Printed circuit board rectangular waveguide and preparation method thereof

Abstract

The invention provides a printed circuit board rectangular waveguide and a preparation method thereof. The printed circuit board is integrated with a feed transmission line, a mode conversion region and a rectangular waveguide cavity which are connected in sequence. The rectangular waveguide cavity comprises a first conductor layer, a second conductor layer, a bonding layer and a connecting via hole array. The first conductor layer comprises a rectangular cavity and is connected with the mode conversion region; and the second conductor layer is combined with the first conductor layer through the bonding layer to jointly form a waveguide cavity structure. And the connecting via hole array is positioned on two sides of the cavity, is connected with the first conductor layer and the second conductor layer, forms an equivalent metal side wall and is electrically connected with the mode conversion region. According to the rectangular waveguide and the preparation method thereof, the connecting via hole arrays are arranged on the two sides of the rectangular waveguide cavity structure and are connected with the first conductor layer and the second conductor layer to form the equivalent metal side wall, so that the process problem that a traditional waveguide cavity depends on high-temperature sintering in the manufacturing of a printed circuit board and is prone to collapse is effectively solved; and the production yield and the reliability are improved.

Description

Technical Field

[0001] This invention belongs to the field of microwave radio frequency technology, specifically relating to a rectangular waveguide on a printed circuit board and its fabrication method. Background Technology

[0002] With the development of wireless communication, radar detection, and other systems towards higher frequencies and higher integration, achieving efficient signal transmission on printed circuit boards (PCBs) has become a key technological challenge. Traditional planar transmission structures such as microstrip lines and feed lines are limited by conductor and dielectric losses, with losses increasing sharply in the millimeter-wave band, restricting system performance. Rectangular waveguides, due to their enclosed metal cavity structure, offer lower transmission loss and higher power capacity, making them an ideal choice for high-frequency applications. However, directly integrating traditional metal-air waveguides onto a PCB requires sintering within the PCB to form a closed cavity. This process involves high temperatures and stringent requirements for material heat resistance, easily leading to reliability issues such as interlayer delamination, cavity collapse, or board bursting. Furthermore, the integration of independent waveguide modules with other circuits on the PCB requires precise alignment and assembly, resulting in poor compatibility and high costs, making it difficult to meet the miniaturization and low-cost manufacturing demands of modern electronic devices. Therefore, there is an urgent need for a solution that is compatible with standard PCB processes, achieves integrated rectangular waveguides and transmission lines, and possesses high reliability. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a rectangular waveguide for printed circuit boards and its fabrication method to solve the aforementioned problems. The rectangular waveguide and its fabrication method employ a via array disposed on both sides of the rectangular waveguide cavity structure and connected to the first conductor layer and the second conductor layer to form an equivalent metal sidewall. This effectively solves the process problems of traditional waveguide cavities relying on high-temperature sintering and prone to board collapse in printed circuit board manufacturing, thereby improving production yield and reliability.

[0004] To address the aforementioned technical problems, this invention provides a rectangular waveguide on a printed circuit board. The printed circuit board integrates a feed transmission line, a mode conversion region, and a rectangular waveguide cavity connected sequentially. The rectangular waveguide cavity includes: a first conductor layer, a second conductor layer, an adhesive layer, and an array of connecting vias; wherein: The first conductor layer includes a rectangular cavity, and the first conductor layer is adjacent to and electrically connected to the mode conversion region; The second conductor layer is disposed on the first conductor layer and is connected to the first conductor layer through an adhesive layer. The second conductor layer is adjacent to and electrically connected to the mode conversion region, thereby forming a rectangular waveguide cavity structure together with the first conductor layer and the adhesive layer. The via array is disposed on both sides of the rectangular waveguide cavity structure. One end of each via is electrically connected to the first conductor layer, and the other end extends to the second conductor layer and is electrically connected thereto. The via array is adjacent to and electrically connected to the mode conversion region to form an equivalent metal sidewall of the rectangular waveguide.

[0005] In the above solution, a rectangular waveguide cavity is constructed by a first conductor layer, a second conductor layer, an adhesive layer, and a via array. The via array is positioned on both sides of the rectangular waveguide cavity structure and connects the first and second conductor layers to form equivalent metal sidewalls. This effectively solves the technological challenges of traditional waveguide cavities in printed circuit board manufacturing, which rely on high-temperature sintering and are prone to board collapse, thus improving production yield and reliability. Secondly, the above solution achieves a high degree of integration between the rectangular waveguide cavity, the feed transmission line, and the mode conversion area on the printed circuit board. It is compatible with standard printed circuit board processes and avoids the problems of high alignment accuracy requirements and complex assembly of discrete waveguide modules, which is beneficial for miniaturization and cost reduction of printed circuit boards.

[0006] It should be noted that the main function of the via array is to form the equivalent metallic sidewall of the rectangular waveguide, thereby confining electromagnetic waves to propagate within the cavity. In practical designs, depending on specific mode control, shielding, or structural layout requirements, the via array can be positioned not only on both sides of the rectangular waveguide cavity structure but also on its front and rear sides, or arranged appropriately around the perimeter of the cavity, thereby achieving more comprehensive electromagnetic enclosure and mode purity. This adjustment of the array position based on actual needs still falls within the scope of the equivalent metallic sidewall construction concept of this invention.

[0007] Furthermore, the rectangular waveguide for printed circuit boards according to the present invention further includes a plurality of vent holes; wherein: The vent is disposed on the rectangular waveguide cavity, penetrating the second conductor layer or the first conductor layer, and is used to balance the internal and external air pressure of the rectangular waveguide cavity.

[0008] In the above solution, vent holes are provided on the rectangular waveguide cavity, penetrating the second or first conductor layer. These vent holes balance the internal and external air pressure within the rectangular waveguide cavity, thereby expelling the expanding gas during process heating and preventing a surge in internal pressure that could lead to interlayer separation or "plate bursting." Simultaneously, the internal and external air pressures are balanced during cooling, preventing the cavity structure from collapsing or deforming. This solution eliminates the reliability risks associated with traditional sealed cavities and improves production yield.

[0009] It should be noted that the vent can be sealed in subsequent processes to ensure the integrity and sealing of the rectangular waveguide cavity in the final product, thereby improving process safety and structural reliability without sacrificing electrical performance.

[0010] Furthermore, the spacing between the connecting vias in the connecting via array is set based on the upper cutoff frequency of the rectangular waveguide cavity, so that the spacing between the connecting vias meets the preset hole spacing constraint condition, thereby forming the equivalent metal sidewall of the rectangular waveguide.

[0011] In the above scheme, the spacing between the connecting vias in the via array is set based on the upper cutoff frequency of the rectangular waveguide cavity, and this spacing satisfies a preset via spacing constraint condition. This allows the via array to effectively form the equivalent metal sidewall of the rectangular waveguide. This scheme ensures that electromagnetic waves are confined to the cavity for propagation, suppressing energy leakage and unnecessary radiation, and while guaranteeing transmission performance, it also considers process feasibility.

[0012] The present invention also provides a method for fabricating a rectangular waveguide on a printed circuit board, the method being applied to the rectangular waveguide cavity in the rectangular waveguide on a printed circuit board as described in the present invention, the method comprising the following steps: A first conductor layer is prepared, and the rectangular cavity is formed on the first conductor layer, thereby making the rectangular waveguide cavity structure adjacent to and electrically connected to the mode conversion region; A second conductor layer and an adhesive layer are fabricated on the first conductor layer, so that the second conductor layer is connected to the first conductor layer through the adhesive layer, thereby making the second conductor layer adjacent to and electrically connected to the mode conversion region, so that the first conductor layer, the second conductor layer and the adhesive layer together constitute a rectangular waveguide cavity structure; The array of connecting vias is fabricated on both sides of the rectangular waveguide cavity structure along the width direction, such that one end of each connecting via is electrically connected to the first conductor layer, and the other end extends to the second conductor layer and is electrically connected thereto, thereby making the equivalent metal sidewall of the rectangular waveguide adjacent to and electrically connected to the mode conversion region to form the equivalent metal sidewall of the rectangular waveguide.

[0013] In the above scheme, a first conductor layer with a rectangular cavity is sequentially fabricated, followed by a second conductor layer and an adhesive layer to form a rectangular waveguide cavity structure. An array of connecting vias connecting the first and second conductor layers is then fabricated on both sides to form equivalent metal sidewalls of the rectangular waveguide. This scheme solves the technological challenges of traditional waveguide cavities, which rely on high-temperature sintering and are prone to collapse, thus improving production yield and reliability. Simultaneously, it achieves a high degree of integration between the rectangular waveguide cavity, the feed transmission line, and the mode conversion region on the printed circuit board, ensuring compatibility with standard printed circuit board processes. This avoids the problems of high alignment accuracy requirements and complex assembly associated with discrete waveguide modules, facilitating miniaturization and cost reduction.

[0014] Further, the array of connecting vias is fabricated on both sides of the rectangular waveguide cavity structure along its width direction, such that one end of each connecting via is electrically connected to the first conductor layer, and the other end extends to and is electrically connected to the second conductor layer, thereby making the equivalent metal sidewall of the rectangular waveguide adjacent to and electrically connected to the mode conversion region, to form the equivalent metal sidewall of the rectangular waveguide; the array of connecting vias is fabricated based on the upper cutoff frequency of the rectangular waveguide cavity, wherein: The spacing between the connecting vias in the array is obtained based on the speed of light, the upper cutoff frequency of the rectangular waveguide cavity, and electromagnetic waveguide transmission theory, so that the spacing between the connecting vias satisfies the preset via spacing constraint relationship. The connection via array is prepared based on the connection via spacing.

[0015] In the above scheme, based on electromagnetic waveguide transmission theory, when the spacing of the periodic metal structure is much smaller than the operating wavelength, its reflection characteristics of electromagnetic waves can be approximately equivalent to a continuous conductor wall. The spacing between the connecting vias in the via array is obtained based on the speed of light, the upper cutoff frequency of the rectangular waveguide cavity, and electromagnetic waveguide transmission theory, and this spacing is made to satisfy a preset via spacing constraint relationship, thereby fabricating the via array. This scheme ensures that the connecting via array can effectively form the equivalent metal sidewall of the rectangular waveguide, constraining the propagation of electromagnetic waves within the cavity.

[0016] Further, the array of connecting vias is fabricated on both sides of the rectangular waveguide cavity structure along its width direction, such that one end of each connecting via is electrically connected to the first conductor layer, and the other end extends to and is electrically connected to the second conductor layer, thereby making the equivalent metal sidewall of the rectangular waveguide adjacent to and electrically connected to the mode conversion region, thus forming the equivalent metal sidewall of the rectangular waveguide; the spacing between the connecting vias in the array and the sidewall of the rectangular waveguide cavity structure is prepared based on the thickness of the bonding dielectric layer, wherein: Obtain the upper cutoff frequency and relative permittivity of the medium in the rectangular waveguide cavity; Based on the upper cutoff frequency of the rectangular waveguide cavity, the relative permittivity of the dielectric, the thickness of the bonding dielectric layer, and the transmission path theory, the distance between the connecting vias in the connecting via array and the sidewall of the rectangular waveguide cavity structure is obtained so that the distance between the connecting vias and the sidewall of the rectangular waveguide cavity structure satisfies the preset distance constraint relationship. The connection via array is prepared based on the distance between the connection via and the sidewall of the rectangular waveguide cavity structure.

[0017] In the above scheme, the distance between the connecting vias and the sidewalls of the rectangular waveguide cavity is obtained based on the upper cutoff frequency of the rectangular waveguide cavity, the relative permittivity of the dielectric, and the thickness of the adhesive layer, and according to the transmission path theory. This distance satisfies a preset spacing constraint relationship, thereby fabricating the connecting via array. This scheme can effectively avoid performance degradation caused by the propagation path, thus ensuring that the electromagnetic field energy is confined within the rectangular waveguide cavity, suppressing unnecessary propagation losses, and improving transmission efficiency. This parametric design method takes into account both electrical performance and the feasibility of printed circuit board manufacturing processes.

[0018] Furthermore, according to the method for fabricating a rectangular waveguide on a printed circuit board according to the present invention, the method further includes fabricating a plurality of vent holes, wherein: A plurality of ventilation holes are formed on the rectangular waveguide cavity so that the ventilation holes penetrate the second conductor layer or the first conductor layer to balance the internal and external air pressure of the rectangular waveguide cavity.

[0019] In the above solution, several vent holes are formed on the rectangular waveguide cavity, penetrating the second or first conductor layer, to balance the internal and external air pressure of the rectangular waveguide cavity. During the manufacturing process, the vent holes can promptly discharge gas, preventing pressure buildup that could lead to interlayer separation, and balance the air pressure during cooling to prevent cavity collapse and deformation, thereby ensuring the integrity of the cavity structure. This solution eliminates the reliability risks associated with traditional closed cavities, improving production yield and product reliability.

[0020] Furthermore, in the case where a plurality of vent holes are formed on the rectangular waveguide cavity, the aperture of the vent holes is determined based on the upper cutoff frequency of the rectangular waveguide cavity, wherein: Obtain the upper cutoff frequency of the rectangular waveguide cavity and preset the vent diameter; The target aperture of the vent is prepared based on the upper cutoff frequency, speed of light, and diameter of the vent in the rectangular waveguide cavity, so that the target aperture of the vent satisfies the preset aperture constraint relationship.

[0021] In the above scheme, according to microwave transmission theory, when the diameter of a circular aperture is smaller than the cutoff diameter of its corresponding mode, electromagnetic waves cannot propagate effectively through the aperture. Based on the upper cutoff frequency, speed of light, and vent diameter of the rectangular waveguide cavity, a target aperture diameter for the vent is prepared that satisfies a preset aperture constraint relationship. This design enables the vent to effectively balance the internal and external air pressures of the rectangular waveguide cavity physically, expel process gases, and prevent interlayer separation or cavity collapse caused by pressure buildup, thereby improving production yield and product reliability. Simultaneously, the aperture diameter that satisfies this constraint relationship electrically ensures the transmission performance of the rectangular waveguide cavity.

[0022] Further, the step of fabricating a first conductor layer and forming the rectangular cavity on the first conductor layer, thereby making the rectangular waveguide cavity structure adjacent to and electrically connected to the mode conversion region, includes: A first conductor layer is prepared, and the rectangular cavity is formed on the first conductor layer by mechanical cutting or laser cutting process, so that the rectangular waveguide cavity structure is adjacent to and electrically connected to the mode conversion region.

[0023] In the above solution, the rectangular cavity is formed on the first conductor layer using mechanical or laser cutting processes, and is then adjacent to and electrically connected to the mode conversion region. This solution ensures the transmission characteristics of the rectangular waveguide cavity, and the fabricated cavity region has accurate dimensions and regular sidewalls. This process is compatible with standard printed circuit board manufacturing processes, effectively avoiding dimensional deviations that may occur with traditional etching processes, thereby improving production yield and product reliability while realizing the rectangular waveguide cavity structure.

[0024] Further, the connection via array is fabricated on both sides of the rectangular waveguide cavity structure along its width direction, such that one end of each connection via is electrically connected to the first conductor layer, and the other end extends to and is electrically connected to the second conductor layer, thereby making the equivalent metal sidewall of the rectangular waveguide adjacent to and electrically connected to the mode conversion region to form the equivalent metal sidewall of the rectangular waveguide; including: The connecting via array is fabricated on both sides of the rectangular waveguide cavity structure along the width direction using a mechanical drilling process. The via array is metallized so that one end of each via is electrically connected to the first conductor layer and the other end extends to and is electrically connected to the second conductor layer, thereby making the rectangular waveguide equivalent metal sidewall adjacent to and electrically connected to the mode conversion region to form a rectangular waveguide equivalent metal sidewall.

[0025] In the above scheme, the via array is fabricated using mechanical drilling, and the via array is then metallized, so that one end of each via is electrically connected to the first conductor layer, and the other end extends to and is electrically connected to the second conductor layer, forming the equivalent metal sidewall of the rectangular waveguide. This scheme ensures the accuracy of the via position and spacing, achieves reliable electrical connection through via metallization, and forms a continuous equivalent metal sidewall. This process reduces fabrication costs and complexity, and ensures good process repeatability and reliability. The formed equivalent metal sidewall effectively confines electromagnetic waves propagating within the rectangular waveguide cavity, suppresses energy leakage, ensures low-loss transmission performance, and improves production yield and product reliability. Attached Figure Description

[0026] Figure 1This is a schematic diagram of a rectangular waveguide structure for a printed circuit board according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a rectangular waveguide cavity structure in a rectangular waveguide on a printed circuit board, provided by an embodiment of the present invention. Figure 3 A schematic diagram of a rectangular waveguide cavity structure in a rectangular waveguide on a printed circuit board according to an embodiment of the present invention; Figure 4 A schematic diagram of another rectangular waveguide structure for a printed circuit board provided in an embodiment of the present invention; Figure 5 This is a schematic flowchart of a method for fabricating a rectangular waveguide on a printed circuit board according to an embodiment of the present invention. Among them: 1. Feed transmission line; 2. Mode conversion region; 3. Rectangular waveguide cavity; 31. First conductor layer; 32. Second conductor layer; 33. Adhesive dielectric layer; 34. Connecting via array; 4. Vent hole. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Please see Figure 1 and Figure 2 This embodiment provides a rectangular waveguide on a printed circuit board. The printed circuit board integrates a feed transmission line 1, a mode conversion region 2, and a rectangular waveguide cavity 3 connected in sequence. The rectangular waveguide cavity includes: a first conductor layer 31, a second conductor layer 32, an adhesive layer 33, and an array of connecting vias 34; wherein: The first conductor layer 31 includes a rectangular cavity, and the first conductor layer 31 is adjacent to and electrically connected to the mode conversion region 2; The second conductor layer 32 is disposed on the first conductor layer 31 and is connected to the first conductor layer 31 through the adhesive layer 33. The second conductor layer 32 is adjacent to and electrically connected to the mode conversion region 2, and together with the first conductor layer 31 and the adhesive layer 33, it forms a rectangular waveguide cavity structure. The via array 34 is disposed on both sides of the rectangular waveguide cavity structure. One end of each via is electrically connected to the first conductor layer 31, and the other end extends to the second conductor layer 32 and is electrically connected thereto. The via array 34 is adjacent to and electrically connected to the mode conversion region 2 to form an equivalent metal sidewall of the rectangular waveguide.

[0029] In this embodiment, a rectangular waveguide cavity 3 is constructed by a first conductor layer 31, a second conductor layer 32, an adhesive layer 33, and a via array 34. The via array 34 is disposed on both sides of the rectangular waveguide cavity structure and connects the first conductor layer 31 and the second conductor layer 32 to form an equivalent metal sidewall. This effectively solves the process problems of traditional waveguide cavities relying on high-temperature sintering and prone to board collapse in printed circuit board manufacturing, thus improving production yield and reliability. Secondly, this embodiment achieves a high degree of integration of the rectangular waveguide cavity, the feed transmission line, and the mode conversion area on the printed circuit board, is compatible with standard printed circuit board processes, and avoids the problems of high alignment accuracy requirements and complex assembly of discrete waveguide modules, which is conducive to the miniaturization and low cost of printed circuit boards.

[0030] It should be noted that the mode conversion region is used to realize efficient conversion between the transmission mode of the feed transmission line (or microstrip line) and the transmission mode of the rectangular waveguide cavity. Its specific structure can be the form of a tapered line, stepped impedance transformer, etc. commonly used in the art, and is not limited here.

[0031] It should be noted that the first and second conductor layers can be made of metallic materials, such as copper foil. In actual printed circuit board manufacturing processes, the conductor layers are usually in the form of copper-clad laminates, meaning that the first or second conductor layer can include a metal layer (such as copper foil) and an attached dielectric substrate. This common structure also falls within the scope of this invention. The adhesive dielectric layer can be a pure adhesive layer, and its material can be a thermosetting or photocurable dielectric film. This pure adhesive layer should have good flowability during the lamination process to fill gaps, and after curing, it should maintain a stable dielectric constant and a low loss tangent to ensure low-loss transmission of high-frequency signals.

[0032] Further, please see Figure 3 and Figure 4 Furthermore, the rectangular waveguide for printed circuit boards according to the present invention further includes a plurality of vent holes 4; wherein: The vent 4 is disposed on the rectangular waveguide cavity structure, penetrating the second conductor layer 32 or the first conductor layer 31, and is used to balance the internal and external air pressure of the rectangular waveguide cavity 3.

[0033] In this embodiment, a vent 4 is provided on the rectangular waveguide cavity structure, penetrating the second conductor layer 32 or the first conductor layer 31. This vent balances the internal and external air pressure of the rectangular waveguide cavity 3, thereby venting the gas that expands during process heating and preventing a sharp increase in internal pressure that could lead to interlayer separation or "plate bursting." Simultaneously, it balances the internal and external air pressure during cooling, preventing the cavity structure from collapsing or deforming. This embodiment eliminates the reliability risks associated with traditional closed cavities and improves production yield.

[0034] It should be noted that the vent can be sealed in subsequent processes to ensure the integrity and sealing of the waveguide cavity in the final product, thereby improving process safety and structural reliability without sacrificing electrical performance.

[0035] It should be noted that the vent is usually made using the same mechanical drilling process as the connecting via array, and its sealing can be performed after all wet processes (such as electroplating and cleaning) are completed.

[0036] Furthermore, the spacing between the connecting vias in the connecting via array is set based on the upper cutoff frequency of the rectangular waveguide cavity, so that the spacing between the connecting vias meets the preset hole spacing constraint condition, thereby forming the equivalent metal sidewall of the rectangular waveguide.

[0037] In this embodiment, the spacing between the connecting vias in the via array is set based on the upper limit cutoff frequency of the rectangular waveguide cavity, and this spacing satisfies a preset via spacing constraint condition. This allows the via array to effectively form the equivalent metal sidewall of the rectangular waveguide. This embodiment ensures that electromagnetic waves are confined to the cavity for propagation, suppressing energy leakage and unnecessary radiation, thus guaranteeing transmission performance while also considering fabrication feasibility.

[0038] It should be noted that the preset hole spacing constraint condition is: the distance between connecting vias. ,in, This is the upper cutoff frequency of the rectangular waveguide cavity. The speed of light. When the via spacing meets the preset via spacing constraint, the equivalent metal sidewall formed by the via array is close to a continuous metal sidewall in suppressing electromagnetic leakage, and can be considered the optimal spacing design, resulting in the best transmission performance. In practical applications, if the via spacing is slightly larger than this constraint value, the shielding effect of the equivalent sidewall will gradually decrease, which may lead to some increase in energy leakage and radiation, and a deterioration in transmission performance. However, in some scenarios with relatively relaxed performance requirements or high leakage tolerance, a slightly larger spacing design can still meet the usage requirements. A comprehensive evaluation based on overall frequency response, radiation, and loss indicators is necessary.

[0039] It should be noted that the fabrication process of the via array typically includes: first, forming vias at designated locations by mechanical drilling or laser drilling; then, performing a via metallization process, such as forming a seed layer on the via wall by chemical copper plating, and then thickening it by electroplating copper to form a reliable metallized via wall, ensuring low-resistance electrical connection with the first conductor layer and the second conductor layer.

[0040] Please see Figure 5This embodiment also provides a method for fabricating a rectangular waveguide on a printed circuit board. This method is applied to the rectangular waveguide cavity in the rectangular waveguide described above. The method includes the following steps: Step S1: Prepare a first conductor layer and form the rectangular cavity on the first conductor layer, thereby making the rectangular waveguide cavity structure adjacent to and electrically connected to the mode conversion region; Step S2: Prepare a second conductor layer and an adhesive layer on the first conductor layer, so that the second conductor layer is connected to the first conductor layer through the adhesive layer, thereby making the second conductor layer adjacent to and electrically connected to the mode conversion region, so that the first conductor layer, the second conductor layer and the adhesive layer together constitute a rectangular waveguide cavity structure; Step S3: Prepare the array of connecting vias on both sides of the rectangular waveguide cavity structure along the width direction, so that one end of each connecting via is electrically connected to the first conductor layer, and the other end extends to the second conductor layer and is electrically connected thereto, thereby making the equivalent metal sidewall of the rectangular waveguide adjacent to and electrically connected to the mode conversion region to form the equivalent metal sidewall of the rectangular waveguide.

[0041] In this embodiment, a rectangular waveguide cavity structure is constructed by sequentially fabricating a first conductor layer with a rectangular cavity, then fabricating a second conductor layer and an adhesive layer on the first conductor layer to form a rectangular waveguide cavity structure, and finally fabricating an array of connecting vias on both sides to connect the first and second conductor layers to form equivalent metal sidewalls of the rectangular waveguide. This solution solves the technological challenges of traditional waveguide cavities, which rely on high-temperature sintering and are prone to collapse, thus improving production yield and reliability. Simultaneously, it achieves a high degree of integration between the rectangular waveguide cavity, the feed transmission line, and the mode conversion region on the printed circuit board, is compatible with standard printed circuit board processes, and avoids the problems of high alignment accuracy requirements and complex assembly of discrete waveguide modules, which is beneficial for miniaturization and cost reduction.

[0042] Further, the array of connecting vias is fabricated on both sides of the rectangular waveguide cavity structure along its width direction, such that one end of each connecting via is electrically connected to the first conductor layer, and the other end extends to and is electrically connected to the second conductor layer, thereby making the equivalent metal sidewall of the rectangular waveguide adjacent to and electrically connected to the mode conversion region, to form the equivalent metal sidewall of the rectangular waveguide; the array of connecting vias is fabricated based on the upper cutoff frequency of the rectangular waveguide cavity, wherein: The spacing between the connecting vias in the array is obtained based on the speed of light, the upper cutoff frequency of the rectangular waveguide cavity, and electromagnetic waveguide transmission theory, so that the spacing between the connecting vias satisfies the preset via spacing constraint relationship. The connection via array is prepared based on the connection via spacing.

[0043] In this embodiment, based on electromagnetic waveguide transmission theory, when the spacing of the periodic metal structure is much smaller than the operating wavelength, its reflection characteristics of electromagnetic waves can be approximately equivalent to a continuous conductor wall. The spacing between the connecting vias in the via array is obtained based on the speed of light, the upper cutoff frequency of the rectangular waveguide cavity, and electromagnetic waveguide transmission theory, and this spacing is made to satisfy a preset via spacing constraint relationship, thereby fabricating the via array. This scheme ensures that the via array can effectively form the equivalent metal sidewall of the rectangular waveguide, constraining the propagation of electromagnetic waves within the cavity.

[0044] It should be noted that the preset hole spacing constraint relationship is specifically as follows: ,in, To connect the via spacing in the via array, This is the upper cutoff frequency of the rectangular waveguide cavity. The speed is the speed of light. During fabrication, the upper cutoff frequency of the rectangular waveguide is determined according to the design requirements. and the speed of light The maximum allowable hole spacing is calculated, and the arrangement spacing of the connecting via array is determined based on this.

[0045] It should be further noted that the aforementioned preset aperture spacing constraint corresponds to a preferred or optimal embodiment of the present invention, which can achieve a good balance between electrical performance and process feasibility. In practical applications, the aperture spacing can also be adjusted within a certain range according to different performance requirements or process constraints. As long as it can maintain the basic mode of the rectangular waveguide and achieve effective signal transmission, it should fall within the reasonable extension and scope of the technical concept of the present invention.

[0046] Further, the array of connecting vias is fabricated on both sides of the rectangular waveguide cavity structure along its width direction, such that one end of each connecting via is electrically connected to the first conductor layer, and the other end extends to and is electrically connected to the second conductor layer, thereby making the equivalent metal sidewall of the rectangular waveguide adjacent to and electrically connected to the mode conversion region, thus forming the equivalent metal sidewall of the rectangular waveguide; the spacing between the connecting vias in the array and the sidewall of the rectangular waveguide cavity structure is prepared based on the thickness of the bonding dielectric layer, wherein: Obtain the upper cutoff frequency and relative permittivity of the medium in the rectangular waveguide cavity; Based on the upper cutoff frequency of the rectangular waveguide cavity, the relative permittivity of the dielectric, the thickness of the bonding dielectric layer, and the transmission path theory, the distance between the connecting vias in the connecting via array and the sidewall of the rectangular waveguide cavity structure is obtained so that the distance between the connecting vias and the sidewall of the rectangular waveguide cavity structure satisfies the preset distance constraint relationship. The connection via array is prepared based on the distance between the connection via and the sidewall of the rectangular waveguide cavity structure.

[0047] In this embodiment, the distance between the connecting vias and the sidewalls of the rectangular waveguide cavity structure is obtained based on the upper cutoff frequency of the rectangular waveguide cavity, the relative permittivity of the dielectric, and the thickness of the adhesive layer, and according to the transmission path theory. This distance satisfies a preset spacing constraint relationship, thereby fabricating the connecting via array. This embodiment effectively avoids performance degradation caused by the propagation path, ensuring that the electromagnetic field energy is confined within the rectangular waveguide cavity, suppressing unnecessary propagation losses, and improving transmission efficiency. This embodiment balances electrical performance with the feasibility of printed circuit board manufacturing processes.

[0048] It should be noted that the preset spacing constraint relationship is specifically as follows: ,in, The distance between the via and the sidewall of the rectangular waveguide cavity structure. The upper limit cutoff frequency, At the speed of light, The relative permittivity of the adhesive dielectric layer is given. The thickness of the adhesive dielectric layer is given. Satisfying the preset spacing constraint relationship ensures that when electromagnetic waves propagate in the region formed by the first conductor layer, the second conductor layer, the adhesive dielectric layer, and the equivalent sidewall, the longest possible path is short enough, thereby avoiding significant phase delay and field distribution distortion, and ensuring that electromagnetic field energy is efficiently confined within the rectangular waveguide cavity.

[0049] It should be further noted that the above-mentioned spacing constraints are theoretical reference values ​​optimized to achieve the best transmission efficiency and minimum loss. In actual manufacturing processes, due to limitations in specific process precision or to adapt to different application scenarios, the spacing is allowed to have a certain deviation near the reference value. As long as this deviation does not substantially affect the constraint effect of the equivalent metal sidewall formed by the connecting via array on the electromagnetic field energy, that is, it can still effectively confine the main mode energy of the electromagnetic wave to the rectangular waveguide cavity for transmission, such implementations should be considered to fall within the protection scope of this invention.

[0050] Furthermore, according to the method for fabricating a rectangular waveguide on a printed circuit board according to the present invention, the method further includes fabricating a plurality of vent holes, wherein: A plurality of ventilation holes are formed on the rectangular waveguide cavity structure so that the ventilation holes penetrate the second conductor layer or the first conductor layer to balance the internal and external air pressure of the rectangular waveguide cavity.

[0051] In this embodiment, a plurality of vent holes are fabricated on the rectangular waveguide cavity structure, penetrating the second conductor layer or the first conductor layer, to balance the internal and external air pressure of the rectangular waveguide cavity. During the manufacturing process, the vent holes can promptly discharge gas, preventing pressure buildup that could lead to interlayer separation, and balance the air pressure during cooling to prevent cavity collapse and deformation, thereby ensuring the integrity of the cavity structure. This embodiment eliminates the process reliability risks associated with traditional closed cavities, improving production yield and product reliability.

[0052] It should be noted that the function of the vent includes: preparing the vent before the pressing process, during which the high-temperature expanding gas is discharged through the vent to achieve pressure balance; after pressing and before entering the wet process (such as electroplating or cleaning), the vent is sealed with sealing tape or other sealing materials to prevent liquid from entering the cavity.

[0053] Furthermore, in the case where a plurality of vent holes are fabricated on the rectangular waveguide cavity structure, the aperture of the vent holes is determined based on the upper cutoff frequency of the rectangular waveguide cavity, wherein: Obtain the upper cutoff frequency of the rectangular waveguide cavity and preset the vent diameter; The target aperture of the vent is prepared based on the upper cutoff frequency, speed of light, and diameter of the vent in the rectangular waveguide cavity, so that the target aperture of the vent satisfies the preset aperture constraint relationship.

[0054] In this embodiment, according to microwave transmission theory, when the diameter of a circular aperture is smaller than the cutoff diameter of its corresponding mode, electromagnetic waves cannot propagate effectively through the aperture. Based on the upper cutoff frequency, speed of light, and vent diameter of the rectangular waveguide cavity, a target aperture diameter for the vent is prepared that satisfies a preset aperture constraint relationship. This embodiment enables the vent to effectively balance the internal and external air pressures of the rectangular waveguide cavity physically, expel process gases, and prevent interlayer separation or cavity collapse caused by pressure buildup, thereby improving production yield and product reliability. Simultaneously, the aperture diameter satisfying this constraint relationship electrically ensures the transmission performance of the rectangular waveguide cavity.

[0055] It should be noted that the preset aperture constraint relationship must simultaneously satisfy the following two points: 1) Based on the cutoff characteristics of a circular waveguide, the aperture... 2) Aperture based on the influence of transmission line direction .in, This is the upper cutoff frequency of the rectangular waveguide cavity. It is the speed of light. During fabrication, it is based on the designed upper cutoff frequency. Calculate the two formulas separately, and take the smaller value as the upper limit of the design of the vent diameter.

[0056] It should be further noted that the value determined by the preset aperture constraint relationship is the theoretical upper limit of the design, taking into account both waveguide electrical performance and ventilation requirements, and belongs to the preferred embodiment of the present invention. In the actual preparation process, the selected ventilation aperture can be appropriately adjusted according to specific process capabilities, dielectric material characteristics, or actual requirements for the air pressure balancing rate, provided that the constraint relationship is met. As long as the adjusted aperture can effectively achieve the physical function of balancing the air pressure inside and outside the cavity, and does not cause substantial damage to the main mode transmission of the rectangular waveguide, such embodiments should be considered as reasonable applications of the technical solution of the present invention and fall within its protection scope.

[0057] Further, the step of fabricating a first conductor layer and forming the rectangular cavity on the first conductor layer, thereby making the rectangular waveguide cavity structure adjacent to and electrically connected to the mode conversion region, includes: A first conductor layer is prepared, and the rectangular cavity is formed on the first conductor layer by mechanical cutting or laser cutting process, so that the rectangular waveguide cavity structure is adjacent to and electrically connected to the mode conversion region.

[0058] In this embodiment, the rectangular cavity is formed on the first conductor layer using mechanical or laser cutting processes, thereby fabricating a rectangular waveguide cavity structure with precise geometric dimensions. This structure is then adjacent to and electrically connected to the mode conversion region. This approach ensures the transmission characteristics of the rectangular waveguide cavity, and the fabricated cavity region has accurate dimensions and regular sidewalls. This process is compatible with standard printed circuit board manufacturing processes, effectively avoiding dimensional deviations that may occur with traditional etching processes. Therefore, while realizing the rectangular waveguide cavity structure, it also improves production yield and product reliability.

[0059] Further, the connection via array is fabricated on both sides of the rectangular waveguide cavity structure along its width direction, such that one end of each connection via is electrically connected to the first conductor layer, and the other end extends to and is electrically connected to the second conductor layer, thereby making the equivalent metal sidewall of the rectangular waveguide adjacent to and electrically connected to the mode conversion region to form the equivalent metal sidewall of the rectangular waveguide; including: The connecting via array is fabricated on both sides of the rectangular waveguide cavity structure along the width direction using a mechanical drilling process. The via array is metallized so that one end of each via is electrically connected to the first conductor layer and the other end extends to and is electrically connected to the second conductor layer, thereby making the rectangular waveguide equivalent metal sidewall adjacent to and electrically connected to the mode conversion region to form a rectangular waveguide equivalent metal sidewall.

[0060] In this embodiment, the via array is fabricated using mechanical drilling, and the vias are then metallized, so that one end of each via is electrically connected to the first conductor layer, and the other end extends to and is electrically connected to the second conductor layer, forming the equivalent metal sidewall of the rectangular waveguide. This embodiment ensures the accuracy of the via position and spacing, achieves reliable electrical connection through via metallization, and forms a continuous equivalent metal sidewall. This process reduces fabrication costs and complexity, and ensures good process repeatability and reliability. The formed equivalent metal sidewall effectively confines electromagnetic waves propagating within the rectangular waveguide cavity, suppresses energy leakage, ensures low-loss transmission performance, and improves production yield and product reliability.

[0061] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A rectangular waveguide for a printed circuit board, characterized in that, The printed circuit board integrates a feed transmission line, a mode conversion region, and a rectangular waveguide cavity connected in sequence. The rectangular waveguide cavity includes: a first conductor layer, a second conductor layer, an adhesive layer, and an array of connecting vias; wherein: The first conductor layer includes a rectangular cavity, and the first conductor layer is adjacent to and electrically connected to the mode conversion region; The second conductor layer is disposed on the first conductor layer and is connected to the first conductor layer through an adhesive layer. The second conductor layer is adjacent to and electrically connected to the mode conversion region, thereby forming a rectangular waveguide cavity structure together with the first conductor layer and the adhesive layer. The via array is disposed on both sides of the rectangular waveguide cavity structure. One end of each via is electrically connected to the first conductor layer, and the other end extends to the second conductor layer and is electrically connected thereto. The via array is adjacent to and electrically connected to the mode conversion region to form an equivalent metal sidewall of the rectangular waveguide.

2. A rectangular waveguide for a printed circuit board according to claim 1, characterized in that, It also includes several vents; among which: The vent is disposed on the rectangular waveguide cavity, penetrating the second conductor layer or the first conductor layer, and is used to balance the internal and external air pressure of the rectangular waveguide cavity.

3. A rectangular waveguide for a printed circuit board according to claim 1, characterized in that, The spacing between the connecting vias in the array is set based on the upper cutoff frequency of the rectangular waveguide cavity, so that the spacing between the connecting vias meets the preset hole spacing constraint condition, thereby forming the equivalent metal sidewall of the rectangular waveguide.

4. A method for fabricating a rectangular waveguide on a printed circuit board, characterized in that, This method is applied to the rectangular waveguide cavity in a printed circuit board rectangular waveguide as described in claim 1, and the method includes the following steps: A first conductor layer is prepared, and the rectangular cavity is formed on the first conductor layer, thereby making the rectangular waveguide cavity structure adjacent to and electrically connected to the mode conversion region; A second conductor layer and an adhesive layer are fabricated on the first conductor layer, so that the second conductor layer is connected to the first conductor layer through the adhesive layer, thereby making the second conductor layer adjacent to and electrically connected to the mode conversion region, so that the first conductor layer, the second conductor layer and the adhesive layer together constitute a rectangular waveguide cavity structure; The array of connecting vias is fabricated on both sides of the rectangular waveguide cavity structure along the width direction, such that one end of each connecting via is electrically connected to the first conductor layer, and the other end extends to the second conductor layer and is electrically connected thereto, thereby making the equivalent metal sidewall of the rectangular waveguide adjacent to and electrically connected to the mode conversion region to form the equivalent metal sidewall of the rectangular waveguide.

5. The method for fabricating a rectangular waveguide on a printed circuit board according to claim 4, characterized in that, The array of connecting vias is fabricated on both sides of the rectangular waveguide cavity structure along the width direction, such that one end of each connecting via is electrically connected to the first conductor layer, and the other end extends to the second conductor layer and is electrically connected thereto, thereby making the equivalent metal sidewall of the rectangular waveguide adjacent to and electrically connected to the mode conversion region, so as to form the equivalent metal sidewall of the rectangular waveguide. The via array is fabricated based on the upper cutoff frequency of the rectangular waveguide cavity, wherein: The spacing between the connecting vias in the array is obtained based on the speed of light, the upper cutoff frequency of the rectangular waveguide cavity, and electromagnetic waveguide transmission theory, so that the spacing between the connecting vias satisfies the preset via spacing constraint relationship. The connection via array is prepared based on the connection via spacing.

6. The method for fabricating a rectangular waveguide on a printed circuit board according to claim 4, characterized in that, The array of connecting vias is prepared on both sides of the rectangular waveguide cavity structure along the width direction, such that one end of each connecting via is electrically connected to the first conductor layer, and the other end extends to the second conductor layer and is electrically connected thereto, thereby making the equivalent metal sidewall of the rectangular waveguide adjacent to and electrically connected to the mode conversion region to form the equivalent metal sidewall of the rectangular waveguide. The spacing between the connecting vias and the sidewalls of the rectangular waveguide cavity structure in the connecting via array is prepared based on the thickness of the adhesive dielectric layer, wherein: Obtain the upper cutoff frequency and relative permittivity of the medium in the rectangular waveguide cavity; Based on the upper cutoff frequency of the rectangular waveguide cavity, the relative permittivity of the dielectric, the thickness of the bonding dielectric layer, and the transmission path theory, the distance between the connecting vias in the connecting via array and the sidewall of the rectangular waveguide cavity is obtained so that the distance between the connecting vias and the sidewall of the rectangular waveguide cavity structure satisfies the preset distance constraint relationship. The connection via array is prepared based on the distance between the connection via and the sidewall of the rectangular waveguide cavity structure.

7. The method for fabricating a rectangular waveguide on a printed circuit board according to claim 4, characterized in that, It also includes a number of vent holes, wherein: A plurality of ventilation holes are formed on the rectangular waveguide cavity so that the ventilation holes penetrate the second conductor layer or the first conductor layer to balance the internal and external air pressure of the rectangular waveguide cavity.

8. The method for fabricating a rectangular waveguide on a printed circuit board according to claim 7, characterized in that, In the case where a plurality of vent holes are formed on the rectangular waveguide cavity, the aperture of the vent holes is determined based on the upper cutoff frequency of the rectangular waveguide cavity, wherein: Obtain the upper cutoff frequency of the rectangular waveguide cavity and preset the vent diameter; The target aperture of the vent is prepared based on the upper cutoff frequency, speed of light and diameter of the vent in the rectangular waveguide cavity, so that the target aperture of the vent satisfies the preset aperture constraint relationship.

9. The method for fabricating a rectangular waveguide on a printed circuit board according to claim 4, characterized in that, The process of fabricating a first conductor layer and forming the rectangular cavity on the first conductor layer, thereby making the rectangular waveguide cavity structure adjacent to and electrically connected to the mode conversion region, includes: A first conductor layer is prepared, and the rectangular cavity is formed on the first conductor layer by mechanical cutting or laser cutting process, so that the rectangular waveguide cavity structure is adjacent to and electrically connected to the mode conversion region.

10. The method for fabricating a rectangular waveguide on a printed circuit board according to claim 4, characterized in that, The method involves fabricating the array of connecting vias on both sides of the rectangular waveguide cavity structure along its width direction, such that one end of each connecting via is electrically connected to the first conductor layer, and the other end extends to and is electrically connected to the second conductor layer, thereby making the equivalent metal sidewall of the rectangular waveguide adjacent to and electrically connected to the mode conversion region to form the equivalent metal sidewall of the rectangular waveguide; including: The connecting via array is fabricated on both sides of the rectangular waveguide cavity structure along the width direction using a mechanical drilling process. The via array is metallized so that one end of each via is electrically connected to the first conductor layer and the other end extends to and is electrically connected to the second conductor layer, thereby making the rectangular waveguide equivalent metal sidewall adjacent to and electrically connected to the mode conversion region to form a rectangular waveguide equivalent metal sidewall.

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