Broadband reflection-type electromagnetic wave polarization converter based on B-shaped metasurface

Abstract

The present invention relates to a broadband reflective electromagnetic wave polarization converter based on a B-shaped metasurface, comprising a plurality of metasurface structural units periodically arranged in the same plane, each of which is composed of a surface metal resonant structure, an intermediate dielectric substrate and a bottom metal backplane. The surface metal resonant structure is similar to a B-shape, that is, it is composed of two metal semicircular rings with the same structural parameters plus a metal strip; the two metal semicircular rings are arranged side by side and there is an overlapping part between the rings; the entire surface metal resonant structure is rotated 45 degrees counterclockwise relative to the vertical direction. The polarization converter can generate cross-polarized waves through reflection of vertically incident linearly polarized electromagnetic waves, and the working bandwidth with a cross-polarization reflectivity greater than 0.9 can reach about 11 GHz. In the frequency range of 8.46~19.61 GHz, the polarization conversion rate of the polarization converter is as low as about 92%, achieving efficient polarization conversion.

Description

Technical Field

[0001] The present invention relates to the field of microwave communication technology, and more specifically, to the field of electromagnetic wave polarization control device technology based on metasurface. Background Art

[0002] A metasurface is an artificially designed metamaterial with a two-dimensional planar structure and a sub-wavelength thickness. It not only has the negative refraction, stealth and other functions of metamaterials, but its structure is also simpler and easier to implement than metamaterials. Many studies have shown that the use of metasurfaces can achieve effective control of electromagnetic waves. This characteristic of metasurfaces has great research value in the field of polarization control. At present, metasurfaces have important applications in many fields such as antennas and stealth technology.

[0003] The polarization state is one of the important properties of electromagnetic waves. The polarization characteristics of electromagnetic waves have important research value in many application fields such as satellite communications and radar anti-interference. The so-called polarization refers to the characteristics of the direction and magnitude of the electric field intensity vector E at a certain point in space changing with time.

[0004] The thickness of traditional electromagnetic wave polarization control materials is greater than the working wavelength. Especially at low frequencies, the disadvantages of these traditional polarization control devices, such as large size and narrow bandwidth, limit their application and integration in engineering. Therefore, there is an urgent need to construct a polarization control device with simple structure and small size. Currently, many studies have shown that by changing the subwavelength unit structure of the metasurface and its combination method, the polarization control of electromagnetic waves can be perfectly achieved. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a reflective electromagnetic wave polarization converter based on a B-shaped metasurface with wide-band characteristics and high polarization conversion rate. The polarization converter of the present invention overcomes the shortcomings of traditional polarization control devices such as narrow working bandwidth and large size, and can achieve a very high polarization conversion rate and polarization conversion effect in an ultra-wide working frequency band. In addition, it also has the advantages of simple structure, easy processing, and easy integration.

[0006] The present invention is achieved in this way: a broadband reflection-type electromagnetic wave polarization converter based on a B-shaped metasurface comprises a plurality of metasurface structural units periodically arranged in the same plane, each metasurface structural unit being composed of a surface metal resonance structure (1), an intermediate dielectric substrate (2) and a bottom metal backplane (3); the shape of the surface metal resonance structure is similar to a B shape, namely, it is composed of two metal semicircular rings (1-1) and a metal strip (1-2); the ring width of the metal semicircular ring is the same as the width of the metal strip; the entire B-shaped metal resonance structure is rotated 45 degrees counterclockwise relative to the vertical direction.

[0007] The technical solution of the present invention is as follows: A broadband reflective electromagnetic wave polarization converter based on a B-shaped metasurface, comprising a plurality of metasurface structural units periodically arranged in the same plane.

[0008] Each metasurface structural unit comprises a metal resonant structure on the surface, a dielectric substrate on the middle layer and a metal back plate on the bottom layer. The centers of the metal resonant structure on the surface, the dielectric substrate on the middle layer and the metal back plate on the bottom layer are located on the same vertical line.

[0009] The shape of the surface metal resonance structure is similar to a slanted capital letter B, that is, it is composed of two metal semicircular rings and a metal strip; the upper and lower structures of the two metal semicircular rings are close together, and there is an overlapping part between the rings, and the width of the overlapping area is equal to the ring width of the metal semicircular rings; the metal strip overlaps with the diameter of the two metal semicircular rings.

[0010] The length of the metal strip (1-2) in the present invention is equal to S1+S2 , S1 Represents the distance from the center of the metasurface structure unit to the upper left port of the metal strip, S2 Indicates the distance from the center of the metasurface structure unit to the lower right port of the metal strip; the relationship between the metal strip and the two semicircular rings includes the following three cases: the first case is that the metal strip and the two semicircular rings form the shape of the letter B; the second case is that the metal strip and the two semicircular rings form the shape of the letter B. S1 or S2 The third case is a metal strip and two semicircular rings forming the letter B. S1 and S2 Both are extended for a period, S1 and S2 The elongation may not be equal; the entire surface structure is rotated 45 degrees counterclockwise relative to the vertical direction.

[0011] The present invention is characterized in that the surface metal resonant structure and the bottom metal backplane material are preferably copper foil.

[0012] The present invention is characterized in that the material of the intermediate dielectric substrate is preferably Taconic TLY-5.

[0013] The present invention is also characterized in that the relative dielectric constant of the intermediate medium Taconic TLY-5 is 2.2 and the loss tangent value is 0.0009.

[0014] The beneficial effects of the present invention are as follows: 1. For vertically incident linearly polarized electromagnetic waves, the present invention can achieve wide-band cross-polarization conversion with a working bandwidth of about 11 GHz with only a simple structural design, and the minimum value of the cross-polarization reflectivity is about 0.9 within the working frequency band, thereby achieving efficient polarization conversion.

[0015] 2. Compared with traditional electromagnetic wave polarization control devices, the polarization converter of the present invention has the advantages of being simple and compact, easy to implement and process, and easy to integrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the partial three-dimensional structure of the polarization converter of the present invention.

[0017] Figure 2 Schematic diagram of the structure of a super-surface structure unit of the polarization converter of the present invention.

[0018] Figure 3 This is a comparison diagram of the cross-polarization reflectivity of the present invention when the length of the metal strip in the metasurface structure unit of the polarization converter of the present invention takes different values.

[0019] At this time, the structural parameters of the metal strip in the metasurface structural unit of the polarization converter of the present invention are S1 and S2 equal; Figure 3 The three curves in the figure are the lengths of the metal strips in the metasurface structure unit of the polarization converter of the present invention. S1+S2 The cross-polarization reflectivity curves are taken at 10mm, 11mm and 12mm respectively.

[0020] Figure 4 This is a schematic diagram of the structure when the metal strip and two metal semicircular rings in the surface metal resonance structure of the metasurface structure unit of the polarization converter of the present invention form the letter B.

[0021] At this time, the length of the metal strip in a super-surface structure unit of the polarization converter of the present invention is S1+S2 =9.5mm, and S1 and S2 equal.

[0022] Figure 5 This is a comparison diagram of the cross-polarization reflectivity when the polarization converter of the present invention has different structural parameters.

[0023] At this time, the structural parameters of the metal strip in the metasurface structural unit of the polarization converter of the present invention are S1 and S2 equal; Figure 5 The curves in S1+S2 =9.5mm and S1+S2 =10mm when the cross-polarization reflectivity of the polarization converter of the present invention.

[0024] Figure 6 The metal strip and two metal semicircular rings in the surface structure of the polarization converter of the present invention form the letter B. S1Schematic diagram of the structure when stretched for a certain distance.

[0025] Figure 7 is the structural parameter of the metal strip in the super-surface structural unit of the polarization converter of the present invention S1 Comparison diagram of the cross-polarization reflectivity of the present invention when taking different values.

[0026] exist Figure 7 middle S1 =5 corresponds to the structural parameters of the metal strip in the super surface structural unit. S1 and S2 Equal length of metal strips S1+S2 =10mm when the cross-polarization reflectivity curve of the polarization converter of the present invention; S1 =5.5 The corresponding curve is the letter B formed by the metal strip and two metal semicircular rings in the surface structure of the super surface structure unit. S1 =5.5mm when the cross-polarization reflectivity curve of the polarization converter of the present invention; S1 =6 The corresponding curve is the letter B formed by the metal strip and two metal semicircular rings in the surface structure of the super surface structure unit. S1 =6mm when the cross-polarization reflectivity curve of the polarization converter of the present invention.

[0027] Figure 8 The metal strip and two metal semicircular rings in the surface structure of the polarization converter of the present invention form the letter B. S2 Schematic diagram of the structure when stretched for a certain distance.

[0028] Fig. 9 is the structural parameter of the metal strip in the super-surface structural unit of the polarization converter of the present invention S2 Comparison diagram of the cross-polarization reflectivity of the present invention when taking different values.

[0029] exist Fig. 9 middle S2 =5 corresponds to the structural parameters of the metal strip in the super surface structural unit. S1 and S2 Equal length of metal strips S1+S2 =10mm when the cross-polarization reflectivity curve of the polarization converter of the present invention; S2 =5.5 The corresponding curve is the letter B formed by the metal strip and two metal semicircular rings in the surface structure of the super surface structure unit. S2 =5.5mm when the cross-polarization reflectivity curve of the polarization converter of the present invention; S2 =6 The corresponding curve is the letter B formed by the metal strip and two metal semicircular rings in the surface structure of the super surface structure unit. S2=6mm when the cross-polarization reflectivity curve of the polarization converter of the present invention.

[0030] Fig.10 The graph is a co-polarization reflectivity and cross-polarization reflectivity curve when the polarization converter of the present invention takes its optimal structural parameters.

[0031] Fig.11 This is a polarization conversion rate curve diagram when the polarization converter of the present invention takes its optimal structural parameters.

[0032] Explanation of the reference numerals: 1 - surface metal resonant structure; 1-1 - two metal semicircular rings; 1-2 - metal strip; 2 - middle layer dielectric substrate; 3 - bottom metal backplane. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention are described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0034] like Figure 1 and Figure 2 As shown, the metasurface structure unit proposed in the present invention includes a metal resonant structure on the surface, a dielectric substrate in the middle layer and a metal backplane on the bottom layer; the dielectric substrate can be a FR-4 glass cloth substrate, a polytetrafluoroethylene high-frequency board, or a Taconic series dielectric substrate material, and the surface metal resonant structure and the bottom metal backplane are metal conductive materials; in a preferred embodiment of the present invention, the dielectric substrate is Taconic TLY-5, and the metal resonant structure and the metal backplane are both copper foil.

[0035] The centers of the dielectric substrate, the surface metal resonant structure and the bottom metal backplane are located on the same vertical line. From the direction perpendicular to the plane where the dielectric substrate is located, the horizontal length of the metasurface structure unit is the same as the vertical length, and its side length is p Defined as the period length of the metasurface structural unit.

[0036] The dielectric substrate is Taconic TLY-5, which has a relative dielectric constant of 2.2, a magnetic permeability of 1, and a loss tangent of 0.0009. The surface metal resonant structure (1) and the bottom metal backplane (3) are copper foil, with a conductivity of σ=5.8×10 7 S / m.

[0037] Preferably, the period length of the super surface structure unit is p The value range is 8mm≤ p ≤12mm. The thickness of the dielectric substrate h The value range is 3.3mm≤ h ≤3.8mm, thickness of the surface metal resonant structure and the bottom metal plate tThe value range is 0.03mm≤ t ≤0.04mm.

[0038] Preferably, the length of the metal strip is S1+S2 The value range is 9mm≤ S1+S2 ≤14mm, width w The range is 0.4mm≤ w ≤0.6mm; the inner and outer radii of the metal semicircular ring of the super surface structural unit r1 and r2 The value range is 1.5mm≤ r1 ≤2.5mm, 2mm≤ r2 ≤3mm; two metal semicircular rings are arranged side by side, and the width of the overlapping area is equal to the ring width of the metal semicircular ring r2 - r1 ,and r2 - r1 = w .

[0039] Figure 3 for Figure 2 The metal strips in the surface metal resonant structure of the metasurface structure unit shown are S1 = S2 Based on the comparison of cross-polarization reflectivity at different lengths, when the incident wave is a y-polarized wave, the magnitude of the cross-polarization reflection coefficient is defined as r xy =|E xr / E yi |, the cross-polarization reflectivity is defined as r xy 2 .

[0040] Figure 3 The horizontal axis is the frequency in GHz; the vertical axis is the cross-polarization reflectivity; Figure 3 It can be seen that as the length of the metal strip S1+S2 With the increase of , the operating frequency band of the polarization converter of the present invention moves toward the low frequency direction and can maintain a relatively high cross-polarization reflectivity.

[0041] Figure 4 It is a schematic diagram of the structure when the metal strip and two metal semicircular rings in the surface metal resonant structure of the metasurface structural unit of the polarization converter of the present invention form the letter B; Figure 5 This is a comparison diagram of the cross-polarization reflectivity when the polarization converter of the present invention takes different structural parameters; at this time, the structural parameters of the metal strips in the metasurface structural unit of the polarization converter of the present invention are S1 and S2 equal; Figure 5 The curves in S1+S2 =9.5mm and S1+S2=10mm when the cross-polarization reflectivity of the polarization converter of the present invention.

[0042] Figure 6 The metal strip and two metal semicircular rings in the surface metal resonant structure of the super surface structure unit of the polarization converter of the present invention form the letter B. S1 Schematic diagram of the structure when stretched for a certain length; Figure 7 is the structural parameter of the metal strip in the super-surface structural unit of the polarization converter of the present invention S1 Comparison diagram of the cross-polarization reflectivity of the present invention when taking different values; Figure 7 It can be seen that when the structural parameters of the metal strip S1 When the polarization converter of the present invention changes, it can still maintain a relatively high cross-polarization reflectivity.

[0043] Figure 8 The metal strip and two metal semicircular rings in the surface metal resonant structure of the super surface structure unit of the polarization converter of the present invention form the letter B. S2 Schematic diagram of the structure when stretched for a certain length; Fig. 9 is the structural parameter of the metal strip in the super-surface structural unit of the polarization converter of the present invention S2 Comparison diagram of the cross-polarization reflectivity of the present invention when taking different values; Fig. 9 It can be seen that when the structural parameters of the metal strip S2 When the polarization converter of the present invention changes, it can still maintain a relatively high cross-polarization reflectivity.

[0044] Fig.10 The co-polarization reflectivity and cross-polarization reflectivity curves of the polarization converter of the present invention with its optimal structural parameters; when the incident wave is a y-polarized wave, the magnitude of the co-polarization reflectivity is defined as r yy =|E yr / E yi |, the co-polarization reflectivity is defined as r yy 2 ; Fig.10 The solid line and the dotted line correspond to the cross-polarization reflectivity and the co-polarization reflectivity of the polarization converter of the present invention, respectively; Fig.10 It can be seen that within the frequency range of 8.46 to 19.61 GHz, the minimum cross-polarization reflectivity of the polarization converter of the present invention is about 0.9.

[0045] Fig.11 The figure shows a polarization conversion rate (PCR) diagram of a broadband reflective electromagnetic wave polarization converter based on a B-shaped metasurface of the present invention; wherein the polarization conversion rate is defined as: PCR = r xy 2 / (r xy 2 + ryy 2 );from Fig.11 It can be seen that within the frequency range of 8.46-19.61 GHz, the polarization conversion rate of the polarization converter of the present invention is as low as about 92%.

[0046] The broadband reflection-type electromagnetic wave polarization converter based on the B-shaped metasurface is composed of a plurality of periodically arranged structural units, and the structural size and structural parameters of each structural unit are the same; the present invention can adjust the arrangement between the two metal semicircular rings and the metal strip and the structural parameters of the metasurface structural unit to make it work in different frequency bands, and after optimizing the structural parameters of the metasurface structural unit, efficient polarization conversion from linearly polarized electromagnetic waves to cross-polarization can be achieved through reflection within a very wide frequency band.

[0047] In a preferred embodiment of the present invention: the polarization converter operates in the X band, Ku band and K band, the dielectric substrate adopts Taconic TLY-5, and the surface metal resonant structure and the bottom metal plate material are both copper; in a preferred embodiment of the present invention, the metal backplane is a copper foil that fully covers the dielectric substrate to play a total reflection role.

[0048] The present invention designs a broadband reflective electromagnetic wave polarization converter based on a B-shaped metasurface, which can realize the polarization conversion of vertically incident line-polarized electromagnetic waves to cross-polarized electromagnetic waves through reflection within a wide frequency band; the polarization converter has the advantages of simple structure, thin thickness, easy processing and wide frequency band, and has good polarization conversion performance in the entire working frequency band, and has a very broad prospect in practical applications.

[0049] The principles, characteristics, and related advantages of the present invention are described in detail above, and the related structural parameters given are preferred implementation schemes. It should be pointed out that the present invention is not limited to the specific details in the above-mentioned implementation schemes, and within the scope of the technical concept of the present invention, any modifications made should also be regarded as the protection scope of the present invention.

Claims

1. A broadband reflective electromagnetic wave polarization converter based on a B-shaped metasurface, characterized in that: It comprises a plurality of metasurface structure units arranged periodically in the same plane, each metasurface structure unit comprises a three-layer structure, namely a surface metal resonant structure (1), an intermediate dielectric substrate (2) and a bottom metal backplane (3); The surface metal resonance structure is in the shape of an oblique capital letter B, i.e., it is composed of two metal semicircular rings (1-1) and a metal strip (1-2); the upper and lower structures of the two metal semicircular rings are close together, and there is an overlapping part between the rings, and the width of the overlapping area is equal to the ring width of the metal semicircular rings; the metal strip overlaps with the diameter of the two metal semicircular rings arranged together; the intersection of the overlapping area of ​​the two metal semicircular rings and the metal strip is located at the center of the metasurface structure unit; the surface metal resonance structure is rotated 45 degrees counterclockwise relative to the vertical direction.

2. A broadband reflective electromagnetic wave polarization converter based on a B-shaped metasurface as claimed in claim 1, characterized in that: The sizes and structural parameters of the two metal semicircular rings (1-1) in the surface metal resonance structure are completely the same; the two metal semicircular rings in the surface metal resonance structure are arranged side by side, r1 and r2 respectively represent the inner and outer radii of the two metal semicircular rings (1-1) in the surface metal resonance structure (1), and the width of the overlapping area is equal to the ring width r2-r1 of the metal semicircular ring.

3. A broadband reflective electromagnetic wave polarization converter based on a B-shaped metasurface as claimed in claim 1, characterized in that: The length of the metal strip (1-2) is equal to S1+S2, S1 represents the distance from the center of the metasurface structure unit to the upper left port of the metal strip, and S2 represents the distance from the center of the metasurface structure unit to the lower right port of the metal strip; the relationship between the metal strip and the two metal semicircular rings includes the following three cases: the first case is that the metal strip and the two metal semicircular rings form the shape of the letter B, the second case is that the metal strip and the two metal semicircular rings form the letter B and S1 or S2 is extended for a section, and the third case is that the metal strip and the two metal semicircular rings form the letter B and S1 and S2 are both extended for a section, and the extension amounts of S1 and S2 may not be equal.

4. A broadband reflective electromagnetic wave polarization converter based on a B-shaped metasurface as claimed in claim 1, characterized in that: The material and thickness of the surface metal resonant structure (1) and the bottom metal back plate (3) are completely the same.

5. The broadband reflective electromagnetic wave polarization converter based on the B-shaped metasurface according to claim 1, characterized in that: The dielectric substrate includes FR-4 glass cloth substrate, polytetrafluoroethylene high frequency board, and Taconic series dielectric substrate materials.

6. The broadband reflective electromagnetic wave polarization converter based on the B-shaped metasurface according to claim 1, characterized in that: The material of the surface metal resonant structure and the bottom metal back plate can be selected from copper, gold, silver, and aluminum.

7. The broadband reflective electromagnetic wave polarization converter based on the B-shaped metasurface according to claim 1, characterized in that: The structural parameter requirements of the polarization converter are as follows: 8mm≤p≤12mm, 0.03mm≤t≤0.04mm, 3.3mm≤h≤3.8mm, 0.4mm≤w≤0.6mm, 9mm≤S1+S2≤14mm, 1.5mm≤r1≤2.5mm, 2mm≤r2≤3mm; wherein p represents the period of the metasurface structural unit, t represents the thickness of the surface metal resonant structure (1) and the bottom metal backplane (3), h represents the thickness of the intermediate dielectric substrate (2), w represents the width of the metal strip (1-2) in the surface metal resonant structure (1), r1 and r2 represent the inner and outer radii of the two metal semicircular rings (1-1) in the surface metal resonant structure (1), respectively, and w=r2-r1, S1 represents the distance from the center of the metasurface unit to one end of the metal strip (upper left), and S2 represents the distance from the center of the metasurface unit to the other end of the metal strip (lower right).

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