A multi-turn tapered impedance edge loaded compact range

Abstract

The application discloses a multi-circle gradually-changing impedance edge loading tight field device, which is a novel device different from traditional sawtooth tight field and edge curl tight field. The device sprays conductive paint with gradually-changing impedance on the edge of a parabolic surface in multiple circles, and controls the impedance value of the conductive paint in the gradually-changing manner. Compared with common sawtooth edge processing and edge curl processing, the design of the multi-circle gradually-changing impedance does not need to process the edge shape into sawtooth or curve, but only needs to load impedance on the edge surface of the parabolic reflecting surface, so that the processing steps of the tight field reflecting surface are greatly simplified, the processing difficulty is reduced, and the cost is saved. The device disclosed by the application fully meets the performance indexes of the tight field, can be used as an upgrade and substitution of the existing tight field product, and is one of the development trends of future low-frequency test fields.

Description

Technical Field

[0001] This invention relates to compacted fields, and more particularly to the design and manufacture of compacted field devices. Its purpose is to achieve both low-frequency limits and high-frequency performance of compacted fields while simplifying the physical structure of the compacted field reflector, reducing processing steps, and lowering manufacturing costs. Background Technology

[0002] Edge treatment of the reflecting surface is a crucial component of a compacted field system, directly impacting its low-frequency performance. Since the actual size of the compacted field reflecting surface is not infinitely large, electromagnetic wave propagation does not follow high-frequency optical principles. Therefore, when the electromagnetic waves emitted by the feed strike the edge of the reflecting surface, a low-frequency diffraction field is inevitably generated. This diffraction significantly interferes with the uniformity of the plane wave in the quiet zone. The plane wave actually generated in the quiet zone is not a truly ideal, uniform plane wave, but rather an approximate quasi-plane wave, a result of the superposition of the reflected field and the edge diffraction field. The presence of edge diffraction causes fluctuations in the amplitude and phase of the plane wave in the quiet zone, leading to significant errors in the compacted field measurement results. Therefore, edge diffraction must be controlled as much as possible.

[0003] To control edge diffraction, a common practice is to treat the edges of the reflecting surface specially. The mainstream techniques in the industry include serrated edge treatment and rolled edge treatment. Serrated edge compaction fields have a simple structure but relatively poor performance, especially at low frequencies, making them unsuitable for low-frequency applications at 15 times the wavelength. Rolled edge compaction fields, while offering better performance, have a complex structure, significantly increasing processing difficulty and manufacturing costs. Both methods require edge treatment of the reflecting surface, each with its own advantages and disadvantages and different application scenarios. Summary of the Invention

[0004] The purpose of this invention is to propose a compact field device with multi-turn gradually varying impedance edge loading. This device greatly simplifies the structure of the reflective surface and significantly reduces the manufacturing cost while ensuring the low-frequency and high-frequency performance of the compact field.

[0005] To achieve the above-mentioned objectives, the present invention employs the following technical design:

[0006] A compacted field device with multi-ring gradient impedance edge loading is characterized in that: the compacted field device includes a reflective surface, which is composed of a base portion and a surface portion; the base portion provides substrate support and determines the basic profile and shape of the reflective surface; the surface portion of the compacted field reflective surface is divided into multiple ring-shaped regions, and each ring-shaped region is sprayed with a conductive paint with gradient impedance, so as to realize the matching transition from the center of the reflective surface to the free space through the edge, thereby reducing the interference of the edge diffraction field on the quiet zone.

[0007] Furthermore, the surface portion of the reflective surface includes a main body and an edge impedance gradient region. The main body is a parabolic surface of revolution. When projected orthogonally along the axis of the parabolic surface, the overall outline of the reflective surface is rectangular or square.

[0008] Furthermore, the reflective surface is divided into multiple annular regions by several curves, presenting a layout resembling the "annual rings" of a tree cross-section; the outline of the annular region is a circle, square, concave, or other curves and combinations thereof; the number of annular regions is not less than 3.

[0009] Furthermore, different annular areas are sprayed with paint, and the sprayed conductive paint has different gradient impedance values, thereby changing the surface electromagnetic parameters of the reflective surface and realizing the control of edge diffraction.

[0010] Furthermore, the innermost region of the reflective surface is the main body of the reflective surface, and its size accounts for 45%-50% of the overall size of the reflective surface. This can be adjusted appropriately depending on the aperture utilization and the size of the quiet zone.

[0011] Furthermore, each annular area is sequentially sprayed with conductive paint of different impedance values, with the impedance values ​​of the conductive paint gradually increasing from the innermost to the outermost ring.

[0012] Furthermore, it is recommended that the curve be concave, which is any ray direction outward from the center of the reflecting surface, with the distance between adjacent concave curves being equal.

[0013] The key to designing a compact field reflector is to suppress edge diffraction. Traditional methods require processing the edge of the reflector, while the multi-ring gradient impedance edge design proposed in this invention processes the surface of the reflector, thereby suppressing the edge diffraction.

[0014] When electromagnetic waves strike different media, they produce different reflection and diffraction fields. By changing the electromagnetic parameters of the medium on the reflective surface, the reflection and diffraction characteristics can be affected. By selecting appropriate media and combining them reasonably, the edge diffraction field can be suppressed as much as possible as required.

[0015] This invention involves spraying a conductive paint onto the surface of a reflective surface to alter its electromagnetic parameters, thereby influencing the reflection and diffraction fields. The conductive paint is composed of several materials with different impedance values ​​and an adhesive; by changing the proportions of each component, its function can be achieved to meet any requirement. By altering the spraying area and impedance value of the conductive paint, control over the edge diffraction field can be achieved, resulting in a more uniform plane wave in the quiet zone and improving the low-frequency performance of the compressed field.

[0016] The advantages of this invention compared to existing compacted field reflective surfaces are:

[0017] (1) Compared with sawtooth edge reflecting surfaces, the multi-turn gradually varying impedance edge-loaded compacted field proposed in this invention can achieve a lower operating frequency, overcoming the shortcomings of poor low-frequency performance of traditional sawtooth edge compacted fields. Its low-frequency limit is less than 15λ. max This is far lower than the commonly accepted 25-30λ value for the compaction field of the serrated edge. max The low-frequency limit.

[0018] (2) Compared with the rolled edge reflective surface, the design proposed in this invention has a simpler physical structure, and the processing and manufacturing difficulty is greatly reduced. While ensuring performance, it solves the disadvantages of the rolled edge shrinkage field structure being complex and costly. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a compressed field with multiple turns of gradually varying impedance edge loading. In this diagram, 1 is the main part of the reflecting surface, 2 is the gradually varying impedance region at the edge of the reflecting surface, 3 is the feed source, 4 is the cross section of the statistical quiet zone, and 5 is the compressed field anechoic chamber.

[0020] Figure 2 It is a front view of the reflecting surface as seen along the axis of the parabola, where 3 is the feed source, 1 is the main body of the reflecting surface, and 2 is the edge impedance gradient region.

[0021] Figure 3 It is the amplitude distribution of the static section of a multi-turn gradually varying impedance compacted field, and the corresponding reflective surface size is 10 times the wavelength of the electromagnetic wave.

[0022] Figure 4 It is the phase distribution of the static section of a multi-turn gradually varying impedance compacted field, and the corresponding reflective surface size is 10 times the wavelength of the electromagnetic wave.

[0023] Figure 5 It is the amplitude distribution of the static section of a multi-turn gradually varying impedance compacted field, and the corresponding reflective surface size is 15 times the wavelength of the electromagnetic wave.

[0024] Figure 6 It is the phase distribution of the static section of a multi-turn gradually varying impedance compacted field, and the corresponding reflective surface size is 15 times the wavelength of the electromagnetic wave.

[0025] Figure 7 It is the amplitude distribution of the static section of a multi-turn gradually varying impedance compacted field, and the corresponding reflective surface size is 20 times the wavelength of the electromagnetic wave.

[0026] Figure 8 It is the phase distribution of the static section of a multi-turn gradually varying impedance compacted field, and the corresponding reflective surface size is 20 times the wavelength of the electromagnetic wave.

[0027] Figure 9 It is the amplitude distribution of the static section of a multi-turn gradually varying impedance compacted field, and the corresponding reflective surface size is 30 times the wavelength of the electromagnetic wave.

[0028] Figure 10 It is the phase distribution of the static section of a multi-turn gradually varying impedance compacted field, and the corresponding reflective surface size is 30 times the wavelength of the electromagnetic wave.

[0029] Figure 11 It is the amplitude distribution of the center cross section of the static zone of the multi-turn gradually varying impedance compact field, and the corresponding reflective surface size is 10 times, 15 times, 20 times, and 30 times the wavelength of the electromagnetic wave.

[0030] Figure 12 It is the amplitude distribution of the vertical cross-section at the center of the static zone of the multi-turn gradually varying impedance compact field, and the corresponding reflective surface size is 10, 15, 20, and 30 times the wavelength of the electromagnetic wave.

[0031] Figure 13 It is the phase distribution of the center cross section of the static zone of the multi-turn gradually varying impedance compacted field, and the corresponding reflective surface size is 10 times, 15 times, 20 times, and 30 times the wavelength of the electromagnetic wave.

[0032] Figure 14 It is the phase distribution of the vertical cross-section at the center of the static zone of a multi-turn gradually varying impedance compacted field, and the corresponding reflective surface size is 10, 15, 20, and 30 times the wavelength of the electromagnetic wave.

[0033] Specific implementation examples

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0035] A preferred embodiment of the present invention:

[0036] A multi-turn gradually varying impedance edge-loaded compaction field device includes a reflective surface. The main body 1 of the reflective surface is a parabolic surface of revolution. When projected orthogonally along the axis of the parabolic surface, the overall outline of the reflective surface is rectangular or square.

[0037] The reflective surface is divided into multiple annular regions by several curves, presenting a layout resembling the "annual rings" of a tree cross-section. The outline of the annular region can be circular, square, concave, or other curves or combinations thereof, with concave being recommended.

[0038] The innermost region of the compact field reflector is the main body 1 of the reflector, and its size accounts for about 45%-50% of the overall size of the reflector. It can be adjusted appropriately according to the aperture utilization rate and the size of the quiet zone.

[0039] The main body 1 of the reflective surface is surrounded by an edge impedance gradient region 2. Each ring region is sprayed with conductive paint of different impedance values ​​in sequence. From the innermost ring to the outermost ring, the impedance value of the conductive paint gradually increases from small to large.

[0040] The multi-ring gradient impedance edge-loaded compacted field described in this invention mainly includes the main body 1 of the reflecting surface and the edge impedance gradient region 2, both of which are coated with conductive paint of different impedance values. By changing the impedance value of the conductive paint and the spraying position, the edge diffraction field is controlled, thereby obtaining a more uniform plane wave in the quiet zone, achieving or even surpassing the performance of traditional sawtooth or rolled-edge compacted fields. This achieves a matched transition from the center of the reflecting surface through the edge to free space, reducing the interference of the edge diffraction field on the quiet zone.

[0041] The reflective surface consists of a substrate and a surface. The substrate provides support and determines the basic profile and shape of the reflective surface, while the surface is a conductive film with varying impedances.

[0042] The reflective surface is divided into multiple annular regions, each with an edge curve that is a straight line, a curve, or a combination thereof. The number of annular regions is no less than three.

[0043] Different annular areas are sprayed with conductive paint, which has different gradient impedance values, thereby changing the surface electromagnetic parameters of the reflective surface.

[0044] like Figure 1 The diagram shows a gradient impedance compacted field reflector. The reflector is placed in a compacted field anechoic chamber 5, with a feed source 3, and calculations are performed on section 4 of the statistical quiet zone. The reflector is located on the xoz plane, with dimensions of 20m × 20m; the feed source is placed along the x-axis with a focal length of 20m; the statistical section is parallel to xoz, 23m from the reflector, and the quiet zone is a circular area with a center diameter of 9m.

[0045] like Figure 2 As shown, the projected aperture of the reflector is square, and its surface is parabolic. The reflector consists of a main body 1 and a gradually changing impedance region 2; the reflector has seven rings of gradually changing impedance. The boundary curves of the multi-ring region are optimally recommended to be concave, characterized by equal distances between adjacent concave curves along any ray direction outward from the center of the reflector. To illustrate the performance of this gradually changing impedance compact field reflector, a full-wave simulation is performed at a frequency of 0.15 GHz (10λ). max ×10λ max ), 0.225GHz (15λ) max ×15λ max ), 0.3GHz (20λ) max ×20λ max ), 0.45GHz (30λ) max ×30λ max ).

[0046] Figures 3-14The results show that the peak-to-peak amplitude variation of the electric field in the quiet zone is less than 2 dB and the peak-to-peak phase variation is less than ±10° at four typical low-frequency conditions, fully meeting the typical evaluation indicators of a compact field. The multi-turn gradually varying impedance compact field proposed in this invention operates at 10λ... max It still maintains good performance, falling below the low-frequency limit of the sawtooth edge compression field, and can serve as an upgrade and replacement for the current mainstream traditional sawtooth edge compression field and rolled edge compression field.

[0047] Table 1: Statistics of Amplitude, Phase, Peak, and Peak Values ​​in the Quiet Zone

[0048]

[0049] Table 1 shows the peak-to-peak amplitude, peak-to-peak phase, peak-to-peak amplitude, peak-to-peak phase, peak-to-peak amplitude, and peak-to-peak phase of the quiet zone at four frequencies.

[0050] The parts of this invention not described in detail are well-known in the field.

Claims

1. A compacted field device with multi-turn gradually varying impedance edge loading, characterized in that: The compacted field device includes a reflective surface, which consists of a substrate and a surface. The substrate provides substrate support and determines the basic profile and shape of the reflective surface. The surface of the compacted field reflective surface is divided into multiple annular regions. Each annular region is sprayed with a conductive paint with varying impedance to achieve a matching transition from the center of the reflective surface to the free space through the edge, thereby reducing the interference of the edge diffraction field on the quiet zone. The surface of the reflective surface includes a main body and an edge impedance gradient region. The main body is a parabolic surface of revolution. When projected orthogonally along the axis of the parabolic surface, the overall outline of the reflective surface is rectangular or square. The reflective surface is divided into multiple ring-shaped areas by several curves, presenting a layout resembling the "annual rings" of a tree cross-section; the outline of the ring-shaped area is a circle, square, concave, or other curves and combinations thereof; the number of ring-shaped areas is not less than 3. Different annular areas are sprayed with conductive paint with different gradient impedance values, thereby changing the surface electromagnetic parameters of the reflective surface. Each annular area is sprayed with conductive paint of different impedance values ​​in sequence, and the impedance values ​​of the conductive paint are arranged in a gradual increase from small to large from the innermost circle to the outermost circle.

2. The compression field device as described in claim 1, characterized in that, The innermost area of ​​the reflective surface is the main body of the reflective surface, and its size accounts for 45%-50% of the overall size of the reflective surface. It can be adjusted appropriately depending on the aperture utilization and the size of the quiet zone.

3. The compression field device as described in claim 1, characterized in that, The curves are concave and are ray-shaped outwards from the center of the reflecting surface. The distance between adjacent concave curves is equal.

4. The compression field device as described in claim 1, characterized in that, By changing the impedance characteristics of the annular region, edge diffraction can be controlled, thereby improving the low-frequency performance of the compacted field.

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