Compact range device with multi-turn gradient impedance edge loading

Abstract

The invention discloses a compact range device with multi-circle gradient impedance edge loading. The compact range device is a brand new device different from a traditional sawtooth compact range and a traditional hemming compact range. According to the device, conductive paint with gradually-changed impedance is sprayed on the edge of the paraboloid by multiple circles, and the impedance value of the conductive paint is controlled by gradually changing the impedance circle by circle. Compared with common sawtooth edge processing and curled edge processing, the design of the multi-circle gradient impedance does not need edge appearance sawtooth or curved surface curled processing, only impedance loading needs to be carried out on the edge surface of the parabolic reflecting surface, and therefore the processing steps of the compact range reflecting surface are greatly simplified, the processing difficulty is reduced, and the cost is saved. The device disclosed by the invention completely meets the performance indexes of the compact range, can be used as an upgrade substitute for the existing compact range product, and is also one of the development trends of a low-frequency test field in the future.

Description

Technical Field

[0001] The present invention relates to a compact range, in particular to the design and manufacturing of a compact range device, with the aim of simplifying the physical structure of the compact range reflector surface, reducing the processing steps and lowering the manufacturing cost while pursuing the low-frequency limit and high-frequency performance of the compact range. Background Art

[0002] The edge processing of the reflection surface is an extremely important component of the compact field, which is directly related to the low-frequency performance of the compact field system. Since the actual size of the compact field reflection surface is not infinite enough, and the propagation of electromagnetic waves does not follow the principle of high-frequency optics, when the electromagnetic waves emitted by the feed source hit the edge of the reflection surface, a low-frequency diffraction field will inevitably be generated. This diffraction will greatly interfere with the uniformity of the plane wave in the quiet zone. The plane wave actually generated in the quiet zone is not an ideal uniform plane wave in the true sense, but an approximate quasi-plane wave, which is the result of the superposition of the reflection field and the edge diffraction field. The existence of edge diffraction causes the amplitude and phase of the quiet zone plane wave to fluctuate, resulting in large errors in the compact field measurement results. Therefore, the edge diffraction must be controlled as much as possible.

[0003] In order to control edge diffraction, it is common to perform special processing on the edge of the reflective surface. The mainstream processing technologies in the industry include sawtooth edge processing and curled edge processing. The sawtooth edge compact field has a simple structure, but relatively poor performance, especially the low-frequency limit is high, which is not suitable for low-frequency applications at 15 times the wavelength of the aperture; while the curled edge compact field has better performance, but the structure is complex, and the processing difficulty and production cost are greatly increased. Both require processing the edge of the reflective surface, and have their own advantages and disadvantages and different application scenarios. Summary of the invention

[0004] The purpose of the present invention is to propose a multi-turn gradient impedance edge-loaded compact field device, which 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] In order to achieve the above-mentioned purpose, the present invention adopts the following technical design:

[0006] A compact field device with multiple turns of gradient impedance edge loading is characterized in that: the compact field device includes a reflecting surface, and the reflecting surface is composed of a base part and a surface part; the base part provides substrate support and determines the basic profile and shape of the reflecting surface; the surface part of the compact field reflecting surface is divided into multiple turns of annular areas, and each turn of the annular area is sprayed with a conductive paint with gradient impedance to achieve a matching transition from the center of the reflecting 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 portion and an edge impedance gradient region, the main body portion is a rotating parabola, and along the axial orthographic projection of the parabola, the overall outline of the reflective surface is rectangular or square.

[0008] Furthermore, the reflecting surface is divided into multiple annular areas by a number of curves, presenting a layout resembling the "annual rings" of a tree cross-section; the outline of the annular area is circular, square, concave or other curves and their combinations; the number of circles in the annular area 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 reflecting surface and achieving control of edge diffraction.

[0010] Furthermore, the innermost area of ​​the reflecting surface is the main part of the reflecting surface, and its size accounts for 45%-50% of the overall size of the reflecting surface, and is appropriately adjusted depending on the aperture utilization and the size of the quiet zone.

[0011] Furthermore, each annular area is sprayed with conductive paint of different impedance values ​​in turn, and the impedance values ​​of the conductive paint are arranged in a gradually increasing manner from small to large from the innermost circle to the outermost circle.

[0012] Furthermore, it is recommended that the curve adopts a concave shape, that is, along any ray direction from the center of the reflecting surface to the outside, the distances between adjacent concave curves are equal.

[0013] The key to designing a compact field reflector is to suppress the edge diffraction field. The traditional approach requires processing the edge of the reflector, while the multi-turn gradient impedance edge design proposed in the present invention processes the surface of the reflector to suppress the edge diffraction field.

[0014] When electromagnetic waves irradiate different media, different reflection fields and diffraction fields will be generated, which will affect the reflection and diffraction characteristics by changing the electromagnetic parameters of the medium on the reflective surface. As long as the appropriate medium and reasonable combination are selected, the edge diffraction field can be suppressed as much as possible as required.

[0015] The present invention sprays conductive paint on the surface of the reflective surface to change its electromagnetic parameters, thereby affecting the reflection field and the diffraction field. The conductive paint is composed of a number of materials with different impedance values ​​and an adhesive, and the function is achieved by changing the proportion of each component to meet any requirements. By changing the spraying area and impedance value of the conductive paint, the edge diffraction field can be controlled, thereby obtaining a more uniform plane wave in the quiet zone and improving the low-frequency performance of the compact field.

[0016] Compared with the existing compact field reflective surface, the present invention has the following advantages:

[0017] (1) Compared with the sawtooth edge reflector, the multi-turn gradient impedance edge loaded compact field proposed by the present invention can achieve a lower operating frequency, overcoming the disadvantage of the poor low-frequency performance of the traditional sawtooth edge compact field. Its low-frequency limit is less than 15λ max , which is much lower than the 25-30λ commonly considered sawtooth edge compression field max low frequency limit.

[0018] (2) Compared with the curled reflective surface, the design proposed in the present invention has a simpler physical structure, and the difficulty of processing and manufacturing is greatly reduced. While ensuring the performance, it solves the shortcomings of the curled compact field with complex structure and high cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a compact field with multi-turn gradient impedance edge loading, where 1 is the main part of the reflector, 2 is the impedance gradient area at the edge of the reflector, 3 is the feed source, 4 is the cross section of the statistical quiet zone, and 5 is the compact field darkroom;

[0020] Figure 2 It is a front view of the reflector along the axial direction of the parabola, where 3 is the feed source, 1 is the main part of the reflector, and 2 is the edge impedance gradient area;

[0021] Figure 3 It is the amplitude distribution of the quiet zone cross section of the multi-turn gradient impedance compact field, and the corresponding reflection surface size is 10 times the wavelength of the electromagnetic wave;

[0022] Figure 4 It is the phase distribution of the quiet zone cross section of the multi-turn gradient impedance compact field, and the corresponding reflection surface size is 10 times the wavelength of the electromagnetic wave;

[0023] Figure 5 It is the amplitude distribution of the quiet zone cross section of the multi-turn gradient impedance compact field, and the corresponding reflection surface size is 15 times the wavelength of the electromagnetic wave;

[0024] Figure 6 It is the phase distribution of the quiet zone cross section of the multi-turn gradient impedance compact field, and the corresponding reflection surface size is 15 times the wavelength of the electromagnetic wave;

[0025] Figure 7 It is the amplitude distribution of the quiet zone cross section of the multi-turn gradient impedance compact field, and the corresponding reflection surface size is 20 times the wavelength of the electromagnetic wave;

[0026] Figure 8 It is the phase distribution of the quiet zone cross section of the multi-turn gradient impedance compact field, and the corresponding reflection surface size is 20 times the wavelength of the electromagnetic wave;

[0027] Fig. 9 It is the amplitude distribution of the quiet zone cross section of the multi-turn gradient impedance compact field, and the corresponding reflection surface size is 30 times the wavelength of the electromagnetic wave;

[0028] Fig.10 It is the phase distribution of the quiet zone cross section of the multi-turn gradient impedance compact field, and the corresponding reflection surface size is 30 times the wavelength of the electromagnetic wave;

[0029] Fig.11 It is the amplitude distribution of the central cross-section of the quiet zone section of the multi-turn gradient impedance compact field, and the corresponding reflection surface size is 10 times, 15 times, 20 times, and 30 times the wavelength of the electromagnetic wave;

[0030] Fig.12 It is the amplitude distribution of the vertical section of the center of the quiet zone section of the multi-turn gradient impedance compact field, and the corresponding reflection surface size is 10 times, 15 times, 20 times, and 30 times the wavelength of the electromagnetic wave;

[0031] Fig.13 It is the phase distribution of the central cross section of the quiet zone section of the multi-turn gradient impedance compact field, and the corresponding reflection surface size is 10 times, 15 times, 20 times, and 30 times the wavelength of the electromagnetic wave;

[0032] Fig.14 It is the phase distribution of the central vertical section of the quiet zone cross section of the multi-turn gradient impedance compact field, and the corresponding reflection surface size is 10 times, 15 times, 20 times, and 30 times the wavelength of the electromagnetic wave.

[0033] Specific implementation examples

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

[0035] A preferred embodiment of the present invention:

[0036] A multi-turn gradient impedance edge-loaded compact field device comprises a reflecting surface, a main part 1 of the reflecting surface is a rotating parabola, and along the axial orthographic projection of the parabola, the overall outline of the reflecting surface is rectangular or square.

[0037] The reflective surface is divided into multiple annular areas by several curves, presenting a layout similar to the "annual rings" of a tree cross section. The outline of the annular area is circular, square, concave or other curves and their combination, and the concave shape is recommended.

[0038] The innermost area of ​​the compact field reflective surface is the main body 1 of the reflective surface, and its size accounts for about 45%-50% of the overall size of the reflective surface, and can be appropriately adjusted depending on the aperture utilization 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, and each annular region is sprayed with conductive paint of different impedance values ​​in turn. From the innermost circle to the outermost circle, the impedance value of the conductive paint is gradually increased from small to large.

[0040] The multi-turn gradient impedance edge-loaded compact field described in the present invention mainly includes a main body 1 of the reflective surface and an edge impedance gradient area 2, both of which are sprayed with conductive paint of different impedance values. By changing the impedance value and spraying position of the conductive paint, the edge diffraction field is controlled, so that a more uniform plane wave is obtained in the quiet zone, reaching or even exceeding the performance of the traditional sawtooth or curled edge compact field. A matching transition from the center of the reflective surface to the free space through the edge is achieved, reducing the interference of the edge diffraction field on the quiet zone.

[0041] The reflective surface is composed of a base part and a surface part. The base part provides substrate support and determines the basic profile and shape of the reflective surface, and the surface part is a conductive film with different gradient impedances.

[0042] The reflection surface is divided into a plurality of annular regions, and the edge curve of each region is a straight line, a curve, or a combination thereof. The number of circles of the annular region is not less than 3.

[0043] 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 reflecting surface.

[0044] like Figure 1 The gradient impedance compact field reflector is shown, wherein the gradient impedance compact field reflector and feed 3 are placed in the compact field darkroom 5, and the calculation is performed at the section 4 of the statistical quiet zone. In the figure, the reflector is located in the xoz plane, with a size of 20m×20m; the feed is placed along the x-axis, with a focal length of 20m; the statistical section is parallel to xoz, and the distance to the reflector is 23m, and the quiet zone is a circular area with a center diameter of 9m in the section.

[0045] like Figure 2 As shown, the aperture projection of the reflector is a square and the profile is a parabola. The reflector includes the main part 1 of the reflector and the edge impedance gradient area 2; the reflector has seven circles of gradient impedance. The boundary curve of the multi-circle annular area is preferably concave, which is characterized by the equal distance between adjacent concave curves along any ray direction from the center of the reflector to the outside. In order to illustrate the performance of the gradient impedance compact field reflector, a full-wave simulation is performed on it, and the simulation frequency is 0.15GHz (10λ max ×10λ max ), 0.225GHz (15λ max ×15λ max ), 0.3GHz (20λ max ×20λ max ), 0.45GHz (30λ max ×30λ max ).

[0046] Figure 3~Figure 14The results show that the peak-to-peak variation of the electric field amplitude in the quiet zone under four typical low-frequency conditions is less than 2 dB, and the peak-to-peak variation of the phase is less than ±10°, which fully meets the typical evaluation indicators of the compact field. max It can still have good performance, which is lower than the low-frequency limit of the sawtooth edge compression field. It can be used as an upgraded replacement for the current mainstream traditional sawtooth edge compression field and curled edge compression field.

[0047] Table 1: Amplitude and phase peak-to-peak statistics in the quiet zone

[0048]

[0049] Table 1 is the statistics of the peak-to-peak value of the quiet zone surface amplitude, the peak-to-peak value of the surface phase, the peak-to-peak value of the cross-section amplitude, the peak-to-peak value of the cross-section phase, the peak-to-peak value of the vertical section amplitude, and the peak-to-peak value of the vertical section phase at four frequencies.

[0050] Parts of the present invention that are not described in detail belong to the well-known technology in the art.

Claims

1. A multi-turn gradient impedance edge-loaded compact field device, characterized in that: The compact field device includes a reflecting surface, which is composed of a base part and a surface part; the base part provides substrate support and determines the basic profile and shape of the reflecting surface; the surface part of the compact field reflecting surface is divided into multiple annular areas, each of which is sprayed with conductive paint with a gradient impedance to achieve a matching transition from the center of the reflecting surface to the edge to the free space, thereby reducing the interference of the edge diffraction field on the quiet zone.

2. The compact field device according to claim 1, characterized in that: The surface of the reflective surface includes a main body and an edge impedance gradient region. The main body is a rotating parabola. Along the axial orthographic projection of the parabola, the overall outline of the reflective surface is a rectangle or a square.

3. The compact field device according to claim 1, characterized in that: The reflecting surface is divided into multiple annular areas by a number of curves, presenting a layout resembling the "annual rings" of a tree cross-section; the outline of the annular area is circular, square, concave or other curves and their combination; the number of circles in the annular area is not less than 3.

4. The compact field device according to claim 3, characterized in that: 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 reflecting surface.

5. The compact field device according to claim 1, characterized in that: The innermost area of ​​the reflecting surface is the main part of the reflecting surface, and its size accounts for 45%-50% of the overall size of the reflecting surface. It can be adjusted appropriately depending on the aperture utilization and the size of the quiet zone.

6. The compact field device according to claim 4, characterized in that: Conductive paint with different impedance values ​​is sprayed on each annular area in turn, and the impedance values ​​of the conductive paint are arranged gradually from small to large from the innermost circle to the outermost circle.

7. The compact field device according to claim 3, characterized in that: The curve is concave, and the distances between adjacent concave curves are equal along any ray direction from the center of the reflecting surface to the outside.

8. The compact field device according to claim 3, characterized in that: By changing the impedance characteristics of the annular area, the edge diffraction can be controlled, which greatly improves the performance of the compact field, especially the low-frequency performance.

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