponding to the center frequency of the stop band filter.

6. The topology of claim 5, wherein a sum of the electrical length of the second microstrip line, the electrical length of the third microstrip line, the electrical length of the fourth microstrip line, the electrical length of the fifth microstrip line, the electrical length of the sixth microstrip line, and the electrical length of the first open branch is one half wavelength corresponding to a center frequency of the stop band filter.

7. The topology of a compact, wide stop band filter with narrow pass characteristics of claim 6, wherein a sum of an electrical length of the seventh microstrip line and an electrical length of the second open circuit branch is a quarter wavelength corresponding to a center frequency of the stop band filter, and wherein a sum of an electrical length of the seventh microstrip line and an electrical length of the third open circuit branch is a quarter wavelength corresponding to a center frequency of the stop band filter.

8. A filter comprising a filter designed based on the topology of any one of claims 1 to 7.

9. The filter of claim 8, further comprising a circuit board having a dielectric constant of 3.38, a dielectric loss of 0.0022, a thickness of 0.813mm, and a dimension of 23.0mm by 10.6mm.

10. The filter of claim 9, wherein the filter is configured to filter the filter,

The line lengths of the first microstrip line and the eighth microstrip line are respectively l ₁ =9.3 mm, and the line widths are respectively w ₁ =0.1 mm;

The second microstrip line has a line length of l ₂ =4.55mm, the third microstrip line has a line length of l ₃ =5.4mm, the fourth microstrip line has a line length of l ₄ =2.5mm, the fifth microstrip line has a line length of l ₅ =12 mm, the sixth microstrip line has a line length of l ₆ =2.5mm, and the first open branch has a line length of l ₇ =3.4mm;

The line widths of the second microstrip line, the third microstrip line, the fourth microstrip line, the fifth microstrip line, the sixth microstrip line and the first open-circuit branch are all set to be w ₂ =0.8 mm;

The line length of the seventh microstrip line is set to be l ₈ =1.7 mm, and the line width is set to be w ₃ =0.2 mm;

The line length of the second open branch and the line length of the third open branch are respectively set to be l ₉ =7.6 mm, and the line width is respectively set to be w ₄ =0.1 mm.