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

Abstract

The invention provides a low-loss substrate integrated transmission line structure and a preparation method thereof.The low-loss substrate integrated transmission line structure comprises a first substrate, a circuit penetrating in the length direction of the first substrate, metal layers arranged on the upper side and the lower side of the first substrate and a second substrate arranged above the metal layers on the two sides; the first substrate is provided with a plurality of air holes penetrating in the height direction of the first substrate, the air holes are evenly divided into two groups to be arranged on the two sides of the circuit, and every two adjacent air holes are arranged at equal intervals. The circuit adopts a periodic line width structure; in the first substrate, the outer sides of the two groups of air holes are respectively provided with a group of metal holes penetrating along the height direction of the first substrate to form shielding. The dielectric loss and the reflection loss of the substrate are reduced, the overall performance of the transmission line is improved, a more reliable solution is provided for high-frequency signal transmission, and wide application prospects are achieved.

Description

Technical Field

[0001] The present application relates to the field of communication technology, in particular to the optimization technology of microwave signal transmission; specifically, to a low-loss substrate integrated transmission line structure based on air holes and line design and a preparation method thereof. Background Art

[0002] In modern communication systems, efficient signal transmission is one of the key factors to ensure system performance. With the continuous increase in information transmission rate, the requirements for signal transmission media are becoming more 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 loss problems during signal transmission, which directly affects the quality and transmission distance of the signal, and further affects the overall performance of the system and the integrity of the signal. Therefore, in stripline transmission, improving the transmission efficiency and stability of the signal has become a technical problem that needs to be solved urgently.

[0003] In the prior art, the transmission loss of strip lines is mainly affected by a variety of factors, including material properties, line width, air hole design, and environmental conditions. Especially in high-frequency applications, signal attenuation and reflection problems are particularly prominent. Although increasing the line diameter can reduce the loss to a certain extent, the effect of this method is often limited due to the existence of the skin effect. In addition, improperly designed air hole layouts may cause signal interference and attenuation, thereby affecting the performance of the overall system.

[0004] In order to improve the transmission performance of stripline, a variety of optimization strategies have been proposed, such as improving the dielectric properties of the material, adjusting the line width and the position of the air hole, adding shielding to form a shielded stripline or substrate integrated coaxial line structure, etc. However, these methods often require trade-offs in complex designs, and it is difficult to meet the requirements of high efficiency and low loss at the same time. Therefore, the development of a systematic stripline transmission loss optimization technology has important theoretical value and practical application significance.

[0005] After searching, we found:

[0006] The Chinese invention patent application "A Low-loss Broadband Transmission Line and Transmission Structure" with publication number CN114759331A, the low-loss broadband transmission line includes a dielectric substrate, a central metal conductor belt and a copper-clad metal floor; the central metal conductor belt and the copper-clad metal floor are both connected to the upper surface of the dielectric substrate, the central metal conductor belt is arranged at the center of the dielectric substrate in the width direction, and the central metal conductor belt extends from one end to the other end along the length direction of the dielectric substrate; the copper-clad metal floor includes a first plate and a second plate, the first plate and the second plate are respectively arranged on both sides of the central metal conductor belt, the first plate and the second plate are both provided with a connecting belt and a convex rib connected to the connecting belt, the width of the connecting belt is less than or equal to the width of the convex rib, the convex rib extends in a direction away from the central metal conductor belt, and a gap is provided between adjacent convex ribs. The transmission structure includes a port and a low-loss broadband transmission line, and the port is connected to the end of the low-loss broadband transmission line in the length direction. The branch structure is used to replace the existing through-hole structure to improve the circuit performance. The transmission line structure still has the following technical problems: the transmission line structure uses a planar slow-wave structure instead of a through hole, which has certain advantages in terms of processing convenience and reduces the edge loss of the coplanar waveguide. However, the structure does not reduce the loss angle of the dielectric substrate, and thus does not improve the reduction of dielectric loss; in addition, the structure can only be applied to the outermost layer of the circuit board, and cannot be applied to the inner layer circuit in a multi-layer circuit board. Summary of the invention

[0007] In view of the above-mentioned deficiencies in the prior art, the present invention provides a low-loss substrate integrated transmission line structure and a preparation method thereof based on a stripline.

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

[0009] The first substrate of the transmission part is provided with a plurality of air holes penetrating along the height direction thereof, the air holes are divided into two groups and arranged on both sides of the circuit respectively, and the two adjacent air holes in each group are arranged at equal intervals; the two symmetrically arranged air holes in the two groups are arranged at equal intervals;

[0010] The circuit adopts a periodic line width 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 material and process, and h is determined by the standard substrate thickness required by the material and process.

[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 holes is d, the distance between two adjacent air holes in each group is t1, and the two groups of air holes are arranged closely to the circuit.

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

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

[0018] Preferably, the d is 0.02 mm, and the t1 is 0.1-0.4 mm.

[0019] Preferably, the circuit adopts a periodic line width structure, including a plurality of uniform line width portions and non-uniform line width portions alternately connected; wherein the non-uniform line width portion adds an arc-shaped protruding structure on the basis of the uniform line width portion, and the width of the widest protrusion of the arc-shaped protruding structure should be less than 0.4 mm.

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

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

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

[0023] Providing a circuit, wherein the circuit adopts a periodic line width structure;

[0024] Providing a first substrate, and installing the circuit through the first substrate along the length direction of the first substrate to form a transmission part of the strip line;

[0025] Punching holes on the first substrate along its height direction to form air holes, wherein the air holes are divided into two groups and are respectively arranged on both sides of the circuit;

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

[0027] Preferably, the above method further comprises:

[0028] A group of metal holes penetrating along the height direction of the first substrate are respectively processed on the outer sides of the two groups of air holes on the first substrate to form a shielding structure.

[0029] Due to the adoption of 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 preparation method thereof provided by the present invention effectively improve the signal transmission efficiency through precise design of air holes and line width and structure of the line, thereby meeting the needs of modern communication technology.

[0031] The low-loss substrate integrated transmission line structure and preparation method provided by the present 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 inconstancy of the characteristic impedance caused by the air holes is compensated, thereby ensuring the constancy of the characteristic impedance and reducing the reflection loss. By setting the metal holes to form a shielding structure, the radiation loss is reduced.

[0032] The low-loss substrate integrated transmission line structure and preparation method thereof provided by the present invention effectively reduce the transmission loss by optimizing the design parameters, and improve the transmission quality and performance of the signal through the optimization scheme implemented for the air hole design, the line width and the structural design of the line, etc., and can provide a more efficient and reliable signal transmission solution for the microwave communication system, and can also ensure the reliability and consistency of the signal in high-frequency applications, and has broad application prospects.

[0033] The low-loss substrate integrated transmission line structure and preparation method provided by the present invention reduce the equivalent loss angle of the dielectric substrate by introducing air holes, thereby reducing dielectric loss; the inconstancy of the characteristic impedance caused by the air holes is compensated by introducing wires of non-uniform width, ensuring that the characteristic impedance is always stable, thereby reducing reflection loss; and the shielding structure is formed by setting metal holes to reduce radiation loss. Therefore, from the three perspectives of dielectric loss, reflection loss and radiation damage, the loss of the transmission line is reduced together. In addition, the present invention is suitable for application in the inner layer circuit of a multi-layer circuit board, and is suitable for the development direction of high density, miniaturization, and three-dimensional multi-layering of integrated circuits. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0035] Figure 1 A top view of a preferred embodiment of the present invention having air holes and non-uniform line width;

[0036] Figure 2 A side view of a preferred embodiment of the present invention having air holes and non-uniform line width;

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

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

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

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

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

[0042] Figure 8 A comparison diagram of S11 in a preferred embodiment of the present invention;

[0043] Fig. 9 It is a comparison 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 DESCRIPTION

[0045] The following is a detailed description of the embodiments of the present invention: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

[0046] Integrated circuits, as the core of modern electronic technology, play a vital role in various electronic products. As the operating frequency of integrated circuits continues to increase, transmission loss has become a key factor affecting circuit performance. In order to effectively reduce losses and improve signal transmission efficiency, an embodiment of the present invention provides a low-loss substrate integrated transmission line structure based on air hole and line design. The structure utilizes air hole design combined with line width variation to effectively reduce transmission loss.

[0047] Specifically, Figure 1 , Figure 2 and Figure 3 As shown, the low-loss substrate integrated transmission line structure provided in this embodiment includes: a transmission part and a grounding and supporting part; wherein the transmission part includes: a first substrate 1 and a line 2 running through the length direction of the first substrate; the grounding and supporting part includes: a metal layer 3 arranged on the upper and lower sides of the first substrate and a second substrate 4 arranged above the metal layers 3 on both sides; wherein:

[0048] The first substrate 1 of the transmission part is provided with a plurality of air holes 5 penetrating along the height direction thereof. The air holes are divided into two groups and arranged on both sides of the circuit respectively. The two adjacent air holes in each group are arranged at equal intervals; the two symmetrically arranged air holes in the two groups are arranged at equal intervals;

[0049] Line 2 adopts or periodic line width structure.

[0050] In some preferred embodiments, the material of the first substrate 1 is Ferro A6, FR4 and / or Rogers5880, etc.

[0051] In some preferred embodiments, the second substrate 4 is made of Ferro A6, FR4 and / or Rogers5880, etc.

[0052] In some preferred embodiments, the dimensions of width×length×height 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 can be provided by the selected material and process, and the range of h needs to be selected from the standard substrate thickness of the selected material and process. Further 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 thickness that can be provided by the selected printed circuit board process; further 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 holes 5 is d, the distance between two adjacent air holes in each group is t1, and the two groups of air holes are arranged closely to the circuit 2.

[0055] In some preferred embodiments, d is preferably 0.02 mm, and t1 is preferably 0.1-0.4 mm.

[0056] In some preferred embodiments, the number of air holes in each group increases as the length of the first substrate increases. After the air holes are introduced, the loss tangent of the dielectric substrate is reduced, thereby reducing the dielectric loss. Further 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 line width structure, including multiple uniform line width parts and non-uniform line width parts connected alternately; wherein the non-uniform line width part adds an arc-shaped protruding structure on the basis of the uniform line width part, and the width of the widest protrusion of the arc-shaped protruding structure should be less than 0.4mm. Further preferably, the width of the uniform line width part is 0.193mm, and the non-uniform line width, on the basis of the width of the uniform line width part, further protrudes up to 0.01mm on both sides to form an arc-shaped protruding structure, and the width of the widest protrusion of the arc-shaped protruding structure is: 0.193mm+0.02mm=0.213mm.

[0058] In some preferred embodiments, the air holes are arranged on both sides of the arc-shaped protruding structure of the periodic line width structure; wherein the widest protrusion of the arc-shaped protruding structure corresponds to the widest part of the cross section of the air hole, and the protruding length of the arc-shaped protruding structure corresponds to the length of the air hole. Further preferably, the protruding length of the arc-shaped protruding structure 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 protruding structure is 0.0235-0.4235 mm.

[0060] In some preferred embodiments, a group of metal holes 6 penetrating along the height direction of the first substrate are respectively provided outside the two groups 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 further provides a method for preparing a low-loss transmission line structure.

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

[0063] Providing a circuit, wherein the circuit adopts a uniform line width structure or a periodic line width structure;

[0064] Providing a first substrate, installing the circuit through the first substrate along the length direction of the first substrate to form a transmission part;

[0065] Punching holes on the first substrate of the transmission part along its height direction to form air holes, the air holes are evenly divided into two groups and are arranged on both sides of the circuit respectively;

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

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

[0068] A group of metal holes 6 penetrating along the height direction of the first substrate are respectively processed on the outer sides of the two groups 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 step flow of the method, that is, the embodiments in the structure can be understood as preferred examples of implementing the method, which will not be elaborated here.

[0070] The technical solution provided by the above embodiment of the present invention is further described in detail below in conjunction with a verification example and the accompanying drawings.

[0071] The above embodiment of the present invention provides a low-loss substrate integrated transmission line structure based on air holes and line design, aiming to improve the efficiency and quality of signal transmission through precise parameter design. This verification example uses the control variable method to conduct a systematic comparison example to further verify the effectiveness of the low-loss transmission line structure provided by the above embodiment of the present invention in improving the efficiency and quality of signal transmission.

[0072] The above embodiments of the present invention are directed to the design of air holes and line widths, and mainly include the following aspects:

[0073] First, the introduction of air holes reduces dielectric loss but leads to inconstant characteristic impedance. Then, by finely designing the line width of the conductor and using periodic small-amplitude arc changes, a non-uniform line width configuration corresponding to the air holes is formed to ensure constant characteristic impedance and reduce reflection loss. This innovation not only optimizes the signal transmission path, but also improves the integrity of the signal. Compared with the traditional uniform line width design, example data shows that subtle line width changes can significantly improve the clarity and stability of signal transmission, thereby providing a more effective solution for high-frequency signal transmission.

[0074] Secondly, the change of the spacing t1 between adjacent air holes was explored. By accurately analyzing the impact of different air hole spacings on signal coupling and transmission efficiency, and adjusting the relative positions of the air holes while keeping other parameters unchanged, the contribution of the air hole layout to signal transmission performance was studied, providing an empirical basis for the optimal design of transmission lines.

[0075] The third aspect is to focus on the change of the distance z between line 2 and the air hole. The simulation studies the influence of the distance change between the two on the signal transmission characteristics. Under the premise of controlling other parameters, the example shows that the appropriate adjustment of the distance between line 2 and the air hole can significantly improve the transmission quality and stability of the signal, thereby optimizing the performance of the overall signal system.

[0076] This verification example verifies the design of the above three aspects through three groups 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=6mm, L=8mm, and h=0.6mm. This material exhibits excellent dielectric properties in the microwave frequency band and is ideal for high-frequency signal transmission. The thickness of the upper and lower metal layers of the substrate is 0.01mm to ensure good conductivity and signal integrity. In addition, to prevent the metal layer from collapsing when drilling air holes, an additional substrate is added above the metal layer on one side to enhance the stability and mechanical strength of the structure.

[0078] In the design, the diameter of the air hole is set to d, and wave ports are added on both sides of w×h to facilitate signal input and output, where d=0.02mm.

[0079] The first group of comparative examples compares the signal transmission performance of the present invention (with air holes and non-uniform line width) with control group 1 (with air holes and uniform line width) and control group 2 (without air holes and uniform line width), thereby demonstrating the advantages of the present invention over the traditional structure. In this group of examples, the uniform line width is set to 0.193mm, while the non-uniform line width adopts a periodic arc protrusion design. Specifically, the non-uniform line width includes a straight line portion (0.193mm) and an arc protrusion portion, the latter of which protrudes an additional 0.02mm, and the length of the protrusion is 0.2mm.

[0080] In terms of the configuration of the air holes, each group is equipped with 25 air holes, and the total number of air holes in the two groups is 50. The air hole spacing is t1, where t1 = 0.1mm. This design ensures that the air holes are close to the wires, which can effectively reduce reflections and interference during signal transmission. Through this compact layout, the signal can pass through the air holes more efficiently, thereby reducing transmission losses.

[0081] In the first set of comparative examples, the focus is on observing the changes in loss, reflection coefficient (S11) and transmission coefficient (S21) during signal transmission under different line width designs, such as Figure 4 and Figure 5 As shown. The example results show that the introduction of air holes can significantly reduce and improve S21; after the introduction of air holes, the S11 parameter of the non-uniform line width is significantly lower than that of the uniform line width, which means that the reflection loss is effectively reduced. In addition, the S21 parameter of the non-uniform line width is higher than that of the uniform line width, indicating that the transmission efficiency of the signal has been improved.

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

[0083] The second and third groups of comparative examples and the third group of comparative examples are intended to illustrate the influence of two relatively sensitive parameters of the present invention on the transmission performance.

[0084] The second group of comparative examples is intended to compare the effect of the spacing t1 between air holes on signal transmission performance. In this example, the transmission line structure with air holes and periodic line width provided by the present invention is used. When other parameters are the same, the spacing t1 of the air holes is set to 0.1 mm (dense air holes) and 0.4 mm (distant air holes).

[0085] like Figure 6 and Figure 7 As shown in the figure, the example results show that when the air hole spacing is 0.1mm, the reflection loss (S11) is significantly higher than that of the design with a spacing of 0.4mm. This shows that a smaller spacing may cause a larger reflection loss during the transmission of the signal, affecting the integrity of the signal. In addition, the transmission loss (S21) varies in these two designs. Although the overall performance is similar, the different air hole spacings still have a certain impact on the stability of signal transmission.

[0086] Comprehensive analysis of the results of the second group of comparative examples shows that the spacing design between air holes plays a key role in signal transmission. Increasing the spacing between air holes may help reduce signal reflection and improve transmission efficiency. By comparing different air hole spacing designs, it is further confirmed that in transmission line optimization, careful adjustment of design parameters is of great significance for improving signal transmission performance.

[0087] The purpose of the third group of comparative examples is to study the influence of the distance z between the line 2 and the air hole on the signal transmission performance. This group of comparative examples adopts the transmission line structure with air holes and periodic line width 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, in the measurement of reflection loss (S11), the S11 parameter under the two design conditions does not change significantly, which indicates that the distance between the line and the air hole has little effect on the reflection characteristics of the signal.

[0089] However, in the comparison of transmission loss (S21), the design with air holes close to the line is significantly higher than the design far from the line, such as Fig. 9 This shows that when the air hole is closer to the line, the signal transmission efficiency is effectively improved, which may be because the signal is subject to relatively less interference and loss when it propagates over a short distance.

[0090] Comprehensive analysis of the last set of results shows that the distance between the line and the air hole plays an important role in signal transmission. The transmission loss shows a significant difference, which provides important guidance for the design and optimization of transmission lines and further emphasizes the key role of design details in improving signal transmission performance.

[0091] The importance of air holes in this structural design is particularly prominent. The loss tangent and dielectric constant of air are very low, which makes the substrate, which was originally a uniform medium, become a non-uniform medium. By introducing air holes, the equivalent loss tangent and dielectric constant will become smaller, thereby reducing the loss generated during signal transmission. But at the same time, the characteristic impedance of the transmission line is determined by the dielectric constant of the substrate material and the geometric dimensions of the structure; the introduction of air holes will change the equivalent dielectric constant of the substrate, so that the characteristic impedance of the transmission line is no longer a constant value. In the section with air holes, the characteristic impedance of each cross section of the transmission line is different. In order to compensate for this change in characteristic impedance, it is necessary to select several cross sections in the section with air holes, and calculate the line width required to achieve a constant characteristic impedance (usually 50 ohms) in each cross section through simulation, and then smoothly connect these different line widths. In the process of designing the line width, simulation and calculation can be performed through tools such as AppCAD and HFSS.

[0092] The periodic air holes and non-uniform line width of the circuit are the core of the present invention. In order to further improve the transmission characteristics, the above embodiment of the present invention proposes two complementary optimization strategies based on the design of the circuit: optimizing the density of air holes and reducing the spacing between the air holes and the circuit 2 within the range allowed by the process. Through these optimization strategies, the line width and structural design of the circuit can be fine-tuned to further improve the overall performance and signal stability.

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

[0094] In 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 can further optimize the signal transmission path and provide the possibility for fine-tuning the design.

[0095] Through the above verification experiments, it can be known that the structure provided by the above embodiments of the present invention, through the design of air holes and lines, can effectively improve signal transmission efficiency and reduce signal loss, and provides a practical solution for the field of high-frequency signal transmission, which has important theoretical research value and broad practical application potential.

[0096] The low-loss substrate integrated transmission line structure and its preparation method provided by the above embodiment of the present invention are intended to reduce transmission loss, improve signal transmission efficiency and improve microwave circuit performance. The structure is realized through three designs: first, by introducing air holes in the substrate, the periodic distribution of the air holes is used to reduce the dielectric constant and loss tangent of the substrate, thereby reducing the transmission loss of the signal; second, the line width is accurately designed according to the periodic changes of the air holes to ensure a constant characteristic impedance and reduce reflection loss; third, metal holes can be added to enhance shielding to reduce radiation damage. In addition, by fine-tuning the increase in the air hole spacing, that is, changing the air hole density, and fine-tuning the distance Z between the air hole and the metal wire, signal interference and reflection loss are reduced, and the overall performance of the transmission line is improved. The results of the comparative example 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 provides a more reliable solution for high-frequency signal transmission and has broad application prospects.

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

[0098] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may 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 running along the length direction of the first substrate, metal layers arranged on the upper and lower sides of the first substrate, and a second substrate arranged above the metal layers on both sides; wherein: The first substrate is provided with a plurality of air holes penetrating along the height direction of the first substrate, the air holes are divided into two groups and arranged on both sides of the circuit respectively, and the two adjacent air holes in each group are arranged at an equal distance; the two symmetrically arranged air holes in the two groups are arranged at an equal distance; The circuit adopts a periodic line width structure.

2. The low-loss substrate integrated transmission structure according to claim 1, characterized in that: Also includes any one or more of the following: -The materials of the first substrate and / or the second substrate include: Ferro A6, FR4 and / or Rogers5880; -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 dimensions that can be provided by the material and process, and h is determined by the standard substrate thickness required by the material and process.

3. The 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: Also includes any one or more of the following: - The diameter of the air holes 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 circuit; - the number of the 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 transmission line structure according to claim 1, characterized in that: The d is 0.02 mm, and the t1 is 0.1 to 0.4 mm.

6. The low-loss substrate integrated transmission line structure according to claim 1, characterized in that: The circuit adopts a periodic line width structure, including a plurality of uniform line width parts and non-uniform line width parts connected alternately; wherein the non-uniform line width part adds an arc-shaped protruding structure on the basis of the uniform line width part, and the width of the widest protrusion of the arc-shaped protruding structure is less than 0.4mm.

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

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

9. The low-loss substrate integrated transmission line structure according to claim 1, characterized in that: Also includes: A group of metal holes penetrating along the height direction of the first substrate are respectively arranged outside the two groups of air holes on the first substrate to form a shielding structure.

10. A method for preparing a low-loss substrate integrated transmission line structure, characterized in that: include: Providing a circuit, wherein the circuit adopts a periodic line width structure; Providing a first substrate, and installing the circuit through the first substrate along the length direction of the first substrate to form a transmission part; Punching holes on the first substrate along its height direction to form air holes, wherein the air holes are divided into two groups and are respectively arranged on both sides of the circuit; A metal layer is disposed on the upper and lower sides of the first substrate respectively, and a second substrate is disposed above the metal layers on the upper and lower sides respectively to form a grounding and supporting portion, thereby constructing a low-loss substrate integrated transmission line structure based on air holes and line design.

11. The method for preparing a low-loss substrate integrated transmission line structure according to claim 10, characterized in that: Also includes: A group of metal holes penetrating along the height direction of the first substrate are respectively processed on the outer sides of the two groups of air holes on the first substrate to form a shielding structure.

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