Compact high-power stainless steel microwave load and processing method thereof

Abstract

The invention relates to the technical field of microwaves, in particular to a compact high-power stainless steel microwave load and a processing method thereof, one end of a transition waveguide is connected with a waveguide input port, one end of a spiral flat waveguide is connected with the other end of the transition waveguide, and the spiral flat waveguide is made of a microwave absorbing material; the whole body is of a spiral coiling structure, and the microwave absorbing material is 430 magnetic stainless steel; the compact high-power stainless steel microwave load provided by the invention has the characteristics of high power capacity of a water load and no liquid leakage and vacuum resistance of a dry load, breaks through the limitation of huge size of a traditional dry load, and has the advantages of compact structure, good broadband matching, high breakdown resistance, easiness in processing and manufacturing and the like.

Description

Technical Field

[0001] This invention relates to the field of microwave technology, specifically to a compact high-power stainless steel microwave load and its processing method. Background Technology

[0002] High-power microwave technology has wide applications in radar detection, high-energy physics accelerators, and free-electron lasers. In these systems, microwave loads are indispensable key passive components. Their main function is to absorb all or part of the microwave energy in the transmission system and convert it into heat energy for dissipation. This prevents excess microwave energy from being reflected back to the microwave source (such as a klystron or magnetron), which could damage the microwave source or even cause leakage and danger. Therefore, it is necessary to absorb excess microwaves to ensure the safe and stable operation of the system.

[0003] Based on the different absorbing media, existing high-power microwave loads are mainly divided into two categories: water loads and dry loads.

[0004] Water loads utilize flowing water directly as microwave absorbers. While they offer advantages such as high power capacity and sensitive water temperature response, their water chambers typically contain dielectric materials like glass. Glass dielectric materials are fragile, and the sealing between the glass and waveguide walls is difficult to guarantee over the long term, posing a risk of water leakage. Once a leak occurs, it will severely damage the microwave system. Furthermore, due to the presence of water, such loads are difficult to operate in high vacuum environments, and their maintenance costs are relatively high.

[0005] Compared to water-based loads, dry loads are more robust and reliable. The absorbent materials in dry loads are typically silicon carbide, ceramics doped with conductive substances, or ferrites. This type of load has a simple structure, no risk of leakage, and can withstand high vacuum environments, making it highly favored in applications requiring high reliability. However, ceramic dry loads are fragile, easily carry air, and contain many impurities, resulting in poor absorption efficiency. While silicon carbide can solve the problem of ceramics, it presents a series of technical and process challenges related to firing and welding. Summary of the Invention

[0006] In order to solve the above-mentioned technical problems, the present invention provides a compact high-power stainless steel microwave load and its processing method, which achieves both the high power capacity of a water load and the leak-free and vacuum-resistant characteristics of a dry load.

[0007] This invention is achieved through the following technical solution:

[0008] A compact, high-power stainless steel microwave load, comprising:

[0009] Waveguide input port;

[0010] A transition waveguide, one end of which is connected to the waveguide input port;

[0011] A spiral flat waveguide, one end of which is connected to the other end of the transition waveguide;

[0012] The spiral flat waveguide is made of microwave absorbing material and has an overall spiral coiled structure.

[0013] Optionally, the microwave absorbing material is 430 magnetic stainless steel.

[0014] Optionally, the cross-section of the helical flat waveguide is rectangular, and the width of the narrow side of the helical flat waveguide decreases along the microwave propagation direction.

[0015] Optionally, the spiral flat waveguide is distributed in a planar rectangular spiral shape;

[0016] The spiral flat waveguide includes several straight waveguide segments and several curved waveguide segments, which are alternately connected so that the spiral flat waveguide is coiled from the outside to the inside.

[0017] Optionally, each of the straight waveguide segments has a constant narrow side width along its length.

[0018] The curved waveguide section is a variable-diameter curved waveguide, and its narrow side width gradually decreases along the microwave propagation direction.

[0019] Any one of the curved waveguide segments connects two adjacent straight waveguide segments, and the narrow side width of the straight waveguide segment located on the microwave input side of the curved waveguide segment is greater than the narrow side width of the straight waveguide segment located on the microwave output side of the curved waveguide segment.

[0020] Optionally, an air extraction gap is provided between two radially adjacent straight waveguide segments, and the two adjacent straight waveguide segments are connected through the air extraction gap.

[0021] Optionally, the air extraction slot has a chamfered edge at the edge of the straight waveguide section wall.

[0022] Optionally, the spiral flat waveguide is wound from the outside in, and the waveguide input port is located on the outside;

[0023] A vacuum evacuation port is provided at the center of the spiral flat waveguide, and the vacuum evacuation port is connected to the internal space of the spiral flat waveguide.

[0024] Furthermore, the load also includes a cooling channel formed on the outer wall or in the substrate of the spiral flat waveguide, the cooling channel being connected to the inlet and outlet of the coolant.

[0025] A method for fabricating a compact high-power stainless steel microwave load, comprising:

[0026] Stainless steel was selected as the load substrate, and the upper and lower substrates were prepared separately.

[0027] Corresponding spiral grooves are machined on the lower surface of the upper substrate and the upper surface of the lower substrate, respectively, and the width of the spiral grooves is controlled to form alternating straight waveguide segments and variable diameter bent waveguide segments;

[0028] An air extraction slit is machined into the adjacent common wall of the spiral groove, and the edges of the air extraction slit are chamfered.

[0029] The upper substrate and the lower substrate are aligned and connected so that the spiral grooves inside the upper substrate and the lower substrate are closed to form the spiral flat waveguide;

[0030] Cooling channels are machined on the outer surface of the upper and / or lower substrates, and sealing covers are installed to seal the cooling channels.

[0031] Compared with the prior art, the present invention has the following features and beneficial effects:

[0032] This invention employs a planar spiral-wound flat waveguide structure to fold a microwave absorption path several meters long, thereby reducing the axial length and overall volume of the load. This successfully solves the problem that traditional straight waveguide stainless steel loads are bulky and difficult to adapt to the installation space limitations of compact systems.

[0033] This invention utilizes a design where the width of the narrow side of the waveguide gradually decreases along the microwave propagation direction, which helps to guide microwave energy to be distributed and lost more evenly throughout the entire helical path. Furthermore, by setting up a chamfered evacuation gap, it not only achieves the internal connectivity of the helical flat waveguide but also smooths the electric field distribution at the gap, eliminates the tip effect, and prevents arcing or breakdown from occurring inside the waveguide.

[0034] The compact high-power stainless steel microwave load provided by this invention combines the high power capacity of water loads with the leak-free and vacuum-resistant characteristics of dry loads. It also breaks through the limitation of the large size of traditional dry loads and has the advantages of compact structure, good wideband matching, strong breakdown resistance and easy processing and manufacturing. Attached Figure Description

[0035] The accompanying drawings illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the principles of the invention. These drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, but do not constitute a limitation on the embodiments of the present invention.

[0036] Figure 1 This is a schematic cross-sectional view of a compact high-power stainless steel microwave load according to the present invention.

[0037] Figure 2This is a left sectional view of a compact high-power stainless steel microwave load according to the present invention.

[0038] Figure 3 This is a schematic diagram of a compact high-power stainless steel microwave load according to the present invention.

[0039] Figure 4 This is a reflection parameter diagram of a compact high-power stainless steel microwave load according to the present invention.

[0040] Figure reference numerals: 1-waveguide input port, 2-transition waveguide, 3-spiral flat waveguide, 31-straight waveguide section, 32-bent waveguide section, 33-upper substrate, 34-lower substrate, 35-sealing cover plate, 4-evacuation gap, 41-chamfer, 5-vacuum evacuation port. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0042] It should also be noted that, for ease of description, only the parts relevant to the present invention are shown in the accompanying drawings.

[0043] Where there is no conflict, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0044] Stainless steel loads utilize the material's resistivity and permeability to absorb energy through surface current losses generated as microwaves propagate along the inner wall of the waveguide. However, existing stainless steel loads typically employ a standard straight waveguide design. Because stainless steel offers relatively limited microwave attenuation per unit length, extremely long waveguide lengths are often required to achieve complete absorption of high-power energy across a wide frequency range and maintain an extremely low port reflection coefficient. For example, in the X-band, to meet high-power absorption requirements, traditional straight waveguide stainless steel loads can reach lengths of several meters.

[0045] Example 1

[0046] like Figure 1 and Figure 2 As shown, this embodiment provides a compact high-power stainless steel microwave load that achieves efficient transmission and absorption of high-power microwave energy within a limited space by combining structural layout and material properties. The basic workflow involves guiding microwave energy in, and after transition adjustment, converting electromagnetic energy into heat energy for dissipation through the tube wall material within the spiral channel.

[0047] Structurally, it mainly includes three sequentially connected parts: waveguide input port 1, transition waveguide 2, and spiral flat waveguide 3.

[0048] The waveguide input port 1 serves as the energy inlet of the entire load and is used to receive high-power microwaves from an external transmission system (such as a radar transmitter, etc.). It is a conventional standard rectangular waveguide.

[0049] One end of the transition waveguide 2 is connected to the waveguide input port 1, and the other end is connected to the spiral flat waveguide 3. Its main function is to provide physical connection and electromagnetic transition between the standard waveguide interface and the spiral flat waveguide 3.

[0050] The spiral flat waveguide 3 is in an overall spiral coiled structure. By coiling, it greatly extends the physical path of microwave transmission within a relatively small geometric size.

[0051] The spiral flat waveguide 3 is made of microwave absorbing material. Optionally, the microwave absorbing material is 430 magnetic stainless steel. 430 stainless steel is a ferritic stainless steel with good magnetic conductivity. In the microwave frequency band, magnetic materials can provide a relatively large surface resistance. Compared with ordinary copper or aluminum, it can generate greater surface loss, thus more efficiently converting microwave energy into heat energy.

[0052] Embodiment 2

[0053] This embodiment describes in detail the spatial layout and the variation law of the internal dimensions of the spiral flat waveguide 3.

[0054] In terms of macroscopic morphology, the spiral flat waveguide 3 is distributed in a planar rectangular spiral shape; that is, it coils from the outside to the inside within a plane like a mosquito coil. At the same time, its overall trajectory presents a rectangular feature of the shape of a Chinese character 'hui'.

[0055] The spiral flat waveguide 3 includes a number of straight waveguide segments 31 and a number of bent waveguide segments 32. The straight waveguide segments 31 and the bent waveguide segments 32 are alternately connected and are alternately connected in the order of'straight segment - bent segment - straight segment - bent segment', so that the spiral flat waveguide 3 coils from the outside to the inside.

[0056] In order to achieve impedance matching during spiral transmission, the cross-section of the spiral flat waveguide 3 is rectangular, and the width of the narrow side of the spiral flat waveguide 3 decreases along the microwave propagation direction.

[0057] Each of the straight waveguide segments 31 has a constant narrow side width in its length direction; the narrow side width generally refers to the shorter side in the cross-section of a rectangular waveguide.

[0058] The curved waveguide section 32 is a variable-diameter curved waveguide, whose narrow side width gradually decreases along the microwave propagation direction; it serves to change the wave propagation direction (usually 90 degrees) and also utilizes the curved transition region to smoothly compress the waveguide size.

[0059] Any one of the curved waveguide segments 32 connects two adjacent straight waveguide segments 31, and the narrow side width of the straight waveguide segment 31 located on the microwave input side of the curved waveguide segment 32 is greater than the narrow side width of the straight waveguide segment 31 located on the microwave output side of the curved waveguide segment 32.

[0060] It should be noted that the descriptions of the helical form, waveguide cross-sectional shape, and processing method in the above embodiments are merely preferred examples among the many specific implementations of the present invention, and not the sole limitation on the technical solution of the present invention. Under the concept of the present invention, those skilled in the art can make various extensions and modifications according to the needs of actual application scenarios.

[0061] Although the embodiments show a planar rectangular helical structure, the core of this invention lies in compressing volume through coiling. Therefore, the coiling form of the helical flat waveguide 3 is not limited to a rectangular helix. It can also be a circular helix (similar to a mosquito coil), an elliptical helix, or a hybrid helix combining straight lines and curves.

[0062] Regardless of the geometric trajectory used, as long as its overall configuration satisfies the design principle of "winding and extending in a plane or three-dimensional space" to increase the effective electrical length and reduce the package volume, it falls within the technical scope of this invention.

[0063] Similarly, although the embodiments describe a flat waveguide with a rectangular cross-section, the cross-sectional shape of the waveguide can be adjusted for certain specific frequencies or power requirements. The waveguide cross-section can be polygonal (such as hexagonal, octagonal, etc.) or a ridged waveguide shape. As long as it can support the transmission of specific microwave modes and achieve energy absorption with lossy materials, it is considered a normal extension of this technical solution.

[0064] Example 3

[0065] This embodiment further optimizes the structure of the spiral flat waveguide 3. In order to prevent high-power microwaves from breaking down during transmission and to effectively remove the absorbed and converted heat energy, an air extraction and cooling structure is also provided.

[0066] A vacuum slit 4 is provided between two radially adjacent straight waveguide segments 31, and the two adjacent straight waveguide segments 31 are connected through the vacuum slit 4. Radially adjacent means that the inner and outer waveguides share the same wall in the direction of outward radiation from the center. The vacuum slit 4 between adjacent flat waveguides is used to reduce the vacuum flow resistance inside the load and improve the error tolerance during processing.

[0067] The extraction slot 4 has a chamfer 41 at its edge on the wall of the straight waveguide section 31. In a high-power microwave environment, sharp metal edges can lead to a high concentration of electric field, which can easily induce point discharge (arson). Chamfering the edge of the slot 41 (i.e., rounding or beveling) can smooth the electric field distribution in this area, eliminate the point effect, and ensure that microwaves do not break down when passing through the slot.

[0068] The spiral flat waveguide 3 is wound from the outside in, and the waveguide input port 1 is located on the outside; microwave energy is injected from the outermost ring.

[0069] A vacuum extraction port 5 is provided at the center of the spiral flat waveguide 3. The vacuum extraction port 5 is connected to the internal space of the spiral flat waveguide 3. Due to the presence of the radial extraction gap 4, the vacuum pump can simultaneously extract gas from each waveguide segment radially from the center to the surrounding areas, quickly establishing and maintaining a high vacuum environment inside the entire load.

[0070] The load also includes cooling channels formed on the outer wall or within the substrate of the spiral flat waveguide 3, the cooling channels connecting the inlet and outlet of the coolant. Heat is carried away through the cooling channels within the substrate.

[0071] Example 4

[0072] This embodiment provides a method for fabricating a compact high-power stainless steel microwave load. It employs a modular manufacturing strategy, transforming a closed waveguide cavity into an open surface groove for processing. The specific process flow is as follows:

[0073] Stainless steel was selected as the load substrate, and upper substrate 33 and lower substrate 34 were prepared respectively.

[0074] Using numerical control (CNC) technology, corresponding spiral grooves are machined on the lower surface of the upper substrate 33 and the upper surface of the lower substrate 34, respectively, and the width of the spiral grooves is controlled to form alternating straight waveguide sections 31 and variable diameter bent waveguide sections 32.

[0075] An air extraction gap 4 is machined on the adjacent common wall of the spiral groove, and the edge of the air extraction gap 4 is chamfered 41. At this time, it is an open structure, and the tool can enter vertically between the adjacent groove walls to cut, which greatly reduces the machining difficulty.

[0076] The upper substrate 33 and the lower substrate 34 are aligned and connected, so that the spiral grooves inside the upper substrate 33 and the lower substrate 34 close to form the spiral flat waveguide 3; the upper and lower cavities are engaged by positioning with pins and welding (such as vacuum brazing or argon arc welding) or tightening with bolts. At this time, the corresponding spiral grooves inside the upper substrate 33 and the lower substrate 34 overlap and close to form the spiral flat waveguide 3.

[0077] Cooling channels are machined on the outer surface of the upper substrate 33 and / or the lower substrate 34, and a sealing cover plate 35 is installed to seal the cooling channels.

[0078] The split-assembly method (34 pairs of upper and lower substrates) mentioned in the embodiments is only a preferred manufacturing process. The load structure protected by this invention can also be achieved through other advanced manufacturing processes. For example, it can be integrally formed using metal 3D printing (additive manufacturing) technology, or it can be precision cast followed by internal surface finishing.

[0079] Example 5

[0080] This embodiment provides an example of a compact high-power stainless steel microwave load for the X-band, and its physical dimensions, reflection parameters and power capacity are tested and simulated.

[0081] like Figure 3 As shown, the main body of this X-band stainless steel load (i.e., the core structure containing the helical waveguide) has geometric dimensions of 160mm × 160mm × 55mm. The maximum size of the microwave load is less than one-third the length of existing X-band stainless steel loads.

[0082] The reflection parameter spectrum of the stainless steel microwave load is as follows: Figure 4 As shown, near the operating frequency of the load design, its reflection parameter is less than -32dB. Within a bandwidth of ±0.5GHz, the reflection parameter is consistently less than -27dB, demonstrating a wide bandwidth effect.

[0083] To verify its reliability under high-power conditions, a high-power simulation was performed on the load.

[0084] The input microwave power was set to 50MW, and the maximum electric field strength on the surface of the load's internal structure was 40MV / m. This demonstrates that the load can meet the high-power requirements of 50MW and has a high safety margin.

[0085] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0086] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0087] Those skilled in the art should understand that the above embodiments are merely for illustrating the present invention and are not intended to limit the scope of the invention. Those skilled in the art can make other changes or modifications based on the above invention, and these changes or modifications still fall within the scope of the present invention.

Claims

1. A compact, high-power stainless steel microwave load, characterized in that, include: Waveguide input port (1); A transition waveguide (2) is connected at one end to the waveguide input port (1); A spiral flat waveguide (3) is connected at one end to the other end of the transition waveguide (2); The spiral flat waveguide (3) is made of microwave absorbing material and has a spiral coiled structure.

2. The compact high-power stainless steel microwave load according to claim 1, characterized in that, The microwave absorbing material is 430 magnetic stainless steel.

3. The compact high-power stainless steel microwave load according to claim 1, characterized in that, The cross-section of the spiral flat waveguide (3) is rectangular, and the width of the narrow side of the spiral flat waveguide (3) decreases along the microwave propagation direction.

4. A compact high-power stainless steel microwave load according to claim 1, characterized in that, The spiral flat waveguide (3) is distributed in a planar rectangular spiral shape; The spiral flat waveguide (3) includes several straight waveguide segments (31) and several curved waveguide segments (32), which are alternately connected so that the spiral flat waveguide (3) is coiled from the outside to the inside.

5. A compact high-power stainless steel microwave load according to claim 4, characterized in that, Each of the straight waveguide segments (31) has a constant narrow side width along its length; The curved waveguide section (32) is a variable-diameter curved waveguide, and its narrow side width gradually decreases along the microwave propagation direction; Any one of the curved waveguide segments (32) connects two adjacent straight waveguide segments (31), and the narrow side width of the straight waveguide segment (31) located on the microwave input side of the curved waveguide segment (32) is greater than the narrow side width of the straight waveguide segment (31) located on the microwave output side of the curved waveguide segment (32).

6. A compact high-power stainless steel microwave load according to claim 4, characterized in that, An air extraction gap (4) is provided between two radially adjacent straight waveguide segments (31), and the two adjacent straight waveguide segments (31) are connected through the air extraction gap (4).

7. A compact high-power stainless steel microwave load according to claim 6, characterized in that, The air extraction gap (4) has a chamfer (41) at the edge of the wall of the straight waveguide section (31).

8. A compact high-power stainless steel microwave load according to claim 4, characterized in that, The spiral flat waveguide (3) is coiled from the outside to the inside, and the waveguide input port (1) is located on the outside; A vacuum vent (5) is provided at the center of the spiral flat waveguide (3), and the vacuum vent (5) is connected to the internal space of the spiral flat waveguide (3).

9. A compact high-power stainless steel microwave load according to claim 1, characterized in that, It also includes a cooling channel formed on the outer wall or in the substrate of the spiral flat waveguide (3), the cooling channel being connected to the inlet and outlet of the coolant.

10. A method for fabricating a compact high-power stainless steel microwave load, characterized in that, include: Stainless steel was selected as the load substrate, and the upper substrate (33) and the lower substrate (34) were prepared respectively. Corresponding spiral grooves are machined on the lower surface of the upper substrate (33) and the upper surface of the lower substrate (34), and the width of the spiral grooves is controlled to form alternating straight waveguide segments (31) and variable diameter bent waveguide segments (32). An air extraction slit (4) is machined on the adjacent common wall of the spiral groove, and the edge of the air extraction slit (4) is chamfered (41). The upper substrate (33) and the lower substrate (34) are aligned and connected so that the spiral grooves inside the upper substrate (33) and the lower substrate (34) are closed to form the spiral flat waveguide (3). Cooling channels are machined on the outer surfaces of the upper substrate (33) and / or the lower substrate (34), and sealing covers (35) are installed to close the cooling channels.

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