A compact field reflector implemented in a building cement

Abstract

The application belongs to the technical field of test and measurement, and particularly relates to a tight-field reflecting surface realized by building cement. The tight-field reflecting surface is used for low-frequency tight-field measurement and mainly comprises a cement support, a cement parabolic reflecting surface arranged on the cement support, a surface geometry of the cement parabolic reflecting surface being a parabolic surface with periodic side teeth, and a metal plating layer formed on the surface of the cement parabolic reflecting surface and used for providing a metal boundary condition for electromagnetic reflection. The application can greatly reduce manufacturing cost and effectively form a high-quality quiet zone in a low-frequency band.

Description

Technical Field

[0001] This application belongs to the field of testing and measurement technology, and specifically relates to a compacted field reflective surface realized by building cement. Background Technology

[0002] With the development of modern electromagnetic technology, the need for accurate electromagnetic characteristic testing and evaluation of targets operating in the low-frequency (0.1-2 GHz) band is becoming increasingly urgent, and corresponding testing technologies are becoming increasingly important. A compact field test facility is a testing facility that can provide a high-performance quasi-plane wave test area (i.e., a quiet zone) at close range. It can be constructed in a microwave anechoic chamber, thus offering advantages such as all-weather testing, well-controlled environmental conditions, and low background electromagnetic levels, making it ideal for measuring the electromagnetic characteristics of low-frequency targets.

[0003] Currently, some progress has been made in low-frequency compaction field technology, but the manufacturing cost of large compaction fields remains very high, mainly due to the high precision and large-scale manufacturing of reflective surfaces. Existing reflective surfaces are typically assembled from multiple independent high-precision metal panels. The forming of a single panel relies on precision forming processes such as "dot matrix molding, vacuum negative pressure, and honeycomb interlayering." After overall assembly, the entire parabolic surface must undergo precision CNC milling to meet extremely high surface accuracy requirements. While such reflective surfaces are necessary in the high-frequency range and help form high-quality quiet zones, their manufacturing process is complex and extremely costly.

[0004] However, at lower operating frequencies, the requirements for the surface processing precision of the reflective surface decrease due to the longer wavelength of electromagnetic waves. While meeting the requirements for low-frequency testing, existing high-cost, high-precision manufacturing processes may not be the most economical solution. Therefore, it is necessary to explore a novel reflective surface realization technology that can significantly reduce manufacturing costs while meeting the performance requirements of low-frequency compacted fields. Summary of the Invention

[0005] To address the aforementioned problems, this application provides a compaction field reflecting surface realized by building cement for measuring low-frequency compaction fields. This compaction field reflecting surface mainly comprises:

[0006] Cement support;

[0007] A parabolic cement reflector is disposed on the cement support, the surface geometry of which is a parabola with periodic edge teeth; and

[0008] A metallic coating formed on the surface of the cement parabolic reflective surface serves to provide metallic boundary conditions for electromagnetic reflection.

[0009] Preferably, a steel reinforcement cage is installed inside the cement support.

[0010] Preferably, after the cement is poured into the cement support, it is treated with a concrete sealing and curing agent.

[0011] Preferably, the interior of the cement parabolic reflective surface is provided with honeycomb-structured reinforcing bars.

[0012] Preferably, the surface of the cement parabolic reflective surface has undergone curing and polishing treatment, and its surface flatness accuracy is ±2cm.

[0013] Preferably, the metal coating is an aluminum coating with a thickness of 50 μm and a thickness uniformity accuracy of ±5%.

[0014] Preferably, the periodic edge teeth are triangular edge teeth.

[0015] Preferably, the focal length of the cement parabolic reflector is 46m, and the focal point is located on the center normal of the lower edge of the metal coating.

[0016] This application uses a cement-cast, one-piece molded reflective surface, eliminating the need for precision manufacturing and splicing of metal panels, thus significantly reducing manufacturing costs. The cement structure offers greater overall stability, and the aluminum plating on the surface avoids the impact of gaps between panels, effectively creating a high-quality quiet zone in the low-frequency range. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a preferred embodiment of the compaction field reflective surface realized by the building cement of this application.

[0018] Figure 2 This is a schematic diagram of a cement support structure.

[0019] Figure 3 This is a schematic diagram of a cement parabolic reflector structure.

[0020] Figure 4 This is a comparison chart of the static zone amplitudes with and without considering processing errors.

[0021] Figure 5 This is a comparison diagram of the static phase with and without considering processing errors.

[0022] Among them, 1-cement support, 2-cement parabolic reflective surface, 3-metal coating. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of this application, not all of them. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0024] This application provides a compaction field reflecting surface realized by building cement for measuring low-frequency compaction fields, such as... Figures 1-3 As shown, it mainly includes:

[0025] Cement support 1;

[0026] A parabolic cement reflector 2 is disposed on the cement support 1, the surface geometry of which is a parabola with periodic edge teeth; and

[0027] The metal coating 3 formed on the surface of the cement parabolic reflective surface 2 serves to provide the metal boundary conditions for electromagnetic reflection.

[0028] refer to Figure 2 The concrete support scaffold 1 of this application has its back against a wall. The lower half of the scaffold adopts a right-angled trapezoidal structure, with a base length of 53m, a width of 20m, a top length of 53m, a width of 14m, and a height of 23.5m. The upper half of the support is a cube, connected to the reflective surface by concrete pouring, with a length of 53m, a width of 14m, and a height of 25m. (Reference) Figure 3 The cement parabolic reflector 2 is a parabolic structure with periodically arranged triangular teeth. The panel is 47m long and 26.5m wide, the triangular teeth are 4m long and 8m high.

[0029] This application leverages the longer wavelength of low-frequency (0.1-2GHz) electromagnetic waves and the relatively lower precision requirements for reflective surfaces, overcoming the expensive process of traditional compaction fields that requires precision metal panel splicing. Specifically, the concrete parabolic reflector 2 and the concrete support 1 are connected by concrete casting, eliminating the complex and costly steps of precision machining, manufacturing, transportation, and high-precision on-site splicing of metal panels in traditional processes, significantly reducing the construction cost of large compaction fields. Simultaneously, this structure avoids the gap problem that is difficult to eliminate when splicing multiple panels, enhancing the overall mechanical stability of the structure and making it ideal for supporting large reflective surfaces. The reflector surface is a parabolic surface with periodic edge teeth, which effectively reduces abrupt changes and edge diffraction in the reflected wavefront, improving the electromagnetic performance of the subsequent quiet zone. Finally, a metal coating 3 is formed on the surface of the formed concrete parabolic surface to provide the necessary metal boundary conditions for electromagnetic wave reflection. The entire solution utilizes mature and low-cost concrete construction technology in the civil engineering field to achieve a significant cost reduction while meeting the electromagnetic performance requirements of low-frequency compaction fields.

[0030] In some alternative embodiments, a steel cage is installed inside the cement support 1.

[0031] This embodiment, which involves installing a reinforcing cage inside a cement support, is a common and effective method for improving the tensile strength of concrete structures in construction engineering. Since compaction field reflectors are typically enormous, their supports must withstand significant self-loads and potential lateral forces. The internal reinforcing cage significantly enhances the integrity and structural strength of the support, preventing cracking or damage caused by the brittleness of cement itself, and ensuring the safety and stability of the entire reflector system during long-term use.

[0032] In some alternative embodiments, after cement is poured into the cement support 1, it is treated with a concrete sealing and curing agent.

[0033] In this embodiment, after using concrete, the hardness and strength are satisfactory in the short term, but after a period of use, dust and pits will appear one after another, and the compressive strength is insufficient. After using concrete sealing and curing agent, the curing agent penetrates into the concrete and fills the voids in the concrete through chemical reaction, making the ground a tight whole, thereby enhancing the compressive strength.

[0034] In some alternative embodiments, the interior of the cement parabolic reflective surface 2 is provided with honeycomb-structured reinforcing bars.

[0035] In this embodiment, the reflective surface itself is a thin-shell structure with a certain curvature and thickness, and it needs to maintain a specific parabolic geometric accuracy on its surface, resulting in complex internal stresses. A honeycomb structure is used to arrange the reinforcing bars, similar to the concept of honeycomb sandwich panels in the aerospace field, which can provide extremely high in-plane stiffness and bending stiffness with minimal material. This structure can effectively resist deformation caused by cement curing shrinkage, temperature deformation, and external loads, ensuring that the surface geometry, i.e., the key parabolic curvature, of the large cement reflective surface remains stable during casting and long-term use, thereby guaranteeing the final electromagnetic performance.

[0036] In some alternative embodiments, the surface of the cement parabolic reflective surface 2 is subjected to curing and polishing treatment, and its surface flatness accuracy is ±2cm.

[0037] To ensure the smoothness of the reflective surface, this embodiment first ensures that there are no cracks on the surface when applying cement. If there are cracks, they need to be repaired first. After the cement is applied, a layer of curing agent needs to be applied to the surface to make the cement surface firm and smooth, and it needs to be cured for seven to ten days to increase its service life. After the curing agent has solidified, the reflective surface is polished.

[0038] In some alternative embodiments, the metal coating 3 is an aluminum coating with a thickness of 50 μm and a thickness uniformity accuracy of ±5%.

[0039] Aluminum plating is required on the polished reflective surface to form a metallic boundary. During aluminum plating, the thickness must be uniform to reduce surface unevenness. The surface sheet resistance method is used for measurement during the plating process, and a thickness limit of 50 μm is set to ensure that the plating thickness is significantly greater than the skin depth of the electromagnetic wave within the target frequency band, thus forming an effective metallic boundary. A thickness uniformity accuracy of ±5% is a core indicator for controlling plating quality. Uneven plating thickness leads to inconsistent equivalent impedance on the reflective surface, introducing additional phase errors. Controlling uniformity accuracy is essential to ensuring that the aluminum plating layer provides a near-ideal conductive plane on a macroscopic scale and does not further degrade the electromagnetic performance of the reflective surface. This is a crucial process requirement bridging the gap between a rough cement substrate and satisfactory electromagnetic reflection performance.

[0040] In some alternative implementations, the periodic edge teeth are triangular edge teeth.

[0041] In this embodiment, the triangle is a simple, easy-to-design and easy-to-construct sawtooth shape. Its periodic arrangement can effectively disperse the diffracted waves at the edge of the reflecting surface, thereby reducing the interference to the central quiet zone and improving the amplitude uniformity and phase flatness of the quiet zone.

[0042] In some alternative embodiments, the focal length of the cement parabolic reflector 2 is 46m, and the focal point is located on the center normal line of the lower edge of the metal coating 3.

[0043] When used in a compact field measurement system, this application employs an offset feed source placed at the focal point to emit electromagnetic waves. These waves are reflected as quasi-plane waves onto the compact field reflecting surface, forming a quiet zone over a short distance. This application incorporates periodically arranged triangular sawtooth edges to reduce abrupt reflections and edge scattering, effectively improving the quiet zone performance.

[0044] Considering that the processing error of cement flatness has a greater impact on the upper sideband, it is sufficient to meet the requirements at 2GHz within the 0.1-20GHz frequency band. The amplitude and phase of the ideal reflecting surface and the reflecting surface considering cement processing errors in this application were simulated and calculated in the 2GHz quiet zone using the commercial simulation software GRASP. Considering the surface roughness of the parabolic surface being analyzed, the influence of edge teeth was not considered in this simulation to save computation time. The surface roughness was represented by an 8*4 random number matrix with a range of ±2cm, which was superimposed on the parabolic reflecting surface. The simulation results are as follows. Figure 4 and Figure 5 As shown. Figure 4 Simulation results of the static amplitude in the Y direction at 2 GHz for an ideal smooth parabolic surface and a parabolic reflector considering unevenness within the error range. Figure 5 The simulation results for the static phase in the Y direction at 2 GHz are shown for an ideally smooth parabolic reflector and a parabolic reflector with unevenness within the error range. As can be seen from the figure, the static amplitude and phase results for the two surfaces are very similar, with a maximum amplitude difference of 0.028 dB and a maximum phase difference of 0.92 degrees. These simulation results indicate that although the flatness of the cement reflector is not as high as that of the metal panel, its static performance at low frequencies is not significantly different and is good, meeting the requirements for low-frequency stealth testing.

[0045] Compared to existing technologies, the reflective surface of this application is formed by cement casting, eliminating the need for the fabrication and splicing of metal panels, thus significantly reducing manufacturing costs. In this application, the reflective surface and the support are directly connected by cement, resulting in greater stability compared to other reflective surface supports. Furthermore, large reflective surfaces in this application do not require splicing multiple panels, eliminating the need to consider the impact of gaps between panels.

[0046] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A compaction field reflecting surface realized by building cement, used for measuring low-frequency compaction fields, characterized in that, include: Cement support (1); The cement parabolic reflective surface (2) is provided on the cement support (1), and the surface geometry of the cement parabolic reflective surface (2) is a parabolic surface with periodic edge teeth; as well as The metal coating (3) formed on the surface of the cement parabolic reflective surface (2) serves to provide the metal boundary conditions for electromagnetic reflection.

2. The compacted field reflective surface achieved by building cement according to claim 1, characterized in that, The cement support (1) has a steel cage installed inside.

3. The compaction field reflective surface achieved by building cement according to claim 1, characterized in that, After cement is poured into the cement support (1), it is treated with a concrete sealing and curing agent.

4. The compacted field reflective surface achieved by building cement according to claim 1, characterized in that, The interior of the cement parabolic reflector (2) is reinforced with a honeycomb structure.

5. The compacted field reflective surface achieved by building cement according to claim 1, characterized in that, The surface of the cement parabolic reflective surface (2) has been cured and polished, and its surface flatness accuracy is ±2cm.

6. The compacted field reflective surface achieved by building cement according to claim 1, characterized in that, The metal coating (3) is an aluminum coating with a thickness of 50 μm and a thickness uniformity accuracy of ±5%.

7. The compacted field reflective surface achieved by building cement according to claim 1, characterized in that, The periodic edge teeth are triangular edge teeth.

8. The compacted field reflective surface achieved by building cement according to claim 1, characterized in that, The focal length of the cement parabolic reflector (2) is 46m, and the focal point is located on the center normal line of the lower edge of the metal coating (3).

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