Topological structure and wide stopband filter with narrow-pass characteristic
By designing a new topological structure, a wide stopband filter with narrow pass characteristics is solved, and a high selectivity and low loss signal transmission is achieved.
Patent Information
- Application Number
- CN202420424310.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-05
- Publication Date
- 2025-03-25
- Estimated Expiration
- 2034-03-05
AI Technical Summary
The existing wide stopband filters do not have narrow pass characteristics, which seriously affects the development of modern wireless communication systems.
A new topology is designed, including specific microstrip lines and open branch connections, to build a wide stopband filter with narrow pass characteristics.
The narrow pass characteristics and high selectivity of the wide stopband filter are realized, which can effectively suppress unnecessary noise and allow useful signals to pass low loss.
Smart Images
Figure CN222673275U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of filters, in particular to a topological structure and a wide stopband filter with narrow-pass characteristics. Background Art
[0002] In order to solve the contradiction between limited spectrum resources and the growing demand for information transmission, radio frequency systems working in different frequency bands and communication modes have been developed. In this context, wide stopband filters with high selectivity have extremely high scientific research and commercial value, attracting the attention of many scholars and engineers.
[0003] Analogous to wide passband filters with notch characteristics, wide stopband filters with narrow pass characteristics in the stopband can not only effectively suppress unwanted noise, but also allow useful signals to pass smoothly with low loss. Unfortunately, however, there are currently few reports on wide stopband filters with narrow pass characteristics, which seriously affects the development of modern wireless communication systems. Utility Model Content
[0004] In view of the above-mentioned deficiencies in the prior art, the main purpose of the present invention is to provide a topological structure and a wide stopband filter with narrowpass characteristics, aiming to solve the problem that the existing wide stopband filter does not have narrowpass characteristics.
[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is:
[0006] A topological structure includes 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, a third open branch, a fourth open branch, an input end, and an output end;
[0007] One end of the second microstrip line is respectively connected to one end of the third microstrip line and one end of the fourth microstrip line, the other end of the third microstrip line is connected to the first open branch, the other end of the fourth microstrip line is connected to the second open branch, the other end of the second microstrip line is respectively connected to one end of the first microstrip line, one end of the fifth microstrip line and one end of the sixth microstrip line, the other end of the fifth microstrip line is respectively connected to the third open branch and the fourth open branch, the other end of the first microstrip line is connected to the input end, and the other end of the sixth microstrip line is connected to the output end;
[0008] The second microstrip line and the fifth microstrip line are located on the same vertical line, the first microstrip line and the sixth microstrip line, the third microstrip line and the fourth microstrip line, the first open branch node and the second open branch node, the third open branch node and the fourth open branch node are all symmetrical about the second microstrip line, the first microstrip line, the third microstrip line, the fourth microstrip line, the sixth microstrip line, the third open branch node and the fourth open branch node are parallel to each other and are all perpendicular to the second microstrip line.
[0009] Optionally, the first microstrip line, the third microstrip line, the fourth microstrip line, the sixth microstrip line, the third open branch and the fourth open branch are all perpendicular to the first open branch and the second open branch.
[0010] Optionally, the electrical length of the first microstrip line is the same as the electrical length of the sixth microstrip line, and both are one-quarter wavelength corresponding to the center frequency of the stopband; the sum of the electrical length of the second microstrip line, the electrical length of the third microstrip line and the electrical length of the first open branch is one-half wavelength corresponding to the center frequency of the stopband; the sum of the electrical length of the second microstrip line, the electrical length of the fourth microstrip line and the electrical length of the second open branch is one-half wavelength corresponding to the center frequency of the stopband; the sum of the electrical length of the fifth microstrip line and the electrical length of the third open branch is one-quarter wavelength corresponding to the center frequency of the stopband; the sum of the electrical length of the fifth microstrip line and the electrical length of the fourth open branch is one-quarter wavelength corresponding to the center frequency of the stopband.
[0011] Optionally, the characteristic impedance of the first microstrip line is the same as the characteristic impedance of the sixth microstrip line; the characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the first open branch node and the characteristic impedance of the second open branch node are the same, and are all twice the characteristic impedance of the second microstrip line; the characteristic impedance of the third open branch node and the characteristic impedance of the fourth open branch node are the same, and are all twice the characteristic impedance of the fifth microstrip line.
[0012] Optionally, the topology structure includes two odd-mode transmission poles, five even-mode transmission poles and three transmission zeros.
[0013] Another technical solution adopted by the utility model is:
[0014] A wide stopband filter with narrow-pass characteristics comprises the above-mentioned topological structure.
[0015] Optionally, it also includes a circuit board, and the topological structure is arranged on the circuit board, the length of the first microstrip line is the same as the length of the sixth microstrip line, the length of the third microstrip line is the same as the length of the fourth microstrip line, the length of the first open branch node is the same as the length of the second open branch node, the length of the third open branch node is the same as the length of the fourth open branch node, the width of the first microstrip line is the same as the width of the sixth microstrip line, the width of the third microstrip line is the same as the width of the fourth microstrip line, the width of the first open branch node is the same as the width of the second open branch node, and the width of the third open branch node is the same as the width of the fourth open branch node.
[0016] Optionally, 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 24.2 mm*14.3 mm.
[0017] Optionally, the length of the first microstrip line and the length of the sixth microstrip line are both set to 9.5mm, the length of the second microstrip line is set to 5.9mm, the length of the third microstrip line and the length of the fourth microstrip line are both set to 10mm, the length of the first open branch node and the length of the second open branch node are both set to 5.5mm, the length of the fifth microstrip line is set to 1.7mm, the length of the third open branch node and the length of the fourth open branch node are both set to 7.8mm, the width of the first microstrip line and the width of the sixth microstrip line are both set to 0.1mm, the width of the second microstrip line is set to 1.6mm, the width of the third microstrip line and the width of the fourth microstrip line are both set to 0.8mm, the width of the first open branch node and the width of the second open branch node are both set to 0.8mm, the width of the fifth microstrip line is set to 0.2mm, and the width of the third open branch node and the width of the fourth open branch node are both set to 0.1mm.
[0018] The beneficial effect of the utility model is that a new topological structure is proposed, which can be used to design a wide stopband filter with narrow-pass characteristics. The wide stopband filter based on the topological structure has the advantages of narrow-pass characteristics and high selectivity. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 Shown is a schematic diagram of the topological structure of an embodiment of the utility model;
[0020] Figure 2 Shown is a schematic diagram of an odd-mode form of the topological structure of an embodiment of the utility model;
[0021] Figure 3 Shown is a schematic diagram of an even-mode form of the topological structure of an embodiment of the utility model;
[0022] Figure 4 Shown is the layout diagram of the wide stopband filter of the embodiment of the utility model;
[0023] Figure 5 Shown is the S parameter simulation result of the filter with narrow pass characteristics according to the embodiment of the utility model. DETAILED DESCRIPTION
[0024] In order to more clearly understand the technical content, achieved purposes and effects of the utility model, the utility model is described in detail below in combination with specific implementation methods and in conjunction with the accompanying drawings. It should be noted that the implementation methods of the utility model and the features in the implementation methods can be combined with each other without conflict. In the following description, many specific details are set forth in order to fully understand the utility model. The implementation methods described are only part of the implementation methods of the utility model, not all of the implementation methods. Based on the implementation methods in the utility model, all other implementation methods obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.
[0025] Please refer to Figure 1-3 As shown, the first embodiment of the utility model is:
[0026] A topology structure mainly consists of four open branches and six microstrip lines. Figure 1 As shown, it includes 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, a third open branch, a fourth open branch, an input end and an output end.
[0027] One end of the second microstrip line is respectively connected to one end of the third microstrip line and one end of the fourth microstrip line, the other end of the third microstrip line is connected to the first open branch, the other end of the fourth microstrip line is connected to the second open branch, the other end of the second microstrip line is respectively connected to one end of the first microstrip line, one end of the fifth microstrip line and one end of the sixth microstrip line, the other end of the fifth microstrip line is respectively connected to the third open branch and the fourth open branch, the other end of the first microstrip line is connected to the input end, and the other end of the sixth microstrip line is connected to the output end.
[0028] The second microstrip line and the fifth microstrip line are located on the same vertical line, the first microstrip line and the sixth microstrip line, the third microstrip line and the fourth microstrip line, the first open branch node and the second open branch node, the third open branch node and the fourth open branch node are symmetrical about the perpendicular midline of the second microstrip line and the perpendicular midline of the fifth microstrip line, the first microstrip line, the third microstrip line, the fourth microstrip line, the sixth microstrip line, the third open branch node and the fourth open branch node are parallel to each other, and are perpendicular to the second microstrip line, the fifth microstrip line, the first open branch node and the second open branch node.
[0029] The electrical length of the first microstrip line is the same as the electrical length of the sixth microstrip line, and both are one-quarter wavelength corresponding to the center frequency of the stopband; the sum of the electrical length of the second microstrip line, the electrical length of the third microstrip line and the electrical length of the first open branch is one-half wavelength corresponding to the center frequency of the stopband; the sum of the electrical length of the second microstrip line, the electrical length of the fourth microstrip line and the electrical length of the second open branch is one-half wavelength corresponding to the center frequency of the stopband; the sum of the electrical length of the fifth microstrip line and the electrical length of the third open branch is one-quarter wavelength corresponding to the center frequency of the stopband; the sum of the electrical length of the fifth microstrip line and the electrical length of the fourth open branch is one-quarter wavelength corresponding to the center frequency of the stopband.
[0030] The characteristic impedance of the first microstrip line is the same as the characteristic impedance of the sixth microstrip line, and both are Z1; the characteristic impedance of the second microstrip line is Z2; the characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the first open branch node and the characteristic impedance of the second open branch node are the same, and both are 2Z2; the characteristic impedance of the fifth microstrip line is Z3; the characteristic impedance of the third open branch node and the characteristic impedance of the fourth open branch node are the same, and both are 2Z3.
[0031] The topological structure includes two odd-mode transmission poles, five even-mode transmission poles and three transmission zeros.
[0032] Since the above topological structure is equivalent to a left-right symmetrical structure, its transmission poles can be obtained using the odd-even mode analysis method.
[0033] like Figure 2 is the odd-mode form of the topology. ino = 0, it can be concluded that the topology has two odd-mode transmission poles. When f0 is the center frequency of the band-stop filter, the frequencies corresponding to the two odd-mode transmission poles are:
[0034] f op1 =0
[0035] f op2 =2f0
[0036] like Figure 3 is the even-mode form of the topological structure. Here, the electrical length of the seventh microstrip line is equal to the electrical length of the second microstrip line, and the characteristic impedance of the seventh microstrip line is equal to twice the characteristic impedance of the second microstrip line; the electrical length of the eighth microstrip line is equal to the electrical length of the fifth microstrip line, and the characteristic impedance of the eighth microstrip line is equal to twice the characteristic impedance of the fifth microstrip line. When Y ine =∞, it can be concluded that the topology has five even-mode transmission poles, which are:
[0037]
[0038]
[0039]
[0040]
[0041]
[0042] in,
[0043]
[0044]
[0045]
[0046] 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; convert the ABCD matrix of the topology into the corresponding S matrix. When |S21| = 0, it can be concluded that the topology has three transmission zeros, and the frequencies corresponding to the three transmission zeros are:
[0047]
[0048] f z2 =f0
[0049]
[0050] From the above analysis, it can be seen that the topology has two odd-mode transmission poles, five even-mode transmission poles, and three transmission zeros. Regardless of the values of parameters Z1, Z2, and Z3, the relative positions of these transmission zero poles, i.e., f op1 <f ep1 <f z1 <f ep2 <f z2 <f ep3 <fz3 <f ep4 <f op2 <f ep5 , will not change. Therefore, based on this topology, a wide stopband filter with narrow pass characteristics can be designed.
[0051] The wide stopband filter with narrow pass characteristics designed based on this topological structure has a reflection coefficient in the passband mainly affected by parameters Z1 and Z2, a bandwidth of the stopband mainly affected by parameter Z2, a bandwidth of the two narrow passbands in the stopband mainly affected by parameters Z1 and Z2, and a center frequency of the two narrow passbands in the stopband mainly affected by parameters Z2 and Z3. By optimizing the values of parameters Z1, Z2, and Z3, a filter with the required performance can be obtained.
[0052] Please refer to Figure 4 and Figure 5 , Embodiment 2 of the present utility model is:
[0053] A wide stopband filter with narrow pass characteristics, comprising a circuit board and the topological structure described in Example 1, 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 24.2 mm*14.3 mm. The layout diagram is shown in FIG. Figure 4 As shown, 10 is the input end, 21 is the first microstrip line, 22 is the second microstrip line, 23 is the third microstrip line, 24 is the fourth microstrip line, 25 is the fifth microstrip line, 26 is the sixth microstrip line, 31 is the first open branch, 32 is the second open branch, 33 is the third open branch, 34 is the fourth open branch, and 40 is the output end.
[0054] The specific parameters on the circuit board are set as follows:
[0055] The length of the first microstrip line and the length of the sixth microstrip line are both recorded as l1, l1=9.5mm; the length of the second microstrip line is recorded as l2, l2=5.9mm; the length of the third microstrip line and the length of the fourth microstrip line are both recorded as l3, l3=10mm; the length of the first open branch node and the length of the second open branch node are both recorded as l4, l4=5.5mm; the length of the fifth microstrip line is recorded as l5, l5=1.7mm; the length of the third open branch node and the length of the fourth open branch node are both recorded as l6, l6=7.8mm; The width of the first microstrip line and the width of the sixth microstrip line are both recorded as w1, w1=0.1mm; the width of the second microstrip line is recorded as w2, w2=1.6mm; the width of the third microstrip line and the width of the fourth microstrip line are both recorded as w3, w3=0.8mm; the width of the first open branch node and the width of the second open branch node are both recorded as w4, w4=0.8mm; the width of the fifth microstrip line is recorded as w5, w5=0.2mm; the width of the third open branch node and the width of the fourth open branch node are both recorded as w6, w6=0.1mm.
[0056] The S parameter simulation results of the wide stopband filter with narrow pass characteristics described in this embodiment are as follows: Figure 5 As shown in the figure. It can be seen from the figure that the stopband range with isolation greater than 20dB is from 1.913 to 7.509GHz, the stopband center frequency is 4.711GHz, the absolute bandwidth is 5.596GHz, and the relative bandwidth is 118.9%. In addition, there are three transmission zeros in the stopband, located at 2.274, 5.02, and 7.02GHz respectively; there are two passbands next to the stopband, and there are five transmission poles in the passband, located at 0, 0.84, 8.64, 9.68, and 10.72GHz respectively. These three transmission zeros and five transmission poles not only ensure the high isolation characteristics of the stopband and the low insertion loss and flatness of the passband, but also ensure the high selectivity of the sideband of the stopband filter.
[0057] In addition, there are two passbands with very narrow bandwidths in the stopband. For the first passband, the passband range with a reflection coefficient less than -10dB is 3.513GHz to 3.581GHz, the passband center frequency is 3.547GHz, the absolute bandwidth is 0.068GHz, and the relative bandwidth is 1.9%; for the second passband, the passband range with a reflection coefficient less than -10dB is 5.895GHz to 5.933GHz, the passband center frequency is 5.914GHz, the absolute bandwidth is 0.038GHz, and the relative bandwidth is 0.6%.
[0058] In summary, the topological structure and the wide stopband filter with narrow-pass characteristics proposed in the present invention have the advantage of high selectivity on the basis of having narrow-pass characteristics.
[0059] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Therefore, any modification, 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 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, a third open branch, a fourth open branch, an input end and an output end; One end of the second microstrip line is respectively connected to one end of the third microstrip line and one end of the fourth microstrip line, the other end of the third microstrip line is connected to the first open branch, the other end of the fourth microstrip line is connected to the second open branch, the other end of the second microstrip line is respectively connected to one end of the first microstrip line, one end of the fifth microstrip line and one end of the sixth microstrip line, the other end of the fifth microstrip line is respectively connected to the third open branch and the fourth open branch, the other end of the first microstrip line is connected to the input end, and the other end of the sixth microstrip line is connected to the output end; The second microstrip line and the fifth microstrip line are located on the same vertical line, the first microstrip line and the sixth microstrip line, the third microstrip line and the fourth microstrip line, the first open branch node and the second open branch node, the third open branch node and the fourth open branch node are all symmetrical about the second microstrip line, the first microstrip line, the third microstrip line, the fourth microstrip line, the sixth microstrip line, the third open branch node and the fourth open branch node are parallel to each other and are all perpendicular to the second microstrip line.
2. The topological structure according to claim 1, characterized in that: The first microstrip line, the third microstrip line, the fourth microstrip line, the sixth microstrip line, the third open branch and the fourth open branch are all perpendicular to the first open branch and the second open branch.
3. The topological structure according to claim 1, characterized in that: The electrical length of the first microstrip line is the same as the electrical length of the sixth microstrip line, and both are one-quarter wavelength corresponding to the center frequency of the stopband; the sum of the electrical length of the second microstrip line, the electrical length of the third microstrip line and the electrical length of the first open branch is one-half wavelength corresponding to the center frequency of the stopband; the sum of the electrical length of the second microstrip line, the electrical length of the fourth microstrip line and the electrical length of the second open branch is one-half wavelength corresponding to the center frequency of the stopband; the sum of the electrical length of the fifth microstrip line and the electrical length of the third open branch is one-quarter wavelength corresponding to the center frequency of the stopband; the sum of the electrical length of the fifth microstrip line and the electrical length of the fourth open branch is one-quarter wavelength corresponding to the center frequency of the stopband.
4. The topological structure according to claim 1, characterized in that: The characteristic impedance of the first microstrip line is the same as the characteristic impedance of the sixth microstrip line; the characteristic impedance of the third microstrip line, the characteristic impedance of the fourth microstrip line, the characteristic impedance of the first open branch node and the characteristic impedance of the second open branch node are the same, and are all twice the characteristic impedance of the second microstrip line; the characteristic impedance of the third open branch node and the characteristic impedance of the fourth open branch node are the same, and are all twice the characteristic impedance of the fifth microstrip line.
5. The topological structure according to claim 1, characterized in that: The topological structure includes two odd-mode transmission poles, five even-mode transmission poles and three transmission zeros.
6. A wide stopband filter with narrow pass characteristics, characterized in that: The topological structure comprises any one of claims 1 to 5.
7. The wide stopband filter with narrow pass characteristics according to claim 6, characterized in that: It also includes a circuit board, and the topological structure is arranged on the circuit board, the length of the first microstrip line is the same as the length of the sixth microstrip line, the length of the third microstrip line is the same as the length of the fourth microstrip line, the length of the first open branch node is the same as the length of the second open branch node, the length of the third open branch node is the same as the length of the fourth open branch node, the width of the first microstrip line is the same as the width of the sixth microstrip line, the width of the third microstrip line is the same as the width of the fourth microstrip line, the width of the first open branch node is the same as the width of the second open branch node, and the width of the third open branch node is the same as the width of the fourth open branch node.
8. The wide stopband filter with narrow pass characteristics according to claim 7, characterized in that: 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 24.2 mm*14.3 mm.
9. The wide stopband filter with narrow pass characteristics according to claim 8, characterized in that: The length of the first microstrip line and the length of the sixth microstrip line are both set to 9.5mm, the length of the second microstrip line is set to 5.9mm, the length of the third microstrip line and the length of the fourth microstrip line are both set to 10mm, the length of the first open branch node and the length of the second open branch node are both set to 5.5mm, the length of the fifth microstrip line is set to 1.7mm, the length of the third open branch node and the length of the fourth open branch node are both set to 7.8mm, the width of the first microstrip line and the width of the sixth microstrip line are both set to 0.1mm, the width of the second microstrip line is set to 1.6mm, the width of the third microstrip line and the width of the fourth microstrip line are both set to 0.8mm, the width of the first open branch node and the width of the second open branch node are both set to 0.8mm, the width of the fifth microstrip line is set to 0.2mm, and the width of the third open branch node and the width of the fourth open branch node are both set to 0.1mm.