A fully polarized omnidirectional matched retroreflector based on optical void materials

Abstract

This invention discloses a fully polarized omnidirectional matched retroreflector based on optical void materials. It mainly consists of a metal shell, which is a concave block. The two convex ends of the metal shell face the incident direction of external electromagnetic waves and serve as the input and output ends of the fully polarized omnidirectional matched retroreflector, respectively. Hollow TM wave air tunnels and TE wave air tunnels are respectively formed inside the metal shell. Both the TM wave and TE wave air tunnels are concave blocks with the same shape as the metal shell. The TM wave and TE wave air tunnels connect from the input end to the output end of the fully polarized omnidirectional matched retroreflector. This invention has a simple structure and can be implemented using only metal. It can work for fully polarized incident waves at all angles and can be widely used in radar target modeling and sensing fields.

Description

Technical Field

[0001] This invention belongs to the field of artificial electromagnetic media, specifically relating to a fully polarized omnidirectional matching retroreflector based on optical void materials. Background Technology

[0002] Retroreflectors reflect incident light back to its source. The reflected light is parallel to the emission direction but in the opposite direction. A pyramidal retroreflector is a device that reflects incident electromagnetic waves at a large angle. Traditional pyramidal retroreflectors use two or three spatial metal plates (e.g., dihedrals or trihedrals) to reflect the incident wave. Pyramidal retroreflectors have wide applications in laser tracking, optical communication, radar target modeling, and sensing, among other fields.

[0003] In recent years, flexible pyramidal back reflectors have attracted widespread attention, and some related devices have been studied in depth, such as mechanically flexible pyramidal back reflectors and planar metasurface reflectors. However, planar back reflectors that simultaneously possess wide incident angles and significant operating bandwidths for fully polarized incident wave operation still face many technical challenges. Summary of the Invention

[0004] To address the problems existing in the background technology, the present invention provides a fully polarized omnidirectional matched retroreflector based on optical void material. It constructs a concave metal with air tunnel to meet the conditions of an effective medium in terms of dielectric constant and magnetic permeability, and makes the propagation speed of a specific frequency electromagnetic wave incident from the input end infinite in the medium. The material formed by the present invention can reflect the fully polarized wave back along the incident direction without any phase change.

[0005] The technical solution adopted in this invention is as follows:

[0006] The fully polarized omnidirectional matched retroreflector is mainly composed of a metal shell, which is a concave block. The two convex end faces of the metal shell face the incident direction of the external electromagnetic wave and serve as the input and output ends of the fully polarized omnidirectional matched retroreflector, respectively. Hollow TM wave air tunnel groups and TE wave air tunnel groups are respectively formed inside the metal shell. The entire TM wave air tunnel group and the entire TE wave air tunnel group are concave blocks with the same shape as the metal shell. The TM wave air tunnel group and the TE wave air tunnel group are connected from the input end to the output end of the fully polarized omnidirectional matched retroreflector. The input end and output end of the TM wave air tunnel group are located on the plane where the input end and output end of the fully polarized omnidirectional matched retroreflector are located, respectively. The input end and output end of the TE wave air tunnel group are located on the plane where the input end and output end of the fully polarized omnidirectional matched retroreflector are located, respectively. The geometric center of the vertical cross-section of the TM wave air tunnel group and the geometric center of the vertical cross-section of the TM wave air tunnel group are on the same straight line.

[0007] The metal casing is made of copper, silver, gold, aluminum, or tungsten.

[0008] The TM wave air tunnel group includes several I-shaped air tunnels evenly spaced from the center of the concave part of the metal shell outwards. The horizontal cross-section of each I-shaped air tunnel is concave, and the vertical cross-section of each I-shaped air tunnel is two "I" shapes. The input end and output end of each I-shaped air tunnel are located on the plane where the input end and output end of the fully polarized omnidirectional matched retroreflector are located, respectively. Each I-shaped air tunnel is connected from the input end to the output end of the fully polarized omnidirectional matched retroreflector.

[0009] Each of the I-shaped air tunnels has a vertical cross-section comprising a long, vertically arranged strip-shaped air tunnel and two short, horizontally arranged strip-shaped air tunnels symmetrically arranged on both sides of the long air tunnel. The vertical lengths of the long air tunnels of different I-shaped air tunnels are all equal. The two horizontal lengths of the two short air tunnels of the I-shaped air tunnel are equal, while the horizontal lengths of the short air tunnels of different I-shaped air tunnels are not equal to each other.

[0010] The TE wave air tunnel group includes several wave-shaped air tunnels evenly spaced from the center of the concave part of the metal shell outwards. Each wave-shaped air tunnel is mainly composed of a W-shaped air tunnel on the upper side and an M-shaped air tunnel on the lower side. The vertical cross-section of each W-shaped air tunnel is two "W" shapes, and the vertical cross-section of each M-shaped air tunnel is two "M" shapes. The horizontal cross-section of each W-shaped air tunnel and each M-shaped air tunnel is concave. The input and output ends of each W-shaped air tunnel are located on the plane where the input and output ends of the fully polarized omnidirectional matched retroreflector are located, respectively. The input and output ends of each M-shaped air tunnel are located on the plane where the input and output ends of the fully polarized omnidirectional matched retroreflector are located, respectively. Each W-shaped air tunnel is connected from the input end to the output end of the fully polarized omnidirectional matched retroreflector, and each M-shaped air tunnel is connected from the input end to the output end of the fully polarized omnidirectional matched retroreflector.

[0011] Each of the W-shaped air tunnels has a vertical cross-section comprising seven straight air tunnels connected end-to-end in sequence; each of the M-shaped air tunnels has a vertical cross-section comprising seven straight air tunnels connected end-to-end in sequence.

[0012] The horizontal lengths of the W-shaped and M-shaped air tunnels in the wave-shaped air tunnels are equal; the horizontal lengths of the W-shaped air tunnels in different wave-shaped air tunnels are not equal, and the horizontal lengths of the M-shaped air tunnels in different wave-shaped air tunnels are not equal.

[0013] The geometric center of the vertical cross-section of the I-shaped air tunnel and the geometric center of the vertical cross-section of the wave-shaped air tunnel are on the same straight line.

[0014] A wave-shaped air tunnel is arranged between each pair of adjacent I-shaped air tunnels.

[0015] The width of each of the wave-shaped air tunnels and each of the I-shaped air tunnels is equal, that is, the width of each straight strip in the vertical cross-section is the same.

[0016] In this invention, the propagation direction of the fully polarized omnidirectional matched retroreflector is such that the external electromagnetic wave from the external device enters the input end of the fully polarized omnidirectional matched retroreflector from the incident direction, is transmitted along the concave shape of the fully polarized omnidirectional matched retroreflector, and is output from the output end of the fully polarized omnidirectional matched retroreflector and received by the external device.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. This invention can reflect a fully polarized wave of a specified operating frequency incident from any incident direction back to its original direction.

[0019] 2. The present invention has a simple structure that can be realized with only metal, and it is perfectly matched with free space. It can be widely used in various military fields such as radar, target modeling and sensing. Attached Figure Description

[0020] Figure 1 This is a three-dimensional diagram of the structure of the present invention;

[0021] Figure 2 This is a three-dimensional perspective view of the structure of the present invention;

[0022] Figure 3 This is a schematic diagram of the porous metal structure in Example 2;

[0023] Figure 4 The figure shows the simulation results of the S-parameters for vertical incidence in Example 2;

[0024] Figure 5 This is a simulation result diagram of the vertical incident field in Example 2. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] like Figure 1 and Figure 2As shown, the fully polarized omnidirectional matched retroreflector of this embodiment 1 is mainly composed of a metal shell. The metal shell is a concave block, and the end faces of the two convex parts of the metal shell face the incident direction of the external electromagnetic wave and serve as the input and output ends of the fully polarized omnidirectional matched retroreflector, respectively. The interior of the metal shell is provided with a hollow, interconnected TM wave air tunnel group and a interconnected TE wave air tunnel group. The entire TM wave air tunnel group and the entire TE wave air tunnel group are both concave blocks with the same shape as the metal shell. The TM wave air tunnel group and the TE wave air tunnel group are connected from the input end to the output end of the fully polarized omnidirectional matched retroreflector. The input end and output end of the TM wave air tunnel group are located on the plane where the input end and output end of the fully polarized omnidirectional matched retroreflector are located, respectively. The input end and output end of the TE wave air tunnel group are located on the plane where the input end and output end of the fully polarized omnidirectional matched retroreflector are located, respectively. The geometric center of the vertical cross-section of the TM wave air tunnel group and the geometric center of the vertical cross-section of the TM wave air tunnel group are on the same straight line.

[0027] In practice, the metal casing is made of copper, silver, gold, aluminum, or tungsten.

[0028] The TM wave air tunnel group includes several I-shaped air tunnels that are evenly spaced from the center of the concave part of the metal shell outwards. The horizontal cross-section of each I-shaped air tunnel is concave, and the vertical cross-section of each I-shaped air tunnel is two spaced "I" shapes. The input and output ends of each I-shaped air tunnel are located on the planes where the input and output ends of the fully polarized omnidirectional matched retroreflector are located, respectively. Each I-shaped air tunnel is connected from the input end to the output end of the fully polarized omnidirectional matched retroreflector.

[0029] The planes containing the input and output ends of the fully polarized omnidirectional matched retroreflector are perpendicular to the incident direction of the external electromagnetic wave. The vertical cross-section is the plane containing the input and output ends of the fully polarized omnidirectional matched retroreflector, and the horizontal cross-section is the plane perpendicular to the vertical cross-section.

[0030] Each I-shaped air tunnel's vertical cross-section includes a long, vertically arranged strip-shaped air tunnel and two short, horizontally arranged strip-shaped air tunnels symmetrically positioned on either side of the long air tunnel. The vertical lengths of the long air tunnels in different I-shaped air tunnels are all equal. The two horizontal lengths of the two short air tunnels in each I-shaped air tunnel are equal, while the horizontal lengths of the short air tunnels in different I-shaped air tunnels are not equal.

[0031] The horizontal direction is the direction of the line connecting the vertical distance between the input and output ends of the I-shaped air tunnel; the vertical direction is the direction perpendicular to the line connecting the vertical distance between the input and output ends of the I-shaped air tunnel; the vertical length is the distance in the vertical direction, and the horizontal direction is the distance in the horizontal direction.

[0032] The TE wave air tunnel group comprises several wave-shaped air tunnels evenly spaced from the center of the concave part of the metal shell outwards. Each wave-shaped air tunnel is mainly composed of a W-shaped air tunnel on the upper side and an M-shaped air tunnel on the lower side, symmetrically arranged. The vertical cross-section of each W-shaped air tunnel is two spaced "W" shapes, and the vertical cross-section of each M-shaped air tunnel is two spaced "M" shapes. The horizontal cross-section of each W-shaped and M-shaped air tunnel is concave. The input and output ends of each W-shaped air tunnel are located on the planes where the input and output ends of the fully polarized omnidirectional matched retroreflector are located, respectively. The input and output ends of each M-shaped air tunnel are located on the planes where the input and output ends of the fully polarized omnidirectional matched retroreflector are located, respectively. Each W-shaped air tunnel connects to the output end of the fully polarized omnidirectional matched retroreflector, and each M-shaped air tunnel connects to the output end of the fully polarized omnidirectional matched retroreflector.

[0033] Each W-shaped air tunnel has a vertical cross-section consisting of seven straight air tunnels connected end-to-end in sequence; each M-shaped air tunnel has a vertical cross-section consisting of seven straight air tunnels connected end-to-end in sequence.

[0034] In practice, the vertical cross-section of each W-shaped air tunnel includes four long air tunnels arranged vertically and three short air tunnels arranged horizontally. The four long air tunnels are evenly spaced along the same horizontal direction, and a short air tunnel connects two adjacent long air tunnels. The two adjacent short air tunnels are staggered, so that the vertical cross-section of the W-shaped air tunnel forms a serpentine connection.

[0035] Each M-shaped air tunnel's vertical cross-section comprises four long air tunnels arranged vertically and three short air tunnels arranged horizontally. The four long air tunnels are evenly spaced along the same horizontal direction, and each adjacent long air tunnel is connected by a short air tunnel. Adjacent short air tunnels are staggered, resulting in a serpentine connection in the vertical cross-section that forms the W-shaped air tunnel. The staggered arrangement means that the tunnels are not in the same horizontal direction.

[0036] The horizontal lengths of the W-shaped and M-shaped air tunnels in each wave-shaped air tunnel are equal; the horizontal lengths of the W-shaped air tunnels in different wave-shaped air tunnels are not equal, and the horizontal lengths of the M-shaped air tunnels in different wave-shaped air tunnels are not equal.

[0037] The geometric center of the vertical cross-section of the I-shaped air tunnel and the geometric center of the vertical cross-section of the wave-shaped air tunnel are on the same straight line.

[0038] The geometric center point is the center point of an I-shaped or wavy geometric figure.

[0039] A wave-shaped air tunnel is arranged between each pair of adjacent I-shaped air tunnels.

[0040] The width of each wavy air tunnel and each I-shaped air tunnel is equal, meaning that the width of each vertical strip is the same.

[0041] The tunnel width is the width of the long air tunnel / short air tunnel / air tunnel of each cuboid.

[0042] In this embodiment, the propagation direction of the fully polarized omnidirectional matched retroreflector is such that the external electromagnetic wave from the external device enters the input end of the fully polarized omnidirectional matched retroreflector from the incident direction, is transmitted along the concave shape of the fully polarized omnidirectional matched retroreflector, and is output from the output end of the fully polarized omnidirectional matched retroreflector and received by the external device.

[0043] The TM wave air tunnel group is for TM waves, and the TE wave air tunnel group is for TE waves.

[0044] Example 2

[0045] The working principle of this invention is as follows: According to the principle of transformation optics, when there is an anisotropic material, the dielectric constant and magnetic permeability satisfy ε=μ={Δ,Δ,1 / Δ}, where Δ represents a constant. When Δ→0, the material can be regarded as an optical void. When a light wave passes through it, the speed of light can be considered infinite, with no phase accumulation. The electromagnetic parameters required for a perfect optical void material are difficult to achieve; therefore, we can consider... Figure 3 The porous metal structure shown is used to simulate optical void materials at specific frequencies. The square holes have a side length of *a*, and the distance between the metal holes is *d*, as shown below. Figure 3 As shown in (a). When the operating wavelength λ satisfies λ>>d and a / d→0, the effective dielectric constant and permeability of the porous metal structure can be considered as… This refers to optical void materials. Their operating frequency is the cutoff frequency of a square waveguide with side length *a* filled with dielectric. However, this structure often requires a high-refractive-index material to fill the void, which is not easily achievable in practical applications, especially at high frequencies. To solve this problem, a cross-section of *a* can be considered. x ×a y , where a x <<a y or a x >>a y If a narrow rectangular hole is used instead of a square hole, then there is no need to fill it with a high refractive index material, such as... Figure 3 As shown in (b).

[0046] Based on the above theory, the concave metal shell of this invention, featuring I-shaped and wave-shaped air tunnels, can achieve perfect transmission performance, with the operating frequency being the cutoff frequency of the tunnels. At this point, the radio frequency transmission efficiency of the fully polarized wave is approximately 1, and there is no phase change. According to the above description, a fully polarized omnidirectional matched retroreflector is constructed using an air tunnel structure. By simulating optical void materials at the operating frequency, the reflected electromagnetic wave is made parallel to and opposite to the incident wave.

[0047] like Figure 1 As shown, the width of each wavy air tunnel and each I-shaped air tunnel in this embodiment is 1 mm.

[0048] This embodiment uses a fully polarized omnidirectional matched retroreflector with three I-shaped air tunnels and two wavy air tunnels uniformly distributed on a concave metal shell. Each tunnel has a width of 1 mm. For example, in this embodiment... Figure 1 A coordinate system is established as shown. The height in the y-direction of the two ends of the concave metal is 28.6 mm, the length in the x-direction is 36 mm, and the depth in the z-direction is 42 mm. The total length in the x-direction of the fully polarized omnidirectional matched retroreflector is 84 mm. The width in the x-direction of each I-shaped air tunnel is different, and the length in the y-direction of each wavy air tunnel is different. Other specific parameters are as follows... Figure 1 The models are shown in the table below:

[0049] <![CDATA[I x (mm)]]> <![CDATA[I y (mm)]]> <![CDATA[I1]]> 3.14 25 <![CDATA[I2]]> 8.66 25 <![CDATA[I3]]> 3.18 25 <![CDATA[W x (mm)]]> <![CDATA[W y (mm)]]> <![CDATA[W1]]> 6 8.49 <![CDATA[W2]]> 6 6.605

[0050] I1, I2, and I3 represent the first, second, and third I-shaped air tunnels, respectively. x and I y W1 and W2 represent the lengths of the I-shaped air tunnel in the x and y directions, respectively, and represent the first and second wavy air tunnels, respectively. x and W y These represent the lengths of the wavy air tunnel in the x and y directions, respectively.

[0051] According to the arrangement in this embodiment, the S-parameters of perpendicular incidence are obtained by simulation using Ansys HFSS software, as follows: Figure 4 As shown, Figure 4 The left figure shows TM polarization, and the right figure shows TE polarization. It can be seen that the present invention ensures that the amplitude and phase of the 6GHz TM wave and TE wave remain unchanged at the output end after they are incident from the input end, and that both the TM wave and TE wave can be reflected back from the original angle. Figure 5 The simulation results of the vertical incident field show that the device is working normally.

[0052] This invention can achieve fully polarized waves incident from any direction at 6 GHz, with the reflected waves parallel to the incident waves and in the opposite direction. If this invention is to work at other frequencies, the width of the I-shaped air tunnel in the x-direction and the length of the wavy air tunnel in the y-direction need to be adjusted according to the working frequency, so that it is equivalent to an optical void material at the working frequency.

[0053] This invention has a simple structure and can be implemented using only metal. It can work for fully polarized incident waves at all angles and can be widely used in radar target modeling and sensing.

[0054] The above examples are not intended to limit the present invention in any way. Any person skilled in the art can make changes or modifications to the above-disclosed technical content to create equivalent examples. However, any simple modifications, equivalent changes and modifications made to the above examples based on the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A fully polarized omnidirectional matching retroreflector based on optical void material, characterized in that: The fully polarized omnidirectional matched retroreflector is constructed of a metal shell, which is a concave block. The two convex end faces of the metal shell face the incident direction of the external electromagnetic wave and serve as the input and output ends of the fully polarized omnidirectional matched retroreflector, respectively. Hollow TM wave air tunnel groups and TE wave air tunnel groups are respectively formed inside the metal shell. The entire TM wave air tunnel group and the entire TE wave air tunnel group are concave blocks with the same shape as the metal shell. The TM wave air tunnel group and the TE wave air tunnel group are connected from the input end to the output end of the fully polarized omnidirectional matched retroreflector. The input end and output end of the TM wave air tunnel group are located on the plane where the input end and output end of the fully polarized omnidirectional matched retroreflector are located, respectively. The input end and output end of the TE wave air tunnel group are located on the plane where the input end and output end of the fully polarized omnidirectional matched retroreflector are located, respectively. The geometric center of the vertical cross-section of the TM wave air tunnel group and the geometric center of the vertical cross-section of the TE wave air tunnel group are on the same straight line. The TM wave air tunnel group includes a number of I-shaped air tunnels evenly spaced from the center of the concave part of the metal shell outwards. The horizontal cross-section of each I-shaped air tunnel is concave, and the vertical cross-section of each I-shaped air tunnel is two "I" shapes. The input end and output end of each I-shaped air tunnel are located on the plane where the input end and output end of the fully polarized omnidirectional matched retroreflector are located, respectively. Each of the I-shaped air tunnels has a vertical cross-section comprising a long air tunnel arranged in the vertical direction and two short air tunnels arranged symmetrically on both sides of the long air tunnel in the horizontal direction. The TE wave air tunnel group includes several wave-shaped air tunnels evenly spaced from the center of the recess in the metal shell outwards. Each wave-shaped air tunnel is symmetrically composed of a W-shaped air tunnel on the upper side and an M-shaped air tunnel on the lower side. The vertical cross-section of each W-shaped air tunnel is two "W" shapes, and the vertical cross-section of each M-shaped air tunnel is two "M" shapes. The horizontal cross-section of each W-shaped air tunnel and each M-shaped air tunnel is concave. The input and output ends of each W-shaped air tunnel are located on the plane where the input and output ends of the fully polarized omnidirectional matched retroreflector are located, respectively. The input and output ends of each M-shaped air tunnel are located on the plane where the input and output ends of the fully polarized omnidirectional matched retroreflector are located, respectively. Each of the W-shaped air tunnels has a vertical cross-section comprising seven straight air tunnels connected end-to-end in sequence; each of the M-shaped air tunnels has a vertical cross-section comprising seven straight air tunnels connected end-to-end in sequence.

2. The fully polarized omnidirectional matched retroreflector based on optical void material according to claim 1, characterized in that: The metal casing is made of copper, silver, gold, aluminum, or tungsten.

3. The fully polarized omnidirectional matched retroreflector based on optical void material according to claim 1, characterized in that: The vertical lengths of the long air tunnels in different I-shaped air tunnels are all equal; The two short air tunnels of an I-shaped air tunnel have equal horizontal lengths, while the short air tunnels of different I-shaped air tunnels have unequal horizontal lengths.

4. The fully polarized omnidirectional matched retroreflector based on optical void material according to claim 1, characterized in that: The horizontal lengths of the W-shaped air tunnel and the M-shaped air tunnel in the wave-shaped air tunnel are equal. The horizontal lengths of W-shaped air tunnels with different wave-shaped air tunnels are not equal, and the horizontal lengths of M-shaped air tunnels with different wave-shaped air tunnels are not equal.

5. The fully polarized omnidirectional matched retroreflector based on optical void material according to claim 1, characterized in that: The geometric center of the vertical cross-section of the I-shaped air tunnel and the geometric center of the vertical cross-section of the wave-shaped air tunnel are on the same straight line.

6. The fully polarized omnidirectional matched retroreflector based on optical void material according to claim 1, characterized in that: A wave-shaped air tunnel is arranged between each pair of adjacent I-shaped air tunnels.

7. The fully polarized omnidirectional matched retroreflector based on optical void material according to claim 1, characterized in that: The width of each of the wave-shaped air tunnels and each of the I-shaped air tunnels is equal.

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