A concrete-based hybrid edge compression field reflector and its design method

Abstract

This invention discloses a concrete-based hybrid edge compaction field reflector and its design method. The reflector includes: a main body, part of a paraboloid of revolution, made of reinforced concrete with a metal-sprayed surface; and a mixed edge of rolled and sawtooth edges surrounding the main body. Measurement systems using this reflector, when placed outdoors, only need to consider ground scattering, eliminating the need to consider the influence of wall scattering on the quiet zone. The concrete reflector structure is stable, easy to form, and can create a high-quality quiet zone at low frequencies, reducing the processing cost of large low-frequency reflectors. The use of the mixed rolled and sawtooth edges effectively suppresses edge diffraction, enabling the formation of a high-quality quiet zone outdoors.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic scattering measurement technology, and more specifically to a concrete-based hybrid edge compaction field reflector and its design method. Background Technology

[0002] With the development of electronic warfare technology, low-frequency stealth testing technology has received increasing attention. Compared to the far field, the compact field method converts the spherical waves generated by the feed into plane waves through a reflecting surface, providing a high-performance plane wave testing area at close range, thus greatly reducing the requirements for the testing site.

[0003] Currently, research on low-frequency compacted fields has yielded some results, but a series of problems still exist. Compacted fields are mostly built in microwave anechoic chambers, which have advantages such as all-weather testing, high confidentiality, and low background levels. However, for low-frequency testing of large targets, the construction of the anechoic chamber requires huge costs and also poses safety hazards. Secondly, the reflective surface of compacted fields is usually made of metal materials, which can achieve high-precision reflective surfaces, but greatly increases the processing cost. At the same time, because the absorption performance of commonly used absorbing materials deteriorates at low frequencies, the scattering from the walls and the ground will have a significant impact on the quiet zone performance. Furthermore, at low frequencies, the edge diffraction of the reflective surface is severe. Some of the edge diffraction will directly enter the quiet zone, and some will enter the quiet zone through secondary scattering from the ground and walls. These electromagnetic waves will generate ripples in the quiet zone, thus affecting the quiet zone performance.

[0004] To suppress edge diffraction, common edge design methods include sawtooth edges and rolled edges. Sawtooth edges use triangular edges to achieve a smooth transition between the reflector body and free space, which can effectively increase aperture utilization efficiency and reduce the portion of edge diffraction entering the quiet zone. However, sawtooth edges are relatively large, generally five maximum operating wavelengths, which increases the difficulty of processing and installation. At the same time, although the introduction of sawtooths eliminates edge diffraction in the main body of the reflector, it will increase new diffraction, which will also enter the quiet zone directly or through multiple scattering.

[0005] The curled edge uses the curved edge to cause electromagnetic waves to form creeping waves at the edge of the reflective surface. Most of these creeping waves will propagate to the opposite side of the reflective surface under the guidance of the curled edge, but some will enter free space along the tangent of the curled edge, and after multiple scatterings, they will affect the quiet zone performance.

[0006] Another edge design method is to use a resistive film or FSS (frequency selective surface) loading. This method can absorb electromagnetic waves at the edge through resistive loss, thus effectively suppressing edge diffraction. However, this method can only work in narrow bands, and the size of the cell is wavelength-dependent, resulting in high cost and large size at low frequencies.

[0007] Therefore, how to overcome the defects of the aforementioned low-frequency compression field is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] In view of this, the present invention provides a concrete-based hybrid edge compaction field reflector and design method, which can solve the defects of the existing low-frequency compaction field technology to a certain extent. Based on the hybrid edge design, the performance of the low-frequency compaction field can be improved.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, embodiments of the present invention provide a concrete-based hybrid edge compression field reflective surface, comprising:

[0011] The main reflective surface, part of a parabolic sphere of revolution, is made of reinforced concrete and coated with metal.

[0012] And a mixed edge of rolled and sawtooth edges disposed around the periphery of the reflective surface body.

[0013] Furthermore, when used in outdoor compacted environments, the upper and left and right edges of the reflective surface body are rolled, and the lower edge is serrated.

[0014] Furthermore, the length and width of the main body of the reflective surface are both greater than 20 maximum operating wavelengths.

[0015] Furthermore, the curled edge is generated using elliptical curve fitting, with the major axis of the elliptical curve being 5 maximum working wavelengths and the minor axis being 3 maximum working wavelengths.

[0016] Furthermore, the upper edge of the reflective surface body is the first rolled edge, and the left and right side rolled edges are the second rolled edges;

[0017] The connection between the first rolled edge and the second rolled edge is a smooth curved surface generated by lofting.

[0018] Furthermore, the serrated edge is a plurality of symmetrically arranged right-angled triangle structures; wherein the right-angled sides are on the outer side and the hypotenuse is on the inner side; the slope of the right-angled triangle structure increases sequentially from the outer side to the inner side.

[0019] Furthermore, the length of the right-angled side is 5 maximum operating wavelengths.

[0020] Furthermore, the apex corner at the junction of the rolled edge and the serrated edge is generated using a lofting method.

[0021] Secondly, embodiments of the present invention also provide a design method for a concrete-based hybrid edge compression field reflective surface, comprising the following steps:

[0022] Step 1: Analyze the main scattering sources of the site where the compact field system is located and the suppression principle of edge diffraction by different edges. For outdoor compact fields, the scattering comes from the ground. Determine that the upper and left and right edges of the reflective surface should be rolled, and the lower edge should be serrated.

[0023] Step 2: Design the main body of the reflector according to the required quiet zone size, determine that the length and width of the reflector are greater than 20 maximum working wavelengths, and determine the reflector offset angle and focal length;

[0024] Step 3: Select the surface fitted by the elliptical curve as the edge of the reflective surface, so that the slope of the curve at different positions is the same as that of the main body of the reflective surface at the connection point; then fit the curve into a surface to form a rolled edge; the top corner of the rolled edge is generated by the lofting method at the connection point between the upper rolled edge and the left and right rolled edges.

[0025] Step 4: Determine that the serrated edge design adopts multiple symmetrically arranged right-angled triangle structures, with the right-angled sides on the outside and the hypotenuse on the inside, and the slope of the right-angled triangle structure increases sequentially from the outside to the inside;

[0026] Step 5: Based on the design conclusions determined in Steps 1-4, the reflective surface is formed by concrete pouring, and the back is fixed to the support by concrete pouring. The reflective surface is then coated with metal.

[0027] Furthermore, in step 1, a mixed edge of rolled edge and sawtooth edge was selected based on the location of the compaction field system.

[0028] Furthermore, in step 3, an elliptical curve-fitted surface is used as the rolled edge, and a lofting method is used to generate the apex of the rolled edge.

[0029] As can be seen from the above technical solution, compared with the prior art, the present invention has the following advantages:

[0030] 1. Compared to indoor compact field measurements, the measurement system for this compact field reflector is placed outdoors, eliminating the need for a large anechoic chamber, thus saving costs and avoiding the safety hazards associated with large anechoic chambers. Considering the poor performance of low-frequency absorbing materials, setting up the system in an open outdoor environment only requires consideration of ground scattering, without needing to consider the impact of wall-scattered waves on the quiet zone.

[0031] 2. Compared to metal reflectors, concrete reflectors can be directly connected to the reflector by erecting steel reinforcement and pouring concrete. The support and reflector are integrated, greatly improving stability and reducing installation and transportation costs. Concrete reflectors have a stable structure, are easy to form, and can reduce the processing cost of large low-frequency reflectors. At the same time, there is no need to consider the impact of joints on the quiet zone as in metal reflectors.

[0032] 3. The reflective surface edge structure adopts a hybrid edge of rolled edge and sawtooth edge. The lower edge adopts a sawtooth edge structure, which can effectively suppress edge diffraction through the ground into the quiet zone. Since there is no wall influence, the upper and left and right sides adopt a rolled edge structure, which can guide electromagnetic waves to the back of the reflective surface and reduce the influence of multiple scattering. The cost of rolled edge is also lower than that of sawtooth edge when processing concrete reflective surface.

[0033] 4. When designing the rolled edge of the reflective surface, an elliptical curve was selected. Compared with a hyperelliptical curve, the design process of the rolled edge can be simplified. At the same time, compared with the common right-angle apex, the apex formed by lofting is a smooth curved surface, which can reduce edge diffraction of the sharp point and can form a climbing wave at the apex to guide the reflection to the back of the reflective surface. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0035] Figure 1 A schematic diagram of a hybrid edge reflective surface provided in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the design of the rolled edge portion of the mixed edge provided in an embodiment of the present invention;

[0037] Figure 3a Simulation comparison diagram of the horizontal static zone amplitude provided for embodiments of the present invention;

[0038] Figure 3b Simulation comparison diagram of the horizontal static zone phase provided for embodiments of the present invention;

[0039] Figure 3c Simulation comparison diagram of the vertical static zone amplitude provided for embodiments of the present invention;

[0040] Figure 3d A simulation comparison diagram of the vertical static zone phase provided for an embodiment of the present invention. Detailed Implementation

[0041] 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.

[0042] This invention discloses a compacted field reflective surface with a mixed edge realized in concrete, comprising: as shown in the following embodiments. Figure 1 The reflective surface body shown and the rolled-serrated edge set around the reflective surface body.

[0043] The main body of the reflective surface is made of concrete, and the surface is polished and then sprayed with metal.

[0044] A blend of rolled and serrated edges can suppress edge diffraction of reflective surfaces.

[0045] The following sections will provide a detailed description of the main reflective surface and the mixed edge of rolled and sawtooth edges:

[0046] 1. Main body of the reflective surface:

[0047] The reflector body is made of reinforced concrete and is used outdoors for low-frequency compaction field testing. The specific manufacturing steps are as follows:

[0048] 1.1: Constructing the foundation; First, construct a foundation using reinforced concrete at the connection between the concrete support and the reflective surface.

[0049] 1.2: Concrete pouring; Concrete is poured according to the reflective surface mold.

[0050] 1.3: Surface Repair; Once the concrete has dried, repair the surface to ensure there are no cracks or uneven areas.

[0051] 1.4: Curing agent treatment; apply a curing agent to the reflective surface to enhance its strength and smoothness.

[0052] 1.5: Polishing treatment; After the curing agent solidifies, the reflective surface is polished to ensure surface smoothness.

[0053] 1.6: Metal Spraying; After polishing, the reflective surface needs to be sprayed with a layer of metal to form a paraboloid of revolution with metal boundaries. During metal spraying, it is necessary to ensure that the metal thickness is uniform to reduce surface unevenness of the reflective surface.

[0054] like Figure 1 As shown, the main body of the reflective surface is a paraboloid of revolution. In practical implementation, the length and width of the reflective surface generally need to be greater than 20 maximum operating wavelengths. In this embodiment, the operating frequency is 0.3-2GHz, the focal length is 22.5m, and the length and width are both 30m. The reflective surface is constructed of concrete. Compared to metal, concrete has better plasticity and structural strength, thus making the structure more stable and easier to form when constructing large-scale compaction field systems.

[0055] The presence of aggregates within concrete inevitably limits the surface finishing precision. Currently, the finishing precision of compacted field reflectors is typically required to be 1 / 60th of the minimum operating wavelength. For the low-frequency compacted field proposed in this invention, the precision requirement is 2.5mm, which current concrete finishing precision can meet. Therefore, errors caused by the finishing precision of the reflector have minimal impact at low frequencies.

[0056] In practice, the back of the concrete reflective surface is fixed to the support and bracket constructed with reinforced concrete, which provides good stability.

[0057] 2. Mixed edge design: curled edge and serrated edge

[0058] The main body of the aforementioned reflective surface adopts a mixed edge of rolled and sawtooth edges.

[0059] Hybrid edges are a combination of serrated and rolled edges. The choice of edge combination method needs to be analyzed in conjunction with the principles of edge diffraction suppression and the application of the compact field. The selection of the combination method is described below:

[0060] Without edge treatment, according to the theory of geometric diffraction, electromagnetic waves under truncated edges will form a Keller cone distribution at the edge. A large number of electromagnetic waves will directly enter the quiet zone or enter the quiet zone through scattering from the ground and walls, affecting the performance of the quiet zone.

[0061] The serrated edge achieves a smooth transition from the main body of the reflective surface to free space, eliminating the original edge diffraction. However, the added serrated edge will generate new diffraction. Since the diffraction of some edges is converted into vertex diffraction, the intensity of the diffracted wave is greatly reduced, but a small part of the diffracted wave can still enter the quiet zone.

[0062] Waves at the rolled edge are divided into creeping waves along the rolled surface and scattered waves along the normal direction. Creeping waves can guide electromagnetic waves to the opposite side of the reflecting surface, avoiding entry into the quiet zone. However, scattered waves along the normal direction may enter the quiet zone through secondary scattering, affecting the quiet zone performance.

[0063] In this embodiment, the compaction field system is placed outdoors and operates at low frequencies, so rolled edges are chosen for the top and left and right sides, and a serrated edge is chosen for the bottom side, for the following reasons:

[0064] Secondary scattering from the ground at low frequencies cannot be suppressed by absorbing materials alone, so the influence of the ground must be considered. Scattered waves along the normal direction of the rolled edge can easily pass through the ground into the quiet zone, while the main scattered waves of the sawtooth edge disperse in all directions and rarely enter the quiet zone and the ground. Therefore, a sawtooth edge is used on the lower side.

[0065] In outdoor compact fields, scattering from walls and ceilings is not a concern, so the scattered waves along the normal direction from the rolled edge will not affect the quiet zone through walls and ceilings, and very little of the creeping wave directly enters the quiet zone. When using concrete to create a reflective surface, rolled edges are less expensive than serrated edges; therefore, rolled edges are used on the top and left / right sides.

[0066] The specific design process is as follows:

[0067] 2.1): Analyze the site characteristics; First, it is necessary to analyze the main scattering sources of the site where the compact field system is located and the suppression principle of edge diffraction by different edges. For outdoor compact fields, scattering originates from the ground. Based on the site characteristics, rolled edges are selected on the upper and left / right sides of the reflective surface, and serrated edges are selected on the lower side.

[0068] 2.2): Hem Rolling Design; The hem rolling is generated using elliptical curve fitting. Appropriate elliptical parameters are selected to ensure that the slope of the hem rolling and the reflective surface body is the same at the connection point. Elliptical curves are designed at multiple discrete points, and then the curves are fitted into a surface, such as... Figure 2 As shown.

[0069] 2.3): Serrated edge design; the serrated edge adopts a right-angled triangle structure, with the right-angled side on the outside and the hypotenuse on the inside. The slope of the right-angled triangle increases sequentially from the outside to the inside. The length of the right-angled side is generally required to be approximately 5 maximum operating wavelengths.

[0070] 2.4): Vertex design; vertexes are generated using a lofting method.

[0071] This invention provides a concrete-based hybrid edge compaction field reflector for outdoor low-frequency (0.3-2GHz) compaction field measurement. The reflector is made of concrete, significantly reducing processing costs. Simultaneously, the edges of the reflector employ a hybrid treatment of rolled and serrated edges, achieving a trade-off between cost and performance, making it more suitable for outdoor use. Concrete has low processing costs; although its accuracy is lower than metal, it meets the accuracy requirements at low frequencies; and it is easy to repair if damaged. Since the compaction field system is used outdoors, only ground scattering needs to be considered, so the bottom edge uses a serrated edge to effectively suppress electromagnetic waves diffracted from the reflector's edge and scattered through the ground into the quiet zone. The remaining edges are rolled to prevent creeping waves from interfering with the quiet zone. The hybrid edge design achieves a trade-off between suppressing edge diffraction and cost.

[0072] Based on the same inventive concept, embodiments of the present invention also provide a design method for a concrete-based hybrid edge compression field reflective surface, comprising the following steps:

[0073] Step 1: Analyze the main scattering sources of the site where the compact field system is located and the suppression principle of edge diffraction by different edges. For outdoor compact fields, the scattering comes from the ground. Determine that the upper and left and right edges of the reflective surface should be rolled, and the lower edge should be serrated.

[0074] The location of the serrated edge and the rolled edge needs to be selected according to the site shape. The rolled edge can be used in the location where the environmental scattering is weak, so that the electromagnetic waves emitted along the tangent will hardly enter the quiet zone after secondary scattering.

[0075] Step 2: Design the main body of the reflector according to the required quiet zone size, determine the length and width of the reflector, which generally needs to be greater than 20 maximum working wavelengths; determine the focal length and offset angle of the reflector;

[0076] Step 3: Select a suitable curve to connect the reflective surface body and the edge, so that the slope of the edge and the body is the same at the connection point; select curve parameters at multiple discrete points, fit the curve into a surface to form a rolled edge; and design the surface at the top corner of the reflective surface; for example, use elliptical curve fitting to form a rolled edge, select the major axis as 5 maximum working wavelengths and the minor axis as 3 maximum working wavelengths.

[0077] Step 4: Determine that the sawtooth edge design uses multiple symmetrically arranged right-angled triangle structures, with the right-angled sides on the outside, approximately 5 maximum working wavelengths in length, and the hypotenuses on the inside. The slopes of these triangles increase sequentially from the outside to the inside.

[0078] Step 5: Construct two perpendicular planes at the apex of the surface connection. Use the lofting method to generate a smooth surface that can guide the electromagnetic waves at the apex to the rear.

[0079] Based on the design conclusions determined in steps 1-5, it is formed by concrete pouring, and the back is fixed to the support by reinforced concrete.

[0080] The technical effects of the present invention are illustrated below through simulation experiments:

[0081] This simulation mainly simulated four models: a reflective surface without edge processing, a reflective surface with serrated edges, a reflective surface with rolled edges, and a mixed reflective surface with serrated and rolled edges.

[0082] Figure 3a Simulation comparison diagram of the horizontal static zone amplitude of the four models; Figure 3b Simulation comparison diagram of the horizontal static phase of the four models; Figure 3c A simulation comparison diagram of the vertical static zone amplitude for the four models; Figure 3d The simulation comparison diagram shows the vertical static phase of the four models.

[0083] pass Figures 3a-3d It can be seen that, without considering ground scattering, the performance of the quiet zone of the reflective surface with mixed edges is better than that of the reflective surface without edge treatment and the reflective surface with rolled edges. This is reflected in the smaller amplitude and phase ripple in the quiet zone, which improves the aperture utilization efficiency of the lower half of the reflective surface. At the same time, the reflective surface with mixed edges can reduce the processing cost.

[0084] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0085] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A concrete-based hybrid edge compression field reflective surface, characterized in that, The reflective surface is used in outdoor compact areas, and the reflective surface includes: The main reflective surface, part of a parabolic sphere of revolution, is made of reinforced concrete and coated with metal. And a mixed edge of rolled and sawtooth edges disposed around the periphery of the reflective surface body; The upper and left and right edges of the reflective surface body are rolled, and the lower edge is serrated. The curled edge is generated by fitting an elliptical curve, with the major axis of the elliptical curve being 5 maximum working wavelengths and the minor axis being 3 maximum working wavelengths. The sawtooth edge is a plurality of symmetrically arranged right-angled triangle structures; wherein the right-angled sides are on the outside and the hypotenuses are on the inside; the slope of the right-angled triangle structure increases sequentially from the outside to the inside; the length of the right-angled side is 5 maximum working wavelengths; The upper edge of the reflective surface body is the first rolled edge, and the left and right rolled edges are the second rolled edges; the connection between the first rolled edge and the second rolled edge is a smooth curved surface generated by lofting.

2. The concrete-based hybrid edge compression field reflective surface according to claim 1, characterized in that, The main body of the reflective surface is longer and wider than 20 maximum operating wavelengths.

3. A design method for a hybrid edge contraction field reflective surface achieved with concrete as described in any one of claims 1-2, characterized in that, Includes the following steps: Step 1: Analyze the main scattering sources of the site where the compact field system is located and the suppression principle of edge diffraction by different edges. For outdoor compact fields, the scattering comes from the ground. Determine that the upper and left and right edges of the reflective surface should be rolled, and the lower edge should be serrated. Step 2: Design the main body of the reflector according to the required quiet zone size, determine that the length and width of the reflector are greater than 20 maximum working wavelengths, and determine the focal length and offset angle of the reflector; Step 3: Select the surface fitted by the elliptical curve as the edge of the reflective surface, so that the slope of the curve at different positions is the same as that of the main body of the reflective surface at the connection point; then fit the curve into a surface to form a rolled edge; Step 4: Determine that the serrated edge design adopts multiple symmetrically arranged right-angled triangle structures, with the right-angled sides on the outside and the hypotenuse on the inside, and the slope of the right-angled triangle structure increases sequentially from the outside to the inside; Step 5: Based on the design conclusions determined in Steps 1-4, the main body of the reflective surface is formed by concrete pouring, and the back is fixed to the support by concrete pouring. In step 1, a mixed edge of rolled edge and sawtooth edge was selected based on the location of the compaction field system; in step 3, a surface fitted by an elliptical curve was used as the rolled edge, and a lofting method was used to generate the apex corner of the rolled edge.

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