A topology of a small and high-selectivity wideband band-stop filter and the filter

Abstract

The application discloses a kind of topology structure of small and high selective wideband band-stop filter and filter, and the topology structure includes vertical microstrip line, one end of vertical microstrip line is symmetrically connected with the one end of first horizontal microstrip line and the one end of second horizontal microstrip line, the other end of first horizontal microstrip line is connected with first vertical open circuit stub, the other end of second horizontal microstrip line is connected with second vertical open circuit stub;The other end of vertical microstrip line is symmetrically connected with the one end of third horizontal microstrip line and the one end of fourth horizontal microstrip line, the other end of third horizontal microstrip line is connected with input terminal, and the other end of fourth horizontal microstrip line is connected with output terminal;Between third horizontal microstrip line and input terminal, fifth horizontal microstrip line and third vertical open circuit stub are terminated, and between fourth horizontal microstrip line and output terminal, sixth horizontal microstrip line and fourth vertical open circuit stub are terminated.The application solves the problems that the existing band-stop filter structure is complex, size is large, selectivity is poor and stop band is narrow.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of filter, in particular to a topology structure of small and high selectivity wideband band-stop filter and the filter. BACKGROUND

[0002] With the rapid development of modern wireless communication technology, the contradiction between limited frequency spectrum resources and increasing information transmission demand is increasingly intense, and various communication systems and communication modes are increasingly close to or even staggered in frequency space, which brings great challenge to the anti-interference ability of each communication system to other systems. In addition, with the increasing integration of future devices, miniaturization of devices is the only way for the development of future devices and microwave systems. Under this background, the miniaturization and high selectivity of the filter have high scientific research and commercial value, attracting the attention of many scholars and engineers. However, compared with the band-pass filter, the research results of the band-stop filter are very few, and basically have the defects of poor selectivity, large size, narrow stop band and complex design process, which seriously affects its use in modern wireless communication systems. SUMMARY

[0003] The main purpose of the present application is to provide a topology structure of small and high selectivity wideband band-stop filter, which aims to solve the problems of complex structure, large size, poor selectivity and narrow stop band of the existing band-stop filter.

[0004] To achieve the above purpose, the present application provides a topology structure of small and high selectivity wideband band-stop filter, which comprises a vertical microstrip line, one end of the vertical microstrip line is symmetrically connected with one end of a first horizontal microstrip line and one end of a second horizontal microstrip line, the other end of the first horizontal microstrip line is connected with a first vertical open-circuit stub, the other end of the second horizontal microstrip line is connected with a second vertical open-circuit stub, the first horizontal microstrip line and the second horizontal microstrip line are symmetrically distributed on both sides of the vertical microstrip line, and the first vertical open-circuit stub and the second vertical open-circuit stub are symmetrically distributed on both sides of the vertical microstrip line.

[0005] The other end of the vertical microstrip line is symmetrically connected with one end of a third horizontal microstrip line and one end of a fourth horizontal microstrip line, the other end of the third horizontal microstrip line is connected with an input end, and the other end of the fourth horizontal microstrip line is connected with an output end.

[0006] The third horizontal microstrip line and the input end are terminated with a fifth horizontal microstrip line and a third vertical open-circuit stub, the fourth horizontal microstrip line and the output end are terminated with a sixth horizontal microstrip line and a fourth vertical open-circuit stub, the fifth horizontal microstrip line and the sixth horizontal microstrip line are symmetrically distributed on both sides of the vertical microstrip line, and the third vertical open-circuit stub and the fourth vertical open-circuit stub are symmetrically distributed on both sides of the vertical microstrip line.

[0007] Optionally, the sum of the electrical length of the fifth horizontal microstrip line and the electrical length of the third vertical open stub is set as a corresponding quarter wavelength at a center frequency of the band-stop filter, and the sum of the electrical length of the sixth horizontal microstrip line and the electrical length of the fourth vertical open stub is set as a corresponding quarter wavelength at the center frequency of the band-stop filter.

[0008] Optionally, the electrical length of the third horizontal microstrip line and the electrical length of the fourth horizontal microstrip line are both set as a corresponding quarter wavelength at a center frequency of the band-stop filter.

[0009] Optionally, the sum of the electrical length of the vertical microstrip line, the electrical length of the first horizontal microstrip line, and the electrical length of the first vertical open stub is set as a corresponding half wavelength at a center frequency of the band-stop filter, and the sum of the electrical length of the vertical microstrip line, the electrical length of the second horizontal microstrip line, and the electrical length of the second vertical open stub is set as a corresponding half wavelength at the center frequency of the band-stop filter.

[0010] Optionally, the characteristic impedance of the first horizontal microstrip line, the characteristic impedance of the second horizontal microstrip line, the characteristic impedance of the first vertical open stub, and the characteristic impedance of the second vertical open stub are all twice the characteristic impedance of the vertical microstrip line, and the characteristic impedance of the third horizontal microstrip line, the characteristic impedance of the fourth horizontal microstrip line, the characteristic impedance of the fifth horizontal microstrip line, the characteristic impedance of the sixth horizontal microstrip line, the characteristic impedance of the third vertical open stub, and the characteristic impedance of the fourth vertical open stub are all the same.

[0011] Optionally, the topology structure includes three odd-mode transmission poles, three even-mode transmission poles, and three transmission zeros.

[0012] To achieve the above-mentioned purposes, the application further provides a filter including the topology structure designed according to any one of the above-mentioned embodiments.

[0013] Optionally, the filter further includes a circuit board, and the circuit board has a dielectric constant of 3.38, a dielectric loss of 0.0022, and a thickness of 0.813 mm.

[0014] Optionally, the circuit board has a size of 25.0 mm*8.5 mm.

[0015] Optionally, the length of the vertical microstrip line is set as l3=6.8mm, the width of the vertical microstrip line is set as w3=1.7mm; the length of the first horizontal microstrip line and the second horizontal microstrip line is set as l4=8.3mm, and the width of the first horizontal microstrip line and the second horizontal microstrip line is set as w4=0.85mm; the length of the first vertical open-circuit stub and the second vertical open-circuit stub is set as l5=3.8mm, and the width of the first vertical open-circuit stub and the second vertical open-circuit stub is set as w5=0.85mm; the length of the third horizontal microstrip line and the fourth horizontal microstrip line is set as l2=8.8mm, and the width of the third horizontal microstrip line and the fourth horizontal microstrip line is set as w2=0.1mm; the length of the fifth horizontal microstrip line and the sixth horizontal microstrip line is set as l 1H =7.9mm, and the width of the fifth horizontal microstrip line and the sixth horizontal microstrip line is set as w1=0.1mm; the length of the third vertical open-circuit stub and the fourth vertical open-circuit stub is set as l 1v =1.2mm.

[0016] The beneficial effects of the present application are that the topology structure of the existing band-stop filter is improved, which comprises a vertical microstrip line, one end of the vertical microstrip line is symmetrically connected with one end of a first horizontal microstrip line and one end of a second horizontal microstrip line, the other end of the first horizontal microstrip line is connected with a first vertical open-circuit stub, and the other end of the second horizontal microstrip line is connected with a second vertical open-circuit stub; the other end of the vertical microstrip line is symmetrically connected with one end of a third horizontal microstrip line and one end of a fourth horizontal microstrip line, the other end of the third horizontal microstrip line is connected with an input end, and the other end of the fourth horizontal microstrip line is connected with an output end; the fifth horizontal microstrip line and the third vertical open-circuit stub are terminated between the third horizontal microstrip line and the input end, and the sixth horizontal microstrip line and the fourth vertical open-circuit stub are terminated between the fourth horizontal microstrip line and the output end. The band-stop filter based on the topology structure of the present application has the advantages of miniaturization, high selectivity, wide stop band, and simple design process. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and other drawings can also be obtained according to the structures shown in the drawings without any creative labor.

[0018] Figure 1 The figure is a schematic diagram of the topology structure of the present application;

[0019] Figure 2 The figure is a schematic diagram of the odd mode form of the topology structure of the present application;

[0020] Figure 3 The figure is a schematic diagram of the even mode form of the topology structure of the present application;

[0021] Figure 4 for the filter layout based on the topological structure of the application;

[0022] Figure 5 for the filter S parameter simulation result of the application;

[0023] The object, functional characteristics and advantages of the application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the application will be clearly and completely described with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

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

[0026] In addition, if the embodiments of the 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. In addition, the meaning of "and / or" appearing throughout the text is that it includes three parallel schemes, for example, "A and / or B" includes A scheme, or B scheme, or A and B schemes are satisfied at the same time. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, and when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the protection scope required by the application.

[0027] An embodiment of the application provides a small and high-selectivity wideband band-stop filter topological structure, which comprises a vertical microstrip line, one end of the vertical microstrip line is symmetrically connected with one end of a first horizontal microstrip line and one end of a second horizontal microstrip line, the other end of the first horizontal microstrip line is connected with a first vertical open-circuit stub, the other end of the second horizontal microstrip line is connected with a second vertical open-circuit stub, the first horizontal microstrip line and the second horizontal microstrip line are symmetrically distributed on both sides of the vertical microstrip line, and the first vertical open-circuit stub and the second vertical open-circuit stub are symmetrically distributed on both sides of the vertical microstrip line.

[0028] The other end of the vertical microstrip line is symmetrically connected with one end of a third horizontal microstrip line and one end of a fourth horizontal microstrip line, the other end of the third horizontal microstrip line is connected with the input end, and the other end of the fourth horizontal microstrip line is connected with the output end.

[0029] The third horizontal microstrip line and the input end are terminated with a fifth horizontal microstrip line and a third vertical open stub, and the fourth horizontal microstrip line and the output end are terminated with a sixth horizontal microstrip line and a fourth vertical open stub; the fifth horizontal microstrip line and the sixth horizontal microstrip line are symmetrically distributed on both sides of the vertical microstrip line, and the third vertical open stub and the fourth vertical open stub are symmetrically distributed on both sides of the vertical microstrip line.

[0030] In this embodiment, the topology adopts a left-right symmetric structure, taking the vertical microstrip line as the center, the first horizontal microstrip line and the second horizontal microstrip line are symmetrically arranged, the first vertical open stub and the second vertical open stub are symmetrically arranged, the third horizontal microstrip line and the fourth horizontal microstrip line are symmetrically arranged, the fifth horizontal microstrip line and the sixth horizontal microstrip line are symmetrically arranged, and the third vertical open stub and the fourth vertical open are symmetrically arranged.

[0031] Further, the sum of the electrical length of the fifth horizontal microstrip line and the electrical length of the third vertical open stub is set to be a quarter wavelength corresponding to the center frequency of the band-stop filter, and the sum of the electrical length of the sixth horizontal microstrip line and the electrical length of the fourth vertical open stub is set to be a quarter wavelength corresponding to the center frequency of the band-stop filter. The electrical length of the third horizontal microstrip line and the electrical length of the fourth horizontal microstrip line are both set to be a quarter wavelength corresponding to the center frequency of the band-stop filter.

[0032] The sum of the electrical length of the vertical microstrip line, the electrical length of the first horizontal microstrip line, and the electrical length of the first vertical open stub is set to be a half wavelength corresponding to the center frequency of the band-stop filter; and the sum of the electrical length of the vertical microstrip line, the electrical length of the second horizontal microstrip line, and the electrical length of the second vertical open stub is set to be a half wavelength corresponding to the center frequency of the band-stop filter.

[0033] Further, the characteristic impedance of the first horizontal microstrip line, the characteristic impedance of the second horizontal microstrip line, the characteristic impedance of the first vertical open stub, and the characteristic impedance of the second vertical open stub are respectively twice the characteristic impedance of the vertical microstrip line; the characteristic impedance of the third horizontal microstrip line, the characteristic impedance of the fourth horizontal microstrip line, the characteristic impedance of the fifth horizontal microstrip line, the characteristic impedance of the sixth horizontal microstrip line, the characteristic impedance of the third vertical open stub, and the characteristic impedance of the fourth vertical open stub are the same.

[0034] In the embodiment, the characteristic impedance of the vertical microstrip line is Z2, the characteristic impedance of the first horizontal microstrip line, the characteristic impedance of the second horizontal microstrip line, the characteristic impedance of the first vertical open stub, and the characteristic impedance of the second vertical open stub are all 2Z2, and the characteristic impedance of the third horizontal microstrip line, the characteristic impedance of the fourth horizontal microstrip line, the characteristic impedance of the fifth horizontal microstrip line, the characteristic impedance of the sixth horizontal microstrip line, the characteristic impedance of the third vertical open stub, and the characteristic impedance of the fourth vertical open stub are all Z1. Therefore, the band-stop filter designed based on the topology structure has only two design parameters.

[0035] In the embodiment, the topology structure includes three odd-mode transmission poles, three even-mode transmission poles, and three transmission zeros. Since the topology structure is a symmetrical structure, the transmission poles can be analyzed by using odd and even modes. Specifically, referring to Figure 2 When Y ino = ∞, it can be concluded that the topology structure has three odd-mode transmission poles. When f0 is the center frequency of the band-stop filter, the frequencies corresponding to the three odd-mode transmission poles are respectively:

[0036] f op1 = 0

[0037] f op2 = f0

[0038] f op3 = 2f0

[0039] Referring to Figure 3 When Y ino = ∞, it can be concluded that the topology structure has three even-mode transmission poles, and the frequencies corresponding to the three even-mode transmission poles are respectively:

[0040]

[0041]

[0042]

[0043] For the topology structure, the transmission zeros can be calculated by the following method: multiply the ABCD matrices of the cascaded resonators that constitute the topology structure in sequence to obtain the ABCD matrix corresponding to the topology structure; and convert the ABCD matrix of the topology structure into the corresponding S matrix. When |S 21 | = 0, it can be concluded that the topology structure has three transmission zeros, and the frequencies corresponding to the three transmission zeros are respectively:

[0044]

[0045] f z2 = f0

[0046]

[0047] From the above analysis, the topology structure has three odd mode transmission poles, three even mode transmission poles, three transmission zeros. And regardless of the value of the parameters Z1, Z2 changes, the relative position of these transmission zero and pole, that is, f op1 <f ep1 <f z1 <f op2 = f z2 <f z3 <f ep2 <f op3 <f ep3 , will not change. In addition, according to the characteristics of the radio frequency filter, when the position of the transmission zero and the transmission pole coincides, only the characteristics of the transmission zero are displayed. Therefore, the radio frequency filter designed based on this topology structure can only be a band-stop filter, and there are three transmission zeros in the stop band, two transmission poles in the lower passband, and three transmission poles in the upper passband.

[0048] In order to make the stop band bandwidth as wide as possible, Z1 should be as large as possible; in order to make the stop band high isolation and the low loss and flatness in the two passbands, Z2 should be as small as possible. It should be noted that the maximum value of Z1 is limited by the dielectric constant and height of the PCB board and the etching precision of the PCB board; the minimum value of Z2 is limited by the dielectric constant and height of the PCB board and the size of the center frequency of the stop band.

[0049] Another embodiment of the present application also provides a filter comprising the filter designed based on the topology structure described above. The filter further comprises a circuit board, and the dielectric constant of the circuit board is 3.38, the dielectric loss is 0.0022, and the thickness is 0.813 mm. The size of the circuit board is 25.0 mm*8.5 mm.

[0050] Further, referring to Figure 4 , the length of the vertical microstrip line is set to l3=6.8 mm, the width of the vertical microstrip line is set to w3=1.7 mm; the length of the first horizontal microstrip line and the second horizontal microstrip line is set to l4=8.3 mm, and the width is set to w4=0.85 mm; the length of the first vertical open-circuit stub and the second vertical open-circuit stub is set to l5=3.8 mm, and the width is set to w5=0.85 mm; the length of the third horizontal microstrip line and the fourth horizontal microstrip line is set to l2=8.8 mm, and the width is set to w2=0.1 mm; the length of the fifth horizontal microstrip line and the sixth horizontal microstrip line is set to l 1H=7.9mm, and the width is set to w1=0.1mm; the length of the third vertical open branch and the fourth vertical open branch is set to l. 1v =1.2mm.

[0051] Based on the above design, the simulation structure of the filter S-parameters in this embodiment is as follows: Figure 5 As shown, the stopband with isolation greater than 20dB ranges from 2.068GHz to 8.264GHz, with a stopband center frequency of 5.166GHz, an absolute bandwidth of 6.196GHz, and a relative bandwidth of 119.9%. Furthermore, there are three transmission zeros within the stopband, located at 2.562, 5.263, and 7.973GHz. Adjacent to the stopband are two passbands, each containing five transmission poles located at 0, 0.643, 9.166, 10.245, and 11.728GHz. These three transmission zeros and poles not only ensure high isolation in the stopband and low insertion loss and flatness in the passband, but also guarantee high selectivity in the sidebands of the band-stop filter.

[0052] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A topology for a small and highly selective wideband bandstop filter, characterized by, The vertical microstrip line is symmetrically connected at one end with one end of the first horizontal microstrip line and one end of the second horizontal microstrip line, the other end of the first horizontal microstrip line is connected with a first vertical open-circuit stub, the other end of the second horizontal microstrip line is connected with a second vertical open-circuit stub, the first horizontal microstrip line and the second horizontal microstrip line are symmetrically distributed on both sides of the vertical microstrip line, and the first vertical open-circuit stub and the second vertical open-circuit stub are symmetrically distributed on both sides of the vertical microstrip line. The other end of the vertical microstrip line is symmetrically connected with one end of the third horizontal microstrip line and one end of the fourth horizontal microstrip line, the other end of the third horizontal microstrip line is connected with the input end, and the other end of the fourth horizontal microstrip line is connected with the output end. The third horizontal microstrip line and the input end are terminated with a fifth horizontal microstrip line and a third vertical open-circuit stub, and the fourth horizontal microstrip line and the output end are terminated with a sixth horizontal microstrip line and a fourth vertical open-circuit stub; the fifth horizontal microstrip line and the sixth horizontal microstrip line are symmetrically distributed on both sides of the vertical microstrip line, and the third vertical open-circuit stub and the fourth vertical open-circuit stub are symmetrically distributed on both sides of the vertical microstrip line. The sum of the electrical length of the fifth horizontal microstrip line and the electrical length of the third vertical open-circuit stub is set to be a quarter wavelength corresponding to the center frequency of the band-stop filter, and the sum of the electrical length of the sixth horizontal microstrip line and the electrical length of the fourth vertical open-circuit stub is set to be a quarter wavelength corresponding to the center frequency of the band-stop filter. The electrical length of the third horizontal microstrip line and the electrical length of the fourth horizontal microstrip line are both set to be a quarter wavelength corresponding to the center frequency of the band-stop filter.

2. The topology of small and high-selectivity wideband band-rejection filter according to claim 1, characterized in that, The sum of the electrical length of the vertical microstrip line, the electrical length of the first horizontal microstrip line, and the electrical length of the first vertical open-circuit stub is set to be a half wavelength corresponding to the center frequency of the band-stop filter; and the sum of the electrical length of the vertical microstrip line, the electrical length of the second horizontal microstrip line, and the electrical length of the second vertical open-circuit stub is set to be a half wavelength corresponding to the center frequency of the band-stop filter.

3. The topology of compact and high-selectivity wideband band-rejection filter according to claim 1, characterized in that, The characteristic impedance of the first horizontal microstrip line, the characteristic impedance of the second horizontal microstrip line, the characteristic impedance of the first vertical open-circuit stub, and the characteristic impedance of the second vertical open-circuit stub are all twice the characteristic impedance of the vertical microstrip line; the characteristic impedance of the third horizontal microstrip line, the characteristic impedance of the fourth horizontal microstrip line, the characteristic impedance of the fifth horizontal microstrip line, the characteristic impedance of the sixth horizontal microstrip line, the characteristic impedance of the third vertical open-circuit stub, and the characteristic impedance of the fourth vertical open-circuit stub are the same.

4. The topology of compact and highly selective wideband band-rejection filter according to claim 1, characterized in that, The topology structure includes three odd-mode transmission poles, three even-mode transmission poles, and three transmission zeros.

5. A filter, characterized by The filter includes the topology structure design of any one of claims 1-4.

6. The filter of claim 5, wherein, The filter further includes a circuit board, the dielectric constant of the circuit board is 3.38, the dielectric loss is 0.0022, and the thickness is 0.813 mm.

7. The filter of claim 6, wherein, The size of the circuit board is 25.0 mm * 8.5 mm.

8. The filter of claim 5, wherein, a length of the vertical microstrip line is set to l 3= 6.8mm, a width of the vertical microstrip line is set to w 3= 1.7 mm; a length of the first horizontal microstrip line and the second horizontal microstrip line is set to l 4= 8.3 mm, a width of the first horizontal microstrip line and the second horizontal microstrip line is set to w 4= 0.85 mm; a length of the first vertical open-circuit stub and the second vertical open-circuit stub is set to l 5= 3.8 mm, a width of the first vertical open-circuit stub and the second vertical open-circuit stub is set to w 5= 0.85 mm; a length of the third horizontal microstrip line and the fourth horizontal microstrip line is set to l 2= 8.8mm, a width of the third horizontal microstrip line and the fourth horizontal microstrip line is set to w 2= 0.1mm; a length of the fifth horizontal microstrip line and the sixth horizontal microstrip line is set to l 1H = 7.9 mm, a width of the fifth horizontal microstrip line and the sixth horizontal microstrip line is set to w 1= 0.1 mm; a length of the third vertical open-circuit stub and the fourth vertical open-circuit stub is set to l 1v = 1.2mm.

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