Cosine triangle mixed concave sawtooth compact range reflecting surface

Abstract

The invention discloses a cosine and triangle mixed concave sawtooth compact range reflecting surface, the low-frequency limit of which can reach 14 times of wavelength, and the low-frequency limit of 25-30 times of wavelength of the traditional sawtooth compact range reflecting surface is greatly broken through. The reflecting surface comprises an edge part and a solid part, the edge part is a combination of cosine sawteeth and triangular sawteeth, the solid part is concave inwards, and any sawtooth shape is realized by changing a mixing coefficient of the cosine sawteeth, the triangular sawteeth and the solid part. The cosine sawtooth edge is proved to have excellent low-frequency performance, the concave solid part can increase the effective area of the reflecting surface, the two parts are combined, the aperture utilization rate and the low-frequency performance of the compact range are further improved, and the method becomes a key technical means for breaking through the low-frequency limit of the sawtooth compact range.

Description

Technical Field

[0001] The invention belongs to the technical field of edge processing of a compact field system reflector surface, and in particular relates to a cosine-triangle mixed concave sawtooth compact field reflector surface. Background Art

[0002] The compact field reflection surface is usually a rotating parabola, which can convert the spherical wave emitted from the feed source into a plane wave, thereby satisfying the far-field conditions for relevant measurements. However, the actual reflection surface size is limited, and the propagation of electromagnetic waves cannot be completely processed optically. Therefore, a diffraction field will be generated at the edge of the reflection surface, which will greatly destroy the uniformity of the quiet zone plane wave. 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, edge diffraction must be controlled as much as possible. In order to control edge diffraction, a common practice is to perform special processing on the edge of the reflection surface. The mainstream processing technology in the industry is sawtooth edge processing, but it still has the disadvantages of a narrow operating frequency band, especially poor performance at low frequencies. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes a cosine-triangle mixed concave sawtooth compact field reflection surface. The concave compact field reflection surface has the inherent characteristic of controlling edge diffraction away from the quiet zone, which can effectively improve the low-frequency performance of the compact field. The sawtooth is designed with cosine to increase the area of ​​the sawtooth, and the performance is significantly better than that of ordinary linear sawtooth. The combination of the two significantly improves the aperture utilization and low-frequency performance of the compact field.

[0004] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical scheme:

[0005] A cosine-trigonometric mixed concave sawtooth compact field reflector, the reflector comprising a coaxially superimposed edge sawtooth portion and a concave solid portion, wherein:

[0006] The edge sawtooth portion is a mixed sawtooth formed by superimposing a triangular sawtooth and a cosine sawtooth;

[0007] The concave solid part is obtained by uniformly concave the four sides of the square toward the center;

[0008] The mixed sawtooth comprises n sawtooths which are arranged non-uniformly along the periphery of the concave solid part. The sawtooth size is smaller as it is closer to the horizontal or vertical symmetry axis of the concave solid part, and the sawtooth size is larger as it is closer to the diagonal of the concave solid part.

[0009] Furthermore, the cosine sawtooth shape of the edge sawtooth portion is determined by the following equation:

[0010] (1)

[0011] Among them, ρc is the polar diameter in the polar coordinate system, φ is the polar angle, n is the number of cosine sawtooth, H is the cosine sawtooth height, and m is the cosine sawtooth width.

[0012] Furthermore, the triangular serrations of the edge serration portion are determined by the following equation:

[0013] (2)

[0014] Among them, ρ s is the polar diameter in the polar coordinate system, φ is the polar angle, h is the height of the triangular sawtooth, n is the number of triangular sawtooth teeth, the sawtooth function represents the generation of triangular sawtooth, and w is the parameter that controls the shape of the triangular sawtooth.

[0015] Furthermore, the height and width of the entire sawtooth of the edge sawtooth portion are jointly determined by the cosine sawtooth height H, the cosine sawtooth width m, and the triangular sawtooth height h.

[0016] Furthermore, the concave solid part has the same distance from any point on its edge to the outer square boundary in any ray direction from the center outward.

[0017] Furthermore, for any point (x0, y0) on the square, let the angle between the line from the point to the origin and the positive semi-axis be θ, then the parametric equation of the concave solid part is:

[0018] (4)

[0019] (5)

[0020] Among them, L is a parameter that determines the shape of the concave solid part. The larger L is, the greater the concave degree of the concave solid part is.

[0021] Furthermore, we rewrite equations (4) and (5) into parametric equations: , add the cosine sawtooth, triangular sawtooth and concave solid part in the polar coordinate system, introduce the proportional coefficient r, and get the equation of the entire reflection surface for:

[0022] (6)

[0023] in, and are the polar coordinate equations of the edge serration part and the concave solid part, respectively. and They are the cosine sawtooth and triangular sawtooth of the edge sawtooth part, and r is the mixing ratio coefficient.

[0024] Furthermore, the proportional coefficient r is used to make the outer dimension of the finally generated reflection surface rectangular or square.

[0025] Furthermore, the shape of the reflecting surface is determined by six parameters: the number of saw teeth n, the cosine saw tooth height H, the cosine saw tooth width m, the triangle saw tooth sharpness parameter h, the concave solid part parameter L and the proportional coefficient r.

[0026] The beneficial effects of the present invention are:

[0027] The present invention cleverly changes the sawtooth layout by rounding the traditional straight line sawtooth and distributing the sawtooth with equal length around the geometric center of the reflection surface, optimizing the inner edge profile of the sawtooth of the traditional rectangular straight line into a concave cosine-shaped profile, increasing the area of ​​the sawtooth and the entity of the reflection surface, effectively controlling the edge diffraction field, and significantly improving the low-frequency performance of the compact field. Compared with the traditional sawtooth edge reflection surface, the cosine-triangular mixed concave sawtooth compact field reflection surface proposed by the present invention can achieve a lower operating frequency, while taking into account the high-frequency performance, it overcomes the disadvantage of the poor low-frequency performance of the traditional sawtooth edge compact field. In addition, it also has the advantages of parameter modeling and easy optimization design. The number of sawtooth, height, width, entity area of ​​the reflection surface, etc. can be arbitrarily changed, and any optimization design can be performed according to needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The cosine sawtooth of the edge sawtooth portion of the present invention;

[0029] Figure 2 The triangular saw teeth of the edge sawtooth portion of the present invention;

[0030] Figure 3 The edge serration part of the present invention;

[0031] Figure 4 It is the concave entity part of the present invention;

[0032] Figure 5 It is a schematic diagram of the projection composition of a cosine-trigonometric mixed concave sawtooth compact field reflection surface of the present invention;

[0033] Figure 6 This is a schematic diagram of the application of a cosine-trigonometric mixed concave sawtooth compact field reflector surface of the present invention;

[0034] Figure 7 A schematic diagram of the amplitude distribution and peak-to-peak amplitude of a cosine-triangle mixed concave sawtooth compact field reflecting surface in the front section of the quiet zone of the present invention;

[0035] Figure 8 A schematic diagram of the phase distribution and phase peak-to-peak value of a cosine-triangle mixed concave sawtooth compact field reflecting surface in the front section of the quiet zone of the present invention;

[0036] Fig. 9 A schematic diagram of the amplitude distribution and peak-to-peak amplitude of a cross section of a cosine-triangle mixed concave sawtooth compact field reflecting surface in a quiet zone of the present invention;

[0037] Fig.10 A schematic diagram of the phase distribution and phase peak-to-peak value of a cross section of a cosine-triangle mixed concave sawtooth compact field reflecting surface in a quiet zone of the present invention;

[0038] Fig.11 A schematic diagram of the amplitude distribution and peak-to-peak amplitude of a cosine-triangle mixed concave sawtooth compact field reflecting surface in the rear section of the quiet zone of the present invention;

[0039] Fig.12 A schematic diagram of the phase distribution and phase peak-to-peak value of a cosine-triangle mixed concave sawtooth compact field reflecting surface in the rear section of the quiet zone of the present invention;

[0040] Fig.13 It is a schematic diagram of the normalized amplitude distribution of the cross-line cross-sections of the cosine-trigonometric mixed concave sawtooth compact field reflection surface in the three quiet zones center;

[0041] Fig.14 It is a schematic diagram of the normalized phase distribution of the cross-line cross-sections of the cosine-trigonometric hybrid concave sawtooth compact field reflection surface at the center of three quiet zones of the present invention;

[0042] Fig.15 It is a schematic diagram of the normalized amplitude distribution of the vertical sections of the cross lines at the center of three quiet zones of a cosine-trigonometric mixed concave sawtooth compact field reflection surface of the present invention;

[0043] Fig.16 It is a schematic diagram of the normalized phase distribution of the vertical sections of the cross lines at the centers of three quiet zones of a cosine-triangle mixed concave sawtooth compact field reflection surface of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] 1. Cosine sawtooth; 2. Triangular sawtooth; 3. Edge sawtooth part; 4. Concave solid part; 5. Reflection surface; 6. Feed source; 301. Front section of quiet zone; 302. Middle section of quiet zone; 303. Back section of quiet zone; 7. Compact field darkroom. DETAILED DESCRIPTION

[0045] The present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0046] like Figure 1As shown, the present invention discloses a cosine-triangle mixed concave sawtooth compact field reflector, wherein the reflector 5 comprises an edge sawtooth portion 3 and a concave solid portion 4 coaxially superimposed. The edge sawtooth portion 3 of the reflector 5 is a combination of a cosine sawtooth 1 and a triangular sawtooth 2, and is characterized in that the cosine sawtooth 1 controls the sawtooth height and sawtooth width, and the triangular sawtooth 2 controls the sharpness of the edge sawtooth. The concave solid portion 4 can increase the effective area of ​​the reflector on the one hand, and on the other hand, it is superimposed with the edge sawtooth portion 3 so that the sawtooth near the diagonal extends outward. Specifically, the reflector 5 is a rotating parabola, and along the axial orthographic projection of the rotating parabola, the projection contour is rectangular or square. The n sawtooths included in the edge sawtooth portion 3 are arranged non-uniformly in the inclined direction. The sawtooth size closer to the horizontal or vertical axis of symmetry is smaller and arranged along the vertical or horizontal direction, and the sawtooth size closer to the diagonal is larger and has a preset angle with the vertical or horizontal direction.

[0047] Furthermore, the concave solid portion 4 occupies half of the overall size of the reflecting surface 5, and this ratio can be adjusted arbitrarily as needed.

[0048] Furthermore, in order to ensure that the sawtooth shape of the reflecting surface 5 is reasonable, the number of sawtooth is an integer multiple of 2 or 4. Preferably, the number of teeth is greater than 16.

[0049] Furthermore, the concave solid part 4 is a concave shape constructed inside the square. From the center of the concave shape to any ray direction outward, the distance from any point on its edge to the outer square boundary remains unchanged. Referring to equations (4) and (5), it can be seen that for any given θ, that is, any ray direction, the point on the concave shape (x m , y m ) to the point (x0, y0) on the square is always L, that is, the distance from a point on the concave shape to the external square along any ray direction is the same, which is always L.

[0050] Furthermore, the edge portion of the reflecting surface is a mixed sawtooth with an equal circumference layout.

[0051] The construction principles of each component are introduced below.

[0052] like Figure 2 As shown, in the polar coordinate system, the shape of the cosine sawtooth 1 of the edge sawtooth portion 3 is determined by the following equation:

[0053] (1)

[0054] Among them, ρ c is the polar diameter in the polar coordinate system, ρ c>1, φ is the polar angle, 0≤φ≤2π, n is the number of saw teeth, which can be set to any even number as needed. H and m determine the height and width of cosine saw tooth 1. The larger H is, the higher the saw tooth is, and the larger m is, the wider the saw tooth is. Figure 2 The schematic diagram of cosine sawtooth 1 normalization under different values ​​of n, m and H is given. Figure 3 As shown, in the polar coordinate system, the triangular sawtooth 2 of the edge sawtooth portion 3 is determined by the following equation:

[0055] (2)

[0056] Among them, ρ s is the polar diameter in the polar coordinate system, ρ s >1, φ is the polar angle, 0≤φ≤2π, h is the height of triangular sawtooth 2, n is the number of sawtooth, sawtooth function represents the generation of triangular sawtooth 2, where w is the parameter controlling the shape of triangular sawtooth 2, here w=0.5, indicating that the generated triangular sawtooth 2 is an isosceles triangle, by changing the value of h, triangular sawtooth 2 of any height can be generated. Figure 3 A normalized schematic diagram of triangular sawtooth 2 with different values ​​of n and h is given. In particular, since the cosine sawtooth and triangular sawtooth need to be superimposed and each sawtooth corresponds to each other, the number of sawtooths of the two is the same, that is, both are expressed as n in the formula.

[0057] like Figure 4 As shown, the edge serration part 3 of the reflecting surface 5 is composed of a cosine serration 1 and a triangular serration 2, which can be expressed as the sum of equations (1) and (2) in the polar coordinate system, that is:

[0058] (3)

[0059] In order to ensure superposition in the polar coordinate system, the number of saw teeth n in equations (1) and (2) must be consistent, that is, the total number of saw teeth on the entire reflective surface 5. Among them, H determines the height of the reflective surface saw teeth, which is recommended to be greater than 1, m determines the width of the reflective surface saw teeth, which is recommended to be a positive integer greater than 2, and h determines the sharpness of the reflective surface saw teeth, which is recommended to be less than 1. Since the cosine saw tooth height H is larger than the triangular saw tooth height h, the final saw tooth height mainly depends on H. Any saw tooth can be designed by adjusting the above parameters. Figure 4 The normalized reflection surface edge portion composed of cosine sawtooth 1 and triangle sawtooth 2 is given when the number of sawtooth is 16 and 24 respectively.

[0060] like Figure 5 As shown, the basic shape of the concave solid part 4 of the reflecting surface 5 is determined by a square. For any point (x0, y0) on the square with a side length of 2, assuming that the angle between the line connecting the arbitrary point to the origin and the positive semi-axis is θ, the parametric equation of the concave solid is:

[0061] (4)

[0062] (5)

[0063] Among them, θ is a parameter of the parametric equation, and its range is 0≤θ≤2π. L is a parameter that determines the shape of the concave solid part 4. The larger L is, the greater the concave degree of the concave solid part 4 is. It is recommended that L is greater than 0 and less than 1. Figure 4 A schematic diagram of the normalized entity part with different values ​​of L is given.

[0064] Rewrite equations (4) and (5) into parametric equations , add the cosine sawtooth 1, the triangular sawtooth 2 and the concave solid part 4 in the polar coordinate system. In order to ensure that the outline of the reflection surface 5 after addition is a square, the proportional coefficient r is introduced, so that the equation of the entire reflection surface 5 is obtained: for,

[0065] (6)

[0066] in, and are the polar coordinate equations of the edge serration part 3 and the concave solid part 4, respectively. and They are the cosine sawtooth 1 and the triangular sawtooth 2 of the edge sawtooth part 3, and r is the mixed proportional coefficient, which ensures that the aperture of the compact field reflection surface is rectangular or square, that is, the overall shape of the reflection surface 5 is determined by the cosine sawtooth 1, the triangular sawtooth 2 and the concave solid part 4. After proper optimization, the low-frequency limit of the reflection surface can reach 14 times the wavelength, effectively controlling the edge diffraction away from the quiet zone, greatly improving the performance of the compact field, especially the low-frequency performance.

[0067] From equations (1) to (6), it can be seen that the shape of the reflective surface 5 is uniquely determined by the number of saw teeth n, the cosine saw tooth height parameter H, the cosine saw tooth width parameter m, the triangular saw tooth height parameter h, the depth parameter L of the concave solid part 4, and the proportional coefficient r. By properly adjusting and optimizing the six parameters, a reflective surface of any shape can be obtained.

[0068] Figure 6This is a schematic diagram of the application of a cosine-trigonometric hybrid concave sawtooth compact field reflector of the present invention. In the compact field darkroom 7, based on the excitation of the feed source 6, the aperture projection of the reflector 5 is a square, and the profile is a parabola, which is projected to the front section 301 of the quiet zone, the middle section 302 of the quiet zone, and the rear interface 303 of the quiet zone in sequence. The reflector 5 has a size of 2m×2m, a focal length of 2m, and a total of 24 sawteeth on the reflector. Without loss of generality, it can also be designed as any other number of sawteeth as needed. The size of the concave entity part 4 is 50% of the overall size of the reflector 5. The distances from the front, middle, and rear sections 301, 302, and 303 of the quiet zone to the virtual vertex of the reflector 1 are 2.1m, 2.55m, and 3m respectively. The statistical quiet zone is a circular area with a diameter of 0.9m. In order to illustrate the performance of the reflecting surface 5, especially the low-frequency performance, its quiet zone field at 14λ is simulated, including the results on the cross section and the center cross line, where the amplitude is normalized by the maximum value on the cross section or the cross section, and the phase is normalized by the phase at the center of the coordinate on the cross section or the cross section.

[0069] Common compact quiet zone indicators include surface amplitude and phase peak-to-peak values, with typical values ​​of amplitude peak-to-peak less than 2dB and phase peak-to-peak less than 15°. Figure 7 , Fig. 9 , Fig.11 They are respectively the amplitude distribution of the reflecting surface in the front, middle and rear sections of the quiet zone and the schematic diagram of the amplitude peak-to-peak value; Figure 8 , Fig.10 , Fig.12 They are the phase distribution and phase peak-to-peak diagram of the reflection surface in the front, middle and rear sections of the quiet zone respectively; Fig.13 , Fig.15 They are schematic diagrams of normalized amplitude distribution of the cross-line transverse section and vertical section of the reflection surface at the center of the three quiet zones; Fig.14 , Fig.16 They are schematic diagrams of normalized phase distribution of the cross-section and vertical section of the reflection surface at the center of the three quiet zones; Figure 7 to Figure 13 The results show that the peak-to-peak value of the electric field amplitude and the peak-to-peak value of the phase in the quiet zone of the sawtooth reflector proposed in the present invention fully meet the typical evaluation indicators of the compact field at a low frequency of 14λ. The cosine-triangle hybrid concave sawtooth compact field proposed in the present invention can achieve a low-frequency limit of 14λ, which is much lower than the low-frequency limit of the sawtooth edge compact field generally believed, and is of great significance for ensuring the test of the low-frequency band.

[0070] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A cosine-triangle mixed concave sawtooth compact field reflector, characterized in that: The reflecting surface includes a coaxially superimposed edge serrated portion and an inner concave solid portion, wherein: The edge sawtooth portion is a mixed sawtooth formed by superimposing a triangular sawtooth and a cosine sawtooth; The concave solid part is obtained by uniformly concave the four sides of the square toward the center; The mixed sawtooth comprises n sawtooths arranged non-uniformly along the periphery of the concave solid part, wherein the sawtooth size is smaller as it is closer to the horizontal or vertical symmetry axis of the concave solid part, and the sawtooth size is larger as it is closer to the diagonal of the concave solid part.

2. The cosine-triangle mixed concave sawtooth compact field reflector according to claim 1, characterized in that: The cosine sawtooth shape of the edge sawtooth portion is determined by the following equation: （1） Among them, ρ c is the polar diameter in the polar coordinate system, φ is the polar angle, n is the number of cosine sawtooth, H is the cosine sawtooth height, and m is the cosine sawtooth width.

3. The cosine-triangle mixed concave sawtooth compact field reflector according to claim 1, characterized in that: The triangular serrations of the edge serration portion are determined by the following equation: （2） Among them, ρ s is the polar diameter in the polar coordinate system, φ is the polar angle, h is the height of the triangular sawtooth, n is the number of triangular sawtooth teeth, the sawtooth function represents the generation of triangular sawtooth, and w is the parameter that controls the shape of the triangular sawtooth.

4. The cosine-trigonometric mixed concave sawtooth compact field reflector according to claim 1, characterized in that: The height and width of the entire sawtooth of the edge sawtooth portion are jointly determined by the cosine sawtooth height H, the cosine sawtooth width m, and the triangular sawtooth height h.

5. The cosine-triangle mixed concave sawtooth compact field reflector according to claim 1, characterized in that: The concave solid part has the same distance from any point on its edge to the outer square boundary in any ray direction from the center outward.

6. The cosine-triangle mixed concave sawtooth compact field reflector according to claim 1, characterized in that: For any point (x0, y0) on the square, let the angle between the line from the point to the origin and the positive semi-axis be θ, then the parametric equation of the concave solid part is: （4） （5） Among them, L is a parameter that determines the shape of the concave solid part. The larger L is, the greater the concave degree of the concave solid part is.

7. The cosine-trigonometric mixed concave sawtooth compact field reflector according to claim 6, characterized in that: Rewrite equations (4) and (5) into parametric equations , add the cosine sawtooth, triangular sawtooth and concave solid part in the polar coordinate system, introduce the proportional coefficient r, and get the equation of the entire reflection surface for: （6） in, and are the polar coordinate equations of the edge serration part and the concave solid part, respectively. and They are the cosine sawtooth and triangular sawtooth of the edge sawtooth part, and r is the mixing ratio coefficient.

8. The cosine-trigonometric mixed concave sawtooth compact field reflector according to claim 7, characterized in that: The proportional coefficient r is used to make the outer dimension of the finally generated reflection surface rectangular or square.

9. The cosine-triangle mixed concave sawtooth compact field reflector according to claim 1, characterized in that: The shape of the reflection surface is determined by six parameters: the number of saw teeth n, the cosine saw tooth height H, the cosine saw tooth width m, the triangle saw tooth sharpness parameter h, the concave solid part parameter L and the proportional coefficient r.

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