An ultra-wideband bidirectional absorptive common-mode filter based on traveling wave mechanism and hybrid transmission line conversion structure

Abstract

The present invention discloses an ultra-wideband bidirectional absorption common-mode filter based on a traveling wave mechanism and a hybrid transmission line conversion structure, comprising: a hybrid transmission line conversion structure for supporting the transmission of differential-mode signals; and a traveling wave absorption unit for absorbing destructive common-mode signals in the hybrid transmission line conversion structure. The hybrid transmission line conversion structure is composed of a grounded coplanar waveguide, a microstrip line, a dielectric integrated coplanar waveguide, and wide-edge isolated differential lines located on the top and bottom layers. The traveling wave absorption unit is composed of a dielectric integrated slot line, a pad, and a lumped resistor. The novel wide-edge isolated differential line proposed in the present invention can effectively suppress the destructive differential-mode parasitic resonance in the traditional design, thereby increasing the bandwidth of the complete transmission of useful differential-mode signals; at the same time, the present invention can couple the destructive common-mode electromagnetic noise in the form of a traveling wave mode and transmit it to the lumped resistor for dissipation, thereby having a larger bidirectional common-mode absorption bandwidth.

Description

Technical Field

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

[0002] In recent years, my country has deployed fifth-generation mobile communication networks on a large scale and is proactively developing future B5G / 6G technology reserves. These networks aim to support the development of strategic emerging industries such as intelligent driving, virtual reality, drone communications, telemedicine, and smart cities with higher data rates, greater channel capacity, and lower transmission latency. In this context, improving the electromagnetic compatibility (EMC) of wireless communication equipment is crucial to ensuring the quality of ultra-high-speed data transmission. Currently, differential transmission has become the de facto industry standard for modern high-speed digital circuits. Therefore, ultra-high-speed data is often transmitted between high-speed chips, circuits, and systems using differential-mode signals. Thanks to the electromagnetic properties of differential-mode signals, which cancel each other out, differential transmission offers strong interference immunity, accurate timing positioning, and excellent signal integrity. However, high-speed digital circuits based on differential transmission still face EMC challenges. Destructive common-mode electromagnetic noise is a major source of radiated and conducted interference in modern high-speed digital circuits, and it can degrade the overall EMC performance of circuits and systems. On the one hand, with the continuous increase in modern circuit integration (including planar wiring density, device integration density, and vertical stacking), differential routing in actual circuits faces numerous imbalances, including crosstalk from adjacent traces, corners, length mismatches, asymmetric loading, via layer transitions, and unequal rise and fall times of differential-mode signals. These imbalances can cause some useful differential-mode signals to convert into destructive common-mode noise within specific frequency bands. Furthermore, parasitic capacitance and inductance generated by chip packaging, as well as thermal noise from internal transistors leaking through pins and packaging, are also significant contributors to common-mode noise. For high-speed digital circuits, destructive common-mode electromagnetic noise has a wide range of sources and is unavoidable. Furthermore, in fifth-generation mobile communication systems, the data transmission rates and encoding methods vary between different circuits and modules, resulting in a discrete and wide-bandwidth distribution of common-mode electromagnetic noise. Therefore, suppressing broadband common-mode electromagnetic noise while protecting the intact transmission of useful differential-mode signals has become a pressing need for modern, high-reliability, high-speed digital circuits.

[0003] Common-mode filters, as important balanced microwave components, effectively protect the integrity of high-speed differential-mode signals and suppress common-mode electromagnetic noise in specific frequency bands. Consequently, they have become a research hotspot in both academia and industry. In the early stages of research, common-mode filters primarily relied on a reflection mechanism. This mechanism involves loading various resonant structures directly beneath edge-coupled microstrip lines. Under common-mode excitation, the differential lines stimulate resonance in the underlying resonators through a perpendicular electric field, resulting in a significant impedance mismatch in the filter's overall common-mode impedance near the resonant frequency. This, in turn, reflects destructive common-mode electromagnetic noise back to the preceding circuitry. Typical resonant structures reported include slotline / defective ground structures, mushroom-type multimode resonators, transmission line resonators, and resonant circuits based on LC lumped elements. These reflective common-mode filters typically achieve a maximum common-mode rejection bandwidth of 100%. This common-mode rejection bandwidth needs to be further improved, and they also face the challenge of limited transmission bandwidth for useful differential-mode signals. Research has shown that common-mode filters loaded with slotline / defective ground structures, when excited by differential-mode signals, are prone to generating differential-mode parasitic resonances at multiples of the common-mode rejection stopband, disrupting the complete transmission of the differential-mode signal and thus limiting data transmission rate increases. Furthermore, it is noteworthy that common-mode electromagnetic noise reflected back to the preceding circuitry still exists in high-speed digital circuits and systems, and the potential electromagnetic interference caused by this common-mode electromagnetic noise has not been completely resolved. To address this issue, absorptive common-mode filters based on the concept of reflectionlessness have been reported. Absorptive common-mode filters employ a lumped resistor in the common-mode electromagnetic noise propagation path, creating a resistive resonant circuit, or utilize the inherent conductor and dielectric losses of high-Q resonators. This converts the energy of the common-mode electromagnetic noise that would otherwise be reflected back to the preceding circuitry into heat and dissipates it, thereby more completely addressing the potential electromagnetic interference caused by this common-mode electromagnetic noise. Currently, reported absorptive common-mode filters generally achieve a maximum common-mode absorption stopband relative bandwidth of 100%, but they also face the challenge of differential-mode parasitic resonances restricting the transmission rate of useful differential-mode signals.

[0004] A comprehensive analysis of reported common-mode filters reveals that both reflective and absorptive common-mode filters require electromagnetic resonant structures. Existing research is based on the resonant standing wave mechanism of the resonator. This restricts the common-mode rejection stopband to a narrow frequency band near the resonant frequency. The common-mode rejection bandwidth is relatively limited, and is gradually failing to meet the performance requirements of fifth-generation mobile communication systems for ultra-wideband and ultra-high-frequency common-mode electromagnetic noise suppression. Innovations and breakthroughs in physical mechanisms are urgently needed. Furthermore, the differential-mode parasitic resonances present in reported common-mode filters significantly limit the improvement of useful data transmission rates, necessitating new solutions to increase the bandwidth for complete differential-mode signal transmission. Summary of the Invention

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

[0006] The technical solution to achieve the purpose of the present invention is: an ultra-wideband bidirectional absorptive common-mode filter based on a traveling wave mechanism and a hybrid transmission line conversion structure, wherein 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 destructive common-mode signals in the hybrid transmission line conversion structure.

[0009] Furthermore, the hybrid transmission line conversion structure includes four groups of hybrid transmission line sub-conversion structures projected as completely axisymmetric, each group of hybrid transmission line sub-conversion structures includes a grounded coplanar waveguide, a microstrip line, a dielectric integrated coplanar waveguide and a broadside isolated differential line connected in sequence, and the broadside isolated differential line adopts a power distribution network solution for feeder design, and the power distribution network is located above and below the traveling wave absorption unit, which is used to couple the destructive common-mode signal in the hybrid transmission line conversion structure into the traveling wave absorption unit.

[0010] Furthermore, the traveling wave absorption unit includes several traveling wave absorption subunits A, which are evenly divided into N groups, where the number 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 subunits A respectively.

[0011] Furthermore, 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 used for metal circuit structure design, the second dielectric layer and the fourth dielectric layer are semi-cured sheets, used as adhesive layers for multi-layer circuit structures; the upper surface of the first dielectric layer is provided with a top metal layer, the lower surface of the fifth dielectric layer is provided with a bottom metal 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 of metal and the third layer of metal are both reference ground layers of the common mode filter.

[0012] Furthermore, the grounded coplanar waveguide includes a central conducting strip microstrip line arranged on the top metal layer, and grounding pads arranged on both sides of the central conducting strip microstrip line and located on the top metal and bottom metal layers. At the same time, the two grounding pads on the top metal layer and the two grounding pads on the bottom metal layer are grounded and interconnected through a first metallized through-hole; at the same time, the wide-side isolated differential lines in the two adjacent hybrid transmission line sub-conversion structures are respectively located on the top metal layer and the bottom metal layer.

[0013] Furthermore, the broadside isolated differential lines in two adjacent hybrid transmission line sub-conversion structures have mirror-symmetrical structural features in the projection direction.

[0014] Furthermore, the dielectric integrated coplanar waveguide includes a central conduction strip arranged on the second metal layer and the third metal layer, and a slot line gap arranged on the second metal layer and the third metal layer, and the periphery of the central conduction strip and the periphery of the slot line gap located on the second metal layer and the third metal layer are interconnected through a first blind hole, respectively, thereby converting the two-layer metal structure into a single conductor structure while avoiding 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 resonance.

[0015] Furthermore, all traveling wave absorption subunits A in each group of traveling wave absorption subunits A are arranged in parallel and coaxially; for each of the traveling wave absorption subunits A: it includes a dielectric integrated slot transmission line, a pad and a lumped resistor, wherein the dielectric integrated slot transmission line includes a slot line etched on the second metal layer and the third metal layer, and the slot line is interconnected by a second blind hole, and the output feeder of the power distribution network is located above and below the center position of the slot line; two lumped resistors are provided on the top metal layer, and the projections are close to the two ends of the slot line, that is, located on both sides of the output feeder; the two ends of each lumped resistor are respectively welded to a pad; the bottom metal layer is provided with pads corresponding to the pads on the top metal layer, and the pads on the bottom metal layer and the top metal layer are grounded and interconnected through second metallized through-holes.

[0016] Furthermore, the dielectric integrated slot transmission line has a structure that is wide at both ends and narrow in the middle, including a first slot line, a second slot line and a third slot line connected in sequence, and the line width of the second slot line is smaller than the line width 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] Furthermore, the common mode filter has a vertically symmetrical structure, that is, the first dielectric layer and the fifth dielectric layer are made of the same material and have the same thickness, and the second dielectric layer and the fourth dielectric layer are made of the same material and have the same thickness.

[0018] Compared with the prior art, the present invention has the following significant advantages:

[0019] (1) A new type of wide-side isolated differential line is proposed, which consists of a second metal layer, a third metal layer, and two mirror-symmetrically distributed wide-side isolated differential lines. This vertical integration design allows the ideal electric boundary and ideal magnetic boundary in odd-mode and even-mode working states to overlap with the middle layer, thereby suppressing the parasitic resonance under differential-mode excitation in traditional common-mode filters, greatly expanding the bandwidth of complete transmission of useful differential-mode signals, and facilitating the improvement of data transmission rates in high-speed digital circuits. This new type of wide-side isolated differential line is original in structure and superior in performance.

[0020] (2) Both the reflective and absorptive common-mode filters reported require the loading of electromagnetic resonant structures. The resonant standing wave characteristics of the resonator strictly limit the common-mode suppression stopband that can be achieved by traditional designs to a narrow frequency band near the resonant frequency. The present invention proposes a design method for an ultra-wideband bidirectional absorptive common-mode filter based on the traveling wave mechanism. Without the need to load an additional resonant structure, 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 by constructing a conversion structure between a wide-side isolated differential line and a dielectric integrated slot transmission line. Thanks to the broadband characteristics of the traveling wave mode, the common-mode absorption bandwidth that can be achieved by the present invention is larger than that of the reported common-mode filters, and the design method is original.

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

[0022] The present invention is further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. 3 is a three-dimensional diagram of an ultra-wideband bidirectional absorptive common mode filter according to an embodiment.

[0024] Figure 2 FIG. 4 is a side view of an ultra-wideband bidirectional absorptive common mode filter according to an embodiment.

[0025] Figure 3 FIG. 1 is a top view of the first layer structure of an ultra-wideband bidirectional absorptive common mode filter in one embodiment.

[0026] Figure 4 FIG1 is a top view of the second and third layer structures of an ultra-wideband bidirectional absorptive common mode filter in one embodiment.

[0027] Figure 5 FIG. 4 is a top view of the fourth layer structure of an ultra-wideband bidirectional absorptive common mode filter in one embodiment.

[0028] Figure 6 Schematic diagram of mixed mode scattering parameters obtained through full-wave simulation of an ultra-wideband bidirectional absorptive common mode filter in one embodiment.

[0029] Figure 7 Schematic diagram of the modal conversion coefficients obtained through full-wave simulation of an ultra-wideband bidirectional absorptive common-mode filter in one embodiment. DETAILED DESCRIPTION

[0030] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only 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 is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to actual proportional relationships. The techniques, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific values ​​should be interpreted as being merely exemplary, not as limitations. Therefore, other examples of the exemplary embodiments may also include different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0032] In the description of the present invention, "several" means more than one, "plurality" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

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

[0034] In one embodiment, the present invention proposes an ultra-wideband bidirectional absorptive common-mode filter based on a traveling wave mechanism and a hybrid transmission line conversion structure, wherein 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 destructive common-mode signals in the hybrid transmission line conversion structure.

[0037] Furthermore, in one embodiment, in combination Figure 1 The hybrid transmission line conversion structure includes four groups of hybrid transmission line sub-conversion structures that are projected as 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 broadside isolated differential line connected in sequence. The broadside isolated differential line adopts a power distribution network solution for feeder design, and the power distribution network is located above and below the traveling wave absorption unit to couple the destructive common-mode signal in the hybrid transmission line conversion structure into the traveling wave absorption unit.

[0038] Here, a power distribution network solution is adopted for feeder design to improve the common-mode absorption impedance matching performance.

[0039] Here, by designing the line width of each transmission line segment, the overall odd-mode impedance of the hybrid transmission line conversion structure can be kept near 50Ω within an ultra-wide frequency band, thereby ensuring complete transmission of useful differential-mode signals.

[0040] Here, preferably, the four groups of hybrid transmission line sub-conversion structures are distributed according to the four vertices of a square. The traveling wave absorption unit is located at the axisymmetric 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 expanded according to actual needs in the above manner.

[0042] Furthermore, in one embodiment, in combination Figure 1The traveling wave absorption unit includes several traveling wave absorption sub-units A, which are evenly divided into N groups, where the number 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.

[0043] Furthermore, in one embodiment, in combination 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 used for metal circuit structure design, the second dielectric layer P2 and the fourth dielectric layer P4 are prepregs used as adhesive layers for the multi-layer circuit structure; 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 metal layer and the third metal layer are both reference ground layers of the common-mode filter.

[0044] Furthermore, in one embodiment, in combination Figures 1 to 5 The grounded coplanar waveguide 1 includes a central conductive strip microstrip line arranged on the top metal layer, and ground pads 5 arranged on both sides of the central conductive strip microstrip line and located on the top metal layer and the bottom metal layer. 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 through-hole 6-1; at the same time, the broadside isolated differential lines in the 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 broadside isolated differential lines in two adjacent hybrid transmission line sub-conversion structures have mirror-symmetric structural features in the projection direction. That is, the first broadside isolated differential line 4-1 and the second broadside isolated differential line 4-2, located on the top metal layer and the bottom metal layer, respectively, have mirror-symmetric structural features in the projection direction.

[0046] Further preferably, in some embodiments, the microstrip line 2, the first wide-side isolated differential line 4-1, and the second wide-side isolated differential line 4-2 improve the impedance matching performance of the hybrid transmission line conversion structure by chamfering the corners, so as to enhance the differential mode transmission and common mode absorption performance. Preferably, the first wide-side isolated differential line 4-1 / the second wide-side isolated differential line 4-2 each includes a first wide microstrip line and a second wide microstrip line connected in sequence and forming a corner, and also includes a plurality of narrow microstrip lines forming a multi-way power division network, 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, 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.

[0047] Furthermore, in one embodiment, in combination Figures 1 to 5 The dielectric integrated coplanar waveguide 3 includes a central conductive strip 3-1 provided on the second metal layer and the third metal layer, and a slot line slot 3-2 provided on the second metal layer and the third metal layer, and the periphery of the central conductive strip 3-1 and the periphery of the slot line slot 3-2 on the second metal layer and the third metal layer are interconnected by a first blind hole 7-1, respectively, 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 resonance.

[0048] Furthermore, in one embodiment, in combination Figures 1 to 5 All traveling wave absorbing subunits A in each group of traveling wave absorbing subunits A are arranged in parallel and coaxially. Each traveling wave absorbing subunit A includes a dielectric integrated slot transmission line 8, a pad 9, and a lumped resistor 10. The dielectric integrated slot transmission line 8 includes a slot line etched on the second and third metal layers, and the slot line is interconnected by a second blind via 7-2 to prevent electromagnetic wave energy from leaking into the resonant cavity formed by the second and third metal layers and exciting destructive parasitic resonances. The output feeder of the power distribution network is located above and below the center of the slot line. Two lumped resistors 10 are provided on the top metal layer, and their projections are close to the ends of the slot line, that is, located on both sides of the output feeder. The two ends of each lumped resistor 10 are soldered to a pad 9. The bottom metal layer is provided with pads 9 that correspond one-to-one with the pads 9 on the top metal layer, and the pads 9 on the bottom and top metal layers are grounded and interconnected via second metallized through-holes 6-2.

[0049] 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), including a first slot line, a second slot line and a third slot line connected in sequence, and the line width of the second slot line is smaller than the line width 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 impedances of the first slotline and the third slotline are greater than the characteristic impedance of the second slotline.

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

[0052] Furthermore, in one embodiment, the common mode filter has a vertically symmetrical structure, that is, the first dielectric layer C1 and the fifth dielectric layer C5 have the same material and thickness, and the second dielectric layer P2 and the fourth dielectric layer P4 have the same material and thickness.

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

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

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

[0056] In this embodiment, combined with Figure 4There are 18 traveling wave absorption subunits A, divided into two groups. The length and line width of the dielectric integrated slot transmission line 8 in the traveling wave absorption subunit A are set to: the length of the second slot line L_slot1 = 9.25mm, the length of the first and third slot lines L_slot2 = 3.8mm, the width of the second slot line W_slot1 = 0.25mm, and the width of the first and third slot lines W_slot2 = 3.8mm; the periodic absorption spacing of the traveling wave absorption subunits A in the same group is set to: P y =4.5mm; in the dielectric integrated coplanar waveguide 3, the length and line width of the central guide strip 3-1 and the slot line gap 3-2 are set as follows: the length L5 of the central guide strip 3-1 = 2.7mm, the width w_cpw of the central guide strip 3-1 = 0.5mm, and the width g_cpw of the slot line gap 3-2 = 0.45mm.

[0057] In this embodiment, the first wide-side isolated differential line 4-1 / the second wide-side isolated differential line 4-2 is a two-way power splitting 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 sequentially connected and form a corner, and the two narrow microstrip lines of the first wide-side isolated differential line 4-1 located on the top metal layer are connected to form a rectangular path, and the two narrow microstrip lines of the second wide-side isolated differential line 4-2 located on the bottom metal layer are connected to form a rectangular path. Figure 4 The length of the first wide-side isolated differential line 4-1 / the second wide-side isolated differential line 4-2 is set to: the length L6 of the rectangular path = 47.5 mm, the width L7 = 22.5 mm; the spacing of the pads 9 is set to: g_pad2 = 0.6 mm.

[0058] Figure 6 The mixed mode scattering parameters obtained from the full-wave simulation of the ultra-wideband bidirectional absorptive common mode filter proposed in this invention are shown in Figure 2. dd21 | remains at a low level, and the differential mode reflection coefficient S dd11 The value can be kept below -15dB in the whole frequency band, which indicates that the common mode filter can protect the complete transmission of differential mode signals in the ultra-wide frequency range of DC-20GHz. At the same time, since the common mode filter has a symmetrical structure in the direction of signal propagation, the bidirectional common mode transmission coefficient S cc21 With S cc12 Phase overlap, bidirectional common mode reflection coefficient S cc11 With S cc22 Phase overlap, and the common mode transmission coefficient S cc21 and the common mode reflection coefficient S cc11The filter maintains a low common-mode absorption stopband bandwidth of 158% across an ultra-wide frequency range of 2 GHz to 17 GHz, while maintaining a low -10 dB differential frequency. This demonstrates the filter's bidirectional, highly efficient absorption of common-mode electromagnetic noise across this ultra-wide frequency range. Compared to existing research, the proposed filter offers the advantages of an ultra-high 3 dB differential-mode cutoff frequency and an ultra-wide bidirectional common-mode absorption bandwidth.

[0059] Figure 7 is the modal conversion coefficient obtained by full-wave simulation of the ultra-wideband bidirectional absorptive common-mode filter proposed in this invention. It can be seen that the differential common-mode conversion coefficient S cd21 and S cd11 It remains below -30dB in the DC-20GHz range, which is at a relatively low level. This shows that the common-mode filter proposed in 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 the differential-mode signal.

[0060] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions based on the principles of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. An ultra-wideband bidirectional absorptive common-mode filter based on a traveling wave mechanism and a 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 destructive common mode signals in the hybrid transmission line conversion structure; The hybrid transmission line conversion structure includes four groups of hybrid transmission line sub-conversion structures projected as 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 broadside isolation differential line connected in sequence, the broadside isolation 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 signal in the hybrid transmission line conversion structure to the traveling wave absorption unit; The traveling wave absorbing unit includes a plurality of traveling wave absorbing subunits A, which are evenly divided into N groups, where the number 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 absorbing subunits A respectively; The common-mode filter comprises 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) which are 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 used for metal circuit structure design, the second dielectric layer (P2) and the fourth dielectric layer (P4) are semi-cured sheets 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 metal layer and the third metal layer are both reference ground layers of the common-mode filter.

2. The ultra-wideband bidirectional absorptive common mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 1, characterized in that: The grounded coplanar waveguide (1) comprises a central conductive microstrip line arranged on a top metal layer, and ground pads (5) arranged on both sides of the central conductive microstrip line and located on the top metal layer and the bottom metal layer, and 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 via a first metallized through-hole (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.

3. The ultra-wideband bidirectional absorptive common mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 2, characterized in that: The broadside isolated differential lines in two adjacent hybrid transmission line sub-conversion structures have a mirror-symmetrical structural feature in the projection direction.

4. The ultra-wideband bidirectional absorptive common mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 1, characterized in that: The dielectric integrated coplanar waveguide (3) comprises a central conductive strip (3-1) arranged on the second metal layer and the third metal layer, and a slot line gap (3-2) arranged on the second metal layer and the third metal layer, and the periphery of the central conductive strip (3-1) and the periphery of the slot line gap (3-2) located on the second metal layer and the third metal layer are interconnected through a first blind hole (7-1), thereby converting 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 resonance.

5. The ultra-wideband bidirectional absorptive common mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 1, characterized in that: All traveling wave absorption subunits A in each group of traveling wave absorption subunits A are arranged in parallel and coaxially; for each of the traveling wave absorption subunits A: it includes a dielectric integrated slot transmission line (8), a pad (9) and a lumped resistor (10), wherein the dielectric integrated slot transmission line (8) includes a slot line etched on the second metal layer and the third metal layer, and the slot line is interconnected through a second blind hole (7-2), and 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 close to the two ends of the slot line, that is, located on both sides of the output feeder; each of the two ends of the lumped resistor (10) is welded to a pad (9) respectively; the bottom metal layer is provided with a pad (9) corresponding to the pad (9) on the top metal layer, and the pads (9) on the bottom metal layer and the top metal layer are grounded and interconnected through the second metallized through hole (6-2).

6. The ultra-wideband bidirectional absorptive common mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 5, characterized in that: 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, wherein the width of the second slot line is smaller than the width of the first slot line and the third slot line; and the output feeder of the power distribution network is located above and below the second slot line.

7. The ultra-wideband bidirectional absorptive common mode filter based on the traveling wave mechanism and the hybrid transmission line conversion structure according to claim 1, characterized in that: The common mode filter has a top-bottom symmetrical structure, that is, the first dielectric layer (C1) and the fifth dielectric layer (C5) are made of the same material and have the same thickness, and the second dielectric layer (P2) and the fourth dielectric layer (P4) are made of the same material and have the same thickness.

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