Ultra-wideband bidirectional absorption type common-mode filter based on traveling wave mechanism and hybrid transmission line conversion structure

Abstract

The invention discloses an ultra-wideband bidirectional absorption type common mode filter based on a traveling wave mechanism and a hybrid transmission line conversion structure, and the filter comprises the hybrid transmission line conversion structure which is used for supporting the transmission of a differential mode signal; and the traveling wave absorption unit is used for absorbing destructive common-mode signals in the hybrid transmission line conversion structure. The hybrid transmission line conversion structure is composed of a grounding coplanar waveguide, a microstrip line, a dielectric integrated coplanar waveguide and broadside isolation differential lines located on the top layer and the bottom layer. The traveling wave absorption unit is composed of a medium integration groove line, a bonding pad and a lumped resistor. According to the novel broadside isolation differential line provided by the invention, destructive differential mode parasitic resonance in a traditional design can be effectively inhibited, and thus the bandwidth of complete transmission of a useful differential mode signal is improved; meanwhile, destructive common-mode electromagnetic noise can be coupled and transmitted to the lumped resistor in a traveling wave mode to be dissipated, and the bidirectional common-mode absorption bandwidth is larger.

Description

Technical Field

[0001] The present invention belongs to the technical field of circuit-level electromagnetic compatibility, and particularly relates to an ultra-wideband bidirectional absorption common-mode filter based on traveling wave mechanism and hybrid transmission line conversion structure. Background Art

[0002] In recent years, China has deployed the fifth-generation mobile communication network on a large scale and prospectively laid out the technical reserves for future B5G / 6G, supporting the development of strategic emerging industries such as intelligent driving, virtual reality, drone communication, remote medical treatment, and smart city with higher data transmission rates, larger channel capacities, and lower transmission delays. In this context, improving the electromagnetic compatibility of wireless communication devices is crucial for ensuring the transmission quality of ultra-high-speed data. Currently, the differential transmission scheme has become the de facto industry standard for modern high-speed digital circuits, so ultra-high-speed data is mostly transmitted between high-speed chips, circuits, and systems in the form of differential-mode signals. Thanks to the electromagnetic characteristics of differential-mode signal cancellation in opposite phases, the differential transmission scheme has the advantages of strong anti-interference ability, accurate timing positioning, and good signal integrity. However, high-speed digital circuits based on the differential transmission scheme still face challenges in electromagnetic compatibility. Among them, destructive common-mode electromagnetic noise is one of the main sources of radiation and conducted interference in modern high-speed digital circuits, and it will reduce the overall electromagnetic compatibility performance of circuits and systems. On the one hand, with the continuous improvement of the integration level of modern circuits (including planar wiring density, device integration density, and the number of vertical layers), differential wiring in actual circuits will face many unbalanced factors, including crosstalk from adjacent wiring, corners, length mismatch, asymmetric loads, via layer conversion, and unequal rise and fall times of differential-mode signals. These unbalanced factors will cause some useful differential-mode signals to convert into destructive common-mode noise in a specific frequency band. On the other hand, parasitic capacitances and inductances generated by chip packaging, as well as thermal noise leaked out through pins and packaging from transistors inside the chip, etc., are also important inducements for the generation of common-mode noise. It can be said that for high-speed digital circuits, the sources of destructive common-mode electromagnetic noise are extensive and inevitable. At the same time, for the fifth-generation mobile communication system, the data transmission rates and coding methods between different circuits and modules are different, which also makes the common-mode electromagnetic noise show the characteristics of discreteness and large distribution bandwidth. Therefore, suppressing broadband common-mode electromagnetic noise and protecting the complete transmission of useful differential-mode signals have become the urgent needs of contemporary highly reliable high-speed digital circuits.

[0003] As an important balanced microwave device, the common-mode filter can effectively protect the complete transmission of high-speed differential-mode signals and suppress the common-mode electromagnetic noise in a specific frequency band. Therefore, it has become a research hotspot in academia and industry. In the initial stage of research, the common-mode filter was mainly based on the reflection mechanism, that is, by loading various resonant structures directly below the edge-coupled microstrip line. Under common-mode excitation, the differential line can excite the resonance of the resonator below through the vertical electric field, causing a large impedance mismatch in the overall common-mode impedance of the filter near the resonance frequency point, and then reflecting the destructive common-mode electromagnetic noise back to the front-stage circuit. Typical reported resonant structures include: slot line / defected ground structure, mushroom-type multimode resonator, transmission line resonator, and resonant circuit based on LC lumped elements, etc. The maximum relative bandwidth of common-mode rejection generally achievable by this type of reflective common-mode filter can reach 100%, and the common-mode rejection bandwidth needs to be further improved. At the same time, it also faces the challenge of limited transmission bandwidth of useful differential-mode signals. Research has shown that for a common-mode filter loaded with a slot line / defected ground structure, under differential-mode signal excitation, differential-mode parasitic resonance is likely to occur at the second harmonic of the common-mode rejection stopband, thus destroying the complete transmission of the differential-mode signal and further restricting the improvement of the data transmission rate. In addition, it is worth noting that the common-mode electromagnetic noise reflected back to the front-stage circuit still exists in high-speed digital circuits and systems, and the potential electromagnetic interference problem caused by the common-mode electromagnetic noise has not been completely solved. In response to this, absorption-type common-mode filters based on the concept of non-reflection have been successively reported. The absorption-type common-mode filter is to load a lumped resistor in the common-mode electromagnetic noise propagation path and the aforementioned typical resonant structures to construct a resistive resonant circuit, or utilize the inherent conductor and dielectric losses during the resonance of a high-Q resonator to convert the energy of the common-mode electromagnetic noise that should originally be reflected back to the front-stage circuit into heat dissipation, thus more thoroughly solving the potential electromagnetic interference problem caused by the common-mode electromagnetic noise. Currently, the maximum relative bandwidth of the common-mode absorption stopband generally achievable by the reported absorption-type common-mode filters can reach 100%, and it also faces the challenge that differential-mode parasitic resonance restricts the improvement of the transmission rate of useful differential-mode signals.

[0004] Based on a comprehensive analysis of the reported common-mode filters, it is not difficult to see that both reflective and absorption-type common-mode filters need to load electromagnetic resonant structures, that is, the existing research work is based on the resonance standing wave mechanism of the resonator. This also strictly limits the common-mode rejection stopband within a relatively narrow frequency band near the resonance frequency point, and the common-mode rejection bandwidth is relatively limited, and it has gradually been unable to meet the performance requirements of the fifth-generation mobile communication system for suppressing ultra-wideband and ultra-high-frequency common-mode electromagnetic noise, and there is an urgent need for innovation and breakthrough in physical mechanisms. At the same time, the phenomenon of differential-mode parasitic resonance existing in the reported common-mode filters greatly restricts the improvement of the transmission rate of useful data, and there is an urgent need for a new solution to increase the bandwidth of the complete transmission of differential-mode signals. Summary of the Invention

[0005] The object of the present invention is to provide an ultra-wideband bidirectional absorption common-mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure, aiming at the problems existing in the prior art. While eliminating the differential-mode parasitic resonance in the traditional design to improve the complete transmission bandwidth of the differential-mode signal, the ultra-wideband and bidirectional common-mode absorption performance is realized based on the traveling wave mechanism, and it has the advantages of simple design and low processing cost compared with the existing research work.

[0006] The technical solution for achieving the object of the present invention is: an ultra-wideband bidirectional absorption common-mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure, the common-mode filter includes a hybrid transmission line conversion structure and a traveling wave absorption unit;

[0007] The hybrid transmission line conversion structure is used to support the transmission of differential-mode signals;

[0008] The traveling wave absorption unit is used to absorb the destructive common-mode signals in the hybrid transmission line conversion structure.

[0009] Further, the hybrid transmission line conversion structure includes four groups of hybrid transmission line sub-conversion structures whose projections are completely axially symmetric. Each group of hybrid transmission line sub-conversion structures includes a grounded coplanar waveguide, a microstrip line, a dielectric integrated coplanar waveguide, and a wide-side isolated differential line connected in sequence. The wide-side isolated differential line adopts a power distribution network scheme for feeder design, and the power distribution network is located above and below the traveling wave absorption unit, and is used to couple the destructive common-mode signals in the hybrid transmission line conversion structure into the traveling wave absorption unit.

[0010] Further, the traveling wave absorption unit includes a number of traveling wave absorption sub-units A, which are evenly divided into N groups, and the number of N is the same as the number of output feeders of the power distribution network; each output feeder of the power distribution network is located above and below a group of traveling wave absorption sub-units A respectively.

[0011] Further, the common-mode filter includes a first dielectric layer, a second dielectric layer, a third dielectric layer, a fourth dielectric layer, and a fifth dielectric layer arranged in sequence from top to bottom; the first dielectric layer, the third dielectric layer, and the fifth dielectric layer are all core boards for metal circuit structure design, and the second dielectric layer and the fourth dielectric layer are prepregs used as bonding layers for the multi-layer circuit structure; a top metal layer is provided on the upper surface of the first dielectric layer, a bottom metal layer is provided on the lower surface of the fifth dielectric layer, a second metal layer is provided between the second dielectric layer and the third dielectric layer, and a third metal layer is provided between the third dielectric layer and the fourth dielectric layer; the second layer metal and the third layer metal are both the reference ground layers of the common-mode filter.

[0012] Further, the grounded coplanar waveguide includes a center conductor microstrip line disposed on the top metal layer, and ground pads disposed on both sides of the center conductor microstrip line and located on the top metal and bottom metal layers. At the same time, the two ground pads on the top metal layer and the two ground pads on the bottom metal layer are grounded and interconnected through first metallized vias. At the same time, the wide-side isolated differential lines in two adjacent hybrid transmission line sub-conversion structures are respectively located on the top metal layer and the bottom metal layer.

[0013] Further, the wide-side isolated differential lines in two adjacent hybrid transmission line sub-conversion structures have a mirror-symmetric structural feature in the projection direction.

[0014] Further, the dielectric integrated coplanar waveguide includes a center conductor disposed on the second metal layer and the third metal layer, and slot line gaps disposed on the second metal layer and the third metal layer. The peripheries of the center conductor located on the second metal layer and the third metal layer and the peripheries of the slot line gaps are respectively interconnected through first blind vias, so as to convert the two-layer metal structure into a single-conductor structure while preventing electromagnetic wave energy from leaking into the resonant cavity formed by the second metal layer and the third metal layer to excite destructive parasitic resonances.

[0015] Further, all the traveling-wave absorber sub-units A in each group of traveling-wave absorber sub-units A are arranged in parallel and coaxially. For each of the traveling-wave absorber sub-units A, it includes a dielectric integrated slot transmission line, a pad and a lumped resistor. Among them, the dielectric integrated slot transmission line includes slot lines etched on the second metal layer and the third metal layer, and the periphery of the slot lines is interconnected through second blind vias. The output feeder of the power distribution network is located above and below the center position of the slot lines. Two lumped resistors are provided on the top metal layer, and the projections are respectively close to both ends of the slot lines, that is, on both sides of the output feeder. Each end of each lumped resistor is welded to a pad. Pads corresponding one-to-one to the pads on the top metal layer are provided on the bottom metal layer, and the pads on the bottom metal layer and the top metal layer are grounded and interconnected through second metallized vias.

[0016] Further, the dielectric integrated slot transmission line has a structure that is wide at both ends and narrow in the middle, and includes a first slot line, a second slot line and a third slot line connected in sequence. The line width of the second slot line is smaller than the line widths of the first slot line and the third slot line. The output feeder of the power distribution network is located above and below the second slot line.

[0017] Further, the common-mode filter has an up-and-down symmetric structure, that is, the materials and thicknesses of the first dielectric layer and the fifth dielectric layer are the same, and the materials and thicknesses of the second dielectric layer and the fourth dielectric layer are the same.

[0018] Compared with the prior art, the remarkable advantages of the present invention are:

[0019] (1) A novel wide - side isolated differential line composed of a second metal layer, a third metal layer, and two mirror - symmetrically distributed wide - side isolated differential lines is proposed. This integrated design in the vertical direction enables the ideal electric boundary and ideal magnetic boundary in both odd - mode and even - mode operating states to overlap with the intermediate layer. As a result, the parasitic resonance under differential - mode excitation in traditional common - mode filters can be suppressed, greatly expanding the bandwidth for the complete transmission of useful differential - mode signals and facilitating the improvement of data transmission rates in high - speed digital circuits. This proposed novel wide - side isolated differential line structure is original and has superiority in performance.

[0020] (2) The reported reflective and absorptive common - mode filters both require loading electromagnetic resonance structures. The resonance standing - wave characteristics of the resonators strictly limit the common - mode rejection stopband achievable by traditional designs to a narrow frequency band near the resonance frequency point. The present invention proposes a design method for an ultra - wideband bidirectional absorptive common - mode filter based on the traveling - wave mechanism. Without loading additional resonance structures, by constructing a conversion structure between the wide - side isolated differential line and the dielectric integrated slot line, the destructive common - mode electromagnetic noise can be coupled and transmitted to the lumped resistor in the form of a traveling - wave mode and dissipated. Benefiting from the broadband characteristics of the traveling - wave mode, compared with the reported common - mode filters, the common - mode absorption bandwidth achievable by the present invention is larger, and this design method is original.

[0021] (3) Compared with the reported reflective and absorptive common - mode filters, the present invention has performance advantages such as a high differential - mode cut - off frequency (which can suppress the destructive differential - mode parasitic resonance in traditional designs), a larger common - mode absorption stopband bandwidth, and bidirectional common - mode absorption.

[0022] The present invention will be further described in detail below with reference to the accompanying drawings. Description of the Drawings

[0023] Figure 1 It is a three - dimensional view of an ultra - wideband bidirectional absorptive common - mode filter in an embodiment.

[0024] Figure 2 It is a side view of an ultra - wideband bidirectional absorptive common - mode filter in an embodiment.

[0025] Figure 3 It is a top view of the first - layer structure of an ultra - wideband bidirectional absorptive common - mode filter in an embodiment.

[0026] Figure 4 It is a top view of the second - layer and third - layer structures of an ultra - wideband bidirectional absorptive common - mode filter in an embodiment.

[0027] Figure 5 It is a top view of the fourth - layer structure of an ultra - wideband bidirectional absorptive common - mode filter in an embodiment.

[0028] Figure 6 Schematic diagram of the hybrid-mode scattering parameters obtained from the full-wave simulation of an ultra-wideband bidirectional absorption common-mode filter in an embodiment.

[0029] Figure 7 Schematic diagram of the mode conversion coefficients obtained from the full-wave simulation of an ultra-wideband bidirectional absorption common-mode filter in an embodiment. Detailed implementation manners

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present invention and its application or use. 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.

[0031] Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps described in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and devices should be regarded as part of the authorization specification. In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may also include different values. It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0032] In the description of the present invention, the meaning of several is more than one, and the meaning of multiple is more than two. Understandings such as greater than, less than, exceeding, etc. do not include the present number, and understandings such as above, below, within, etc. include the present number. If there is a description of first and second, it is only for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0033] In the description of the present invention, the descriptions with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0034] In one embodiment, the present invention provides an ultra-wideband bidirectional absorption common-mode filter based on the traveling-wave mechanism and a hybrid transmission line conversion structure. The common-mode filter includes a hybrid transmission line conversion structure and a traveling-wave absorption unit.

[0035] The hybrid transmission line conversion structure is used to support the transmission of differential-mode signals.

[0036] The traveling-wave absorption unit is used to absorb the destructive common-mode signals in the hybrid transmission line conversion structure.

[0037] Further, in one of the embodiments, in combination with Figure 1 , the hybrid transmission line conversion structure includes four groups of hybrid transmission line sub-conversion structures whose projections are completely axially symmetric. Each group of hybrid transmission line sub-conversion structures includes a grounded coplanar waveguide 1, a microstrip line 2, a dielectric integrated coplanar waveguide 3, and a wide-side isolated differential line connected in sequence. The wide-side isolated differential line is designed for feeding using a power distribution network scheme, and the power distribution network is located above and below the traveling-wave absorption unit for coupling the destructive common-mode signals in the hybrid transmission line conversion structure into the traveling-wave absorption unit.

[0038] Here, a power distribution network scheme is used for feeding design to improve the common-mode absorption impedance matching performance.

[0039] Here, by designing the line widths of each section of the transmission line, the odd-mode impedance of the overall hybrid transmission line conversion structure can be ensured to be maintained near 50 Ω within an ultra-wide frequency band to ensure the complete transmission of useful differential-mode signals.

[0040] Preferably here, the four groups of hybrid transmission line sub-conversion structures are distributed at the four vertices of a square. The traveling-wave absorption unit is located at the axially symmetric center position of the four groups of hybrid transmission line sub-conversion structures.

[0041] It should be noted here that the number of hybrid transmission line sub-conversion structures is not limited to the above four groups and can be extended in the above manner according to actual requirements.

[0042] Further, in one of the embodiments, in combination with Figure 1, the traveling wave absorption unit includes a plurality of traveling wave absorption sub-units A, which are evenly divided into N groups, and the number of N is the same as the number of output feeders of the power distribution network; each output feeder of the power distribution network is respectively located above and below a group of traveling wave absorption sub-units A.

[0043] Further, in one embodiment, in combination with Figure 2 , the common mode filter includes a first dielectric layer C1, a second dielectric layer P2, a third dielectric layer C3, a fourth dielectric layer P4, and a fifth dielectric layer C5 arranged in sequence from top to bottom; the first dielectric layer C1, the third dielectric layer C3, and the fifth dielectric layer C5 are all core boards for metal circuit structure design, and the second dielectric layer P2 and the fourth dielectric layer P4 are prepregs used as adhesive layers for multi-layer circuit structures; a top metal layer is provided on the upper surface of the first dielectric layer C1, a bottom metal layer is provided on the lower surface of the fifth dielectric layer C5, a second metal layer is provided between the second dielectric layer P2 and the third dielectric layer C3, and a third metal layer is provided between the third dielectric layer C3 and the fourth dielectric layer P4; the second layer metal and the third layer metal are both reference ground layers of the common mode filter.

[0044] Further, in one embodiment, in combination with Figures 1 to 5 , the grounded coplanar waveguide 1 includes a center conductor microstrip line provided on the top metal layer, and ground pads 5 provided on both sides of the center conductor microstrip line and located on the top metal and bottom metal layers. At the same time, the two ground pads 5 on the top metal layer and the two ground pads 5 on the bottom metal layer are grounded and interconnected through the first metallized via 6-1; at the same time, the wide-side isolated differential lines in two adjacent hybrid transmission line sub-conversion structures are respectively located on the top metal layer and the bottom metal layer.

[0045] Preferably, in some embodiments, the wide-side isolated differential lines in two adjacent hybrid transmission line sub-conversion structures have a mirror-symmetric structural feature in the projection direction. That is, the adjacent first wide-side isolated differential line 4-1 and the second wide-side isolated differential line 4-2, which are respectively located on the top metal layer and the bottom metal layer, have a mirror-symmetric structural feature in the projection direction.

[0046] Further preferably, in some embodiments, the microstrip line 2, the first wide-edge isolated differential line 4-1, and the second wide-edge isolated differential line 4-2 improve the impedance matching performance of the hybrid transmission line conversion structure by corner chamfering to enhance the differential-mode transmission and common-mode absorption performance. Preferably, each of the first wide-edge isolated differential line 4-1 / the second wide-edge isolated differential line 4-2 includes a first wide microstrip line and a second wide microstrip line that are sequentially connected and form a corner, and further includes a plurality of narrow microstrip lines forming a multi-way power division network, and the narrow microstrip lines of the two first wide-edge isolated differential lines 4-1 located on the top metal layer are correspondingly connected, and the narrow microstrip lines of the two second wide-edge isolated differential lines 4-2 located on the bottom metal layer are correspondingly connected.

[0047] Further, in one of the embodiments, in combination with Figures 1 to 5 , the dielectric integrated coplanar waveguide 3 includes a center conductor strip 3-1 disposed on the second metal layer and the third metal layer, and a slot line gap 3-2 disposed on the second metal layer and the third metal layer. The peripheries of the center conductor strip 3-1 and the slot line gap 3-2 located on the second metal layer and the third metal layer are respectively interconnected through the first blind vias 7-1, so as to convert the two-layer metal structure into a single-conductor structure while preventing electromagnetic wave energy from leaking into the resonant cavity formed by the second metal layer and the third metal layer to excite destructive parasitic resonances.

[0048] Further, in one of the embodiments, in combination with Figures 1 to 5 , all the traveling-wave absorber sub-units A in each group of traveling-wave absorber sub-units A are arranged in parallel and coaxially; for each of the traveling-wave absorber sub-units A: it includes a dielectric integrated slot transmission line 8, a pad 9, and a lumped resistor 10. Among them, the dielectric integrated slot transmission line 8 includes a slot line etched on the second metal layer and the third metal layer, and the periphery of the slot line is interconnected through the second blind vias 7-2 to prevent electromagnetic wave energy from leaking into the resonant cavity formed by the second and third metal layers to excite destructive parasitic resonances; the output feeder of the power distribution network is located above and below the center position of the slot line; two lumped resistors 10 are provided on the top metal layer, and the projections are respectively close to both ends of the slot line, that is, on both sides of the output feeder; both ends of each lumped resistor 10 are respectively welded to a pad 9; pads 9 corresponding to the pads 9 on the top metal layer are provided on the bottom metal layer, and the pads 9 on the bottom metal layer and the top metal layer are grounded and interconnected through the second metallized vias 6-2..

[0049] Here, preferably, in some embodiments, the dielectric integrated slot transmission line 8 has a structure that is wide at both ends and narrow in the middle (wide-narrow-wide), and includes a first slot line, a second slot line, and a third slot line that are sequentially connected. The line width of the second slot line is smaller than the line widths of the first slot line and the third slot line; the output feeder of the power distribution network is located above and below the second slot line.

[0050] Further preferably, in some embodiments, the characteristic impedance of the first slot line and the third slot line is greater than that of the second slot line.

[0051] Here, by adjusting the line widths of the wider slot lines, namely the first slot line and the third slot line, the impedance matching performance of the absorptive common-mode filter is adjusted and improved, and the ultra-wideband common-mode absorption performance is enhanced.

[0052] Further, in one of the embodiments, the common-mode filter has an up-down symmetric structure, that is, the materials and thicknesses of the first dielectric layer C1 and the fifth dielectric layer C5 are the same, and the materials and thicknesses of the second dielectric layer P2 and the fourth dielectric layer P4 are the same.

[0053] Preferably, as a specific example, in some embodiments, the present invention is further verified and illustrated.

[0054] In this embodiment, the materials of the first, third, and fifth dielectric layers are all selected as Rogers RO4003 (relative dielectric constant is 3.55, loss tangent is 0.0027), and the materials of the second and fourth dielectric layers are selected as Rogers RO4450F (relative dielectric constant is 3.52, loss tangent is 0.004), combined with Figure 2 , the thicknesses of each dielectric layer are set as: H1 = H3 = H5 = 0.3048 mm, H2 = H4 = 0.2032 mm.

[0055] In this embodiment, combined with Figure 3 , the lengths, line widths, pad spacings, and resistances of each section of the transmission line in the hybrid transmission line conversion structure are set as: the length L1 of the center conductor microstrip line of the grounded coplanar waveguide 1 is 11.1 mm, the length L2 of the microstrip line 2 is 12.5 mm, the length L3 of the first wide microstrip line is 13.05 mm, the length L4 of the second wide microstrip line is 4 mm, the width W_diff3 of the center conductor microstrip line of the grounded coplanar waveguide 1 is 1.1 mm, the width W_diff4 of the narrow microstrip line is 0.25 mm, the spacing g_pad1 between the center conductor microstrip line of the grounded coplanar waveguide 1 and the grounded pad 5 is 1.6 mm, and the resistance value R of the lumped resistor 10 is 50 Ω.

[0056] In this embodiment, combined with Figure 4, there are a total of 18 traveling-wave absorber sub-units A, which are evenly divided into two groups. In the traveling-wave absorber sub-unit A, the length and line width of the dielectric integrated slot line 8 are set as follows: the length of the second slot line L_slot1 = 9.25 mm, the lengths of the first slot line and the third slot line L_slot2 = 3.8 mm, the width of the second slot line W_slot1 = 0.25 mm, and the widths of the first slot line and the third slot line W_slot2 = 3.8 mm; the periodic absorption spacing of the traveling-wave absorber sub-units A in the same group is set as: P y = 4.5 mm; in the dielectric integrated coplanar waveguide 3, the lengths and line widths of the center conductor strip 3-1 and the slot line gap 3-2 are set as: the length of the center conductor strip 3-1 L5 = 2.7 mm, the width of the center conductor strip 3-1 w_cpw = 0.5 mm, and the width of the slot line gap 3-2 g_cpw = 0.45 mm.

[0057] In this embodiment, the first wide-side isolated differential line 4-1 / second wide-side isolated differential line 4-2 is a two-way power division network formed by two narrow microstrip lines. Each narrow microstrip line includes a first narrow microstrip line and a second narrow microstrip line that are connected in sequence and form a corner, and the narrow microstrip lines of the two first wide-side isolated differential lines 4-1 located on the top metal layer are correspondingly connected to form a rectangular path, and the narrow microstrip lines of the two second wide-side isolated differential lines 4-2 located on the bottom metal layer are correspondingly connected to form a rectangular path. Combining Figure 4 , the lengths of the first wide-side isolated differential line 4-1 / second wide-side isolated differential line 4-2 are set as: the length of the rectangular path L6 = 47.5 mm, and the width L7 = 22.5 mm; the spacing of the pads 9 is set as: g_pad2 = 0.6 mm.

[0058] Figure 6 are the hybrid-mode scattering parameters obtained from the full-wave simulation of the ultra-wideband bidirectional absorption-type common-mode filter proposed by the present invention. It can be seen that in the ultra-wide frequency band of DC - 20 GHz, the differential-mode insertion loss |S dd21 | remains at a low level, and the differential-mode reflection coefficient S dd11 can basically be maintained below -15 dB throughout the frequency band, indicating that this common-mode filter can protect the complete transmission of differential-mode signals in the ultra-wide frequency range of DC - 20 GHz. At the same time, due to the structural symmetry of the entire common-mode filter in the signal propagation direction, the bidirectional common-mode transmission coefficients S cc21 and S cc12 overlap, the bidirectional common-mode reflection coefficients S cc11 and S cc22 overlap, and the common-mode transmission coefficient S cc21 and the common-mode reflection coefficient S cc11It can be maintained below -10 dB simultaneously within the ultra-wide frequency band range of 2 GHz - 17 GHz, and the relative bandwidth of the common-mode absorption stopband reaches 158%, demonstrating that this common-mode filter can achieve two-way and efficient absorption performance of common-mode electromagnetic noise within the ultra-wide frequency band range of 2 GHz - 17 GHz. Compared with existing research work, the present invention has the performance advantages of an extremely high 3 dB differential-mode cut-off frequency and an extremely wide two-way common-mode absorption bandwidth.

[0059] Figure 7 It is the mode conversion coefficient obtained from the full-wave simulation of the ultra-wideband two-way absorption common-mode filter proposed by the present invention. It can be seen that the differential common-mode conversion coefficients S cd21 and S cd11 are maintained below -30 dB within DC - 20 GHz, at a relatively low level, indicating that the common-mode filter proposed by the present invention has excellent circuit balance and can effectively suppress the conversion of useful differential-mode signals into destructive common-mode electromagnetic noise, thereby protecting the signal integrity of differential-mode signals.

[0060] The above are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the concept of the present invention belong to the protection scope of the present invention. It should be noted that for those of ordinary skill in the art, several improvements and refinements made without departing from the principle of the present invention should be regarded as within the protection scope of the present invention.

Claims

1. A ultra-wideband bidirectional absorption common-mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure, characterized in that The common-mode filter includes a hybrid transmission line conversion structure and a traveling wave absorption unit; The hybrid transmission line conversion structure is used to support the transmission of differential-mode signals; The traveling wave absorption unit is used to absorb the destructive common-mode signals in the hybrid transmission line conversion structure.

2. The ultra-wideband bidirectional absorption common-mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 1, characterized in that, The hybrid transmission line conversion structure includes four groups of hybrid transmission line sub-conversion structures whose projections are completely axisymmetric. Each group of hybrid transmission line sub-conversion structures includes a grounded coplanar waveguide (1), a microstrip line (2), a dielectric integrated coplanar waveguide (3), and a wide-side isolated differential line connected in sequence. The wide-side isolated differential line adopts a power distribution network scheme for feeder design, and the power distribution network is located above and below the traveling wave absorption unit, and is used to couple the destructive common-mode signals in the hybrid transmission line conversion structure into the traveling wave absorption unit.

3. The ultra-wideband bidirectional absorption common-mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 2, characterized in that, The traveling wave absorption unit includes a number of traveling wave absorption sub-units A, which are evenly divided into N groups, and the number of N is the same as the number of output feeders of the power distribution network; each output feeder of the power distribution network is respectively located above and below a group of traveling wave absorption sub-units A.

4. The ultra-wideband bidirectional absorption common-mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 2 or 3, characterized in that, The common-mode filter includes a first dielectric layer (C1), a second dielectric layer (P2), a third dielectric layer (C3), a fourth dielectric layer (P4), and a fifth dielectric layer (C5) arranged in sequence from top to bottom; the first dielectric layer (C1), the third dielectric layer (C3), and the fifth dielectric layer (C5) are all core boards for metal circuit structure design, and the second dielectric layer (P2) and the fourth dielectric layer (P4) are prepregs used as bonding layers for multi-layer circuit structures; a top metal layer is provided on the upper surface of the first dielectric layer (C1), a bottom metal layer is provided on the lower surface of the fifth dielectric layer (C5), a second metal layer is provided between the second dielectric layer (P2) and the third dielectric layer (C3), and a third metal layer is provided between the third dielectric layer (C3) and the fourth dielectric layer (P4); the second layer metal and the third layer metal are both reference ground layers of the common-mode filter.

5. The ultra-wideband bidirectional absorption common-mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 4, wherein The grounded coplanar waveguide (1) includes a center conductor microstrip line provided on the top metal layer, and ground pads (5) provided on both sides of the center conductor microstrip line and located on the top metal and bottom metal layers. At the same time, the two ground pads (5) on the top metal layer and the two ground pads (5) on the bottom metal layer are grounded and interconnected through the first metallized vias (6-1); at the same time, the wide-side isolated differential lines in two adjacent hybrid transmission line sub-conversion structures are respectively located on the top metal layer and the bottom metal layer.

6. The ultra-wideband bidirectional absorption common-mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 5, wherein, The wide-side isolated differential lines in two adjacent hybrid transmission line sub-conversion structures have a mirror-symmetric structural feature in the projection direction.

7. The ultra-wideband bidirectional absorption common-mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 4, characterized in that The dielectric integrated coplanar waveguide (3) includes a center conductor strip (3-1) disposed on the second metal layer and the third metal layer, and a slot line gap (3-2) disposed on the second metal layer and the third metal layer. The peripheries of the center conductor strip (3-1) and the slot line gap (3-2) on the second metal layer and the third metal layer are respectively interconnected through first blind vias (7-1), so as to convert the two-layer metal structure into a single-conductor structure while preventing the leakage of electromagnetic wave energy into the resonant cavity formed by the second metal layer and the third metal layer to excite destructive parasitic resonances.

8. The ultra-wideband bidirectional absorption common-mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 4, wherein All the traveling-wave absorber units A in each group of traveling-wave absorber units A are arranged in parallel and coaxially; for each of the traveling-wave absorber units A: it includes a dielectric integrated slot transmission line (8), a pad (9) and a lumped resistor (10). Among them, the dielectric integrated slot transmission line (8) includes a slot line etched on the second metal layer and the third metal layer, and the periphery of the slot line is interconnected through second blind vias (7-2). The output feeder of the power distribution network is located above and below the center position of the slot line; two lumped resistors (10) are provided on the top metal layer, and the projections are respectively close to both ends of the slot line, that is, on both sides of the output feeder; both ends of each lumped resistor (10) are respectively welded to a pad (9); pads (9) corresponding to the pads (9) on the top metal layer are provided on the bottom metal layer, and the pads (9) on the bottom metal layer and the top metal layer are grounded and interconnected through second metallized vias (6-2).

9. The ultra-wideband bidirectional absorption common-mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 8, wherein The dielectric integrated slot transmission line (8) has a structure that is wide at both ends and narrow in the middle, and includes a first slot line, a second slot line and a third slot line connected in sequence. The line width of the second slot line is smaller than the line widths of the first slot line and the third slot line; the output feeder of the power distribution network is located above and below the second slot line.

10. The ultra-wideband bidirectional absorption common-mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 4, characterized in that, The common-mode filter has an up-and-down symmetric structure, that is, the materials and thicknesses of the first dielectric layer (C1) and the fifth dielectric layer (C5) are the same, and the materials and thicknesses of the second dielectric layer (P2) and the fourth dielectric layer (P4) are the same.

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