Miniaturized broadband filter topological structure and filter

Abstract

The utility model discloses a miniaturized broadband filter topological structure and a filter, the topological structure comprises a first parallel three-line, a first parallel line and a second parallel three-line which are connected in sequence, the other end of the first parallel three-line is connected with an input end, and the other end of the second parallel three-line is connected with an output end; a first microstrip line is connected between the first parallel three line and the first parallel line, and the other end of the first microstrip line is symmetrically connected with a first short-circuit branch knot and a second short-circuit branch knot; a second microstrip line is connected between the second parallel three line and the first parallel line, and the other end of the second microstrip line is symmetrically connected with a third short-circuit branch knot and a fourth short-circuit branch knot; the broadband filter with high selectivity solves the problem that an existing broadband filter with high selectivity is large in size.

Description

Technical Field

[0001] The utility model relates to the technical field of filters, and in particular to a miniaturized broadband filter topology structure and a filter. Background Art

[0002] With the rapid evolution of modern wireless communication technology, the development of high-performance broadband communication systems that meet the demand for high-speed data transmission is an inevitable trend. In this context, bandpass filters, as key components in communication systems, have attracted the attention of scholars and engineers due to their high selectivity, wide stopband, and high isolation. Their high scientific and commercial value have attracted considerable attention. However, existing high-selectivity broadband filters often suffer from large size, which seriously hinders their use in modern wireless communication systems. Utility Model Content

[0003] The main purpose of the utility model is to provide a miniaturized broadband filter topology structure and a filter, aiming to solve the problem that the existing broadband filters with high selectivity are large in size.

[0004] To achieve the above object, the present invention proposes a miniaturized broadband filter topology structure, comprising a first parallel three-wire, a first parallel wire, and a second parallel three-wire connected in sequence, wherein the other end of the first parallel three-wire is connected to an input end, and the other end of the second parallel three-wire is connected to an output end;

[0005] A first microstrip line is connected between the first three parallel lines and the first parallel line, and a first short-circuit branch and a second short-circuit branch are symmetrically connected at the other end of the first microstrip line;

[0006] A second microstrip line is connected between the second three parallel lines and the first parallel line, and a third short-circuit branch and a fourth short-circuit branch are symmetrically connected to the other end of the second microstrip line;

[0007] The first three parallel lines, the first parallel line, the second three parallel lines, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are all arranged along the first direction, the first microstrip line and the second microstrip line are both arranged along the second direction, and the first direction is perpendicular to the second direction.

[0008] Optionally, the electrical length of the first parallel line, the electrical length of the first three parallel lines, and the electrical length of the second three parallel lines are equal, and are all equal to a quarter wavelength corresponding to the center frequency of the broadband filter.

[0009] Optionally, the electrical length of the first microstrip line is equal to the electrical length of the second microstrip line;

[0010] The electrical length of the first short-circuit branch, the electrical length of the second short-circuit branch, the electrical length of the third short-circuit branch, and the electrical length of the fourth short-circuit branch are equal.

[0011] Optionally, the sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit branch is greater than the electrical length of the first parallel line; the sum of the electrical length of the first microstrip line and the electrical length of the second short-circuit branch is greater than the electrical length of the first parallel line;

[0012] The sum of the electrical lengths of the second microstrip line and the third short-circuit branch is greater than the electrical length of the first parallel line; the sum of the electrical lengths of the second microstrip line and the fourth short-circuit branch is greater than the electrical length of the first parallel line.

[0013] Optionally, the odd-mode characteristic impedance of the first three parallel lines is equal to the odd-mode characteristic impedance of the second three parallel lines; and the even-mode characteristic impedance of the first three parallel lines is equal to the even-mode characteristic impedance of the second three parallel lines.

[0014] Optionally, the characteristic impedance of the first microstrip line is equal to the characteristic impedance of the second microstrip line.

[0015] Optionally, the characteristic impedance of the first short-circuit branch, the characteristic impedance of the second short-circuit branch, the characteristic impedance of the third short-circuit branch and the characteristic impedance of the fourth short-circuit branch are all equal and are twice the characteristic impedance of the first microstrip line or the characteristic impedance of the second microstrip line.

[0016] To achieve the above objectives, the present invention further provides a filter comprising any of the above-mentioned topological structures.

[0017] Optionally, the filter further includes a circuit board, the circuit board has a dielectric constant of 3.38, a dielectric loss of 0.0022, a thickness of 0.813 mm, and a size of 37.6 mm*9.5 mm.

[0018] Optionally, the line width of the transmission lines in the first three parallel lines and the second three parallel lines is set to w T =0.2mm, line spacing is set to s T =0.1mm, line length is set to l T =10.2mm;

[0019] The line width of the transmission line in the first parallel line is set to w p =0.2mm, line spacing is set to s p =0.1mm, line length is set to l p =10.2mm;

[0020] The line lengths of the first microstrip line and the second microstrip line are both set to l1=4.1 mm, and the line widths are both set to w1=1.8 mm;

[0021] The line lengths of the first short-circuit branch, the second short-circuit branch, the third short-circuit branch, and the fourth short-circuit branch are all set to l2 = 7.3 mm, and the line widths are all set to w2 = 0.9 mm.

[0022] The beneficial effects of the present utility model are: improving the topological structure of the existing broadband filter, the topological structure includes a first parallel three lines, a first parallel line, and a second parallel three lines connected in sequence, the other end of the first parallel three lines is connected to the input end, and the other end of the second parallel three lines is connected to the output end; a first microstrip line is connected between the first parallel three lines and the first parallel line, and the other end of the first microstrip line is symmetrically connected to a first short-circuit branch and a second short-circuit branch; a second microstrip line is connected between the second parallel three lines and the first parallel line, and the other end of the second microstrip line is symmetrically connected to a third short-circuit branch and a fourth short-circuit branch; the first parallel three lines, the first parallel line, the second parallel three lines, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are all arranged along the first direction, the first microstrip line and the second microstrip line are both arranged along the second direction, and the first direction and the second direction are perpendicular to each other. The filter based on this topology has four odd-mode transmission poles, four even-mode transmission poles, and two transmission zeros. No matter how the characteristic impedance of each branch is changed, the relative positions of the transmission zero poles will not change. Therefore, a broadband bandpass filter can be designed based on this topology. There are eight transmission poles in the passband to ensure its flatness within the band, and two transmission zeros in the stopband to ensure high selectivity and high isolation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0024] Figure 1 This is a schematic diagram of the topological structure of the filter of the utility model;

[0025] Figure 2 It is an odd-mode diagram of the topological structure of the utility model;

[0026] Figure 3 It is an even-mode diagram of the topological structure of the utility model;

[0027] Figure 4 This is a layout diagram of the filter of the utility model;

[0028] Figure 5This is the S parameter simulation result diagram of the utility model filter;

[0029] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] It should be noted that if the embodiments of the present invention 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 status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0032] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if the meaning of "and / or" appearing in the full text is to include three parallel schemes, taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0033] An embodiment of the present invention proposes a miniaturized broadband filter topology structure, referring to Figure 1 , comprising a first parallel three wires, a first parallel wire, and a second parallel three wires connected in sequence, wherein the other end of the first parallel three wires is connected to the input end, and the other end of the second parallel three wires is connected to the output end;

[0034] A first microstrip line is connected between the first three parallel lines and the first parallel line, and a first short-circuit branch and a second short-circuit branch are symmetrically connected at the other end of the first microstrip line;

[0035] A second microstrip line is connected between the second three parallel lines and the first parallel line, and a third short-circuit branch and a fourth short-circuit branch are symmetrically connected to the other end of the second microstrip line;

[0036] The first three parallel lines, the first parallel line, the second three parallel lines, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are all arranged along the first direction, the first microstrip line and the second microstrip line are both arranged along the second direction, and the first direction is perpendicular to the second direction.

[0037] This embodiment improves the topology of existing filters, consisting of one parallel line, a pair of parallel three lines, two microstrip lines, and four short-circuit branches. The first and second parallel three lines are symmetrical about the first parallel line; the first and second short-circuit branches are symmetrical about the first microstrip line; and the third and fourth short-circuit branches are symmetrical about the second microstrip line. The first and second parallel three lines, the first parallel line, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch, and the fourth short-circuit branch are parallel to each other and perpendicular to the first and second microstrip lines.

[0038] Furthermore, the electrical length of the first parallel line, the electrical length of the first three parallel lines, and the electrical length of the second three parallel lines are equal, and are all equal to a quarter wavelength corresponding to the center frequency of the broadband filter.

[0039] Furthermore, the electrical length of the first microstrip line is equal to the electrical length of the second microstrip line;

[0040] The electrical length of the first short-circuit branch, the electrical length of the second short-circuit branch, the electrical length of the third short-circuit branch, and the electrical length of the fourth short-circuit branch are equal.

[0041] Furthermore, the sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit branch is greater than the electrical length of the first parallel line; the sum of the electrical length of the first microstrip line and the electrical length of the second short-circuit branch is greater than the electrical length of the first parallel line;

[0042] The sum of the electrical lengths of the second microstrip line and the third short-circuit branch is greater than the electrical length of the first parallel line; the sum of the electrical lengths of the second microstrip line and the fourth short-circuit branch is greater than the electrical length of the first parallel line.

[0043] Furthermore, the odd-mode characteristic impedance of the first three parallel lines is equal to the odd-mode characteristic impedance of the second three parallel lines; the even-mode characteristic impedance of the first three parallel lines is equal to the even-mode characteristic impedance of the second three parallel lines. In this embodiment, the odd-mode characteristic impedance of the first three parallel lines is set to Z o2, the even-mode characteristic impedance of the first parallel three-wire and the even-mode characteristic impedance of the second parallel three-wire are set to Z e2 The odd-mode characteristic impedance of the first parallel line is recorded as Z o1 ; The even-mode characteristic impedance of the first parallel line is recorded as Z e1 .

[0044] Furthermore, the characteristic impedance of the first microstrip line and the characteristic impedance of the second microstrip line are equal. In this embodiment, the characteristic impedance of the first microstrip line and the characteristic impedance of the second microstrip line are set to Z1.

[0045] Furthermore, the characteristic impedance of the first short-circuit stub, the characteristic impedance of the second short-circuit stub, the characteristic impedance of the third short-circuit stub, and the characteristic impedance of the fourth short-circuit stub are all equal and are twice the characteristic impedance of the first microstrip line or the characteristic impedance of the second microstrip line. In this embodiment, the characteristic impedance of the first short-circuit stub, the characteristic impedance of the second short-circuit stub, the characteristic impedance of the third short-circuit stub, and the characteristic impedance of the fourth short-circuit stub are set to 2Z1.

[0046] The following is an analysis of this topology. Since this topology can be considered a symmetrical structure, its transmission poles can be calculated using the odd-even mode method. To simplify the calculation process, we first assume that the sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit branch is equal to the electrical length of the first parallel three-wire. At this time, Figure 2 is the odd-mode form of the simplified topological structure. The electrical length of the odd-mode transmission line is the electrical length of the first parallel line; and the characteristic impedance of the odd-mode transmission line is the odd-mode characteristic impedance of the first parallel line.

[0047] When Y ino = 0, it can be concluded that the topology has four transmission poles. When f0 is the center frequency of the bandpass filter, the frequencies corresponding to the four odd-mode transmission poles are:

[0048]

[0049] Here

[0050] Δ o1 =2Z o2 (Z e2 -Z o2 )

[0051] Δ o2 =4Z1Z o1 (Z e2 +Z o2 )+8Z1Z e2 Z o2 +Z o1 (Z e2 -Z o2 ) 2

[0052] Δ o3 =4Z o1 Z e2 Z o2

[0053] Figure 3 It is an even-mode form of the simplified topological structure, wherein the electrical length of the even-mode transmission line is the electrical length of the first parallel line; and the characteristic impedance of the even-mode transmission line is the even-mode characteristic impedance of the first parallel line.

[0054] When Y ine = 0, it can be concluded that the topology has four transmission poles. When f0 is the center frequency of the bandpass filter, the frequencies corresponding to the four even-mode transmission poles are:

[0055]

[0056] Here

[0057] Δ e1 =2Z e2 (Z e2 -Z o2 )

[0058] Δ e2 =4Z1Z e1 (Z e2 +Z o2 )+8Z1Z e2 Z o2 +Z e1 (Z e2 -Z o2 ) 2

[0059] Δ e3 =4Z e1 Z e2 Z o2

[0060] For this topology, its transmission zero can be calculated by the following method: multiply the ABCD matrices of the cascaded resonators that make up the topology in sequence to obtain the ABCD matrix corresponding to the topology; and convert the ABCD matrix of the topology into the corresponding S matrix. 21 When |=0, it can be concluded that this topology has two transmission zeros, and the frequencies corresponding to the two transmission zeros are:

[0061] f z1 =0

[0062] f z2 =2f0

[0063] From the above analysis, it can be seen that when the sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit stub is equal to a quarter wavelength corresponding to the center frequency of the broadband bandpass filter, the topology has four odd-mode transmission poles, four even-mode transmission poles, and two transmission zeros. Returning to this topology, when the sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit stub is appropriately increased, two additional transmission zeros (f z3 ,f z4 ,f z5 ), but the number of original zeros and poles remains unchanged. And no matter how the parameter Z is changed o1 , Z e1 , Z o2 , Z e2 , the value of Z1, the relative position of the transmission zero pole, that is, f z1 <f z3 <f ep1 <f op1 <f op2 <f ep2 <f ep3 <f op3 <f op 4 <f ep4 <f z4 <f z2 <f z5 , will not change. Therefore, based on this topology, a broadband bandpass filter can be designed with eight transmission poles in the passband to ensure its in-band flatness and two transmission zeros in the stopband to ensure high selectivity and high isolation.

[0064] An embodiment of the present invention provides a filter including any of the above-mentioned topological structures.

[0065] Furthermore, the filter also includes a circuit board, the circuit board has a dielectric constant of 3.38, a dielectric loss of 0.0022, a thickness of 0.813 mm, and a size of 37.6 mm*9.5 mm.

[0066] Furthermore, the line width of the transmission line in the first parallel three lines and the second parallel three lines is set to w T =0.2mm, line spacing is set to s T =0.1mm, line length is set to l T =10.2mm;

[0067] The line width of the transmission line in the first parallel line is set to w p =0.2mm, line spacing is set to s p =0.1mm, line length is set to l p =10.2mm;

[0068] The line lengths of the first microstrip line and the second microstrip line are both set to l1=4.1 mm, and the line widths are both set to w1=1.8 mm;

[0069] The line lengths of the first short-circuit branch, the second short-circuit branch, the third short-circuit branch, and the fourth short-circuit branch are all set to l2 = 7.3 mm, and the line widths are all set to w2 = 0.9 mm.

[0070] The S parameter simulation results of the bandpass filter corresponding to the optimized size are as follows: Figure 5 As shown in the figure. Its passband, with a reflection coefficient better than -10dB, ranges from 2.18GHz to 7.04GHz, with a center frequency of 4.61GHz, an absolute bandwidth of 4.86GHz, and a relative bandwidth of 105.4%. Furthermore, because the microstrip lines in the theoretical model are independent of each other, while in the simulation model they interact, one transmission pole within the passband is merged with an adjacent transmission pole and is not displayed. The simulation results show only seven transmission poles, located at 2.24, 2.72, 2.86, 4.08, 5.16, 6.39, and 6.95GHz. These seven transmission poles ensure passband flatness. There are five transmission zeros in the stopband, located at 0, 0.26, 8.28, 10.2, and 10.58GHz, respectively. These five transmission zeros ensure the filter's high selectivity, wide stopband, and high isolation.

[0071] It can be seen from the above that the topological structure design of this embodiment has the advantages of miniaturization, high selectivity, wide stopband and high isolation.

[0072] 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 by utilizing the contents of the present invention specification and drawings under the utility model concept, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A miniaturized broadband filter topology, characterized in that: It includes three first parallel lines, a first parallel line, and three second parallel lines connected in sequence, wherein the other end of the first three parallel lines is connected to the input end, and the other end of the second three parallel lines is connected to the output end; A first microstrip line is connected between the first three parallel lines and the first parallel line, and a first short-circuit branch and a second short-circuit branch are symmetrically connected at the other end of the first microstrip line; A second microstrip line is connected between the second three parallel lines and the first parallel line, and a third short-circuit branch and a fourth short-circuit branch are symmetrically connected to the other end of the second microstrip line; The first three parallel lines, the first parallel line, the second three parallel lines, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are all arranged along the first direction, the first microstrip line and the second microstrip line are both arranged along the second direction, and the first direction is perpendicular to the second direction.

2. The miniaturized broadband filter topology structure according to claim 1, characterized in that: The electrical length of the first parallel line, the electrical length of the first three parallel lines, and the electrical length of the second three parallel lines are equal, and are all equal to a quarter wavelength corresponding to the center frequency of the broadband filter.

3. The miniaturized broadband filter topology structure according to claim 2, characterized in that: The electrical length of the first microstrip line is equal to the electrical length of the second microstrip line; The electrical length of the first short-circuit branch, the electrical length of the second short-circuit branch, the electrical length of the third short-circuit branch, and the electrical length of the fourth short-circuit branch are equal.

4. The miniaturized broadband filter topology structure according to claim 3, characterized in that: The sum of the electrical length of the first microstrip line and the electrical length of the first short-circuit branch is greater than the electrical length of the first parallel line; the sum of the electrical length of the first microstrip line and the electrical length of the second short-circuit branch is greater than the electrical length of the first parallel line; The sum of the electrical lengths of the second microstrip line and the third short-circuit branch is greater than the electrical length of the first parallel line; the sum of the electrical lengths of the second microstrip line and the fourth short-circuit branch is greater than the electrical length of the first parallel line.

5. The miniaturized broadband filter topology structure according to claim 1, characterized in that: The odd-mode characteristic impedance of the first three parallel lines is equal to the odd-mode characteristic impedance of the second three parallel lines; the even-mode characteristic impedance of the first three parallel lines is equal to the even-mode characteristic impedance of the second three parallel lines.

6. The miniaturized broadband filter topology structure according to claim 5, characterized in that: The characteristic impedance of the first microstrip line is equal to the characteristic impedance of the second microstrip line.

7. The miniaturized broadband filter topology structure according to claim 6, characterized in that: The characteristic impedance of the first short-circuit branch, the characteristic impedance of the second short-circuit branch, the characteristic impedance of the third short-circuit branch and the characteristic impedance of the fourth short-circuit branch are all equal and are twice the characteristic impedance of the first microstrip line or the characteristic impedance of the second microstrip line.

8. A filter, characterized in that: The topological structure includes any one of claims 1 to 7.

9. The filter according to claim 8, characterized in that The filter further includes a circuit board having a dielectric constant of 3.38, a dielectric loss of 0.0022, a thickness of 0.813 mm, and a size of 37.6 mm*9.5 mm.

10. The filter according to claim 9, characterized in that The line width of the transmission lines in the first parallel three lines and the second parallel three lines is set to w T =0.2mm, line spacing is set to s T =0.1mm, line length is set to l T =10.2mm; The line width of the transmission line in the first parallel line is set to w p =0.2mm, line spacing is set to s p =0.1mm, line length is set to l p =10.2mm; The line lengths of the first microstrip line and the second microstrip line are both set to l1=4.1 mm, and the line widths are both set to w1=1.8 mm; The line lengths of the first short-circuit branch, the second short-circuit branch, the third short-circuit branch, and the fourth short-circuit branch are all set to l2 = 7.3 mm, and the line widths are all set to w2 = 0.9 mm.

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