Wide dual-passband filter topological structure and filter

Abstract

The utility model discloses a wide dual-passband filter topological structure and a filter. The topological structure comprises 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 a first microstrip line and an input end, and the second end of the first transmission line is sequentially connected with a second microstrip line, a third microstrip line and a first open circuit branch knot; the first end of the second transmission line is sequentially connected with a sixth microstrip line and an output end, and the second end of the second transmission line is sequentially connected with a fourth microstrip line, a fifth microstrip line and a second open-circuit branch knot; the first transmission line, the second transmission line, the third microstrip line, the fifth microstrip line and the sixth microstrip line are arranged along a first direction; the first microstrip line, the second microstrip line, the fourth microstrip line, the first open-circuit branch knot and the second open-circuit branch knot are arranged along a second direction, and the first direction is perpendicular to the second direction. According to the utility model, the defect that the existing dual-passband filter is large in size is overcome.

Description

Technical Field

[0001] The utility model relates to the technical field of filters, in particular to a wide dual-passband filter topology structure and a 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, low-cost, light-weight, low-profile, and easy-to-integrate micro-bandwidth dual-passband filters 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 large size, which seriously affects their use in modern high-speed information transmission communication systems. Utility Model Content

[0003] The main purpose of the utility model is to provide a wide dual-passband filter topology structure and a filter, aiming to solve the defect of large size of the existing dual-passband filter.

[0004] To achieve the above object, the utility model proposes a wide dual-passband filter topology structure, comprising a first transmission line and a second transmission line arranged in parallel;

[0005] The first end of the first transmission line is connected to the first microstrip line and the input end in sequence, and the second end of the first transmission line is connected to the second microstrip line, the third microstrip line and the first open branch in sequence;

[0006] The first end of the second transmission line is connected to the sixth microstrip line and the output end in sequence, and the second end of the second transmission line is connected to the fourth microstrip line, the fifth microstrip line and the second open branch in sequence;

[0007] The first transmission line, the second transmission line, the third microstrip line, the fifth microstrip line and the sixth microstrip line are all arranged along the first direction; the first microstrip line, the second microstrip line, the fourth microstrip line, the first open branch and the second open branch are all arranged along the second direction, and the first direction is perpendicular to the second direction.

[0008] Optionally, the first transmission line and the second transmission line form a parallel line, and the parallel line has an odd-mode characteristic impedance and an even-mode characteristic impedance.

[0009] Optionally, 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 first open-circuit branch and the characteristic impedance of the second open-circuit branch are equal.

[0010] Optionally, the electrical length of the parallel lines is a quarter wavelength corresponding to a center frequency of a stop band between two pass bands of the wide dual-passband filter.

[0011] Optionally, the electrical length of the first microstrip line is equal to the electrical length of the sixth microstrip line; the electrical length of the second microstrip line is equal to the electrical length of the fourth microstrip line; the electrical length of the third microstrip line is equal to the electrical length of the fifth microstrip line; the electrical length of the first open branch is equal to the electrical length of the second open branch.

[0012] Optionally, 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 a quarter wavelength corresponding to the stopband center frequency between the two passbands of the wide dual-passband filter.

[0013] Optionally, the sum of the electrical lengths of the sixth microstrip line, the fourth microstrip line, the fifth microstrip line and the second open-circuit branch is a quarter wavelength corresponding to the stopband center frequency between the two passbands of the wide dual-passband filter.

[0014] To achieve the above object, the utility model further proposes a filter, comprising any of the wide dual-passband filter topology structures described above.

[0015] Optionally, the filter further includes a circuit board, and the topological structure is integrated on the circuit board.

[0016] Optionally, the length of the first transmission line is equal to the length of the second transmission line, which is set to l p ; The distance between the first transmission line and the second transmission line is set to s p The width of the first transmission line is equal to the width of the second transmission line, set to w p ;

[0017] The length of the first microstrip line is equal to the length of the sixth microstrip line, which is set to l1; the length of the second microstrip line is equal to the length of the fourth microstrip line, which is set to l2; the length of the third microstrip line is equal to the length of the fifth microstrip line, which is set to l3; the length of the first open branch is equal to the length of the second open branch, which is set to l4;

[0018] The width of the first microstrip line, the width of the second microstrip line, the width of the third microstrip line, the width of the fourth microstrip line, the width of the fifth microstrip line, the width of the sixth microstrip line, the width of the first open branch node and the width of the second open branch node are equal and set to w1.

[0019] The beneficial effect of the utility model is that the topological structure of the existing dual-passband filter is improved, and the dual-passband filter designed based on the topological structure is a wide dual-passband filter. In the first passband, the maximum insertion loss is 0.51dB; in the second passband, the maximum insertion loss is 0.66dB. The wide dual-passband filter based on the topological structure has the advantages of low insertion loss characteristics and miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0021] Figure 1 This is a schematic diagram of the topological structure of the filter of the utility model;

[0022] Figure 2 It is an odd-mode diagram of the topological structure of the utility model;

[0023] Figure 3 It is an even-mode diagram of the topological structure of the utility model;

[0024] Figure 4 This is a layout diagram of the filter of the utility model;

[0025] Figure 5 This is a diagram of the S parameter simulation results of the utility model filter;

[0026] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0028] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0029] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the utility model, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the 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 that satisfies both A and B. 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 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 utility model.

[0030] An embodiment of the present invention provides a wide dual-passband filter topology structure, referring to Figure 1 , comprising a first transmission line and a second transmission line arranged in parallel;

[0031] The first end of the first transmission line is connected to the first microstrip line and the input end in sequence, and the second end of the first transmission line is connected to the second microstrip line, the third microstrip line and the first open branch in sequence;

[0032] The first end of the second transmission line is connected to the sixth microstrip line and the output end in sequence, and the second end of the second transmission line is connected to the fourth microstrip line, the fifth microstrip line and the second open branch in sequence;

[0033] The first transmission line, the second transmission line, the third microstrip line, the fifth microstrip line and the sixth microstrip line are all arranged along the first direction; the first microstrip line, the second microstrip line, the fourth microstrip line, the first open branch and the second open branch are all arranged along the second direction, and the first direction is perpendicular to the second direction.

[0034] This embodiment improves the topological structure of the existing dual-passband filter, which is composed of two transmission lines, six microstrip lines and two open branches. The first transmission line and the second transmission line are parallel and placed close to each other, forming a parallel line. The first transmission line, the second transmission line, the third microstrip line, the fifth microstrip line and the sixth microstrip line are parallel to each other and are perpendicular to the first microstrip line, the second microstrip line, the fourth microstrip line, the first open branch and the second open branch.

[0035] Furthermore, a parallel line is formed between the first transmission line and the second transmission line, and the parallel line has an odd-mode characteristic impedance and an even-mode characteristic impedance. In this embodiment, the odd-mode characteristic impedance of the parallel line is set to Z oo The even-mode characteristic impedance of the parallel line is set to Z oe.

[0036] Furthermore, 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 first open-circuit branch and the characteristic impedance of the second open-circuit branch are equal.

[0037] In this embodiment, 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 first open branch and the characteristic impedance of the second open branch are all set to Z1.

[0038] Furthermore, the electrical length of the parallel lines is a quarter wavelength corresponding to the center frequency of the stop band between the two pass bands of the wide dual-passband filter.

[0039] The electrical length of the first microstrip line is equal to the electrical length of the sixth microstrip line; the electrical length of the second microstrip line is equal to the electrical length of the fourth microstrip line; the electrical length of the third microstrip line is equal to the electrical length of the fifth microstrip line; the electrical length of the first open branch is equal to the electrical length of the second open branch.

[0040] Specifically, the sum of the electrical lengths of the first microstrip line, the second microstrip line, the third microstrip line and the first open-circuit branch node is a quarter wavelength corresponding to the center frequency of the stopband between the two passbands of the wide dual-passband filter; the sum of the electrical lengths of the sixth microstrip line, the fourth microstrip line, the fifth microstrip line and the second open-circuit branch node is a quarter wavelength corresponding to the center frequency of the stopband between the two passbands of the wide dual-passband filter.

[0041] 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 length of the second microstrip line, the electrical length of the third microstrip line, and the electrical length of the first open 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 wide dual-passband filter, and the characteristic impedance of the odd-mode transmission line is Z oo .

[0042] refer to Figure 2 , 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:

[0043]

[0044]

[0045] 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 wide dual-passband filter, and the characteristic impedance of the even-mode transmission line is Z oe .

[0046] refer to Figure 3 , when Y ino = 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:

[0047]

[0048]

[0049] For this topology, the transmission zero can be calculated using the following formula:

[0050]

[0051] After calculation, it can be concluded that the topology has three transmission zeros, and the frequencies corresponding to the three transmission zeros are:

[0052] f z1 =0

[0053] f z2 =f0

[0054] f z3 =2f0

[0055] From the above analysis, it can be seen that the filter based on this topology has two odd-mode transmission poles, two 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.

[0056] An embodiment of the present invention provides a filter, comprising any of the wide dual-passband filter topology structures described above.

[0057] Furthermore, the filter further comprises a circuit board, and the topological structure is integrated on the circuit board. The length of the first transmission line is equal to the length of the second transmission line, and is set to be l p ; The distance between the first transmission line and the second transmission line is set to s p The width of the first transmission line is equal to the width of the second transmission line, set to w p ;

[0058] The length of the first microstrip line is equal to the length of the sixth microstrip line, which is set to l1; the length of the second microstrip line is equal to the length of the fourth microstrip line, which is set to l2; the length of the third microstrip line is equal to the length of the fifth microstrip line, which is set to l3; the length of the first open branch is equal to the length of the second open branch, which is set to l4;

[0059] The width of the first microstrip line, the width of the second microstrip line, the width of the third microstrip line, the width of the fourth microstrip line, the width of the fifth microstrip line, the width of the sixth microstrip line, the width of the first open branch node and the width of the second open branch node are equal and set to w1.

[0060] In this embodiment, in order to verify the conclusion of the above topological structure, a dual-passband filter is designed based on the above topological structure. It is designed on a circuit board with a dielectric constant of 3.38, a dielectric loss of 0.0022, and a thickness of 0.813 mm, and the size of the circuit board is 10.4 mm*5.2 mm.

[0061] refer to Figure 4 , the length of the first transmission line is equal to the length of the second transmission line, set to l p =6.4mm; the distance between the first transmission line and the second transmission line is set to s p =0.1mm; the width of the first transmission line is equal to the width of the second transmission line, set to w p =0.1mm.

[0062] The length of the first microstrip line is equal to the length of the sixth microstrip line, and is set to l1=1.2 mm; the length of the second microstrip line is equal to the length of the fourth microstrip line, and is set to l2=1.55 mm; the length of the third microstrip line is equal to the length of the fifth microstrip line, and is set to l3=3.5 mm; the length of the first open branch is equal to the length of the second open branch, and is set to l4=1 mm;

[0063] The width of the first microstrip line, the width of the second microstrip line, the width of the third microstrip line, the width of the fourth microstrip line, the width of the fifth microstrip line, the width of the sixth microstrip line, the width of the first open branch node and the width of the second open branch node are equal, and are set to w1=0.1mm.

[0064] Based on the filter designed based on the above topology, S parameter simulation is performed, and the simulation results are referenced Figure 5 It can be seen that in the first passband, the impedance bandwidth with a reflection coefficient less than -10dB ranges from 3.03 to 4.79GHz, the passband center frequency is 3.91GHz, the passband absolute bandwidth is 1.76GHz, and the passband relative bandwidth is 45%; in its second passband, the impedance bandwidth with a reflection coefficient less than -10dB ranges from 10.01 to 11.43GHz, the passband center frequency is 10.72GHz, the passband absolute bandwidth is 1.42GHz, and the passband relative bandwidth is 13.2%. 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 0.51dB; in the second passband, the maximum insertion loss is 0.66dB. It can be seen that the wide dual-passband filter based on this topology has a low insertion loss characteristic. In addition, the filter has two transmission poles in the first passband, located at 3.38 and 4.27 GHz respectively; and two transmission poles in the second passband, located at 10.38 and 11.1 GHz respectively. These four transmission poles can ensure the flatness in the passband. There are also three transmission zeros in the stopband, located at 0, 7.55, and 14.94 GHz respectively. These three transmission zeros ensure the high isolation of the wide dual passband filter.

[0065] Therefore, the topological structure of this embodiment can be used to design a wide dual-passband filter, and the filter has the advantages of miniaturization and low loss.

[0066] The above description is only an optional embodiment of the utility model, and does not limit the patent scope of the utility model. All equivalent structural changes made by using the contents of the utility model specification and drawings under the utility model concept, or directly / indirectly used in other related technical fields are included in the patent protection scope of the utility model.

Claims

1. A wide dual passband filter topology, characterized in that: comprising a first transmission line and a second transmission line arranged in parallel; The first end of the first transmission line is connected to the first microstrip line and the input end in sequence, and the second end of the first transmission line is connected to 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 sixth microstrip line and the output end in sequence, and the second end of the second transmission line is connected to the fourth microstrip line, the fifth microstrip line and the second open branch in sequence; The first transmission line, the second transmission line, the third microstrip line, the fifth microstrip line and the sixth microstrip line are all arranged along the first direction; the first microstrip line, the second microstrip line, the fourth microstrip line, the first open branch and the second open branch are all arranged along the second direction, and the first direction is perpendicular to the second direction.

2. The wide dual passband filter topology structure according to claim 1, characterized in that: A parallel line is formed between the first transmission line and the second transmission line, and the parallel line has an odd-mode characteristic impedance and an even-mode characteristic impedance.

3. The wide dual-passband filter topology structure according to claim 2, 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 first open branch and the characteristic impedance of the second open branch are equal.

4. The wide dual passband filter topology structure according to claim 2, characterized in that: The electrical length of the parallel lines is a quarter wavelength corresponding to the center frequency of the stop band between the two pass bands of the wide dual-pass band filter.

5. The wide dual passband filter topology structure according to claim 4, characterized in that: The electrical length of the first microstrip line is equal to the electrical length of the sixth microstrip line; the electrical length of the second microstrip line is equal to the electrical length of the fourth microstrip line; the electrical length of the third microstrip line is equal to the electrical length of the fifth microstrip line; the electrical length of the first open branch is equal to the electrical length of the second open branch.

6. The wide dual passband filter topology structure according to claim 5, characterized in that: 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 a quarter wavelength corresponding to the stopband center frequency between the two passbands of the wide dual-passband filter.

7. The wide dual passband filter topology structure according to claim 5, characterized in that: The sum of the electrical lengths of the sixth microstrip line, the fourth microstrip line, the fifth microstrip line and the second open branch is a quarter wavelength corresponding to the stopband center frequency between the two passbands of the wide dual-passband filter.

8. A filter, characterized in that: It comprises the wide dual-passband filter topology structure described in any one of claims 1 to 7.

9. The filter according to claim 8, characterized in that The filter further includes a circuit board, and the topological structure is integrated on the circuit board.

10. The filter according to claim 9, characterized in that The length of the first transmission line is equal to the length of the second transmission line, which is set to l p ; The distance between the first transmission line and the second transmission line is set to s p The width of the first transmission line is equal to the width of the second transmission line, which is set to w p ; The length of the first microstrip line is equal to the length of the sixth microstrip line, which is set to l1; the length of the second microstrip line is equal to the length of the fourth microstrip line, which is set to l2; the length of the third microstrip line is equal to the length of the fifth microstrip line, which is set to l3; the length of the first open branch is equal to the length of the second open branch, which is set to l4; The width of the first microstrip line, the width of the second microstrip line, the width of the third microstrip line, the width of the fourth microstrip line, the width of the fifth microstrip line, the width of the sixth microstrip line, the width of the first open branch node and the width of the second open branch node are equal and set to w1.

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