Topological structure and 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 seventh micro-strip line, an eighth 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 sequentially connected with the first microstrip line and the input end, and the second end of the first transmission line is sequentially connected with the second microstrip line, the third microstrip line, the fourth microstrip line and the first open-circuit branch knot. The first end of the second transmission line is sequentially connected with the fifth microstrip line, the sixth microstrip line, the seventh microstrip line and the second open circuit branch knot, and the second end of the second transmission line is sequentially connected with the eighth microstrip line and the output end. The invention further discloses a wide dual-passband filter based on the topological structure, and the wide dual-passband filter has the advantage of miniaturization.

Description

Technical Field

[0001] The present invention relates to the technical field of filters, and in particular to a topological structure and a 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, the microstrip dual-passband filter with low cost, light weight, low profile and easy integration has attracted the attention of many scholars and engineers and has been studied in depth. However, most of the wide dual-passband filters reported so far have the defect of large size, which seriously affects their use in modern high-speed transmission information communication systems. 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 topology structure and a wide dual-passband filter, 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 seventh microstrip line, an eighth 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 first microstrip line and the input end in sequence, a second end of the first transmission line is connected to the second microstrip line, the third microstrip line, the fourth microstrip line and the first open branch in sequence, a first end of the second transmission line is connected to the fifth microstrip line, the sixth microstrip line, the seventh microstrip line and the second open branch in sequence, and a second end of the second transmission line is connected to the eighth microstrip line and the output end in sequence.

[0006] Optionally, the parallel lines, the third microstrip line, the sixth microstrip line, the first open branch and the second open branch are parallel to each other and are perpendicular to the first microstrip line, the second microstrip line, the fourth microstrip line, the fifth microstrip line, the seventh microstrip line and the eighth 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 second microstrip line, the third microstrip line, the fourth microstrip line, and the first open stub are distributed in a "mouth" shape, and the fifth microstrip line, the sixth microstrip line, the seventh microstrip line, and the second open stub are distributed in a "mouth" shape.

[0009] Optionally, the electrical length of the parallel lines is 0.25λ; the electrical length of the first microstrip line is equal to the electrical length of the eighth microstrip line, the electrical length of the second microstrip line is equal to the electrical length of the fifth microstrip line, the electrical length of the third microstrip line is equal to the electrical length of the sixth microstrip line, the electrical length of the fourth microstrip line is equal to the electrical length of the seventh microstrip line, and the electrical length of the first open stub is equal to the electrical length of the second open stub; the sum of the electrical lengths of the first microstrip line, the second microstrip line, the third microstrip line, the fourth microstrip line, and the first 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.

[0010] Optionally, the sum of the electrical lengths of the second microstrip line, the third microstrip line, the fourth microstrip line, and the first open stub is greater than the electrical length of the first microstrip line.

[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 seventh microstrip line, the eighth 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 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 7.6 mm * 6.8 mm.

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

[0016] l P = 6.4 mm, l P represents the physical length of the parallel lines;

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

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

[0019] l1=1.5 mm, l1 represents the physical length of the first microstrip line and the physical length of the eighth microstrip line;

[0020] l2=1.8 mm, l2 represents the physical length of the second microstrip line and the physical length of the fifth microstrip line;

[0021] l3=2.7 mm, l3 represents the physical length of the third microstrip line and the physical length of the sixth microstrip line;

[0022] l4=1 mm, l4 represents the physical length of the fourth microstrip line and the physical length of the seventh microstrip line;

[0023] l5=1.3 mm, where l5 represents the physical length of the first open branch and the physical length of the second open branch;

[0024] 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 seventh microstrip line, the physical width of the eighth microstrip line, the physical width of the first open branch node and the physical width of the second open branch node.

[0025] 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 miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Shown is a schematic diagram of the topological structure of an embodiment of the present invention;

[0027] Figure 2 Shown is a schematic diagram of an odd-mode form of a topological structure of an embodiment of the present invention;

[0028] Figure 3 Shown is a schematic diagram of an even-mode form of a topological structure of an embodiment of the present invention;

[0029] Figure 4 Shown is a layout diagram of a wide dual-passband filter according to an embodiment of the present invention;

[0030] Figure 5Another layout diagram of the wide dual-passband filter according to an embodiment of the present invention is shown;

[0031] 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

[0032] 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.

[0033] Please refer to Figure 1-3 As shown, the first embodiment of the present invention is:

[0034] A topological structure mainly consists of a parallel line, eight 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 seventh microstrip line, an eighth 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; the first end of the first transmission line is sequentially connected to the first microstrip line and the input end, the second end of the first transmission line is sequentially connected to the second microstrip line, the third microstrip line, the fourth microstrip line and the first open branch, the first end of the second transmission line is sequentially connected to the fifth microstrip line, the sixth microstrip line, the seventh microstrip line and the second open branch, and the second end of the second transmission line is sequentially connected to the eighth microstrip line and 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.

[0035] The parallel lines, the third microstrip line, the sixth microstrip line, the first open branch and the second open branch are parallel to each other and are perpendicular to the first microstrip line, the second microstrip line, the fourth microstrip line, the fifth microstrip line, the seventh microstrip line and the eighth microstrip line.

[0036] The second microstrip line, the third microstrip line, the fourth microstrip line and the first open branch are distributed in a "mouth" shape, and the fifth microstrip line, the sixth microstrip line, the seventh microstrip line and the second open branch are distributed in a "mouth" shape.

[0037] The electrical length of the parallel lines is 0.25λ; the electrical length of the first microstrip line is equal to the electrical length of the eighth microstrip line, the electrical length of the second microstrip line is equal to the electrical length of the fifth microstrip line, the electrical length of the third microstrip line is equal to the electrical length of the sixth microstrip line, the electrical length of the fourth microstrip line is equal to the electrical length of the seventh microstrip line, and the electrical length of the first open branch is equal to the electrical length of the second open branch; the sum of the electrical lengths of the first microstrip line, the second microstrip line, the third microstrip line, the fourth microstrip line and the first 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. The sum of the electrical lengths of the second microstrip line, the third microstrip line, the fourth microstrip line and the first open branch is greater than the electrical length of the first microstrip line.

[0038] 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 characteristic impedance of the fifth microstrip line, the characteristic impedance of the sixth microstrip line, the characteristic impedance of the seventh microstrip line, the characteristic impedance of the eighth microstrip line, the characteristic impedance of the first open branch node and the characteristic impedance of the second open branch node are equal and are all Z1.

[0039] Since this topology is equivalent to a symmetrical structure, its transmission poles can be obtained by odd-even mode analysis. In order to more easily calculate the transmission poles of this topology, first assume that the sum of the electrical lengths of the second microstrip line, the third microstrip line, the fourth microstrip line, and the first short-circuit branch is much greater than the electrical length of the first microstrip line. At this time, 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 .

[0040] When Y ino= 0, it can be concluded that the topology has two transmission poles. When f0 is the center frequency of the stopband between the two passbands, the frequencies corresponding to the two odd-mode transmission poles are:

[0041]

[0042] The even mode form of this topology 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 .

[0043] When Y ine = 0, it can be concluded that the topology has two even-mode transmission poles. When f0 is the center frequency of the stopband between the two passbands, the frequencies corresponding to the two even-mode transmission poles are:

[0044]

[0045]

[0046] For this topology, the transmission zero can be calculated using the following formula:

[0047]

[0048] After calculation, it can be concluded that the topology has three transmission zeros, and the frequencies corresponding to the three transmission zeros are:

[0049] f z1 =0

[0050] f z2 =f0

[0051] f z3 =2f0

[0052] 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 the value of Z1, the relative position of the transmission zero pole, that is, f z1 <f ep1 <f op1 <f2<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.

[0053] Please refer to Figure 4-6 As shown, the second embodiment of the present invention is:

[0054] A 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 7.6 mm*6.8 mm. Figure 4 and 5 FIG. 1 is a layout diagram of the wide dual-passband filter of this embodiment. In the figure, 10 represents the input end, and 50 represents the output end.

[0055] The specific parameters on the circuit board are set as follows:

[0056] l P =6.4mm, l P represents the physical length of the parallel line 30;

[0057] s P =0.1mm,s P represents the distance between the first transmission line 301 and the second transmission line 302;

[0058] w P =0.1mm, w P represents the physical width of the first transmission line 301 and the physical width of the second transmission line 302;

[0059] l1=1.5 mm, l1 represents the physical length of the first microstrip line 20 and the physical length of the eighth microstrip line 27;

[0060] l2=1.8 mm, l2 represents the physical length of the second microstrip line 21 and the physical length of the fifth microstrip line 24;

[0061] l3=2.7 mm, l3 represents the physical length of the third microstrip line 22 and the physical length of the sixth microstrip line 25;

[0062] l4=1 mm, l4 represents the physical length of the fourth microstrip line 23 and the physical length of the seventh microstrip line 26;

[0063] l5=1.3 mm, l5 represents the physical length of the first open branch 40 and the physical length of the second open branch 41;

[0064] w1=0.1mm, w1 represents the physical width of the first microstrip line 20, the physical width of the second microstrip line 21, the physical width of the third microstrip line 22, the physical width of the fourth microstrip line 23, the physical width of the fifth microstrip line 24, the physical width of the sixth microstrip line 25, the physical width of the seventh microstrip line 26, the physical width of the eighth microstrip line 27, the physical width of the first open branch 40 and the physical width of the second open branch 41.

[0065] The simulation results of the wide dual-channel filter of this embodiment are as follows: Figure 6 As 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 2.89 to 4.43GHz, the passband center frequency is 3.66GHz, the passband absolute bandwidth is 1.54GHz, and the passband relative bandwidth is 42.1%; in its second passband, the impedance bandwidth with a reflection coefficient less than -10dB ranges from 9.41 to 10.75GHz, the passband center frequency is 10.08GHz, the passband absolute bandwidth is 1.34GHz, and the passband relative bandwidth is 13.3%. 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 0.5dB; in the second passband, the maximum insertion loss is 0.62dB. It can be seen that the wide dual-passband filter based on this topology has a low insertion loss characteristic.

[0066] In addition, there are two transmission poles in the first passband, located at 3.25 and 4.01 GHz respectively, and there are two transmission poles in the second passband, located at 9.79 and 10.45 GHz respectively. These four transmission poles can ensure the flatness in the passband.

[0067] There are three transmission zeros in the stopband, located at 0, 6.95, and 14.53 GHz. These three transmission zeros ensure high isolation of the wide dual-passband filter.

[0068] In summary, the topological structure proposed in the present invention can be used to design a wide dual-passband filter. The wide dual-passband filter designed based on the topological structure has the advantage of miniaturization.

[0069] 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 seventh microstrip line, an eighth 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 first microstrip line and the input end in sequence, a second end of the first transmission line is connected to the second microstrip line, the third microstrip line, the fourth microstrip line and the first open branch in sequence, a first end of the second transmission line is connected to the fifth microstrip line, the sixth microstrip line, the seventh microstrip line and the second open branch in sequence, and a second end of the second transmission line is connected to the eighth microstrip line and the output end in sequence.

2. The topological structure according to claim 1, characterized in that: The parallel lines, the third microstrip line, the sixth microstrip line, the first open branch and the second open branch are parallel to each other and are perpendicular to the first microstrip line, the second microstrip line, the fourth microstrip line, the fifth microstrip line, the seventh microstrip line and the eighth 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 second microstrip line, the third microstrip line, the fourth microstrip line and the first open branch are distributed in a "mouth" shape, and the fifth microstrip line, the sixth microstrip line, the seventh 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 electrical length of the parallel lines is 0.25λ; the electrical length of the first microstrip line is equal to the electrical length of the eighth microstrip line, the electrical length of the second microstrip line is equal to the electrical length of the fifth microstrip line, the electrical length of the third microstrip line is equal to the electrical length of the sixth microstrip line, the electrical length of the fourth microstrip line is equal to the electrical length of the seventh microstrip line, and the electrical length of the first open branch node is equal to the electrical length of the second open branch node; The sum of the electrical lengths of the first microstrip line, the second microstrip line, the third microstrip line, the fourth microstrip line and the first open-circuit 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.

6. The topological structure according to claim 1, characterized in that: The sum of the electrical length of the second microstrip line, the electrical length of the third microstrip line, the electrical length of the fourth microstrip line and the electrical length of the first open branch is greater than the electrical length of the first microstrip line.

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 characteristic impedance of the fifth microstrip line, the characteristic impedance of the sixth microstrip line, the characteristic impedance of the seventh microstrip line, the characteristic impedance of the eighth microstrip line, the characteristic impedance of the first open branch and the characteristic impedance of the second open branch are equal.

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

9. The 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 7.6 mm*6.8 mm.

10. The wide dual passband filter according to claim 9, characterized in that: The specific parameters on the circuit board are set as follows: l P =6.4mm, 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=1.5 mm, l1 represents the physical length of the first microstrip line and the physical length of the eighth microstrip line; l2=1.8 mm, l2 represents the physical length of the second microstrip line and the physical length of the fifth microstrip line; l3=2.7 mm, l3 represents the physical length of the third microstrip line and the physical length of the sixth microstrip line; l4=1 mm, l4 represents the physical length of the fourth microstrip line and the physical length of the seventh microstrip line; l5=1.3 mm, where l5 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 seventh microstrip line, the physical width of the eighth 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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