Wide-passband filter topological structure with notch characteristic and filter

Abstract

The utility model discloses a wide-passband filter topological structure with a notch characteristic, which comprises a first parallel line, a second parallel line and a third parallel line which are connected, the first parallel line is connected with an input end, and the third parallel line is connected with an output end; a first microstrip line and a first open circuit branch are connected between the first parallel line and the input end; a second micro-strip line and a fourth micro-strip line are connected between the first parallel line and the second parallel line, the second micro-strip line is connected with a third micro-strip line and a first short-circuit branch knot, and the fourth micro-strip line is connected with a fifth micro-strip line and a second short-circuit branch knot; a sixth micro-strip line and an eighth micro-strip line are connected between the second parallel line and the third parallel line, the sixth micro-strip line is connected with a seventh micro-strip line and a third short-circuit branch knot, and the eighth micro-strip line is connected with a ninth micro-strip line and a fourth short-circuit branch knot; a tenth microstrip line and a second open-circuit branch knot are connected between the third parallel line and the output end; the broadband band-pass filter overcomes the defects that an existing broadband band-pass filter is poor in selectivity and not compact.

Description

Technical Field

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

[0002] With the rapid development of modern 5G communication technology, as one of the key components of wireless communication systems, broadband bandpass filters have attracted more and more attention from scholars and engineers. In this context, bandpass filters that can suppress in-band interference and transmit signals at high speed, that is, broadband bandpass filters with notch characteristics, have been developed in large numbers. However, at present, the vast majority of broadband bandpass filters with notch characteristics often have the defects of poor selectivity and non-compact structure, which greatly limits their use in modern wireless communication systems. Summary of the Utility Model

[0003] The main purpose of the utility model is to provide a wideband filter topology structure and a filter with notch characteristics, aiming to solve the defects of poor selectivity and non-compactness of existing broadband bandpass filters with notch characteristics.

[0004] To achieve the above purpose, the utility model proposes a wideband filter topology structure with notch characteristics, including a first parallel line, a second parallel line and a third parallel line connected in sequence along a first direction, the other end of the first parallel line is connected with an input end, and the other end of the third parallel line is connected with an output end;

[0005] A first microstrip line and a first open stub are sequentially connected between the first parallel line and the input end;

[0006] A second microstrip line and a fourth microstrip line are symmetrically connected between the first parallel line and the second parallel line, the other end of the second microstrip line is sequentially connected with a third microstrip line and a first short stub, and the other end of the fourth microstrip line is sequentially connected with a fifth microstrip line and a second short stub;

[0007] A sixth microstrip line and an eighth microstrip line are symmetrically connected between the second parallel line and the third parallel line, the other end of the sixth microstrip line is sequentially connected with a seventh microstrip line and a third short stub, and the other end of the eighth microstrip line is sequentially connected with a ninth microstrip line and a fourth short stub;

[0008] A tenth microstrip line and a second open stub are sequentially connected between the third parallel line and the output end;

[0009] The first microstrip line, the third microstrip line, the fifth microstrip line, the seventh microstrip line, the ninth microstrip line, and the tenth microstrip line are all arranged along the first direction; the second microstrip line, the fourth microstrip line, the sixth microstrip line, the eighth microstrip line, the first open stub, the second open stub, the first short stub, the second short stub, the third short stub, and the fourth short stub are all arranged along the second direction, and the first direction is perpendicular to the second direction.

[0010] Optionally, each of the first parallel line, the second parallel line, and the third parallel line includes two mutually parallel transmission lines.

[0011] Optionally, the electrical lengths of the first parallel line, the second parallel line, and the third parallel line are equal, and each is equal to a quarter wavelength corresponding to the center frequency of the wideband filter.

[0012] Optionally, the electrical length of the first microstrip line is equal to the electrical length of the tenth microstrip line; the electrical length of the first open stub is equal to the electrical length of the second open stub;

[0013] The sum of the electrical length of the first microstrip line and the electrical length of the first open stub, and the sum of the electrical length of the tenth microstrip line and the electrical length of the second open stub are both equal to a quarter wavelength corresponding to the center frequency of the wideband filter; or the sum of the electrical length of the first microstrip line and the electrical length of the first open stub, and the sum of the electrical length of the tenth microstrip line and the electrical length of the second open stub are both equal to a quarter wavelength corresponding to the notch center frequency of the wideband filter.

[0014] Optionally, the electrical lengths of the second microstrip line, the fourth microstrip line, the sixth microstrip line, and the eighth microstrip line are equal;

[0015] The electrical lengths of the third microstrip line, the fifth microstrip line, the seventh microstrip line, and the ninth microstrip line are equal;

[0016] The electrical lengths of the first short stub, the second short stub, the third short stub, and the fourth short stub are equal;

[0017] 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 short stub is greater than a quarter wavelength corresponding to the center frequency of the wideband filter;

[0018] The sum of the electrical length of the fourth microstrip line, the electrical length of the fifth microstrip line, and the electrical length of the second short stub is greater than a quarter wavelength corresponding to the center frequency of the wideband filter;

[0019] The sum of the electrical lengths of the sixth microstrip line, the seventh microstrip line, and the electrical length of the third short - circuit stub is greater than a quarter - wavelength corresponding to the center frequency of the wide - bandpass filter;

[0020] The sum of the electrical lengths of the eighth microstrip line, the ninth microstrip line, and the electrical length of the fourth short - circuit stub is greater than a quarter - wavelength corresponding to the center frequency of the wide - bandpass filter.

[0021] Optionally, the odd - mode characteristic impedance of the first parallel line is equal to that of the third parallel line; the even - mode characteristic impedance of the first parallel line is equal to that of the third parallel line.

[0022] Optionally, the characteristic impedance of the first microstrip line, the characteristic impedance of the tenth microstrip line, the characteristic impedance of the first open - circuit stub, and the characteristic impedance of the second open - circuit stub are all equal.

[0023] Optionally, 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 ninth microstrip line, the characteristic impedance of the first short - circuit stub, the characteristic impedance of the second short - circuit stub, the characteristic impedance of the third short - circuit stub, and the characteristic impedance of the fourth short - circuit stub are all equal.

[0024] To achieve the above object, the present utility model further provides a filter, including any one of the above - mentioned topological structures.

[0025] Optionally, the filter further includes a circuit board, the dielectric constant of the circuit board is 3.38, the dielectric loss is 0.0022, the thickness is 0.813 mm, and the size is 35.8 mm * 11.8 mm;

[0026] The line lengths of the transmission lines in the first parallel line and the third parallel line are both set to l p1 = 10.2 mm, the line widths are both set to w p1 = 0.2 mm, and the line spacings are both set to s p1 = 0.1 mm;

[0027] The line lengths of the transmission lines in the second parallel line are both set to l p2 = 10.2 mm, the line widths are both set to w p2 = 0.2 mm, and the line spacings are both set to s p2 = 0.15 mm;

[0028] The line lengths of the first microstrip line and the tenth microstrip line are both set to l 1 = 9.55 mm, and the line lengths of the first open - circuit stub and the second open - circuit stub are both set to l 2= 1.85 mm; the line widths of the first microstrip line, the tenth microstrip line, the first open stub, and the second open stub are all set to w 1 = 0.45 mm;

[0029] The distances between the first microstrip line and the first parallel line, and between the tenth microstrip line and the third parallel line are both set to s 1 = 0.1 mm;

[0030] The line lengths of the second microstrip line, the fourth microstrip line, the sixth microstrip line, and the eighth microstrip line are all set to l 3 = 5.15 mm; the line lengths of the third microstrip line, the fifth microstrip line, the seventh microstrip line, and the ninth microstrip line are all set to l 4 = 4.5 mm; the line lengths of the first short - circuit stub, the second short - circuit stub, the third short - circuit stub, and the fourth short - circuit stub are all set to l 5 = 2.2 mm;

[0031] The line widths of the second microstrip line, the fourth microstrip line, the sixth microstrip line, the eighth microstrip line, the third microstrip line, the fifth microstrip line, the seventh microstrip line, the ninth microstrip line, the first short - circuit stub, the second short - circuit stub, the third short - circuit stub, and the fourth short - circuit stub are all set to w 2 = 0.7 mm.

[0032] The beneficial effects of the present utility model are as follows: The topological structure of the existing wide - bandpass filter is improved. The topological structure includes connected first, second, and third parallel lines. The first parallel line is connected to the input end, and the third parallel line is connected to the output end; between the first parallel line and the input end, there are connected a first microstrip line and a first open stub; between the first parallel line and the second parallel line, there are connected a second microstrip line and a fourth microstrip line. The second microstrip line is connected to a third microstrip line and a first short - circuit stub, and the fourth microstrip line is connected to a fifth microstrip line and a second short - circuit stub; between the second parallel line and the third parallel line, there are connected a sixth microstrip line and an eighth microstrip line. The sixth microstrip line is connected to a seventh microstrip line and a third short - circuit stub, and the eighth microstrip line is connected to a ninth microstrip line and a fourth short - circuit stub; between the third parallel line and the output end, there are connected a tenth microstrip line and a second open stub;

[0033] Based on this topological structure, the filter has four odd - mode transmission poles, four even - mode transmission poles, and six transmission zeros. Moreover, no matter how the characteristic impedance values of its respective stubs are changed, the relative positions of the transmission poles and zeros will not change. Therefore, based on this topological structure, a wide - band band - pass filter with notch characteristics can be designed. There are eight transmission poles in the passband to ensure the flatness within the passband, five transmission zeros in the stopband to ensure high selectivity and high isolation, and one transmission zero in the passband to form the required notch. Description of the Drawings

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0035] Figure 1 Schematic diagram of the topological structure of the filter of the present invention;

[0036] Figure 2 Odd-mode form diagram of the topological structure of the present invention;

[0037] Figure 3 Even-mode form diagram of the topological structure of the present invention;

[0038] Figure 4 Layout layout of the filter of the present invention;

[0039] Figure 5 S-parameter simulation result diagram of the filter of the present invention;

[0040] The realization, functional features and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the drawings. Detailed implementation manners

[0041] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0042] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0043] In addition, if the descriptions such as "first" and "second" are involved in the embodiments of the present utility model, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text is that it includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, or solution B, or the solution where A and B are satisfied simultaneously. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement it. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0044] An embodiment of the present utility model provides a wideband filter topology structure with notch characteristics. Referring to Figure 1 , it includes a first parallel line, a second parallel line, and a third parallel line connected in sequence along a first direction. The other end of the first parallel line is connected to an input terminal, and the other end of the third parallel line is connected to an output terminal;

[0045] A first microstrip line and a first open stub are sequentially connected between the first parallel line and the input terminal;

[0046] A second microstrip line and a fourth microstrip line are symmetrically connected between the first parallel line and the second parallel line. The other end of the second microstrip line is sequentially connected to a third microstrip line and a first short stub, and the other end of the fourth microstrip line is sequentially connected to a fifth microstrip line and a second short stub;

[0047] A sixth microstrip line and an eighth microstrip line are symmetrically connected between the second parallel line and the third parallel line. The other end of the sixth microstrip line is sequentially connected to a seventh microstrip line and a third short stub, and the other end of the eighth microstrip line is sequentially connected to a ninth microstrip line and a fourth short stub;

[0048] A tenth microstrip line and a second open stub are sequentially connected between the third parallel line and the output terminal;

[0049] The first microstrip line, the third microstrip line, the fifth microstrip line, the seventh microstrip line, the ninth microstrip line, and the tenth microstrip line are all arranged along the first direction; the second microstrip line, the fourth microstrip line, the sixth microstrip line, the eighth microstrip line, the first open stub, the second open stub, the first short stub, the second short stub, the third short stub, and the fourth short stub are all arranged along a second direction, and the first direction is perpendicular to the second direction.

[0050] This embodiment improves the topological structure of the existing filter. It is composed of three parallel lines, ten microstrip lines, two open stubs, and four short - circuit stubs. Among them, the first parallel line, the second parallel line, and the third parallel line each include two mutually parallel transmission lines. Specifically, the first parallel line is composed of a first transmission line and a second transmission line placed in parallel, the second parallel line is composed of a third transmission line and a fourth transmission line placed in parallel, and the third parallel line is composed of a fifth transmission line and a sixth transmission line placed in parallel. One end of the first transmission line is connected to the input end and one end of the first microstrip line; one end of the second transmission line is connected to one end of the second microstrip line, one end of the fourth microstrip line, and one end of the third transmission line; one end of the fourth transmission line is connected to one end of the sixth microstrip line, one end of the eighth microstrip line, and one end of the fifth transmission line; one end of the sixth transmission line is connected to the output end and one end of the tenth microstrip line.

[0051] Furthermore, the electrical lengths of the first parallel line, the second parallel line, and the third parallel line are equal, and each is equal to a quarter - wavelength corresponding to the center frequency of the wide - bandpass filter. In this embodiment, the electrical lengths of the first parallel line, the second parallel line, and the third parallel line are denoted as θ.

[0052] Furthermore, the electrical length of the first microstrip line is equal to the electrical length of the tenth microstrip line; the electrical length of the first open stub is equal to the electrical length of the second open stub. In this embodiment, the electrical lengths of the first microstrip line and the tenth microstrip line are denoted as θ 1 ; the electrical lengths of the first open stub and the second open stub are denoted as θ 2 ;

[0053] The sum of the electrical length of the first microstrip line and the electrical length of the first open stub, and the sum of the electrical length of the tenth microstrip line and the electrical length of the second open stub are both equal to a quarter - wavelength corresponding to the center frequency of the wide - bandpass filter; or the sum of the electrical length of the first microstrip line and the electrical length of the first open stub, and the sum of the electrical length of the tenth microstrip line and the electrical length of the second open stub are both equal to a quarter - wavelength corresponding to the notch center frequency of the wide - bandpass filter. That is, the sum of the electrical length of the first microstrip line and the electrical length of the first open stub, and the sum of the electrical length of the tenth microstrip line and the electrical length of the second open stub are denoted as θ 1 +θ 2 =θ.

[0054] Furthermore, the electrical lengths of the second microstrip line, the fourth microstrip line, the sixth microstrip line, and the eighth microstrip line are equal. In this embodiment, the electrical lengths of the second microstrip line, the fourth microstrip line, the sixth microstrip line, and the eighth microstrip line are denoted as θ 3 ;

[0055] The electrical lengths of the third microstrip line, the fifth microstrip line, the seventh microstrip line, and the ninth microstrip line are equal; in this embodiment, the electrical lengths of the third microstrip line, the fifth microstrip line, the seventh microstrip line, and the ninth microstrip line are denoted as θ 4 ;

[0056] The electrical lengths of the first short - circuit stub, the second short - circuit stub, the third short - circuit stub, and the fourth short - circuit stub are equal; in this embodiment, the electrical lengths of the first short - circuit stub, the second short - circuit stub, the third short - circuit stub, and the fourth short - circuit stub are denoted as θ 5 ;

[0057] The sum of the electrical lengths of the second microstrip line, the third microstrip line, and the first short - circuit stub is greater than a quarter - wavelength corresponding to the center frequency of the wide - bandpass filter;

[0058] The sum of the electrical lengths of the fourth microstrip line, the fifth microstrip line, and the second short - circuit stub is greater than a quarter - wavelength corresponding to the center frequency of the wide - bandpass filter;

[0059] The sum of the electrical lengths of the sixth microstrip line, the seventh microstrip line, and the third short - circuit stub is greater than a quarter - wavelength corresponding to the center frequency of the wide - bandpass filter;

[0060] The sum of the electrical lengths of the eighth microstrip line, the ninth microstrip line, and the fourth short - circuit stub is greater than a quarter - wavelength corresponding to the center frequency of the wide - bandpass filter;

[0061] That is: θ 3 +θ 4 +θ 5 >θ.

[0062] Furthermore, the odd - mode characteristic impedance of the first parallel line is equal to the odd - mode characteristic impedance of the third parallel line; the even - mode characteristic impedance of the first parallel line is equal to the even - mode characteristic impedance of the third parallel line. In this embodiment, the odd - mode characteristic impedance of the first parallel line and the odd - mode characteristic impedance of the third parallel line are denoted as Z o1 ; the even - mode characteristic impedance of the first parallel line and the even - mode characteristic impedance of the third parallel line are denoted as Z e1 ;

[0063] Furthermore, the characteristic impedance of the first microstrip line, the characteristic impedance of the tenth microstrip line, the characteristic impedance of the first open - circuit stub, and the characteristic impedance of the second open - circuit stub are all equal. In this embodiment, the characteristic impedance of the first microstrip line, the characteristic impedance of the tenth microstrip line, the characteristic impedance of the first open - circuit stub, and the characteristic impedance of the second open - circuit stub are denoted as Z1 .

[0064] Furthermore, the characteristic impedances of 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 ninth microstrip line, the first short - circuit stub, the second short - circuit stub, the third short - circuit stub, and the fourth short - circuit stub are all equal. In this embodiment, the characteristic impedances of 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 ninth microstrip line, the first short - circuit stub, the second short - circuit stub, the third short - circuit stub, and the fourth short - circuit stub are denoted as Z 2 .

[0065] Since this topological structure can be equivalent to a symmetric structure, its transmission poles can be calculated by the odd - even mode method. To simplify the calculation process, first assume that the sum of the electrical lengths of the second microstrip line, the third microstrip line, and the first short - circuit stub is equal to a quarter - wavelength corresponding to the center frequency of the broadband band - pass filter, that is, θ 3 +θ 4 +θ 5 =θ.

[0066] Figure 2 is the odd - mode form diagram of this topological structure. Among them, the electrical length of the odd - mode transmission line is the electrical length of the second parallel line, that is, θ; the characteristic impedance of the odd - mode transmission line is the odd - mode characteristic impedance of the second parallel line, that is, Z o2 .

[0067]

[0068]

[0069] When Y ino = 0, it can be obtained that this topological structure has four odd - mode transmission poles. When f 0 is the center frequency of the band - pass filter, the frequencies corresponding to the four odd - mode transmission poles are:

[0070]

[0071]

[0072]

[0073]

[0074] Among them,

[0075] Δ o1 = 2Z 2 (Z e1 - Z o1 ) 2

[0076] Δ o2 = 4Z 2 Z o2 (Z e1 + Z o1 + 2) + 8Z 2 Z e1 Z o1 + Z o2 (Z e1 - Z o1 ) 2 + 4Z 1 Z 2 (Z e1 + Z o1 )

[0077] Δ o3 = 4Z o2 Z e1 Z o1 + Z 1 Z o2

[0078] Figure 3 is the even - mode form diagram of this topological structure. Among them, the electrical length of the even - mode transmission line is the electrical length of the second parallel line, that is, θ; the characteristic impedance of the even - mode transmission line is the even - mode characteristic impedance of the second parallel line, that is, Z e2 .

[0079]

[0080]

[0081] When Y ine = 0, it can be obtained that this topological structure has four even - transmission poles. When f 0 is the center frequency of the band - pass filter, the frequencies corresponding to the four even - mode transmission poles are:

[0082]

[0083]

[0084]

[0085]

[0086] Among them,

[0087] Δ e1 = 2Z 2 (Z e1 - Z o1 ) 2

[0088] Δ e2 = 4Z 2 Z e2 (Z e1 + Z o1 + 2) + 8Z 2 Z e1 Z o1 + Z e2 (Z e1 - Z o1 ) 2 + 4Z 1 Z 2 (Z e1 + Z o1 )

[0089] Δ o3 = 4Z e2 Z e1 Z o1 + Z 1 Z e2

[0090] For this topology, its transmission zeros 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 this topology; convert the ABCD matrix of this topology into the corresponding S matrix. When |S 21 | = 0, it can be obtained that this topology has three transmission zeros, and the frequencies corresponding to the three transmission zeros are respectively:

[0091] f z1 = 0

[0092] f z2 = f 0

[0093] f z3 = 2f 0

[0094] From the above analysis, when the sum of the electrical lengths of the second microstrip line, the third microstrip line, and the first short-circuited stub is equal to a quarter wavelength corresponding to the center frequency of the broadband bandpass filter, this topology has four odd-mode transmission poles, four even-mode transmission poles, and three transmission zeros. Returning to this topology, appropriately increasing the sum of the electrical lengths of the second microstrip line, the third microstrip line, and the first short-circuited stub will additionally increase three transmission zeros (f z4 , f z5 , fz6 ) However, the number of original poles and zeros remains unchanged. And no matter how the parameters Z o1 , Z e1 , Z o2 , Z e2 , Z 1 and Z 2 are changed, the relative positions of the transmission poles and zeros, that is, f z1 <f 3 <f ep1 <f op1 <f op2 <f ep2 <f 2 <f ep3 <f op3 <f op4 <f ep4 <f z4 <f z5 <f z6 will not change. Therefore, a broadband bandpass filter with notch characteristics can be designed based on this topological structure, with eight transmission poles in the passband to ensure its in-band flatness, five transmission zeros in the stopband to ensure high selectivity and high isolation, and one transmission zero in the passband to form the required notch.

[0095] An embodiment of the present utility model provides a filter, including the topological structure described in any one of the above.

[0096] Further, the filter further includes a circuit board, the dielectric constant of the circuit board is 3.38, the dielectric loss is 0.0022, the thickness is 0.813 mm, and the size is 35.8 mm * 11.8 mm;

[0097] Referring to Figure 4 , the line lengths of the transmission lines in the first parallel line and the third parallel line are both set to l p1 = 10.2 mm, the line widths are both set to w p1 = 0.2 mm, and the line spacings are both set to s p1 = 0.1 mm;

[0098] The line lengths of the transmission lines in the second parallel line are both set to l p2 = 10.2 mm, the line widths are both set to w p2 = 0.2 mm, and the line spacings are both set to s p2 = 0.15 mm;

[0099] The line lengths of the first microstrip line and the tenth microstrip line are both set to l 1 = 9.55 mm, and the line lengths of the first open stub and the second open stub are both set to l 2= 1.85 mm; the line widths of the first microstrip line, the tenth microstrip line, the first open stub, and the second open stub are all set to w 1 = 0.45 mm;

[0100] The distances between the first microstrip line and the first parallel line, and between the tenth microstrip line and the third parallel line are both set to s 1 = 0.1 mm;

[0101] The line lengths of the second microstrip line, the fourth microstrip line, the sixth microstrip line, and the eighth microstrip line are all set to l 3 = 5.15 mm; the line lengths of the third microstrip line, the fifth microstrip line, the seventh microstrip line, and the ninth microstrip line are all set to l 4 = 4.5 mm; the line lengths of the first short - circuit stub, the second short - circuit stub, the third short - circuit stub, and the fourth short - circuit stub are all set to l 5 = 2.2 mm;

[0102] The line widths of the second microstrip line, the fourth microstrip line, the sixth microstrip line, the eighth microstrip line, the third microstrip line, the fifth microstrip line, the seventh microstrip line, the ninth microstrip line, the first short - circuit stub, the second short - circuit stub, the third short - circuit stub, and the fourth short - circuit stub are all set to w 2 = 0.7 mm.

[0103] The simulation results of its S - parameters are as Figure 5 shown. The pass - band range with a reflection coefficient better than - 10 dB is from 2.252 GHz to 7.084 GHz, the center frequency is 4.668 GHz, the absolute bandwidth is 4.832 GHz, and the relative bandwidth is 103.5%. In addition, there are seven transmission poles in the pass - band, located at 2.321, 2.658, 4.373, 5.203, 5.881, 6.699, 7.042 GHz respectively. These seven transmission poles ensure the flatness of the pass - band; there is also a transmission zero in the pass - band, located at 4.485 GHz, to form the required notch, and the isolation at the center frequency of the notch is 39.8 dB, showing good isolation. There are five transmission zeros in the stop - band, located at 0, 0.438, 8.039, 9.882, 10.499 GHz respectively. These five transmission zeros ensure the high selectivity and high stop - band isolation of the filter.

[0104] Therefore, the topological structure of this embodiment can design a wide - pass - band filter with notch characteristics, having the advantages of high selectivity and miniaturization.

[0105] The above are only optional embodiments of the present utility model, and do not limit the patent scope of the present utility model accordingly. Any equivalent structural transformation made by using the content of the specification and drawings of the present utility model under the inventive concept of the present utility model, or any direct / indirect application in other related technical fields is included in the patent protection scope of the present utility model.

Claims

1. A wide passband filter topology with notch characteristics, characterized in that: It includes a first parallel line, a second parallel line and a third parallel line connected in sequence along a first direction, the other end of the first parallel line is connected to an input end, and the other end of the third parallel line is connected to an output end; A first microstrip line and a first open-circuit branch are sequentially connected between the first parallel line and the input end; A second microstrip line and a fourth microstrip line are symmetrically connected between the first parallel line and the second parallel line, the other end of the second microstrip line is sequentially connected to a third microstrip line and a first short-circuit branch, and the other end of the fourth microstrip line is sequentially connected to a fifth microstrip line and a second short-circuit branch; A sixth microstrip line and an eighth microstrip line are symmetrically connected between the second parallel line and the third parallel line, the other end of the sixth microstrip line is sequentially connected to a seventh microstrip line and a third short-circuit branch, and the other end of the eighth microstrip line is sequentially connected to a ninth microstrip line and a fourth short-circuit branch; A tenth microstrip line and a second open-circuit branch are sequentially connected between the third parallel line and the output end; The first microstrip line, the third microstrip line, the fifth microstrip line, the seventh microstrip line, the ninth microstrip line and the tenth microstrip line are all arranged along the first direction; the second microstrip line, the fourth microstrip line, the sixth microstrip line, the eighth microstrip line, the first open-circuit branch, the second open-circuit branch, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are all arranged along the second direction, and the first direction is perpendicular to the second direction.

2. The wide passband filter topology structure with notch characteristics according to claim 1, characterized in that: The first parallel line, the second parallel line and the third parallel line each include two transmission lines parallel to each other.

3. The wide passband filter topology structure with notch characteristics according to claim 1, characterized in that: The electrical length of the first parallel line, the electrical length of the second parallel line and the electrical length of the third parallel line are equal and are all equal to a quarter wavelength corresponding to the center frequency of the wide passband filter.

4. The wide passband filter topology structure with notch characteristics according to claim 3, characterized in that: The electrical length of the first microstrip line is equal to the electrical length of the tenth microstrip line; the electrical length of the first open-circuit branch node is equal to the electrical length of the second open-circuit branch node; The sum of the electrical length of the first microstrip line and the electrical length of the first open branch, and the sum of the electrical length of the tenth microstrip line and the electrical length of the second open branch are all one-quarter wavelength corresponding to the center frequency of the wide passband filter; or the sum of the electrical length of the first microstrip line and the electrical length of the first open branch, and the sum of the electrical length of the tenth microstrip line and the electrical length of the second open branch are all one-quarter wavelength corresponding to the notch center frequency of the wide passband filter.

5. The wide passband filter topology structure with notch characteristics according to claim 4, characterized in that: The electrical length of the second microstrip line, the electrical length of the fourth microstrip line, the electrical length of the sixth microstrip line and the electrical length of the eighth microstrip line are equal; The electrical length of the third microstrip line, the electrical length of the fifth microstrip line, the electrical length of the seventh microstrip line and the electrical length of the ninth microstrip line are equal; The electrical length of the first short-circuit branch, the electrical length of the second short-circuit branch, the electrical length of the third short-circuit branch and the electrical length of the fourth short-circuit branch are equal; 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 short-circuit branch is greater than a quarter wavelength corresponding to the center frequency of the wide passband filter; The sum of the electrical length of the fourth microstrip line, the electrical length of the fifth microstrip line and the electrical length of the second short-circuit branch is greater than a quarter wavelength corresponding to the center frequency of the wide passband filter; The sum of the electrical length of the sixth microstrip line, the electrical length of the seventh microstrip line and the electrical length of the third short-circuit branch is greater than a quarter wavelength corresponding to the center frequency of the wide passband filter; The sum of the electrical length of the eighth microstrip line, the electrical length of the ninth microstrip line and the electrical length of the fourth short-circuit branch is greater than a quarter wavelength corresponding to the center frequency of the wide passband filter.

6. The wide passband filter topology structure with notch characteristics according to claim 1, characterized in that: The odd-mode characteristic impedance of the first parallel line is equal to the odd-mode characteristic impedance of the third parallel line; the even-mode characteristic impedance of the first parallel line is equal to the even-mode characteristic impedance of the third parallel line.

7. The wide passband filter topology structure with notch characteristics according to claim 6, characterized in that: The characteristic impedance of the first microstrip line, the characteristic impedance of the tenth microstrip line, the characteristic impedance of the first open-circuit branch, and the characteristic impedance of the second open-circuit branch are all equal.

8. The wide passband filter topology structure with notch characteristics according to claim 7, characterized in that: 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 ninth microstrip line, the characteristic impedance of the first short-circuit branch, the characteristic impedance of the second short-circuit branch, the characteristic impedance of the third short-circuit branch and the characteristic impedance of the fourth short-circuit branch are all equal.

9. A filter, characterized in that: It comprises the topological structure described in any one of claims 1 to 8.

10. The filter according to claim 9, characterized in that The filter further comprises a circuit board, the circuit board has a dielectric constant of 3.38, a dielectric loss of 0.0022, a thickness of 0.813 mm, and a size of 35.8 mm*11.8 mm; The lengths of the transmission lines in the first parallel line and the third parallel line are both set to l p1 =10.2mm, line width is set to w p1 =0.2mm, line spacing is set to s p1 =0.1mm; The length of the transmission lines in the second parallel lines is set to l p2 =10.2mm, line width is set to w p2 =0.2mm, line spacing is set to s p2 =0.15mm; The line lengths of the first microstrip line and the tenth microstrip line are both set to l1=9.55 mm, and the line lengths of the first open branch node and the second open branch node are both set to l2=1.85 mm; the line widths of the first microstrip line, the tenth microstrip line, the first open branch node, and the second open branch node are all set to w1=0.45 mm; The spacing between the first microstrip line and the first parallel line, and the spacing between the tenth microstrip line and the third parallel line are both set to s1=0.1 mm; The lengths of the second microstrip line, the fourth microstrip line, the sixth microstrip line and the eighth microstrip line are all set to l3=5.15 mm; the lengths of the third microstrip line, the fifth microstrip line, the seventh microstrip line and the ninth microstrip line are all set to l4=4.5 mm; the lengths of the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are all set to l5=2.2 mm; The line widths of the second microstrip line, the fourth microstrip line, the sixth microstrip line, the eighth microstrip line, the third microstrip line, the fifth microstrip line, the seventh microstrip line, the ninth microstrip line, the first short-circuit branch, the second short-circuit branch, the third short-circuit branch and the fourth short-circuit branch are all set to w2=0.7mm.

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