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

Abstract

The application discloses a kind of topology structure of high-selectivity wideband band-stop filter and filter, the topology structure includes vertical microstrip line, one end of vertical microstrip line is symmetrically connected with the one end of first horizontal open stub and the one end of second horizontal open stub, the other 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 input end, the other end of second horizontal microstrip line is connected output end;First horizontal microstrip line and input end are also terminated with third horizontal microstrip line and first vertical open stub between, second horizontal microstrip line and output end are also terminated with fourth horizontal microstrip line and second vertical open stub between;Third horizontal microstrip line and fourth horizontal microstrip line are symmetrically distributed on both sides of vertical microstrip line, and first vertical open stub and second vertical open stub are symmetrically distributed on both sides of vertical microstrip line.The application solves the problems that the existing band-stop filter structure is complex, the selectivity is poor, and the 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 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 challenges to the anti-interference ability of each communication system to other systems. In addition, radio frequency devices based on microstrip structure have the advantages of low cost, small size, low profile, light weight, easy integration, etc. Under this background, the high selectivity research of microstrip filter has very high scientific research and commercial value, attracting the attention of many scholars and engineers. However, compared with band-pass filters, the research results of band-stop filters are not only very few, but also basically have the defects of poor selectivity, narrow stop band, complex topology structure and design process, which seriously affects their use in modern wireless communication systems. SUMMARY

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

[0004] To achieve the above purpose, the present application provides a topology structure of 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 open stub and one end of a second horizontal open stub, the other 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 an input end, and the other end of the second horizontal microstrip line is connected with an output end.

[0005] The first horizontal microstrip line and the input end are also terminated with a third horizontal microstrip line and a first vertical open stub, and the second horizontal microstrip line and the output end are also terminated with a fourth horizontal microstrip line and a second vertical open stub; the third horizontal microstrip line and the fourth horizontal microstrip line are symmetrically distributed on both sides of the vertical microstrip line, and the first vertical open stub and the second vertical open stub are symmetrically distributed on both sides of the vertical microstrip line.

[0006] Optionally, the electrical length of the vertical microstrip line, the electrical length of the first horizontal open stub, the electrical length of the second horizontal open stub, the electrical length of the first horizontal microstrip line and the electrical length of the second horizontal microstrip line are the same.

[0007] Optionally, the electrical length of the vertical microstrip line, the electrical length of the first horizontal open stub, the electrical length of the second horizontal open stub, the electrical length of the first horizontal microstrip line, and the electrical length of the second horizontal microstrip line are all set to the corresponding quarter wavelength at the center frequency of the band-stop filter.

[0008] Optionally, the sum of the electrical length of the third horizontal microstrip line and the electrical length of the first vertical open stub is set to the corresponding quarter wavelength at the center frequency of the band-stop filter, and the sum of the electrical length of the fourth horizontal microstrip line and the electrical length of the second vertical open stub is set to the corresponding quarter wavelength at the center frequency of the band-stop filter.

[0009] Optionally, the parameters of the topology structure include the characteristic impedance of the vertical microstrip line, the characteristic impedance of the first horizontal open stub and the characteristic impedance of the second horizontal open stub, the characteristic impedance of the first horizontal microstrip line and the characteristic impedance of the second horizontal microstrip line, the characteristic impedance of the third horizontal microstrip line and the characteristic impedance of the fourth horizontal microstrip line, the characteristic impedance of the first vertical open stub and the characteristic impedance of the second vertical open stub.

[0010] The characteristic impedance of the first horizontal open stub and the characteristic impedance of the second horizontal open stub are the same, the characteristic impedance of the first horizontal microstrip line and the characteristic impedance of the second horizontal microstrip line are the same, and the characteristic impedance of the third horizontal microstrip line, the characteristic impedance of the fourth horizontal microstrip line, the characteristic impedance of the first vertical open stub, and the characteristic impedance of the second vertical open stub are the same.

[0011] Optionally, the topology structure design 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 comprising the topology structure design of any of the above.

[0013] Optionally, 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.

[0014] Optionally, the size of the circuit board of the filter is 26.0 mm*11.0 mm.

[0015] Optionally, the length of the vertical microstrip line is set as l3=9.35mm, the width of the vertical microstrip line is set as w3=3.3mm; the length of the first horizontal open stub and the second horizontal open stub is set as l4=9.35mm, and the width is set as w4=0.9mm; the length of the first horizontal microstrip line and the second horizontal microstrip line is set as l2=9.35mm, and the width is set as w2=0.1mm; the length of the third horizontal microstrip line and the fourth horizontal microstrip line is set as l 1H =8.45mm, and the width is set as w1=0.1mm; the length of the first vertical open stub and the second vertical open stub is set as l 1V =0.9mm.

[0016] The present application has the advantages 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 open stub and one end of a second horizontal open stub, the other 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 an input end, and the other end of the second horizontal microstrip line is connected with an output end; a third horizontal microstrip line and a first vertical open stub are further terminated between the first horizontal microstrip line and the input end, and a fourth horizontal microstrip line and a second vertical open stub are further terminated between the second horizontal microstrip line and the output end; the third horizontal microstrip line and the fourth horizontal microstrip line are symmetrically distributed on both sides of the vertical microstrip line, and the first vertical open stub and the second vertical open stub are symmetrically distributed on both sides of the vertical microstrip line; the band-stop filter designed based on the topology structure has the advantages of high selectivity, wide stop band, and simple design process. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in 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 by those skilled in the art without any creative effort based on the drawings shown.

[0018] Figure 1 The topology structure of the filter of the present application is shown in the figure;

[0019] Figure 2 The odd mode form of the topology structure of the present application is shown in the figure;

[0020] Figure 3 The even mode form of the topology structure of the present application is shown in the figure;

[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 graph of the application;

[0023] The object, functional features 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 directionality indications (such as up, down, left, right, front, back, etc.), the directionality 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 directionality 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. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of those skilled in the art, 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 of the application.

[0027] An embodiment of the application provides a topological structure of a high-selectivity wideband band-stop filter, referring to Figure 1 , comprising a vertical microstrip line, one end of the vertical microstrip line is symmetrically connected with one end of a first horizontal open-circuit stub and one end of a second horizontal open-circuit stub, the other 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 an input end, and the other end of the second horizontal microstrip line is connected with an output end;

[0028] The third horizontal microstrip line and the fourth horizontal microstrip line are symmetrically distributed on both sides of the vertical microstrip line, and the first vertical open stub and the second vertical open stub are symmetrically distributed on both sides of the vertical microstrip line.

[0029] In the embodiment, the topology adopts a left-right symmetric structure, taking the vertical microstrip line as a central axis, the first horizontal open stub and the second horizontal open stub are symmetric, the first horizontal microstrip line and the second horizontal microstrip line are symmetric, the third horizontal microstrip line and the fourth horizontal microstrip line are symmetric, and the first vertical open stub and the second vertical open stub are symmetric.

[0030] Further, the electrical length of the vertical microstrip line, the electrical length of the first horizontal open stub, the electrical length of the second horizontal open stub, the electrical length of the first horizontal microstrip line, and the electrical length of the second horizontal microstrip line are all the same. In the embodiment, the electrical length of the vertical microstrip line, the electrical length of the first horizontal open stub, the electrical length of the second horizontal open stub, the electrical length of the first horizontal microstrip line, and the electrical length of the second horizontal microstrip line are all set to the corresponding quarter wavelength at the center frequency of the band-stop filter.

[0031] Further, the sum of the electrical length of the third horizontal microstrip line and the electrical length of the first vertical open stub is set to the corresponding quarter wavelength at the center frequency of the band-stop filter, and the sum of the electrical length of the fourth horizontal microstrip line and the electrical length of the second vertical open stub is set to the corresponding quarter wavelength at the center frequency of the band-stop filter.

[0032] Further, the characteristic impedance of the first horizontal open stub and the characteristic impedance of the second horizontal open stub are the same, the characteristic impedance of the first horizontal microstrip line and the characteristic impedance of the second horizontal microstrip line are the same, and the characteristic impedance of the third horizontal microstrip line, the characteristic impedance of the fourth horizontal microstrip line, the characteristic impedance of the first vertical open stub, and the characteristic impedance of the second vertical open stub are the same.

[0033] In the embodiment, for the upper half of the topology structure, the characteristic impedance of the first horizontal open stub and the characteristic impedance of the second horizontal open stub are the same, which is Z4, and the characteristic impedance of the vertical microstrip line is Z3; for the lower half of the topology structure, the characteristic impedance of the first horizontal microstrip line and the characteristic impedance of the second horizontal microstrip line are the same, which is Z2, and the characteristic impedance of the third horizontal microstrip line, the characteristic impedance of the fourth horizontal microstrip line, the characteristic impedance of the first vertical open stub, and the characteristic impedance of the second vertical open stub are the same, which is Z1.

[0034] Further, the topology includes three odd mode transmission poles, three even mode transmission poles and three transmission zeros. In this embodiment, since the topology is a symmetric structure, the transmission poles can be analyzed by odd and even modes. Specifically, referring to Figure 2 When Y ino =∞, it can be concluded that the topology has three odd mode transmission poles. When f0is the center frequency of the band-stop filter, the frequencies corresponding to the three odd mode transmission poles are respectively:

[0035] f op1 =0

[0036] f op2 =f0

[0037] f op3 =2f0

[0038] Referring to Figure 3 When Y ino =∞, it can be concluded that the topology has three even mode transmission poles, and the frequencies corresponding to the three even mode transmission poles are respectively:

[0039]

[0040]

[0041]

[0042] For this topology, the transmission zeros can be calculated by the following method: multiply the ABCD matrices of the cascaded resonators constituting the topology in sequence to obtain the ABCD matrix corresponding to the topology; convert the ABCD matrix of the topology into the corresponding S matrix. When ︱S 21 ︱=0, it can be concluded that the topology has three transmission zeros, and the frequencies corresponding to the three transmission zeros are respectively:

[0043]

[0044] f z2 =f0

[0045]

[0046] From the above analysis, it can be concluded that the topology has three odd mode transmission poles, three even mode transmission poles and three transmission zeros. And regardless of the value of the parameters Z1, Z2, Z3 and Z4, the relative positions of these transmission poles and zeros, i.e. op1 <f ep1 <f z1 <f op2 =f z2 <f z3 <fep2 <f op3 <f ep3 , and the transmission zero point and the transmission pole point coincide, only the characteristic of the transmission zero point is displayed. Therefore, the radio frequency filter designed based on the topology structure can only be a band-stop filter, and there are three transmission zero points in the stop band, two transmission pole points in the lower pass band, and three transmission pole points in the upper pass band.

[0047] The band-stop filter designed based on the topology structure, and the stop band bandwidth is mainly determined by the ratio of the characteristic impedances Z3 and Z4. The greater the ratio of the characteristic impedances Z3 and Z4, the greater the stop band bandwidth. The isolation of the stop band and the reflection coefficient of the pass band are mainly determined by the values of Z3 and Z4. The smaller the values of Z3 and Z4, the higher the isolation of the stop band and the smaller the reflection coefficient of the pass band.

[0048] Another embodiment of the present application also provides a filter, which comprises 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 of the filter is 26.0 mm*11.0 mm.

[0049] Further, with reference to 4, the length of the vertical microstrip line is set as l3=9.35 mm, and the width of the vertical microstrip line is set as w3=3.3 mm; the length of the first horizontal open-circuit stub and the second horizontal open-circuit stub is set as l4=9.35 mm, and the width is set as w4=0.9 mm; the length of the first horizontal microstrip line and the second horizontal microstrip line is set as l2=9.35 mm, and the width is set as w2=0.1 mm; the length of the third horizontal microstrip line and the fourth horizontal microstrip line is set as l 1H =8.45 mm, and the width is set as w1=0.1 mm; the length of the first vertical open-circuit stub and the second vertical open-circuit stub is set as l 1V =0.9 mm.

[0050] Based on the above design, the S parameter simulation result of the filter in the embodiment is as shown in Figure 5As shown, the stopband with isolation greater than 20 dB ranges from 2.233 GHz to 8.075 GHz, the center frequency of the stopband is 5.154 GHz, the absolute bandwidth of the stopband is 5.842 GHz, and the relative bandwidth of the stopband is 113.3%. In addition, there are three transmission zeros in the stopband, which are located at 2.762, 5.028, and 7.845 GHz respectively; there are five transmission poles in the passband, which are located at 0, 0.903, 8.868, 9.769, and 10.901 GHz respectively. The three transmission zeros and the five transmission poles not only ensure the high isolation characteristic of the stopband and the low insertion loss and flatness of the passband, but also guarantee the high selectivity characteristic of the bandstop filter sideband.

[0051] The above merely describes optional embodiments of the present application, and does 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 under the inventive concept of the present application, using the content of the present application specification and drawings, is included in the patent protection scope of the present application.

Claims

1. A topology for a high-selectivity wide-band stop filter, characterized by, The vertical microstrip line has one end symmetrically connected with one end of the first horizontal open stub and one end of the second horizontal open stub, and the other end of the vertical microstrip line is symmetrically connected 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 the input end, and the other end of the second horizontal microstrip line is connected with the output end. The first horizontal microstrip line and the input end are further terminated with the third horizontal microstrip line and the first vertical open stub, and the second horizontal microstrip line and the output end are further terminated with the fourth horizontal microstrip line and the second vertical open stub; the third horizontal microstrip line and the fourth horizontal microstrip line are symmetrically distributed on both sides of the vertical microstrip line, and the first vertical open stub and the second vertical open stub are symmetrically distributed on both sides of the vertical microstrip line. The electrical length of the vertical microstrip line, the electrical length of the first horizontal open stub, the electrical length of the second horizontal open stub, the electrical length of the first horizontal microstrip line, and the electrical length of the second horizontal microstrip line are all the same. The sum of the electrical length of the third horizontal microstrip line and the electrical length of the first 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 fourth horizontal microstrip line and the electrical length of the second vertical open stub is set to be a quarter wavelength corresponding to the center frequency of the band-stop filter.

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

3. The topology of a high-selectivity wideband band-rejection filter according to claim 1, wherein, The parameters of the topology structure include the characteristic impedance of the vertical microstrip line, the characteristic impedance of the first horizontal open stub and the characteristic impedance of the second horizontal open stub, the characteristic impedance of the first horizontal microstrip line and the characteristic impedance of the second horizontal microstrip line, the characteristic impedance of the third horizontal microstrip line and the characteristic impedance of the fourth horizontal microstrip line, the characteristic impedance of the first vertical open stub and the characteristic impedance of the second vertical open stub. The characteristic impedance of the first horizontal open stub and the characteristic impedance of the second horizontal open stub are the same, the characteristic impedance of the first horizontal microstrip line and the characteristic impedance of the second horizontal microstrip line are the same, and the characteristic impedance of the third horizontal microstrip line, the characteristic impedance of the fourth horizontal microstrip line, the characteristic impedance of the first vertical open stub, and the characteristic impedance of the second vertical open stub are the same.

4. The topology of a high-selectivity wideband band-rejection filter according to claim 1, wherein, 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, and the circuit board has a dielectric constant of 3.38, a dielectric loss of 0.0022, and a thickness of 0.813 mm.

7. The filter of claim 6, wherein, The size of the circuit board of the filter is 26.0 mm*11.0 mm.

8. The filter of claim 5, wherein, a length of the vertical microstrip line is set to l 3= 9.35mm, a width of the vertical microstrip line is set to w 3= 3.3 mm; a length of the first horizontal open-circuit stub and the second horizontal open-circuit stub is set to l 4= 9.35 mm, a width of each is set to w 4= 0.9 mm; a length of the first horizontal microstrip line and the second horizontal microstrip line is set to l 2= 9.35 mm, a width of each is set to w 2= 0.1 mm; a length of the third horizontal microstrip line and the fourth horizontal microstrip line is set to l 1H = 8.45 mm, a width of each is set to w 1= 0.1mm; a length of the first vertical open-circuit stub and the second vertical open-circuit stub is set to l 1V = 0.9 mm.

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