An ultra-wideband linear-circular polarization converter based on a wheel-shaped metasurface

Abstract

This application belongs to the field of microwave technology and discloses an ultra-wideband linear-circular polarization converter based on a wheel-shaped metasurface. The linear-circular polarization converter is composed of periodically arranged reflective polarization conversion units. Each reflective polarization conversion unit includes an upper wheel-shaped metal pattern layer, an intermediate dielectric substrate, and a bottom metal layer. The upper surface of the intermediate dielectric substrate is tightly connected to the upper wheel-shaped metal pattern layer, and the lower surface of the intermediate dielectric substrate is tightly bonded to the bottom metal layer. The upper wheel-shaped metal pattern layer, the intermediate dielectric substrate, and the bottom metal layer work together to achieve a polarization control function. This application achieves efficient conversion from linearly polarized waves to circularly polarized waves through the design of a wheel-shaped metal pattern. While ensuring ultra-wide bandwidth characteristics and excellent angular stability, it also has the advantages of a simple structure and convenient processing. It has good application prospects and development potential in technical fields such as communications and microwaves.

Description

Technical Field

[0001] The present application belongs to the field of microwave technology, and more specifically relates to an ultra-wideband linear circular polarization converter based on a wheel-shaped metasurface. Background Art

[0002] Electromagnetic wave control technology, especially electromagnetic wave polarization control, has always been a research focus in the field of electromagnetic propagation. Common electromagnetic wave polarization forms include linear polarization, circular polarization, and elliptical polarization. Different polarization methods have their own unique advantages and practical value in specific application scenarios. Taking circularly polarized waves as an example, their anti-interference ability in complex electromagnetic environments is particularly significant: in satellite communication scenarios, the reflection of signals through the ionosphere can easily cause multipath effects. Circularly polarized waves can effectively suppress the interference of reflected signals due to their rotational characteristics; in 5G base station communications, circularly polarized waves can alleviate signal fading caused by environments such as rain and fog, thereby ensuring the stability and reliability of information transmission in strong interference environments. Therefore, it has become the key to improving the performance of modern communication systems. As the core component for realizing circularly polarized waves, linear circular polarization converters have broad application potential in microwave communications, microscopic imaging, broadcasting and television, and other fields.

[0003] Early traditional polarization converters mainly relied on the optical rotation effect of natural materials to achieve polarization control of electromagnetic waves, but they generally suffered from narrow bandwidth, poor angular stability, large size, and low integration, which seriously restricted their application and promotion in practical scenarios. Compared with traditional solutions, metasurface polarization converters can efficiently control the phase and polarization characteristics of electromagnetic waves through the precise design of unit structures, and have unique electromagnetic response characteristics such as anisotropy and abnormal reflection / transmission. In addition, this type of converter also has significant advantages such as small size, thin thickness, light weight, low loss, and easy integration with other components, making it an ideal solution to solve the defects of traditional polarization converters.

[0004] Although research on metasurface polarization converters has made some progress, their large-scale application still faces multiple challenges. First, existing converters are mostly targeted at a single frequency band, such as the Ku band (12 GHz to 18 GHz), and cannot meet the full coverage requirements of the C / Ku / K bands (4 GHz to 27 GHz), resulting in bandwidth limitations. Second, existing metasurface polarization converters lack angular stability, and their axial ratio deteriorates significantly with increasing angle of incidence, limiting their application in wide-angle scanning scenarios such as phased array radars. Third, process cost is a key factor restricting the industrialization of metasurface technology, especially the need for subwavelength metal patterns to maintain a machining accuracy of ±5 μm, and the high cost of high-performance dielectric substrates. Therefore, the development of linear circular polarization converters with wide bandwidth, high angular stability, and low cost is of great practical significance. Summary of the Invention

[0005] In response to the technical limitations of existing linear-circular polarization converters in bandwidth expansion, angular stability and processing complexity, this application proposes an ultra-wideband linear-circular polarization converter based on a wheel-shaped metasurface. This application successfully achieves efficient conversion of linearly polarized waves to circularly polarized waves through the innovative design of a wheel-shaped metal pattern. While significantly improving the working bandwidth and angular stability, it still retains the core advantages of simple structure and convenient processing, and has important theoretical research value and engineering application potential.

[0006] In order to achieve the above objectives, this application is implemented through the following technical solutions:

[0007] This application is an ultra-wideband linear circular polarization converter based on a wheel-shaped metasurface

[0008] The present application is an ultra-wideband linear circular polarization converter based on a wheel-shaped metasurface. The ultra-wideband linear circular polarization converter based on the wheel-shaped metasurface is composed of periodically arranged reflective polarization conversion units, and each reflective polarization conversion unit adopts a stacked structure. Each reflective polarization conversion unit includes an upper wheel-shaped metal pattern layer, an intermediate dielectric substrate, and a bottom metal layer. The upper surface of the intermediate dielectric substrate is tightly connected to the upper wheel-shaped metal pattern layer, and the lower surface of the intermediate dielectric substrate is tightly combined with the bottom metal layer. The upper wheel-shaped metal pattern layer, the intermediate dielectric substrate, and the bottom metal layer work together to achieve a polarization control function. Specifically, when a linearly polarized wave is incident on the polarization converter, the upper wheel-shaped metal pattern layer converts the incident linearly polarized wave into a circularly polarized wave, the intermediate dielectric substrate extends the linearly polarized wave transmission path, generates resonance, and the bottom metal layer is used to reflect the incident linearly polarized wave.

[0009] A further improvement of the present application is that: the upper wheel-shaped metal pattern layer is a wheel-shaped structure, consisting of a cross-shaped metal sheet, a circular metal sheet and a rectangular metal strip, wherein the cross-shaped metal sheet is symmetrically distributed along the diagonal direction with the center of the surface of the reflective polarization conversion unit as the symmetry point, the cross-shaped metal sheet includes orthogonal long-axis direction metal sheets and short-axis direction metal sheets, the short-axis direction metal sheets are vertically overlapped at the center point of the surface of the reflective polarization conversion unit, two circular metal sheets are symmetrically arranged at the end of the long-axis direction metal sheet, the centers of the two circular metal sheets are located on the diagonal of the reflective polarization conversion unit, each of the circular metal sheets is provided with six rectangular metal strips of the same size, and each of the rectangular metal strips is rotationally symmetrically distributed with an equal angular interval of 30° around the center of the circular metal sheet.

[0010] A further improvement of the present application is that: the length L1 of the metal sheet in the long axis direction is 6.2 mm, and the width W1 is 0.3 mm; the length L2 of the metal sheet in the short axis direction is 0.8 mm, and the width W2 is 0.4 mm; the distance between the center of the circular metal sheet and the center of the surface of the reflective polarization conversion unit is 3.1 mm; the diameter D of each circular metal sheet is 1.6 mm; the length L3 of each rectangular metal strip is 2 mm, and the width W3 is 0.3 mm.

[0011] A further improvement of the present application is that the intermediate dielectric substrate is selected from a relative dielectric constant =4.3, loss tangent =0.025 FR4 dielectric material, the size of the intermediate dielectric substrate is length×width×thickness=8.2mm×8.2mm×2.4mm.

[0012] A further improvement of the present application is that the upper wheel-shaped metal pattern layer and the bottom metal layer are both made of metallic copper material and have the same thickness as that of the bottom metal layer, which is 0.035 mm.

[0013] A further improvement of the present application is that the side length p of the reflective polarization conversion unit is 8.2 mm

[0014] The beneficial effects of the present application are: (1) The present application utilizes a unique wheel-shaped metal pattern to successfully achieve efficient conversion of linearly polarized waves to circularly polarized waves. (2) In the frequency range of 7.05 GHz to 18.91 GHz, the present application can convert vertically incident linearly polarized waves into circularly polarized waves, with a 3 dB axial ratio bandwidth of 91.37%, and has ultra-wide frequency band characteristics. (3) When the incident angle is 40°, the bandwidth of the converter can be maintained within 7.05 to 15.34 GHz, with a 3 dB axial ratio bandwidth of 74.05%, and has good angular stability. (4) The phase difference of the electric vector component of the reflected electromagnetic wave is stable, and the amplitudes of the two components are almost equal. (5) The present invention has a simple structure and a small size, specifically 0.355 λ 0.355 λ 0.104 λ. (6) This application uses a single-layer FR4 dielectric substrate, which has a low profile, is easy to manufacture, and has a low production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a three-dimensional structural diagram of the ultra-wideband linear circular polarization converter unit structure of the present application.

[0016] Figure 2 This is a dimensional diagram of the unit structure of the ultra-wideband linear circular polarization converter of this application.

[0017] Figure 3 This is a diagram of the reflection coefficient amplitude and phase difference when the y-polarized wave is vertically incident in the ultra-wideband linear circular polarization converter of the present application.

[0018] Figure 4 This is a 3 dB axial ratio diagram of the y-polarized wave in the ultra-wideband linear circular polarization converter of the present application when the incident angles are 0°, 20° and 40°.

[0019] Figure 5 This is a reflection coefficient amplitude diagram of the ultra-wideband linear circular polarization converter of the present application when u-polarized waves and v-polarized waves are incident.

[0020] Figure 6 This is the reflection coefficient phase and phase difference diagram of the ultra-wideband linear circular polarization converter of the present application when u-polarized wave and v-polarized wave are incident.

[0021] Among them, 1 is an upper wheel-shaped metal pattern layer; 2 is an intermediate dielectric substrate; and 3 is a bottom metal layer. DETAILED DESCRIPTION

[0022] The following drawings illustrate embodiments of the present invention. For clarity, many practical details are included in the following description. However, it should be understood that these practical details are not intended to limit the present invention. In other words, in some embodiments of the present invention, these practical details are not essential. Furthermore, to simplify the drawings, some commonly used structures and components are depicted in simplified schematic form.

[0023] like Figure 1-2 As shown, the present application is an ultra-wideband linear circular polarization converter based on a wagon wheel-shaped metasurface, wherein the side length p of the reflective polarization conversion unit is 8.2 mm. The ultra-wideband linear circular polarization converter based on the wagon wheel-shaped metasurface is composed of periodically arranged reflective polarization conversion units, each of which adopts a stacked structure. Each reflective polarization conversion unit includes an upper wagon wheel-shaped metal pattern layer 1, an intermediate dielectric substrate 2, and a bottom metal layer 3. The upper surface of the intermediate dielectric substrate 2 is tightly connected to the upper wagon wheel-shaped metal pattern layer 1, and the lower surface of the intermediate dielectric substrate 2 is tightly bonded to the bottom metal layer 3.

[0024] The upper wheel-shaped metal pattern layer 1, the intermediate dielectric substrate 2, and the bottom metal layer 3 work together to achieve ultra-wideband, high-angle stability polarization control functions. Specifically, when a linearly polarized wave is incident on the polarization converter, the upper wheel-shaped metal pattern layer 1 decomposes the incident linearly polarized wave into two orthogonal polarization components, introduces a 90° phase difference, and realizes the conversion of the linearly polarized wave to a circularly polarized wave. The intermediate dielectric substrate 2 extends the linearly polarized wave transmission path through dielectric control to generate resonance. The bottom metal layer 3 is used to reflect the incident linearly polarized wave.

[0025] The upper wheel-shaped metal pattern layer 1 is made of copper with a thickness of 0.035 mm. The upper wheel-shaped metal pattern layer 1 is a wheel-shaped structure, consisting of a cross-shaped metal sheet, a circular metal sheet and a rectangular metal strip. The cross-shaped metal sheets are symmetrically distributed along the diagonal direction with the center of the surface of the reflective polarization conversion unit as the symmetry point. The cross-shaped metal sheets include orthogonal long-axis metal sheets and short-axis metal sheets. The length L1 of the long-axis metal sheet is 6.2 mm, and the width W1 is 0.3 mm. The short-axis metal sheet vertically overlaps the center point of the surface of the reflective polarization conversion unit. The length L2 of the short-axis metal sheet is 0.8 mm, and the width W2 is 0.4 mm. Two circular metal sheets are symmetrically arranged at the end of the long-axis metal sheet. The distance between the center of the circular metal sheet and the center of the surface of the reflective polarization conversion unit is 3.1 mm. The centers of the two circular metal sheets are located on the diagonal of the reflective polarization conversion unit. The diameter D of each circular metal sheet is 1.6 mm. Each circular metal sheet is provided with six rectangular metal strips of the same size. The length L3 of each rectangular metal strip is 2 mm, and the width W3 is 0.3 mm. Each of the rectangular metal strips is rotationally symmetrically distributed at equal angular intervals of 30° with the center of the circular metal sheet as the center.

[0026] The intermediate dielectric substrate 2 is selected from the relative dielectric constant =4.3, loss tangent =0.025 FR4 dielectric material, which is inexpensive and easy to process. The size of the intermediate dielectric substrate 2 is length×width×thickness=8.2mm×8.2mm×2.4mm.

[0027] The bottom metal layer 3 is a complete metal panel, attached to the lower surface of the intermediate dielectric substrate 2, and is used to reflect incident linearly polarized waves. It is made of copper with a thickness of 0.035 mm. This thickness is standard for PCB copper foil, conforming to industrial processing specifications and facilitating large-scale production.

[0028] Due to the symmetry of the metasurface unit structure, the vertically incident x-polarized waves and y-polarized waves have the same polarization rotation characteristics. In this embodiment, taking the y-polarized wave as an example, the reflected electric field can be expressed as:

[0029]

[0030] in, and denote the cross-polarization and co-polarization reflection coefficients, respectively, and is its corresponding phase, when ,and When , the reflected wave is a circularly polarized wave, and n is an integer.

[0031] like Figure 3 As shown, there is an ultra-wide frequency range. and The polarization converter converts the incident linearly polarized wave into a circularly polarized wave.

[0032] like Figure 4 As shown in the figure, when the incident angle is 0°, the line-to-circle converter can maintain the axial ratio of the reflected wave below 3 dB in the frequency range of 7.05 GHz to 18.91 GHz, and the bandwidth reaches 91.37%. When the incident angle is 20°, the line-to-circle converter can maintain the axial ratio of the reflected wave below 3 dB in the frequency range of 7.05 GHz to 16.56 GHz, and the bandwidth reaches 80.56%. When the incident angle is 40°, the converter's bandwidth remains within 7.05 to 15.34 GHz, with a relative bandwidth of 74.05%. This demonstrates that the polarization converter has an ultra-wide bandwidth and excellent angular stability.

[0033] To further explain the mechanism of polarization conversion, the xy coordinate system is rotated 45° counterclockwise to obtain the uv coordinate system. In the uv coordinate system, the incident field can be expressed as: The reflected field can be expressed as:

[0034]

[0035] in, 、 、 、 are the reflection coefficients for u-polarized and v-polarized incident waves, respectively. 、 、 、 is its corresponding phase. , and When , the reflected wave is a circularly polarized wave, and n is an integer.

[0036] like Figure 5 and 6 As shown, there is an ultra-wide frequency range. and is approximately equal to 0, and The phase difference is approximately equal to 1 and close to 90° or -270°. Within this range, the polarization converter converts the incident linearly polarized wave into a circularly polarized wave.

[0037] The foregoing is merely an embodiment of the present invention and is not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are intended to be included within the scope of the claims of the present invention.

Claims

1. An ultra-wideband linear-circular polarization converter based on a wheel-shaped metasurface, characterized by: The ultra-wideband linear circular polarization converter based on the wheel-shaped metasurface is composed of periodically arranged reflective polarization conversion units, and each reflective polarization conversion unit adopts a stacked structure. Each reflective polarization conversion unit comprises an upper wheel-shaped metal pattern layer (1), an intermediate dielectric substrate (2), and a bottom metal layer (3). The upper surface of the intermediate dielectric substrate (2) is tightly connected to the upper wheel-shaped metal pattern layer (1), and the lower surface of the intermediate dielectric substrate (2) is tightly combined with the bottom metal layer (3). The upper wheel-shaped metal pattern layer (1), the intermediate dielectric substrate (2), and the bottom metal layer (3) work together to realize a polarization control function, specifically: when a linearly polarized wave is incident on the ultra-wideband linear circular polarization converter, the upper wheel-shaped metal pattern layer (1) converts the incident linearly polarized wave into a circularly polarized wave, and the intermediate dielectric substrate (2) extends the transmission of the linearly polarized wave. The path generates resonance, the bottom metal layer (3) is used to reflect the incident linear polarization wave, the upper wheel-shaped metal pattern layer (1) is a wheel-shaped structure, composed of a cross-shaped metal sheet, a circular metal sheet and a rectangular metal strip, wherein the cross-shaped metal sheet is symmetrically distributed along the diagonal direction with the center of the surface of the reflective polarization conversion unit as the symmetry point, the cross-shaped metal sheet includes an orthogonal long-axis direction metal sheet and a short-axis direction metal sheet, the short-axis direction metal sheet is vertically overlapped at the center point of the surface of the reflective polarization conversion unit, two circular metal sheets are symmetrically arranged at the end of the long-axis direction metal sheet, the centers of the two circular metal sheets are located on the diagonal of the reflective polarization conversion unit, each of the circular metal sheets is provided with six rectangular metal strips of the same size, each of the rectangular metal strips is rotationally symmetrically distributed with the center of the circular metal sheet as the center at an equal angle of 30 degrees, and the length of the long-axis direction metal sheet is symmetrical. L 1 is 6.2mm, width W 1 is 0.3 mm, the length of the metal sheet in the short axis direction L 2 is 0.8mm, width W 2 is 0.4 mm, the distance between the center of the circular metal piece and the center of the surface of the reflective polarization conversion unit is 3.1 mm, and the diameter of each circular metal piece is D The length of each rectangular metal strip is 1.6 mm. L 3 is 2mm, width W 3 is 0.3mm.

2. The ultra-wideband linear circular polarization converter based on a wheel-shaped metasurface according to claim 1, characterized in that: The intermediate dielectric substrate (2) is selected from a relative dielectric constant =4.3, loss tangent =0.025 FR4 dielectric material, the size of the intermediate dielectric substrate (2) is length×width×thickness=8.2mm×8.2mm×2.4mm.

3. The ultra-wideband linear-circular polarization converter based on a wheel-shaped metasurface according to claim 1, characterized in that: The upper wheel-shaped metal pattern layer (1) and the bottom metal layer (3) are both made of copper metal material, and the upper wheel-shaped metal pattern layer (1) and the bottom metal layer (3) have the same thickness, which is 0.035 mm.

4. The ultra-wideband linear-circular polarization converter based on a wheel-shaped metasurface according to claim 1, characterized in that: The side length of the reflective polarization conversion unit p It is 8.2mm.

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