Topological structure and structure compact type wide dual-passband filter

Abstract

The topological structure comprises a parallel line, a first micro-strip line, a second micro-strip line, a third micro-strip line, a fourth micro-strip line, a fifth micro-strip line, a sixth micro-strip line, a first open-circuit branch knot, a second open-circuit branch knot, an input end and an output end, and the parallel line is composed of a first transmission line and a second transmission line which are arranged in parallel; the first end of the first transmission line is connected with the input end, and the second end of the first transmission line is sequentially connected with the first microstrip line, the second microstrip line, the third microstrip line and the first open circuit branch. The first end of the second transmission line is sequentially connected with the fourth microstrip line, the fifth microstrip line, the sixth microstrip line and the second open circuit branch knot, and the second end of the second transmission line is connected with the output end. The invention further discloses a compact-structure wide dual-passband filter based on the topological structure, and the compact-structure wide dual-passband filter has the advantage of miniaturization.

Description

Technical Field

[0001] The invention relates to the technical field of filters, and in particular to a topological structure and a compact wide dual-passband filter. Background Art

[0002] With the rapid development of modern wireless communication technology, the RF receiving front end needs to be compatible with different communication standards and provide more abundant services to meet people's growing demand for digital applications. In this context, microstrip dual-passband filters with low cost, light weight, low profile and easy integration have attracted the attention of many scholars and engineers and have been studied in depth. However, most of the wide dual-passband filters reported so far have the defect of non-compact structure, which seriously affects their use in modern miniaturized communication systems with high-speed information transmission. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the main purpose of the present invention is to provide a wide dual-passband filter with a topological structure and a compact structure, aiming to solve the problem of large size of the existing wide dual-passband filter.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A topological structure includes parallel lines, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, a first open branch, a second open branch, an input end and an output end, wherein the parallel lines are composed of a first transmission line and a second transmission line arranged in parallel; a first end of the first transmission line is connected to the input end, a second end of the first transmission line is connected to the first microstrip line, the second microstrip line, the third microstrip line and the first open branch in sequence, a first end of the second transmission line is connected to the fourth microstrip line, the fifth microstrip line, the sixth microstrip line and the second open branch in sequence, and a second end of the second transmission line is connected to the output end.

[0006] Optionally, the parallel lines, the second microstrip line, the fifth microstrip line, the first open branch node and the second open branch node are parallel to each other and are perpendicular to the first microstrip line, the third microstrip line, the fourth microstrip line and the sixth microstrip line.

[0007] Optionally, the first end of the first transmission line and the first end of the second transmission line are located on the same side, and the second end of the first transmission line and the second end of the second transmission line are located on the same side.

[0008] Optionally, the first microstrip line, the second microstrip line, the third microstrip line, and the first open stub are distributed in a "mouth" shape, and the fourth microstrip line, the fifth microstrip line, the sixth microstrip line, and the second open stub are distributed in a "mouth" shape.

[0009] Optionally, the first transmission line and the second transmission line are arranged in a staggered manner, and the input end, the parallel line, and the output end are arranged in sequence along the same direction.

[0010] Optionally, the electrical length of the parallel line is 0.25λ; the sum of the electrical lengths of the first microstrip line, the second microstrip line, the third microstrip line, and the first open stub is 0.25λ; the sum of the electrical lengths of the fourth microstrip line, the fifth microstrip line, the sixth microstrip line, and the second open stub is 0.25λ; λ is the wavelength corresponding to the center frequency of the stopband between the two passbands of the dual-band filter based on the topological structure.

[0011] Optionally, the characteristic impedances of the first microstrip line, the second microstrip line, the third microstrip line, the fourth microstrip line, the fifth microstrip line, the sixth microstrip line, the first open stub, and the second open stub are equal.

[0012] Another technical solution adopted by the present invention is:

[0013] A structurally compact wide dual-band filter includes the above topological structure.

[0014] Optionally, it further includes a circuit board. The topological structure is disposed on the 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 11.8 mm * 5.8 mm.

[0015] Optionally, the specific parameters set on the circuit board are as follows:

[0016] l P = 8.2 mm, l P represents the physical length of the parallel line;

[0017] s P = 0.1 mm, s P represents the distance between the first transmission line and the second transmission line;

[0018] w P = 0.1 mm, w P represents the physical width of the first transmission line and the physical width of the second transmission line;

[0019] l 1 =2.05mm, l 1 represents the physical length of the first microstrip line and the physical length of the fourth microstrip line;

[0020] l 2 =4.8mm, l 2 represents the physical length of the second microstrip line and the physical length of the fifth microstrip line;

[0021] l 3 =1.4mm, l 3 represents the physical length of the third microstrip line and the physical length of the sixth microstrip line;

[0022] l 4 =1.3mm, l 4 Indicates the physical length of the first open branch and the physical length of the second open branch;

[0023] w 1 =0.1mm, w 1 Represents the physical width of the first microstrip line, the physical width of the second microstrip line, the physical width of the third microstrip line, the physical width of the fourth microstrip line, the physical width of the fifth microstrip line, the physical width of the sixth microstrip line, the physical width of the first open branch node, and the physical width of the second open branch node.

[0024] The beneficial effect of the present invention is that a new topological structure is proposed, based on which a wide dual-passband filter can be designed, which has the advantage of a compact structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Shown is a schematic diagram of the topological structure of an embodiment of the present invention;

[0026] Figure 2 Shown is a schematic diagram of an odd-mode form of a topological structure of an embodiment of the present invention;

[0027] Figure 3 Shown is a schematic diagram of an even-mode form of a topological structure of an embodiment of the present invention;

[0028] Figure 4 Shown is a layout diagram of a wide dual-passband filter according to an embodiment of the present invention;

[0029] Figure 5 Another layout diagram of the wide dual-passband filter according to an embodiment of the present invention is shown;

[0030] Figure 6 Shown is the S parameter simulation result of the wide dual-passband filter according to the embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to more clearly understand the technical content, achieved purposes and effects of the present invention, the present invention is described in detail below in conjunction with specific implementation methods and in conjunction with the accompanying drawings. It should be noted that, in the absence of conflict, the implementation methods of the present invention and the features in the implementation methods can be combined with each other. In the following description, many specific details are set forth in order to fully understand the present invention. The described implementation methods are only part of the implementation methods of the present invention, not all implementation methods. Based on the implementation methods in the present invention, all other implementation methods obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0032] Please refer to Figure 1-3 As shown, the first embodiment of the present invention is:

[0033] A topological structure mainly consists of a parallel line, six microstrip lines and two open branches. Figure 1 As shown, it includes parallel lines, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, a first open branch, a second open branch, an input end and an output end. The parallel lines are composed of a first transmission line and a second transmission line that are parallel and staggered; the input end, the parallel lines and the output end are arranged in sequence along the horizontal direction. The first end of the first transmission line is connected to the input end, the second end of the first transmission line is connected to the first microstrip line, the second microstrip line, the third microstrip line and the first open branch in sequence, the first end of the second transmission line is connected to the fourth microstrip line, the fifth microstrip line, the sixth microstrip line and the second open branch in sequence, and the second end of the second transmission line is connected to the output end. The first end of the first transmission line and the first end of the second transmission line are located on the same side, and the second end of the first transmission line and the second end of the second transmission line are located on the same side.

[0034] The parallel lines, the second microstrip line, the fifth microstrip line, the first open branch node and the second open branch node are parallel to each other and are perpendicular to the first microstrip line, the third microstrip line, the fourth microstrip line and the sixth microstrip line.

[0035] The first microstrip line, the second microstrip line, the third microstrip line and the first open branch are distributed in a "mouth" shape, and the fourth microstrip line, the fifth microstrip line, the sixth microstrip line and the second open branch are distributed in a "mouth" shape.

[0036] The electrical length of the parallel lines is 0.25λ; the sum of the electrical lengths of the first microstrip line, the second microstrip line, the third microstrip line and the first open branch is 0.25λ; the sum of the electrical lengths of the fourth microstrip line, the fifth microstrip line, the sixth microstrip line and the second open branch is 0.25λ; λ is the wavelength corresponding to the center frequency of the stopband between the two passbands of the dual-passband filter based on the topological structure.

[0037] The odd-mode characteristic impedance of the parallel line is Z oo , the even-mode characteristic impedance of the parallel line is Z oe , the characteristic impedance of the first microstrip line, 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 fifth microstrip line, the sixth microstrip line, the characteristic impedance of the first open-circuit branch and the characteristic impedance of the second open-circuit branch are equal and are all Z 1 .

[0038] Since this topology is equivalent to a symmetrical structure, its transmission poles can be obtained by odd-even mode analysis. The odd-mode form of this topology is as follows: Figure 2 As shown, the electrical length of the odd-mode transmission line is a quarter wavelength corresponding to the stopband center frequency between the two passbands of the dual-passband filter based on the topology structure, that is, 0.25λ, and the characteristic impedance of the odd-mode transmission line is Z oo .

[0039] When Y ino = 0, it can be concluded that the topology has two transmission poles. 0 When is the center frequency of the stopband between the two passbands, the frequencies corresponding to the two odd-mode transmission poles are:

[0040]

[0041] The even mode form of this topological structure is as follows Figure 3 As shown, the electrical length of the even-mode transmission line is a quarter wavelength corresponding to the stopband center frequency between the two passbands of the dual-passband filter based on the topology structure, that is, 0.25λ, and the characteristic impedance of the even-mode transmission line is Z oe .

[0042] When Y ine = 0, it can be concluded that the topology has two even-mode transmission poles. 0 When is the center frequency of the stopband between the two passbands of the dual-passband filter based on the topology, the frequencies corresponding to the two even-mode transmission poles are:

[0043]

[0044] For this topology, its transmission zero point 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 three transmission zeros, and the frequencies corresponding to the three transmission zeros are:

[0045] f z1 =0

[0046] f z2 =f 0

[0047] f z3 =2f 0

[0048] From the above analysis, it can be seen that the filter based on this topology has two odd-mode transmission poles, three even-mode transmission poles and three transmission zeros. oo , Z oe and Z 1 The value of the transmission zero and pole relative position, that is, f z1 <f ep1 <f op1 <f 2 <f op2 <f ep2 <f z3 , will not change. Therefore, based on this topology, a dual-passband filter can be designed, and there are two transmission poles in each of the two passbands to ensure its in-band flatness, a transmission zero below the first passband edge and above the fourth passband edge to ensure high selectivity, and a transmission zero between the second passband edge and the third passband edge to ensure high isolation.

[0049] Please refer to Figure 4-6 As shown, the second embodiment of the present invention is:

[0050] A compact wide dual-passband filter comprises a circuit board and the topological structure described in the first embodiment, wherein the topological structure is arranged on the circuit board, and 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 11.8 mm*5.8 mm. Figure 4 and 5 The layout diagram of the compact wide dual-passband filter of this embodiment is shown in FIG. 10 in the figure represents the input end, and 50 represents the output end.

[0051] The specific parameters on the circuit board are set as follows:

[0052] lP =8.2mm, l P represents the physical length of the parallel line 20;

[0053] s P =0.1mm,s P represents the distance between the first transmission line 201 and the second transmission line 202;

[0054] w P =0.1mm, w P represents the physical width of the first transmission line 201 and the physical width of the second transmission line 202;

[0055] l 1 =2.05mm, l 1 represents the physical length of the first microstrip line 30 and the physical length of the fourth microstrip line 33;

[0056] l 2 =4.8mm, l 2 represents the physical length of the second microstrip line 31 and the physical length of the fifth microstrip line 34;

[0057] l 3 =1.4mm, l 3 represents the physical length of the third microstrip line 32 and the physical length of the sixth microstrip line 35;

[0058] l 4 =1.3mm, l 4 represents the physical length 40 of the first open branch and the physical length 41 of the second open branch;

[0059] w 1 =0.1mm, w 1 It represents the physical width of the first microstrip line 30 , the physical width of the second microstrip line 31 , the physical width of the third microstrip line 32 , the physical width of the fourth microstrip line 33 , the physical width of the fifth microstrip line 34 , the physical width of the sixth microstrip line 35 , the physical width of the first open branch 40 , and the physical width of the second open branch 41 .

[0060] The simulation results of the compact wide dual-passband filter of this embodiment are shown in FIG. Figure 6As shown. It can be seen from the figure that in the first passband, the impedance bandwidth with a reflection coefficient less than -10dB ranges from 2.42 to 3.72GHz, the passband center frequency is 3.07GHz, the passband absolute bandwidth is 1.3GHz, and the passband relative bandwidth is 42.3%; in its second passband, the impedance bandwidth with a reflection coefficient less than -10dB ranges from 7.69 to 8.94GHz, the passband center frequency is 8.315GHz, the passband absolute bandwidth is 1.25GHz, and the passband relative bandwidth is 15%. From the bandwidth simulation of the two passbands, it can be seen that the dual-passband filter based on this topology is a wide dual-passband filter. In the first passband, the maximum insertion loss is 0.55dB; in the second passband, the maximum insertion loss is 0.61dB. It can be seen that the wide dual-passband filter based on this topology has a low insertion loss characteristic.

[0061] In addition, there are two transmission poles in the first passband, located at 2.72 and 3.39 GHz respectively, and there are two transmission poles in the second passband, located at 8.08 and 8.66 GHz respectively. These four transmission poles can ensure the flatness in the passband.

[0062] There are three transmission zeros in the stopband, located at 0, 5.61, and 10.46 GHz. These three transmission zeros ensure high isolation of the wide dual-passband filter.

[0063] In summary, the topological structure proposed in the present invention can be used to design a wide dual-passband filter. The compact wide dual-passband filter designed based on the topological structure has the advantage of miniaturization while ensuring wide channels and low insertion loss, and the size can be as small as 11.8mm*5.8mm.

[0064] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Therefore, any modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A topological structure, characterized in that: It includes parallel lines, a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, a first open branch, a second open branch, an input end and an output end. The parallel lines are composed of a first transmission line and a second transmission line arranged in parallel; a first end of the first transmission line is connected to the input end, a second end of the first transmission line is connected to the first microstrip line, the second microstrip line, the third microstrip line and the first open branch in sequence, a first end of the second transmission line is connected to the fourth microstrip line, the fifth microstrip line, the sixth microstrip line and the second open branch in sequence, and a second end of the second transmission line is connected to the output end.

2. The topological structure according to claim 1, characterized in that: The parallel lines, the second microstrip line, the fifth microstrip line, the first open branch node and the second open branch node are parallel to each other and are perpendicular to the first microstrip line, the third microstrip line, the fourth microstrip line and the sixth microstrip line.

3. The topological structure according to claim 1, characterized in that: The first end of the first transmission line and the first end of the second transmission line are located on the same side, and the second end of the first transmission line and the second end of the second transmission line are located on the same side.

4. The topological structure according to claim 1, characterized in that: The first microstrip line, the second microstrip line, the third microstrip line and the first open branch are distributed in a "mouth" shape, and the fourth microstrip line, the fifth microstrip line, the sixth microstrip line and the second open branch are distributed in a "mouth" shape.

5. The topological structure according to claim 1, characterized in that: The first transmission line and the second transmission line are arranged in a staggered manner, and the input end, the parallel line and the output end are arranged in sequence along the same direction.

6. The topological structure according to claim 1, characterized in that: The electrical length of the parallel lines is 0.25λ; the sum of the electrical lengths of the first microstrip line, the second microstrip line, the third microstrip line and the first open branch is 0.25λ; the sum of the electrical lengths of the fourth microstrip line, the fifth microstrip line, the sixth microstrip line and the second open branch is 0.25λ; λ is the wavelength corresponding to the center frequency of the stopband between the two passbands of the dual-passband filter based on the topological structure.

7. The topological structure according to claim 1, characterized in that: The characteristic impedance of the first microstrip line, 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 fifth microstrip line, the sixth microstrip line, the characteristic impedance of the first open branch and the characteristic impedance of the second open branch are equal.

8. A compact wide dual-passband filter, characterized in that: The topological structure comprises any one of claims 1 to 7.

9. The compact wide dual-passband filter according to claim 8, characterized in that: It also includes a circuit board, on which the topological structure is arranged. 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 11.8 mm*5.8 mm.

10. The compact wide dual-passband filter according to claim 9, characterized in that: The specific parameters on the circuit board are set as follows: l P =8.2mm, l P represents the physical length of said parallel lines; s P =0.1mm,s P represents the distance between the first transmission line and the second transmission line; w P =0.1mm, w P represents a physical width of the first transmission line and a physical width of the second transmission line; l1=2.05 mm, l1 represents the physical length of the first microstrip line and the physical length of the fourth microstrip line; l2=4.8 mm, l2 represents the physical length of the second microstrip line and the physical length of the fifth microstrip line; l3=1.4 mm, l3 represents the physical length of the third microstrip line and the physical length of the sixth microstrip line; l4=1.3 mm, where l4 represents the physical length of the first open branch and the physical length of the second open branch; w1=0.1mm, w1 represents the physical width of the first microstrip line, the physical width of the second microstrip line, the physical width of the third microstrip line, the physical width of the fourth microstrip line, the physical width of the fifth microstrip line, the physical width of the sixth microstrip line, the physical width of the first open branch node and the physical width of the second open branch node.

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