An open field for antenna calibration

Abstract

This invention discloses an open-field method for antenna calibration, comprising a metal plate laid on the ground. The metal plate is a convex quadrilateral plate, and any two opposite sides of the quadrilateral plate are not parallel, thereby preventing the electromagnetic waves reflected from the edges of the quadrilateral plate from superimposing and forming standing waves. This invention modifies the shape of the open-field metal plate to create a phase difference in the reflected waves generated at the edge of the field near the measuring antenna, thus reducing the generated standing waves and achieving a final result with a deviation from the ideal value far less than the limiting requirements.

Description

Technical Field

[0001] This utility model relates to the field of antenna technology, and in particular to an open field antenna for calibration. Background Technology

[0002] EMC measurement antennas are key equipment for electromagnetic compatibility testing and anechoic chamber performance evaluation. In addition to being closely related to calibration methods and measuring instruments, the measurement site plays a particularly important role in the traceability of antenna parameters.

[0003] Ideally, a standard EMC measurement antenna requires an open field with ideal grounding at the edges. However, due to the limitations of the actual field, the open field we constructed did not have ideal grounding. During the design simulation, it was found that reflections occurred at all four edges of the field, which superimposed standing waves near the receiving measurement antenna, thus affecting the field insertion loss and causing a large measurement deviation. Utility Model Content

[0004] To address the issue of large standing waves generated by reflections at the edge of the site, which leads to significant measurement deviations, this invention proposes an open field for antenna calibration. By optimizing the shape of the open field edge, the reflected waves generated at the site edge produce a phase difference near the measuring antenna, thereby reducing the generated standing waves and resulting in smaller measurement deviations.

[0005] The technical solution adopted in this utility model is to design an open field for antenna calibration, including a metal plate laid on the ground. The metal plate is a convex quadrilateral plate, and any two opposite sides of the quadrilateral plate are not parallel, thereby avoiding the superposition of electromagnetic waves reflected from the edges of the quadrilateral plate to form standing waves.

[0006] In some embodiments, all the vertices of the quadrilateral plate are 60 to 120 degrees.

[0007] In some embodiments, one of the apex angles of the quadrilateral plate is a right angle.

[0008] In some embodiments, each side of the quadrilateral plate is provided with an outwardly extending plate surface, and the extending plate surface is arched.

[0009] In some embodiments, the extended plate surface is semi-circular or semi-elliptical.

[0010] In some embodiments, the arched chord length of the extended plate surface is 1 / 4 to 1 / 2 of the side on which the extended plate surface is located.

[0011] In some embodiments, the maximum distance from the edge of the extended plate surface to the side where the extended plate surface is located is 1 / 8 to 1 / 2 of the length of the side.

[0012] In some embodiments, each side of the quadrilateral plate is provided with an outwardly extending plate surface, the extending plate surface being a polygon, and one side of the polygon coinciding with one side of the quadrilateral plate.

[0013] In some embodiments, the side of the polygon that coincides with the quadrilateral plate is 1 / 4 to 1 / 2 of the length of the side of the quadrilateral plate, and the maximum distance from the edge of the polygon to the side of the extended plate surface is 1 / 8 to 1 / 2 of the length of that side.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] This invention modifies the shape of the open-field metal plate to create a phase difference in the reflected waves generated at the edge of the field near the measuring antenna, thereby reducing the generated standing waves. This achieves the goal of making the final result deviate from the ideal value much less than the limit requirement, limiting the result deviation to within ±1.5dB. Attached Figure Description

[0016] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings. To illustrate the details and facilitate understanding of its principles, the drawings are not necessarily to scale, and similar reference numerals may describe similar components in different views. The accompanying drawings generally illustrate the embodiments discussed herein by way of example and not limitation. Wherein:

[0017] Figure 1 This is a schematic diagram of the open-field metal plate in this embodiment.

[0018] Figure 2 This is the insertion loss curve of the antenna.

[0019] Figure 3 This is a standing wave distribution diagram for a 20m x 30m open field.

[0020] Figure 4 The simulation results of standing waves in the open field of this embodiment are shown in the figure.

[0021] Figure 5 This is a comparison chart of the normalized curves of the open field and the 20m x 30m open field in Example 1.

[0022] Figure 6 This is a schematic diagram of Example 2.

[0023] In the diagram, 1 is the first side, 2 is the second side, 3 is the third side, 4 is the fourth side, and 5 is the extended side of the board. Detailed Implementation

[0024] The following are specific embodiments of this utility model, and the technical solution of this utility model will be further described with reference to the accompanying drawings. However, this utility model is not limited to these embodiments, and the following embodiments do not limit the utility model involved in the claims. In addition, all combinations of features described in the embodiments are not necessarily necessary for the solution of the utility model.

[0025] The principle and structure of this utility model will be described in detail below with reference to the accompanying drawings and embodiments.

[0026] Example 1

[0027] like Figure 1 As shown, an open field for antenna calibration includes a metal plate for laying on the ground. The metal plate is a convex quadrilateral plate, and any two opposite sides of the quadrilateral plate are not parallel, that is, the extensions of any two opposite sides intersect. The purpose is to break the parallel relationship of the sides of the traditional rectangular metal plate, thereby avoiding the superposition of electromagnetic waves reflected from the edges of the quadrilateral plate to form standing waves.

[0028] Each side of the quadrilateral plate is provided with an outwardly extending plate surface 5, thereby further preventing the electromagnetic waves reflected from the edges of the quadrilateral plate from superimposing to form standing waves. The extending plate surface is arched, for example, the extending plate surface can be a semicircle, or it can be a long ellipse or a short ellipse.

[0029] The arched chord length of the extended plate surface is 1 / 4 to 1 / 2 of the side containing the extended plate surface. When the extended plate surface is a semicircle, the chord length of the extended plate surface is the diameter of the semicircle. The maximum distance from the edge of the extended plate surface to the side containing the extended plate surface is 1 / 8 to 1 / 2 of the side length. When the extended plate surface is a semicircle, the maximum distance from the extended plate surface to the side containing the extended plate surface is the radius R of the semicircle.

[0030] The distances from the extended plates on the four sides to the vertices of the quadrilateral are not equal, making the structure of the metal plate more irregular, thereby preventing the electromagnetic waves reflected from the edges of the quadrilateral plate from superimposing to form standing waves.

[0031] Specifically, in this embodiment, the extended plate surface is semi-circular. For ease of explanation, the four sides of the quadrilateral plate are defined as first side 1, second side 2, third side 3, and fourth side 4. One of the vertex angles of the quadrilateral plate is a right angle, that is, the first side is perpendicular to the second side, and the angle between the third side and the fourth side is greater than 90 degrees.

[0032] The extended plate surface is located approximately at the middle of the first side and the second side. The extended plate surface is semi-circular, and the radius of the semi-circle is 1 / 7 to 1 / 5 of the length of the second side, preferably 1 / 6. The extended plate surface is semi-circular, and the radius of the semi-circle is 1 / 5 to 1 / 3 of the length of the first side, preferably 1 / 4.

[0033] The distance from the extended plate surface on the fourth side to the third plate surface is less than the distance from the first side, and the distance from the extended plate surface on the third side to the fourth plate surface is less than the distance from the second side. The angle between the third side and the fourth side is 60 to 120 degrees, preferably 110 degrees. The first side is 1 / 2 to 3 / 4 of the second side, preferably 2 / 3. The extended plate surface is semi-circular, and the distance from the center of the semi-circle on the fourth side to the third side is 2 / 5 to 1 / 2 of its distance to the first side.

[0034] Of course, it should be noted that when all the vertices of the quadrilateral plate are in the range of 60 to 120 degrees, it is also possible to make any one of the vertices of the quadrilateral plate not equal to 90 degrees. In this case, it also has a good effect of reducing the formation of standing waves by electromagnetic waves. As long as it can be ensured that any two opposite sides of the quadrilateral plate are not parallel, it has a certain effect of preventing the formation of standing waves. The specific solution given in this embodiment, in which one of the vertices is 90 degrees and the other vertices are not 90 degrees, is a better implementation method obtained through simulation and experiment.

[0035] In this embodiment, the length L1 of the first side of the quadrilateral plate is 20.2m, the length L2 of the second side is 30.3m, and the radius R of the semicircle extending from the plate surface is 5m. The distance L3 from the angle between the third and fourth sides to the first side is 25.9m, the distance L4 from the angle between the third and fourth sides to the second side is 17.6m, the distance L5 from the center of the semicircle on the third side to the second side is 11.11m, and the distance L6 from the center of the semicircle on the fourth side to the first side is 18.18m. The distance L7 between the center of the semicircle on the third side and the first side is 27.52m, the distance L8 between the center of the semicircle on the first side and the second side is 10.61m, the distance L9 between the center of the semicircle on the second side and the first side is 16.16m, and the distance L10 between the center of the semicircle on the fourth side and the third side is 18.38m.

[0036] When in use, the transmitting antenna and the receiving antenna are placed vertically at their respective positions above the quadrilateral plate.

[0037] like Figure 2The figure shows the insertion loss curves of the antenna. The solid line represents the insertion loss curve S21 under ideal ground conditions, the dotted line represents the insertion loss curve S21 under a 20m*30m rectangular open field, and the segmented dotted line represents the insertion loss curve S21 under the open field conditions in this embodiment. As can be seen from the figure, the open field under metallic ground conditions is not large enough, and the ground outside the open field will have a significant impact, causing abnormal fluctuations in the S21 curve.

[0038] The standing wave distribution diagram of the open field obtained by simulation software is as follows: Figure 3 As shown in the figure, standing wave clusters appear on the site. These clusters are formed by the superposition of reflections from the long and wide edges. The electric field of these standing waves is not a perfect standing wave because the boundary reflections in a two-dimensional plane cannot restrict the diffusion of the field within three-dimensional space, so they are not completely stationary. However, they do not propagate like traveling waves either. Some clusters fall between standing and traveling waves, exhibiting small positional shifts and then amplitude changes with phase at a certain position. Analysis of the causes and patterns of standing waves reveals that: analyzing the reflections from the wide and long edges separately shows that when there are an odd number of harmonic wavelengths within the metallic ground, harmonic peaks superimpose on the S21 curve; when there are an even number, troughs superimpose. Superimposing the reflections from the wide and long edges together yields the standing wave clusters generated by the complete finite-sized metallic ground. The narrowband harmonic superposition of the standing wave clusters on the S21 curve can be obtained by simply adding the sine curves from the wide and long edges; since the standing waves on the site are formed by the superposition of reflections from both the long and wide edges... If the long and short sides are not regular rectangles, then the boundary reflection will not form a stable standing wave cluster within the site, but will form a flowing standing wave cluster, thus reducing its impact on S21.

[0039] like Figure 4 The figure shown is a simulation result of standing waves in an open field according to this embodiment. It can be seen that due to the change in shape, the standing wave at the receiving and measuring antenna on the right is significantly weakened.

[0040] like Figure 5 The figure shows the normalized curves for the open field and the open field in this embodiment. It can be seen that by designing the shape of the four edges of the field, the reflected waves generated at the edges produce a phase difference near the measuring antenna, thereby reducing the generated standing waves and limiting the result deviation to within ±1.5dB.

[0041] Example 2

[0042] The extended plate surface can also be polygonal, with one side of the polygon coinciding with one side of the quadrilateral plate. The polygonal extended plate surface has a simple structure, is easy to manufacture and process, and still breaks the symmetry of the metal plate, thus preventing the generation of standing waves.

[0043] Furthermore, the side of the polygon that coincides with the quadrilateral plate is 1 / 4 to 1 / 2 of the length of the side of the quadrilateral plate on which the polygon is located, and the maximum distance from the edge of the polygon to the side of the quadrilateral plate on which the extended plate surface is located is preferably 1 / 8 to 1 / 2 of the length of the side of the quadrilateral plate.

[0044] like Figure 6 As shown in the figure, this embodiment illustrates the case where the extended plate surface is an irregular pentagon. Of course, the extended plate surface can also be other polygonal shapes, as long as it meets the above-mentioned size range, it will have a good effect on suppressing standing waves.

[0045] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

Claims

1. An open field for antenna calibration, comprising a metal plate laid on the ground, characterized in that: The metal plate is a convex quadrilateral plate, and any two opposite sides of the quadrilateral plate are not parallel, thereby preventing the electromagnetic waves reflected from the edges of the quadrilateral plate from superimposing to form standing waves.

2. The open field antenna calibration method according to claim 1, characterized in that, All the vertices of the quadrilateral plate are between 60 and 120 degrees.

3. The open field antenna calibration method according to claim 2, characterized in that, One of the vertex angles of the quadrilateral plate is a right angle.

4. The open field antenna calibration method according to claim 1, characterized in that, Each side of the quadrilateral plate is provided with an outwardly extending plate surface, and the extending plate surface is arched.

5. The open field antenna calibration method according to claim 4, characterized in that, The extended plate surface is semi-circular or semi-elliptical.

6. The open field antenna calibration according to claim 4, characterized in that, The arched chord length of the extended plate is 1 / 4 to 1 / 2 of the side on which the extended plate is located.

7. The open field antenna calibration according to claim 4, characterized in that, The maximum distance from the edge of the extended plate to the side where the extended plate is located is 1 / 8 to 1 / 2 of the length of the side.

8. The open field antenna calibration according to claim 1, characterized in that, Each side of the quadrilateral plate is provided with an outwardly extending plate surface, the extending plate surface being a polygon, and one side of the polygon coinciding with one side of the quadrilateral plate.

9. The open field antenna calibration according to claim 8, characterized in that, The side of the polygon that coincides with the quadrilateral plate is 1 / 4 to 1 / 2 of the length of the side of the quadrilateral plate, and the maximum distance from the edge of the polygon to the side of the extended plate surface is 1 / 8 to 1 / 2 of the length of that side.

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