Low-loss substrate integrated transmission line structure and preparation method thereof

Abstract

This invention provides a low-loss substrate integrated transmission line structure and its fabrication method. The low-loss substrate integrated transmission line structure includes: a first substrate, a circuit extending along the length of the first substrate, metal layers disposed on the upper and lower sides of the first substrate, and a second substrate disposed above the metal layers on both sides. The first substrate has multiple air holes extending along its height, evenly arranged in two groups on both sides of the circuit, with equal spacing between adjacent air holes. The circuit adopts a periodic linewidth structure. Furthermore, on the outer side of each of the two groups of air holes, a set of metal holes extending along the height of the first substrate can be provided to form a shield. This invention reduces the dielectric loss and reflection loss of the substrate, improves the overall performance of the transmission line, provides a more reliable solution for high-frequency signal transmission, and has broad application prospects.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to optimization technology for microwave signal transmission; specifically, it relates to a low-loss substrate integrated transmission line structure based on air hole and line design and its fabrication method. Background Technology

[0002] In modern communication systems, efficient signal transmission is a key factor in ensuring system performance. With the continuous increase in information transmission rates, the requirements for signal transmission media are becoming increasingly stringent. Stripline, as a commonly used transmission structure, is widely used in microwave circuits, radio frequency equipment, and various communication systems. However, stripline inevitably faces signal loss during transmission, which directly affects signal quality and transmission distance, thus impacting the overall system performance and signal integrity. Therefore, improving signal transmission efficiency and stability in stripline transmission has become a pressing technical challenge.

[0003] In existing technologies, the transmission loss of striplines is mainly affected by a variety of factors, including material properties, linewidth, air hole design, and environmental conditions. Signal attenuation and reflection are particularly prominent in high-frequency applications. While increasing the wire diameter can reduce loss to some extent, the effect is often limited due to the skin effect. Furthermore, improperly designed air hole layouts can lead to signal interference and attenuation, thus affecting the overall system performance.

[0004] To improve the transmission performance of striplines, various optimization strategies have been proposed, such as improving the dielectric properties of materials, adjusting linewidth and air hole positions, and adding shielding to form shielded striplines or substrate-integrated coaxial cable structures. However, these methods often require trade-offs in complex designs and struggle to simultaneously meet the requirements of high efficiency and low loss. Therefore, developing a systematic stripline transmission loss optimization technique has significant theoretical and practical value.

[0005] The search revealed:

[0006] Chinese invention patent application CN114759331A, entitled "A Low-Loss Broadband Transmission Line and Transmission Structure," describes a low-loss broadband transmission line comprising a dielectric substrate, a central metal conductor strip, and a copper-clad metal ground plane. Both the central metal conductor strip and the copper-clad metal ground plane are connected to the upper surface of the dielectric substrate. The central metal conductor strip is located at the center of the dielectric substrate along its width and extends from one end to the other along the length of the dielectric substrate. The copper-clad metal ground plane comprises a first plate and a second plate, respectively disposed on both sides of the central metal conductor strip. Both the first and second plates have connecting strips and ribs connected to the connecting strips. The width of the connecting strip is less than or equal to the width of the ribs, and the ribs extend away from the central metal conductor strip. A gap is provided between adjacent ribs. The transmission structure includes a port and a low-loss broadband transmission line, with the port connected to the end of the low-loss broadband transmission line along its length. A stub structure is used instead of the existing through-hole structure to improve circuit performance. This transmission line structure still has the following technical problems: While its planar slow-wave structure, rather than vias, offers advantages in terms of ease of fabrication and reduces edge loss of the coplanar waveguide, it does not reduce the loss angle of the dielectric substrate, thus offering no improvement in reducing dielectric loss. Furthermore, this structure can only be applied to the outermost layer of a circuit board and cannot be used in the inner layers of multilayer circuit boards. Summary of the Invention

[0007] To address the aforementioned shortcomings in the prior art, this invention provides a low-loss substrate integrated transmission line structure and its fabrication method, based on striplines.

[0008] According to one aspect of the present invention, a low-loss substrate integrated transmission line structure is provided, comprising: a transmission section and a grounding and support section; wherein, the transmission section comprises: a first substrate and a line extending through the length of the first substrate; the grounding and support section comprises: metal layers disposed on the upper and lower sides of the first substrate and a second substrate disposed above the metal layers on both sides; wherein:

[0009] The first substrate of the transmission unit is provided with a plurality of air holes that penetrate along its height direction. The air holes are divided into two groups and arranged on both sides of the line respectively. In each group, two adjacent air holes are equally spaced; in the two groups, two symmetrically arranged air holes are equally spaced.

[0010] The line adopts a periodic linewidth structure.

[0011] Preferably, the material of the first substrate includes: Ferro A6, FR4 and / or Rogers 5880.

[0012] Preferably, the material of the second substrate includes: Ferro A6, FR4 and / or Rogers 5880.

[0013] Preferably, the width × length × height dimensions of the first substrate and / or the second substrate are w × L × h, where w and L are determined by the maximum substrate size that can be provided by the materials and processes, and h is determined by the standard substrate thickness required by the materials and processes.

[0014] Preferably, the thickness of the metal layer is 0.01 mm, 0.018 mm, or 0.035 mm.

[0015] Preferably, the diameter of the air hole is d, the distance between two adjacent air holes in each group is t1, and the two groups of air holes are arranged close to the line.

[0016] Preferably, the number of air holes in each group increases as the length of the first substrate increases.

[0017] Preferably, the number of air holes in each group is 25.

[0018] Preferably, t1 is 0.1 to 0.4 mm.

[0019] Preferably, the line adopts a periodic linewidth structure, including multiple alternating uniform linewidth sections and non-uniform linewidth sections; wherein, the non-uniform linewidth section adds an arc-shaped protrusion structure on the basis of the uniform linewidth section, and the width of the widest part of the arc-shaped protrusion structure should be less than 0.4mm.

[0020] Preferably, the air holes are respectively arranged on both sides of the arc-shaped protrusion of the periodic linewidth structure; wherein, the widest part of the arc-shaped protrusion corresponds to the widest part of the cross-section of the air hole, and the protrusion length of the arc-shaped protrusion corresponds to the length of the air hole.

[0021] Preferably, the distance z between the edge of the air hole and the widest part of the arc-shaped protrusion is 0.0235-0.4235mm.

[0022] According to another aspect of the present invention, a method for fabricating a low-loss substrate integrated transmission line structure is provided, comprising:

[0023] A line is provided, wherein the line adopts a periodic linewidth structure;

[0024] A first substrate is provided, and the circuit is installed through the first substrate along the length direction of the first substrate to form a transmission section of a strip line.

[0025] Holes are drilled along the height direction on the first substrate to form air holes. The air holes are divided into two groups and arranged on both sides of the circuit.

[0026] Metal layers are respectively disposed on the upper and lower sides of the first substrate, and a second substrate is disposed above the metal layers on both sides to form a grounding and support portion, thereby constructing a low-loss transmission line structure based on air holes and line design.

[0027] Preferably, the above method further includes:

[0028] A set of metal holes that penetrate along the height direction of the first substrate are respectively processed on the outer side of the two sets of air holes on the first substrate to form a shielding structure.

[0029] By adopting the above technical solution, the present invention has at least one of the following beneficial effects compared with the prior art:

[0030] The low-loss substrate integrated transmission line structure and its fabrication method provided by this invention effectively improve signal transmission efficiency through precise design of air holes, linewidth, and structure, thereby meeting the needs of modern communication technology.

[0031] The low-loss substrate integrated transmission line structure and its fabrication method provided by this invention reduce the loss tangent of the dielectric substrate by setting air holes, thereby reducing dielectric loss. By setting a periodic non-uniform bandwidth, the non-constant characteristic impedance caused by the air holes is compensated, thereby ensuring the constant characteristic impedance and reducing reflection loss. By setting metal holes to form a shielding structure, radiation loss is reduced.

[0032] The low-loss substrate integrated transmission line structure and its fabrication method provided by this invention effectively reduce transmission loss by optimizing design parameters. Through optimization schemes implemented for air hole design, line width and structural design, the transmission quality and performance of the signal are improved. It can provide a more efficient and reliable signal transmission solution for microwave communication systems, and can also ensure the reliability and consistency of signals in high-frequency applications, thus having broad application prospects.

[0033] The low-loss substrate integrated transmission line structure and its fabrication method provided by this invention reduce dielectric loss by introducing air vias to lower the equivalent loss angle of the dielectric substrate; by introducing non-uniform width conductors to compensate for the inconstancy of characteristic impedance caused by air vias, ensuring that the characteristic impedance remains stable, thereby reducing reflection loss; and by setting metal vias to form a shielding structure, radiation loss is reduced. Therefore, from the perspectives of dielectric loss, reflection loss, and radiation damage, the transmission line loss is reduced collectively. Furthermore, this invention is suitable for application in the inner layer circuits of multilayer circuit boards, aligning with the development trend of high-density, miniaturized, and three-dimensional multilayer integrated circuits. Attached Figure Description

[0034] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0035] Figure 1 This is a top view of a preferred embodiment of the present invention, showing air holes and non-uniform line width.

[0036] Figure 2 This is a side view of a preferred embodiment of the present invention, showing air holes and non-uniform line width.

[0037] Figure 3 This is a diagram of a sandwich structure with air holes and non-uniform line width in a preferred embodiment of the present invention;

[0038] Figure 4 This is a comparison diagram of S11 in a preferred embodiment of the present invention and the control group;

[0039] Figure 5 This is a comparison diagram of S21 in a preferred embodiment of the present invention and the control group;

[0040] Figure 6 This is a comparison diagram of S11 in a preferred embodiment of the present invention;

[0041] Figure 7 This is a comparison diagram of S21 in a preferred embodiment of the present invention;

[0042] Figure 8 This is a comparative diagram of S11 in a set of preferred embodiments of the present invention;

[0043] Figure 9 This is a comparative diagram of S21 in a preferred embodiment of the present invention.

[0044] In the figure, 1 is the first substrate, 2 is the circuit, 3 is the metal layer, 4 is the second substrate, 5 is the air hole, and 6 is the metal hole. Detailed Implementation

[0045] The embodiments of the present invention are described in detail below: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0046] Integrated circuits, as the core of modern electronic technology, play a crucial role in various electronic products. With the continuous increase in the operating frequency of integrated circuits, transmission loss has become a key factor affecting circuit performance. To effectively reduce loss and improve signal transmission efficiency, one embodiment of the present invention provides a low-loss substrate integrated transmission line structure based on air hole and line width design. This structure utilizes air hole design combined with linewidth variation to effectively reduce transmission loss.

[0047] Specifically, such as Figure 1 , Figure 2 and Figure 3 As shown, the low-loss substrate integrated transmission line structure provided in this embodiment includes: a transmission section and a grounding and support section; wherein, the transmission section includes: a first substrate 1 and a line 2 extending along the length direction of the first substrate; the grounding and support section includes: metal layers 3 disposed on the upper and lower sides of the first substrate and a second substrate 4 disposed above the metal layers 3 on both sides; wherein:

[0048] The first substrate 1 of the transmission section is provided with a plurality of air holes 5 that penetrate along its height direction. The air holes are divided into two groups and arranged on both sides of the line respectively. In each group, two adjacent air holes are equally spaced; in the two groups, two symmetrically arranged air holes are equally spaced.

[0049] Line 2 adopts a periodic linewidth structure.

[0050] In some preferred embodiments, the material of the first substrate 1 is Ferro A6, FR4 and / or Rogers 5880, etc.

[0051] In some preferred embodiments, the material of the second substrate 4 is Ferro A6, FR4 and / or Rogers 5880, etc.

[0052] In some preferred embodiments, the width × length × height dimensions of the first substrate 1 and / or the second substrate 4 are w × L × h; wherein the ranges of w and L are limited by the maximum substrate size that the selected materials and processes can provide, and the range of h needs to be selected from the standard substrate thickness of the selected materials and processes. More preferably, w is 6 mm, L is 8 mm, and h is 0.6 mm.

[0053] In some preferred embodiments, the thickness of the metal layer needs to be selected from the metal layer thicknesses that the selected printed circuit board process can provide; more preferably, the thickness of the metal layer 3 is 0.01 mm, and can also be 0.018 mm or 0.035 mm.

[0054] In some preferred embodiments, the diameter of the air hole 5 is d, the distance between two adjacent air holes in each group is t1, and the two groups of air holes are arranged close to the line 2.

[0055] In some preferred embodiments, t1 is preferably 0.1 to 0.4 mm.

[0056] In some preferred embodiments, the number of air holes in each group increases with the length of the first substrate. Introducing air holes reduces the loss tangent of the dielectric substrate, thereby reducing dielectric loss. More preferably, the number of air holes 5 in each group is 25, for a total of 50.

[0057] In some preferred embodiments, line 2 adopts a periodic linewidth structure, including multiple alternating uniform linewidth sections and non-uniform linewidth sections; wherein, the non-uniform linewidth section adds an arc-shaped protrusion structure to the uniform linewidth section, and the width of the widest part of the arc-shaped protrusion structure should be less than 0.4mm. More preferably, the width of the uniform linewidth section is 0.193mm, and the non-uniform linewidth section, based on the width of the uniform linewidth section, protrudes an additional width on both sides.

[0058] In some preferred embodiments, air holes are respectively arranged on both sides of the arc-shaped protrusion of the periodic linewidth structure; wherein, the widest part of the arc-shaped protrusion corresponds to the widest part of the cross-section of the air hole, and the protrusion length of the arc-shaped protrusion corresponds to the length of the air hole. More preferably, the protrusion length of the arc-shaped protrusion is 0.2 mm.

[0059] In some preferred embodiments, the distance z between the edge of the air hole and the widest part of the arc-shaped protrusion is 0.0235 to 0.4235 mm.

[0060] In some preferred embodiments, a set of metal holes 6 extending along the height direction of the first substrate are respectively provided on the outer side of the two sets of air holes on the first substrate to form a shielding structure.

[0061] Based on the same inventive concept, an embodiment of the present invention also provides a method for preparing a low-loss transmission line structure.

[0062] Specifically, the method for fabricating the low-loss transmission line structure provided in this embodiment may include the following operations:

[0063] Provide a line, which adopts a uniform linewidth structure or a periodic linewidth structure;

[0064] A first substrate is provided, and a circuit is installed through the first substrate along the length direction of the first substrate to form a transmission section;

[0065] Holes are drilled along the height direction on the first substrate of the transmission section to form air holes. The air holes are divided into two groups and arranged on both sides of the line.

[0066] A metal layer is disposed on the upper and lower sides of the first substrate of the transmission section, and a second substrate is disposed above the metal layers on both sides to form a grounding and support section, thereby constructing a low-loss transmission line structure based on air hole and line design.

[0067] In some preferred embodiments, the above method further includes:

[0068] A set of metal holes 6, extending along the height direction of the first substrate, are respectively processed on the outer side of the two sets of air holes on the first substrate to form a shielding structure.

[0069] It should be noted that the steps in the method provided by the present invention can be implemented using the corresponding components in the structure. Those skilled in the art can refer to the technical solution of the structure to implement the steps of the method. That is, the embodiments in the structure can be understood as preferred examples of the method, and will not be elaborated here.

[0070] The technical solution provided by the above embodiments of the present invention will be further described in detail below with reference to a verification example and accompanying drawings.

[0071] The embodiments of the present invention provide a low-loss substrate integrated transmission line structure based on air hole and line design, aiming to improve the efficiency and quality of signal transmission through precise parameter design. This verification example uses the controlled variable method for systematic comparative examples to further verify the effectiveness of the low-loss transmission line structure provided by the embodiments of the present invention in improving the efficiency and quality of signal transmission.

[0072] The above embodiments of the present invention address the design of air holes and line widths, mainly including the following aspects:

[0073] Firstly, while introducing air holes reduces dielectric loss, it leads to inconsistent characteristic impedance. Therefore, by finely designing the conductor width using periodic, small-amplitude arc-shaped variations, a non-uniform linewidth configuration corresponding one-to-one with the air holes is created, ensuring constant characteristic impedance and reducing reflection loss. This innovation not only optimizes the signal transmission path but also improves signal integrity. Compared to traditional uniform linewidth designs, example data shows that subtle linewidth variations can significantly improve signal clarity and stability, thus providing a more effective solution for high-frequency signal transmission.

[0074] Secondly, the variation of the spacing t1 between adjacent air holes was explored. By precisely analyzing the impact of different air hole spacings on signal coupling and transmission efficiency, and keeping other parameters constant, the contribution of the air hole layout to signal transmission performance was studied by adjusting the relative positions of the air holes, providing empirical evidence for the optimized design of transmission lines.

[0075] Thirdly, we focus on the change in distance z between line 2 and the air hole. Simulations were used to study the impact of this distance change on signal transmission characteristics. Under the premise of controlling other parameters, examples show that appropriately adjusting the distance between line 2 and the air hole can significantly improve signal transmission quality and stability, thereby optimizing the overall signal system performance.

[0076] This verification example verifies the design of the above three aspects through three sets of comparative examples.

[0077] In this verification example, the substrate material used is Ferro A6, with a structure of dimensions w×L×h, where w = 6 mm, L = 8 mm, and h = 0.6 mm. This material exhibits excellent dielectric properties in the microwave band, making it ideal for high-frequency signal transmission. The thickness of both the top and bottom metal layers of the substrate is 0.01 mm to ensure good conductivity and signal integrity. Furthermore, to prevent metal layer collapse during the drilling of air holes, an additional substrate is added above the metal layer on one side to enhance structural stability and mechanical strength.

[0078] In the design, the diameter of the air hole was set to d, and wave ports were added on both sides of w×h to facilitate signal input and output.

[0079] The first set of comparative examples compares the signal transmission performance of the present invention (with air holes and non-uniform linewidth) with control group 1 (with air holes and uniform linewidth) and control group 2 (without air holes and uniform linewidth), thus demonstrating the advantages of the present invention over conventional structures. In this set of examples, the uniform linewidth is set to 0.193 mm, while the non-uniform linewidth employs a periodic arc-shaped protrusion design. Specifically, the non-uniform linewidth includes a straight portion (0.193 mm) and an arc-shaped protrusion. The length of the protrusion is 0.2 mm.

[0080] Regarding the configuration of the air holes, each group has 25 air holes, for a total of 50 air holes across both groups. The spacing between the air holes is t1, where t1 = 0.1 mm. This design ensures that the air holes are close to the wires, effectively reducing reflections and interference during signal transmission. This compact layout allows signals to pass through the air holes more efficiently, thereby reducing transmission loss.

[0081] In the first set of comparative examples, the focus is on observing the changes in signal loss, reflection coefficient (S11), and transmission coefficient (S21) during signal transmission under different linewidth designs. Figure 4 and Figure 5As shown in the example results, introducing air holes significantly reduces and improves S21; after introducing air holes, the S11 parameter of the non-uniform linewidth is significantly lower than that of the uniform linewidth, which means that the reflection loss is effectively reduced. Furthermore, the S21 parameter of the non-uniform linewidth is higher than that of the uniform linewidth, indicating that the signal transmission efficiency is improved.

[0082] In summary, the above embodiments of the present invention, through refined structural and parameter design, significantly improve the signal transmission efficiency of the transmission line and ensure the stability and integrity of high-frequency signals. The design of the air holes and circuitry in the above embodiments of the present invention provides reliable technical support for microwave signal transmission, with broad application prospects, especially in modern communications, wireless transmission, and high-frequency circuit design, where it can play a crucial role.

[0083] The second and third sets of comparative examples aim to illustrate the impact of two parameters that are relatively sensitive to the present invention on transmission performance.

[0084] The second set of comparative examples aims to compare the impact of the spacing t1 between air holes on signal transmission performance. In this example, the transmission line structure with air holes and periodic linewidth provided by this invention was used. With other parameters being the same, the spacing t1 between the air holes was set to 0.1 mm (dense air holes) and 0.4 mm (sparse air holes).

[0085] like Figure 6 and Figure 7 As shown in the example results, the reflection coefficient (S11) is significantly higher when the air hole spacing is 0.1 mm than that of the design with a spacing of 0.4 mm. This indicates that a smaller spacing may lead to greater reflection loss during signal transmission, affecting signal integrity. Furthermore, the transmission coefficient (S21) varies between the two designs; although the overall performance is similar, different air hole spacings still have a certain impact on the stability of signal transmission.

[0086] A comprehensive analysis of the results from the second set of comparative examples demonstrates that the spacing between air holes plays a crucial role in signal transmission. Increasing the air hole spacing may help reduce signal reflection and improve transmission efficiency. A comparison of different air hole spacing designs further confirms the significant importance of meticulous design parameter adjustments for improving signal transmission performance in transmission line optimization.

[0087] The purpose of the third set of comparative examples is to study the effect of the distance z between line 2 and the air hole on signal transmission performance. This set of comparative examples uses the transmission line structure with air holes and periodic linewidth provided by the present invention, and sets two design conditions: one is that the air hole is close to the non-uniform line, z = 0.0235mm, and the other is that the air hole is far away from the line, z = 0.4235mm.

[0088] like Figure 8 As shown, the S11 parameter does not change significantly under the two design conditions in the measurement of reflection coefficient (S11), which indicates that the distance between the line and the air hole has little effect on the signal reflection characteristics.

[0089] However, in the comparison of transmission coefficient (S21), the design with the air hole close to the line is significantly better than the design with the air hole far away from the line, such as... Figure 9 As shown in the figure. This indicates that when the air hole is close to the line, the signal transmission efficiency is effectively improved, possibly because the signal experiences relatively less interference and loss when propagating over short distances.

[0090] A comprehensive analysis of the final set of results reveals that the distance between the line and the air hole plays a crucial role in signal transmission. The transmission loss shows a significant difference, a finding that provides important guidance for transmission line design and optimization, further emphasizing the critical role of design details in improving signal transmission performance.

[0091] The importance of air holes in this structural design is particularly prominent. Air has a very low loss tangent and dielectric constant, which transforms a normally homogeneous substrate into a non-homogeneous one. By introducing air holes, the equivalent loss tangent and dielectric constant decrease, thereby reducing signal transmission losses. However, the characteristic impedance of the transmission line is determined by both the dielectric constant of the substrate material and the geometry of the structure; the introduction of air holes alters the equivalent dielectric constant of the substrate, making the characteristic impedance of the transmission line no longer a constant value. In sections with air holes, the characteristic impedance of each cross-section of the transmission line is different. To compensate for this variation in characteristic impedance, several cross-sections need to be selected in the sections with air holes. For each cross-section, the linewidth required to achieve a constant characteristic impedance (typically 50 ohms) is calculated through simulation, and these different linewidths are then smoothly connected. Simulation and calculation can be performed using tools such as AppCAD and HFSS during the linewidth design process.

[0092] The periodic air holes and non-uniform linewidth of the line are the core of this invention. To further improve transmission characteristics, the above embodiments of this invention, based on the line design, also propose two supplementary optimization strategies: optimizing the air hole density and reducing the spacing between the air holes and line 2 within the limits of process allowance. By fine-tuning the linewidth and structural design through these optimization strategies, the overall performance and signal stability can be further improved.

[0093] The results of the examples show that fine-tuning the air hole spacing within a certain range can effectively improve signal transmission quality, thereby improving the overall performance of the transmission line.

[0094] During the process of adjusting the distance between the line and the air hole, by observing the changes in signal transmission parameters, it was found that reducing the distance could further optimize the signal transmission path, providing the possibility for fine-tuning the design.

[0095] The above verification experiments demonstrate that the structure provided by the embodiments of the present invention, through the design of air holes and circuits, can effectively improve signal transmission efficiency and reduce signal loss, providing a practical solution for the field of high-frequency signal transmission. It has significant theoretical research value and broad practical application potential.

[0096] The low-loss substrate integrated transmission line structure and its fabrication method provided in the above embodiments of the present invention aim to reduce transmission loss, improve signal transmission efficiency, and enhance microwave circuit performance. This structure is achieved through three design approaches: first, by introducing air holes in the substrate and utilizing the periodic distribution of these air holes to reduce the substrate's dielectric constant and loss tangent, thereby reducing signal transmission loss; second, by precisely designing the linewidth based on the periodic variation of the air holes to ensure a constant characteristic impedance and reduce reflection loss; and third, by adding metal holes to enhance shielding and reduce radiation damage. Furthermore, by fine-tuning the air hole spacing (i.e., changing the air hole density) and the distance Z between the air holes and the metal lines, signal interference and reflection loss are reduced, improving the overall performance of the transmission line. Comparative examples show that the transmission line loss is significantly reduced, and the overall performance of the microwave circuit is improved. The technical solution provided by the present invention offers a more reliable solution for high-frequency signal transmission and has broad application prospects.

[0097] Any matters not covered in the above embodiments of the present invention are well-known in the art.

[0098] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A low-loss substrate integrated transmission line structure, characterized in that, include: A first substrate, a circuit extending along the length of the first substrate, metal layers disposed on the upper and lower sides of the first substrate, and a second substrate disposed above the metal layers on both sides; wherein: The first substrate has a plurality of air holes that penetrate along the height direction of the first substrate. The air holes are divided into two groups and arranged on both sides of the circuit. In each group, two adjacent air holes are equally spaced. In the two groups, two symmetrically arranged air holes are equally spaced. The line adopts a periodic linewidth structure, including multiple alternating uniform linewidth sections and non-uniform linewidth sections; wherein, the non-uniform linewidth section adds an arc-shaped protrusion structure on the basis of the uniform linewidth section, and the width of the widest part of the arc-shaped protrusion structure is less than 0.4mm.

2. The low-loss substrate integrated transmission line structure according to claim 1, characterized in that, The materials of the first substrate and / or the second substrate include: Ferro A6, FR4 and / or Rogers 5880; The width × length × height dimensions of the first substrate and / or the second substrate are w × L × h, wherein w and L are determined by the maximum substrate size that can be provided by the materials and processes, and h is determined by the standard substrate thickness required by the materials and processes.

3. The low-loss substrate integrated transmission line structure according to claim 1, characterized in that, The thickness of the metal layer is 0.01 mm, 0.018 mm, or 0.035 mm.

4. The low-loss substrate integrated transmission line structure according to claim 1, characterized in that, The diameter of the air hole is d, and the distance between two adjacent air holes in each group is t1. The two groups of air holes are arranged close to the line. The number of air holes in each group increases as the length of the first substrate increases; The number of air holes in each group is 25.

5. The low-loss substrate integrated transmission line structure according to claim 4, characterized in that, The t1 is 0.1~0.4mm.

6. The low-loss substrate integrated transmission line structure according to claim 1, characterized in that, The air holes are respectively arranged on both sides of the arc-shaped protrusion of the periodic linewidth structure; wherein, the widest part of the arc-shaped protrusion corresponds to the widest part of the cross-section of the air hole, and the protrusion length of the arc-shaped protrusion corresponds to the length of the air hole.

7. The low-loss substrate integrated transmission line structure according to claim 6, characterized in that, The distance z between the edge of the air hole and the widest part of the arc-shaped protrusion is 0.0235~0.4235mm.

8. The low-loss substrate integrated transmission line structure according to claim 1, characterized in that, Also includes: The first substrate has a set of metal holes extending along the height of the first substrate on the outer side of the two sets of air holes, forming a shielding structure.

9. A method for fabricating a low-loss substrate integrated transmission line structure, characterized in that, include: A line is provided, the line adopting a periodic linewidth structure, including multiple alternating uniform linewidth portions and non-uniform linewidth portions; wherein, the non-uniform linewidth portion is supplemented with an arc-shaped protrusion structure on the basis of the uniform linewidth portion, and the width of the widest part of the arc-shaped protrusion structure is less than 0.4mm; A first substrate is provided, and the circuit is installed through the first substrate along the length direction of the first substrate to form a transmission section; Holes are drilled along the height direction on the first substrate to form air holes. The air holes are divided into two groups and arranged on both sides of the circuit. A metal layer is disposed on the upper and lower sides of the first substrate, and a second substrate is disposed on the upper and lower metal layers to form a grounding and support portion, thereby constructing a low-loss substrate integrated transmission line structure based on air hole and line design.

10. The method for fabricating a low-loss substrate integrated transmission line structure according to claim 9, characterized in that, Also includes: A set of metal holes that penetrate along the height direction of the first substrate are respectively processed on the outer side of the two sets of air holes on the first substrate to form a shielding structure.

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