Novel half-mode slot gap waveguide based on mushroom-type periodic units

Abstract

The invention discloses a novel half-mode slot gap waveguide based on mushroom type periodic units. The novel half-mode slot gap waveguide comprises an upper mushroom type periodic unit array cover plate and a lower slotted metal bottom plate, the upper layer mushroom type periodic unit array cover plate comprises a metal reference ground, a dielectric substrate, a metal patch and a metalized via hole; the upper surface of the dielectric substrate is completely covered with a metal reference ground, metal patches which are periodically distributed are arranged on the lower surface of the dielectric substrate, and each metal patch is connected with the metal reference ground through a metalized via hole; the metal reference ground and the slotted metal bottom plate are oppositely arranged, the dielectric substrate is located between the metal reference ground and the slotted metal bottom plate, an air gap layer is arranged between the dielectric substrate and the slotted metal bottom plate, and the air gap layer and a slot in the slotted metal bottom plate form a transmission path of electromagnetic waves. According to the invention, the problem that the upper and lower cover plates are misplaced due to the processing error of the half-mode slot gap waveguide, so that the phase of the transmission structure has an error when the upper and lower cover plates are perfectly aligned can be solved.

Description

Technical Field

[0001] The invention relates to the field of electromagnetic field and microwave technology, and in particular to a novel half-mode slot gap waveguide based on a mushroom-type periodic unit. Background Art

[0002] In millimeter-wave circuits and systems, transmission lines play a key role, and their characteristics (such as loss, size, integration, cost, and weight) directly affect the overall performance. Traditional transmission lines include rectangular waveguides using transverse electric or transverse magnetic modes, and microstrip lines, striplines, and coplanar waveguides using transverse electromagnetic modes. Among them, rectangular waveguides, as a classic transmission line, are known for their low loss, wide bandwidth, and high power resistance. Due to their fully metallized structure, rectangular waveguides provide comprehensive shielded transmission and effectively avoid radiation losses. However, the application of rectangular waveguides in the millimeter-wave frequency band is limited by the difficulty of manufacturing. In addition, their non-planar characteristics make integration with other transmission lines challenging, especially considering complex transition design and packaging issues. Microstrip lines, as a compact solution based on printed circuit technology, are popular because of their simple structural integration, light weight, and low cost. However, in high-frequency applications, their transmission losses are quite large due to high dielectric loss, conductor loss, and radiation leakage. These characteristics make it challenging to implement low-loss millimeter-wave systems using microstrip lines. Both coplanar waveguide and stripline offer high design freedom and wide bandwidth, but they still face huge challenges in terms of loss. As a combination of metal waveguide and microstrip line, substrate integrated waveguide has been widely used since it was proposed. It inherits the advantages of metal waveguide and microstrip line, but also bears the disadvantages of both.

[0003] Based on the above background, in 2008, Professor Per-Simon Kildal proposed the gap waveguide technology based on the research on hard and soft surfaces. This technology is considered to be one of the more promising transmission line technologies for millimeter waves. The working principle of the gap waveguide is based on the joint action of ideal electrical conductors and artificial magnetic conductors, which limit the propagation of electromagnetic fields in narrow gaps. One of the core advantages of this structure is that it can simplify the manufacturing and assembly process. Since perfect electrical connections are not required, only a few screws are needed to prevent the leakage of electromagnetic waves. And because of the open structure, the gap waveguide does not require traditional packaging methods or sealed metal shells, which makes it particularly good in millimeter wave electronic packaging. At the same time, because it inherits the low loss of waveguides, it is very suitable for millimeter wave antenna applications. However, despite its many advantages, the gap waveguide still faces some challenges. For example, in the subtractive manufacturing process, it is more expensive to make a groove surrounded by many pins than to mill a simple groove on a metal plate. Although this trade-off is usually worthwhile, the manufacturing cost will increase exponentially with the increase in frequency, and further technical improvements are urgently needed.

[0004] At present, scholars are trying to solve the problems in gap waveguide manufacturing from two aspects. On the one hand, improving the processing technology, and on the other hand, changing the shape of the perfect magnetic conductor pin is an important means to reduce the complexity of manufacturing. However, even after these improvements, there are still three problems in designing the gap waveguide structure: First, in the gap, the groove forming the waveguide and the nail bed are located on the same metal plate, and the bending, curve or transition of the groove forming the waveguide in the feeding network will affect the period and shape of the pin, which may cause the stop band to not be fully covered, and the structural strength will be greatly weakened due to the narrowing or thinning of the pin. Secondly, each different network needs to design the pin arrangement separately, and the design efficiency is low. Finally, for more complex structures, the simulation speed in the simulation software is usually 3 times slower than that of the rectangular metal waveguide, and the optimization process is prone to errors.

[0005] In response to the above problems, relevant scholars have proposed a half-slot gap waveguide technology, which is an innovative and improved structure based on the traditional gap waveguide. This design moves all pins to the top plate instead of the traditional bottom plate, and processes the waveguide and the artificial magnetic conductor composed of the nail bed as independent components. This technology improves the above disadvantages: the artificial magnetic conductor part realizes a standardized design, and no matter how many cavities or bends the feeding network contains, evenly arranged artificial magnetic conductors can be used, which significantly reduces the design complexity and improves the design efficiency, and reduces the difficulty of processing; at the same time, the upper surface can be replaced by a perfect magnetic conductor surface, which greatly shortens the simulation time, and because the cross section is reduced by half, the simulation time of this approach is even lower than that of conventional waveguides.

[0006] However, in the half-mode slot gap waveguide, the relative position of the slot and the pin has a significant effect on the phase. This is because the artificial magnetic conductor formed by the pins is not a perfect magnetic conductor. When the period of the pins is comparable to the width of the bottom waveguide, the pins will have a significant effect on the phase. This means that when using this technology, all plates must be precisely aligned and all structures involved in the phase must maintain perfect symmetry. These strict requirements limit the development of this technology to a certain extent.

[0007] Therefore, although the half-slot gap waveguide effectively reduces the time cost and processing cost, there are significant technical limitations in practical applications. The structure is extremely sensitive to the position of the pin periodic unit, and its performance is highly dependent on the precise alignment of the upper and lower metal plates. When the upper and lower metal plates are misaligned, it will cause uncontrollable phase shift, seriously affecting the stability of the transmission performance, increasing the manufacturing cost, and even offsetting the advantages of the pin half-slot gap waveguide.

[0008] The invention with publication number CN117239379A discloses an improved printed ridge gap waveguide and communication system packaged with an electromagnetic bandgap structure, including a waveguide structure and an electromagnetic packaging structure on both sides. The waveguide structure consists of an upper metal plate placed in parallel and an intermediate metal strip with a grounded metallized through hole. The electromagnetic packaging structure is located on both sides of the waveguide structure, including an upper metal plate placed in parallel and periodically arranged vertically stacked mushroom-type electromagnetic bandgap structural units. The packaging of the invention adopts a stacked mushroom-type electromagnetic bandgap structure to achieve advantages such as non-electrical contact, high structural stability and low installation cost. However, although the invention adopts gap waveguide technology to allow electromagnetic waves to propagate in the air, there is no way to solve the problem that the upper and lower cover plates of the half-mold gap waveguide are misaligned due to processing errors, which in turn leads to errors in the phase of the transmission structure when the upper and lower cover plates are perfectly aligned, and the simulation process is also relatively complicated.

[0009] The invention with publication number CN119108777A discloses a band-stop filter based on a printed ridge gap waveguide, including: a bottom dielectric substrate; periodic mushroom units; a metal top plate; a microstrip transmission line placed on the upper surface of the bottom dielectric substrate; on both sides of the feeding network, the periodic mushroom units are evenly arranged, with M columns on the left and right sides of the dielectric substrate in the wide side direction and N rows in the long side direction. The energy in the band-stop filter of this invention is transmitted in the air gap, so it can effectively reduce dielectric loss and improve transmission efficiency, especially in the millimeter wave frequency band, and it has a simple structure and low processing difficulty, which is conducive to the miniaturization and high-efficiency design of millimeter wave systems. Similarly, this invention cannot solve the problem that the upper and lower cover plates of the semi-mode slot gap waveguide are misaligned due to processing errors, which in turn leads to errors in the phase of the transmission structure and the phase when the upper and lower cover plates are perfectly aligned, and the simulation process is still complicated. Summary of the invention

[0010] The present invention discloses a novel half-slot gap waveguide based on a mushroom-shaped periodic unit, which can solve the problem that the upper and lower cover plates of the half-slot gap waveguide are misaligned due to processing errors, which then leads to errors in the phase of the transmission structure when the upper and lower cover plates are perfectly aligned; in addition, the waveguide structure of the present invention is similar to a rectangular waveguide, and the design and simulation processes are greatly simplified, which greatly saves time costs.

[0011] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0012] A novel half-mode slot gap waveguide based on mushroom-type periodic units, the waveguide comprising an upper mushroom-type periodic unit array cover plate and a lower slotted metal bottom plate;

[0013] The upper mushroom-shaped periodic unit array cover comprises a metal reference ground, a dielectric substrate, a metal patch and a metalized via; the upper surface of the dielectric substrate is completely covered with the metal reference ground, the lower surface of the dielectric substrate is arranged with periodically distributed metal patches, and each metal patch is connected to the metal reference ground through a metalized via;

[0014] The metal reference ground and the slotted metal bottom plate are arranged opposite to each other, the dielectric substrate is located between the two and is parallel to the metal reference ground, and an air gap layer is provided between the dielectric substrate and the slotted metal bottom plate, so that a half-mode slot gap waveguide based on the mushroom-shaped periodic unit is formed between the upper mushroom-shaped periodic unit array cover plate and the lower slotted metal bottom plate, and the air gap layer and the slots on the slotted metal bottom plate constitute a transmission path for electromagnetic waves.

[0015] Furthermore, the operating frequency band of the waveguide is a frequency band greater than 10 GHz.

[0016] Furthermore, the height of the air gap layer does not exceed one quarter of the wavelength.

[0017] Furthermore, the height of the grooves on the grooved metal bottom plate is less than half a wavelength.

[0018] Furthermore, the period p of the mushroom-shaped periodic unit array is less than half of the wavelength.

[0019] Furthermore, the patch is a square patch.

[0020] Furthermore, the side length w of the square patch is 1 Smaller than the period p of the mushroom-type periodic unit array.

[0021] Furthermore, the diameter d of the metallized through hole 1 Smaller than the side length w of the square patch 1 .

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] First, the novel half-mode slot gap waveguide based on mushroom-type periodic units of the present invention significantly optimizes the space utilization of the transmission line structure by introducing the half-mode principle. Specifically, a mushroom-type periodic unit array is used as the cover structure. Compared with the traditional metal pin cover design, the overall structure can be compressed in the vertical dimension while maintaining the same electromagnetic performance, thereby greatly improving the compactness of the system and providing a technical basis for high-density integration.

[0024] Second, the novel half-mode slot gap waveguide based on the mushroom-type periodic unit of the present invention effectively solves the stringent requirements of the traditional waveguide structure on the electrical contact accuracy between the upper and lower metal plates by introducing the gap waveguide technology. Specifically, by forming a controllable sub-wavelength gap between the upper and lower metal plates, efficient confinement of the electromagnetic field is achieved. Even in the presence of process tolerances or assembly gaps, the parasitic resonance caused by high-order mode excitation can be significantly suppressed, thereby greatly improving the mechanical tolerance and environmental adaptability of the structure. Moreover, since the electromagnetic waves are propagated in the air medium, low-loss transmission performance comparable to that of conventional metal waveguides can be achieved, and there is no dielectric loss.

[0025] Third, the novel half-mode slot gap waveguide based on mushroom-type periodic units of the present invention compensates for the phase deviation caused by the alignment error of the upper and lower plates by introducing a mushroom-type periodic unit array cover plate, greatly reduces the structural alignment accuracy requirements, and greatly reduces the manufacturing difficulty.

[0026] Fourth, compared with the existing gap waveguide structure, the novel half-mode slot gap waveguide based on the mushroom-shaped periodic unit of the present invention significantly simplifies the design process while maintaining excellent electromagnetic performance: its design and optimization process is similar to that of the rectangular waveguide, and it is easy to establish an accurate electromagnetic model and perform simulation optimization, which greatly improves the design efficiency.

[0027] Fifth, the manufacturing process of the novel half-mode slot gap waveguide based on the mushroom-type periodic unit of the present invention is significantly simplified. It is only necessary to load the mushroom-type periodic unit array on the dielectric substrate to achieve efficient transmission of electromagnetic waves. In addition, since the mushroom-type periodic unit array cover effectively compensates for the phase shift caused by the misalignment of the upper and lower plates, the upper mushroom-type periodic unit array cover produced in this way can be used in combination with any lower metal slotted cover within the frequency band, which greatly improves the reusability and universality of the mushroom periodic unit array cover. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of a novel half-mode slot gap waveguide structure based on a mushroom-type periodic unit proposed according to the present invention (27-40GHz);

[0029] Figure 2 A schematic diagram of the structure of a novel half-mode slot gap waveguide based on a mushroom-shaped periodic unit after bending 90 degrees according to the present invention (27-40GHz);

[0030] Figure 3 A schematic diagram of a novel half-mode slot gap waveguide structure based on a mushroom-type periodic unit proposed according to the present invention (12-18GHz);

[0031] Figure 4A schematic diagram of the structure of a novel half-mode slot gap waveguide based on a mushroom-shaped periodic unit after bending 90 degrees according to the present invention (12-18GHz);

[0032] Figure 5 A schematic diagram of performance simulation results of a novel half-mode slot gap waveguide based on a mushroom-type periodic unit proposed in the present invention (27-40GHz);

[0033] Figure 6 A schematic diagram of the performance simulation results of a novel half-mode slot gap waveguide based on a mushroom-type periodic unit proposed in the present invention after bending 90 degrees (27-40GHz);

[0034] Figure 7 A schematic diagram of performance simulation results of a novel half-mode slot gap waveguide based on a mushroom-type periodic unit proposed in the present invention (12-18GHz);

[0035] Figure 8 A schematic diagram of the performance simulation results of a novel half-mode slot gap waveguide based on a mushroom-shaped periodic unit proposed in the present invention after bending 90 degrees (12-18GHz); DETAILED DESCRIPTION

[0036] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0037] The present invention discloses a novel half-mode slot gap waveguide based on mushroom-shaped periodic units, an upper mushroom-shaped periodic unit array cover plate and a lower slotted metal cover plate; the upper mushroom-shaped periodic unit array cover plate is composed of a metal reference ground, a dielectric substrate, a metal patch and a metallized via hole, the upper surface of the dielectric substrate is covered with a complete metal grounding layer, and the lower surface is arranged with periodically distributed metal patches. In order to realize electrical interconnection between the upper and lower surfaces of the substrate, metallized via holes are processed at specific positions, and the lower patch unit array is reliably connected to the metal reference ground through a vertical interconnection structure (metallized through hole); the metal reference ground and the slotted metal bottom plate are arranged oppositely, and the dielectric substrate layer is located between the two and parallel to the metal reference ground.

[0038] A novel half-mode slot gap waveguide based on a mushroom-shaped periodic unit of the present invention is as follows Figure 1 and Figure 3As shown, the upper mushroom-shaped periodic unit array cover plate is used as an artificial magnetic conductor, and the lower metal A slotted cover plate is used as a perfect electrical conductor, so as to effectively prevent the leakage of electromagnetic waves and unwanted resonance when the gap between the two layers does not exceed a quarter of a wavelength. The height of the slot in the waveguide is less than half a wavelength, and the upper mushroom-shaped periodic unit array cover plate is placed parallel to the slotted metal A metal cover plate to form a new type of half-mode slot gap waveguide based on mushroom-shaped periodic units. The slots of the slotted metal A bottom plate constitute the path for the electromagnetic wave transmission of the half-mode slot gap waveguide. Figure 2 and Figure 4 The schematic diagram of the structure of a novel half-mode slot gap waveguide based on a mushroom-shaped periodic unit proposed in the present invention after bending 90 degrees. In the present invention, the metal patch can be a square patch, but is not limited to a square, and can also be a rectangle, a circle or a polygon.

[0039] Example 1

[0040] The mushroom-shaped periodic unit array of Example 1 is manufactured using printed circuit board technology, and its substrate dielectric substrate is Rogers4350B with a relative dielectric constant ε r and loss tangent tanδ are 3.66 and 0.004 respectively, and its operating frequency band is 27-40GHz.

[0041] like Figure 1 As shown in the figure, the specific structural dimensions of the new half-mode slot gap waveguide based on the mushroom-type periodic unit are: w = 14mm, l = 18mm, h = 5mm, h sub =1.52mm,h g =3.45mm,w g =2mm,d 1 =0.2mm,h 1 =h sub ,h air =0.05mm,w 1 =0.5mm.

[0042] Figure 2 Schematic diagram of the structure of a novel half-mode slot gap waveguide based on a mushroom-shaped periodic unit after 90-degree bending according to the present invention, the structural dimensions and Figure 1 The structures shown are consistent.

[0043] The stopband characteristics of the electromagnetic bandgap structure are mainly regulated by key parameters such as the thickness of the dielectric substrate, the diameter of the metallized through hole, the period of the array unit and the side length of the patch. Among them, the thickness of the dielectric substrate is the core factor that determines the stopband range of the mushroom-shaped periodic unit. The experimental results show that with the increase of the thickness of the dielectric substrate, the upper and lower cutoff frequencies of the stopband show a monotonically decreasing trend. This characteristic provides a theoretical basis for achieving the regulation of different frequency bands by adjusting the thickness of the dielectric substrate. In this Example 1, considering the performance requirements of the target frequency band and the requirements of industrial standardization, the thickness of the dielectric substrate is finally determined to be 1.52mm. There is an inverse relationship between the diameter of the metallized through hole and the bandwidth of the stopband. Therefore, in actual design, the diameter of the through hole should be reduced as much as possible, but due to the limitations of the PCB process, the minimum size of the metallized through hole is limited. In this Example 1, the optimal value range of the metallized through hole diameter is 0.15-0.2mm(0.017λ 0 -0.022λ 0 , where λ 0 The relationship between the array unit period and the stopband bandwidth is nonlinear, and there is an optimal point where the stopband bandwidth reaches the maximum value. In Example 1, the optimal value range of the array unit period is 0.8-1.2mm (0.09λ 0 -0.13λ 0 ), and finally 1mm was selected as the optimal design value. Compared with the thickness of the dielectric substrate, the effect of the patch side length on the stopband characteristics is relatively weak, but its change will also cause a regular shift in the upper and lower cutoff frequencies of the stopband. Under the premise that the thickness of the dielectric substrate is determined, the fine tuning of the stopband characteristics can be achieved by adjusting the patch side length. In this example 1, the optimization range of the patch side length is 0.5-0.7mm (0.056λ 0 -0.078λ 0 ), and after comprehensive evaluation, 0.5mm was selected as the optimal design parameter.

[0044] Example 2

[0045] The mushroom-shaped periodic unit array of Example 2 is manufactured using printed circuit board technology, and its substrate dielectric substrate is Rogers4350B, with a relative dielectric constant ε r and loss tangent tanδ are 3.66 and 0.004 respectively, and its operating frequency band is 12-18GHz.

[0046] like Figure 3 As shown in the figure, the specific structural dimensions of the new half-mode slot gap waveguide based on the mushroom-type periodic unit are: w'=20mm, l'=50mm, h'=15mm, h sub '=3mm,h g '=9mm,w g '=7mm,d1 '=0.4mm,h 1 '=h sub ',h air '=0.05mm,w 1 '=1mm.

[0047] Figure 5 and Figure 6 The simulation performance diagram of a new type of half-mode slot gap waveguide based on mushroom-shaped periodic unit and the simulation performance diagram after bending 90 degrees (27-40GHz). 11 and S 21 They represent reflection coefficient and transmission coefficient respectively. The former represents the ratio of the signal reflected from port 1 to the input signal, while the latter represents the ratio of the signal transmitted from port 1 to port 2 to the input signal. It can be observed that normal transmission is possible within the frequency band of 27-40 GHz.

[0048] Figure 7 and Figure 8 The simulation performance diagram of a new type of half-mode slot gap waveguide based on mushroom-shaped periodic unit and the simulation performance diagram after bending 90 degrees (12-18GHz). 11 and S 21 They represent reflection coefficient and transmission coefficient respectively. The former represents the ratio of the signal reflected from port 1 to the input signal, while the latter represents the ratio of the signal transmitted from port 1 to port 2 to the input signal. It can be observed that normal transmission is possible within the 12-18 GHz frequency band.

[0049] In the present invention, electromagnetic waves propagate in the air, thereby achieving low-loss transmission performance comparable to that of conventional metal waveguides; by introducing the half-mode principle, the longitudinal size of the structure is significantly reduced, and the compactness is improved; the use of gap waveguide technology effectively eliminates the strict requirements of conventional metal waveguides for perfect electrical contact between the upper and lower metal plates, and even in the presence of an assembly gap, parasitic resonance and electromagnetic leakage can still be effectively suppressed, thereby reducing manufacturing costs; in particular, the present invention adopts a mushroom-shaped artificial magnetic conductor structure, which can effectively compensate for the phase deviation caused by the alignment error of the upper and lower plates, and significantly reduce the requirements for structural alignment accuracy; in addition, compared with the existing gap waveguide structure, the present invention further improves the convenience of design and optimization while maintaining excellent electromagnetic performance, and improves design efficiency. In summary, the present invention has significant advantages such as low transmission loss, high compactness, low cost, and high design efficiency, and is particularly suitable for various radar and communication systems, and has important application value.

[0050] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0051] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A novel half-mode slot gap waveguide based on mushroom-type periodic unit, characterized in that: The waveguide comprises an upper mushroom-shaped periodic unit array cover plate and a lower slotted metal bottom plate; The upper mushroom-shaped periodic unit array cover comprises a metal reference ground, a dielectric substrate, a metal patch and a metalized via hole; the upper surface of the dielectric substrate is completely covered with the metal reference ground, the lower surface of the dielectric substrate is arranged with periodically distributed metal patches, and each metal patch is connected to the metal reference ground through a metalized via hole, forming a mushroom-shaped periodic unit; The metal reference ground and the slotted metal bottom plate are arranged opposite to each other, the dielectric substrate is located between the two and is parallel to the metal reference ground, an air gap layer is provided between the dielectric substrate and the slotted metal bottom plate, and the air gap layer and the slots on the slotted metal bottom plate constitute a transmission path for electromagnetic waves.

2. The novel half-mode slot gap waveguide based on mushroom-type periodic unit according to claim 1 is characterized in that: The operating frequency band of the waveguide is a frequency band greater than 10 GHz.

3. The novel half-mode slot gap waveguide based on mushroom-type periodic unit according to claim 1 is characterized in that: The height of the air gap layer does not exceed one quarter of the wavelength.

4. The novel half-mode slot gap waveguide based on mushroom-type periodic unit according to claim 1 is characterized in that: The height of the grooves on the grooved metal base plate is less than half a wavelength.

5. The novel half-mode slot gap waveguide based on mushroom-type periodic unit according to claim 1 is characterized in that: The period p of the mushroom-type periodic unit array is less than half of the wavelength.

6. The novel half-mode slot gap waveguide based on mushroom-type periodic unit according to claim 1 is characterized in that: The patch is a square patch.

7. The novel half-mode slot gap waveguide based on mushroom-type periodic unit according to claim 6 is characterized in that: The side length w1 of the square patch is smaller than the period p of the mushroom-type periodic unit array.

8. The novel half-mode slot gap waveguide based on mushroom-type periodic unit according to claim 6 is characterized in that: The diameter d1 of the metallized through hole is smaller than the side length w1 of the square patch.

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