A broadband circularly polarized patch antenna based on non-uniform metasurface

Abstract

The application discloses a kind of wideband circularly polarized patch antennas based on non-uniform super surface, including two layers of dielectric substrate, a layer of air layer, three layers of metal layer.From top to bottom, it is first layer metal, first layer dielectric substrate, air layer, second layer metal, second layer dielectric substrate and third layer metal.The first layer metal layer is 4x4 non-uniform super surface unit array;Second layer metal layer is the truncated square patch connected with an L-shaped branch and an extended trapezoidal strip;Third layer metal layer is the metal ground plane consistent with the size of dielectric substrate.The application generates additional high-frequency resonance points and axial ratio minimum points by loading L-shaped branch on truncated square patch and designing non-uniform super surface, thereby realizing relatively wide impedance bandwidth and axial ratio bandwidth, and explaining the circularly polarized radiation mechanism of the antenna and the principle of forming wideband through characteristic mode analysis.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, and more specifically to a broadband circularly polarized patch antenna based on a non-uniform metasurface. Background Technology

[0002] In recent years, with the rapid development of wireless communication technology, the performance requirements for antennas in wireless communication systems have become increasingly stringent, and simple linearly polarized antennas can no longer meet communication needs. Circularly polarized antennas have attracted widespread attention from researchers due to their advantages such as reducing losses, overcoming multipath interference, and receiving waves of arbitrary polarization.

[0003] Single-fed microstrip patch antennas offer advantages such as low profile, small size, simple design, and ease of conformal design, often making them a candidate antenna for achieving circular polarization. However, due to their high mass factor, microstrip antennas inherently suffer from narrow impedance bandwidth. While using a low dielectric constant or increasing the overall antenna profile can improve bandwidth, the improvement is ultimately limited and can easily result in a high profile.

[0004] Metasurfaces, or two-dimensional metamaterials, are composed of periodic or aperiodic arrangements of subwavelength structures. When the structural dimensions of the basic units are at the subwavelength scale, they exhibit unique medium properties. Compared to naturally occurring matter, the medium properties of metasurfaces depend on the basic structure and spatial arrangement of the units, possessing extraordinary electromagnetic wave manipulation capabilities. Metasurface antennas can improve the performance of traditional antennas in multiple aspects, including operating bandwidth, directivity, radiation efficiency, and gain. Summary of the Invention

[0005] The purpose of this invention is to provide a broadband circularly polarized patch antenna based on a non-uniform metasurface, which aims to solve the technical problem of narrow bandwidth of low-profile circularly polarized antennas in the prior art. By loading L-shaped stubs onto a square truncated patch and designing a non-uniform metasurface structure, additional high-frequency resonant points and the lowest axial ratio point are generated, thereby achieving a wider impedance bandwidth and axial ratio bandwidth.

[0006] To achieve the above objectives, the present invention employs a broadband circularly polarized patch antenna based on a non-uniform metasurface, comprising a first dielectric substrate, a second dielectric substrate, an air layer, a first metal layer, a second metal layer, and a third metal layer, which, from top to bottom, are the first metal layer, the first dielectric substrate, the air layer, the second metal layer, the second dielectric substrate, and the third metal layer.

[0007] The first metal layer is composed of 4×4 non-uniform metasurface units, consisting of eight square metasurface units and eight rectangular metasurface units. The square metasurface units are located at the center and four corners of the 4×4 non-uniform metasurface units, and the rectangular metasurface units are located at the center of the outer ring of the 4×4 non-uniform metasurface units. The spacing between each metasurface unit is the same.

[0008] The lower surface of the first metal layer is the first dielectric substrate that coincides with its center; the lower surface of the first dielectric substrate is the air layer; the lower surface of the air layer is the second metal layer, and the center of the second metal layer is a diagonally truncated square patch, on which an L-shaped branch and an extending trapezoidal strip are connected.

[0009] The third metal layer is located on the lower surface of the second dielectric substrate, and its size is the same as that of the second dielectric substrate.

[0010] Working principle of the invention:

[0011] After being fed, the second metal layer is excited to generate a circularly polarized wave. This circularly polarized wave passes through the third metal layer, where surface waves propagating on the third metal layer are excited, generating additional resonance and a minimum axial ratio, thus achieving a wider impedance bandwidth and axial ratio bandwidth. To better understand how the broadband and circular polarization characteristics are achieved, Characteristic Mode Analysis (CMA) is used to analyze both the first and second metal layers simultaneously. CMA allows analysis of the antenna without excitation, revealing its inherent characteristic modes and radiation characteristics. Figure 5 The current distribution and radiation patterns of the first six modes at their resonant frequencies (mode significance MS=1) are presented. It can be seen that the current directions of each metasurface unit in modes 1, 2, 5, and 6 are approximately in the same direction; therefore, modes 1, 2, 5, and 6 can be considered as side-radiation modes. In modes 3 and 4, the surface currents have opposite distributions in the plane, and the radiation fields in the side-radiation direction cancel each other out. Therefore, the radiation patterns of modes 3 and 4 show a radiation null point in the z-axis direction. Thus, modes 1, 2, 5, and 6 are the desired operating modes. Figure 6 The mode significance (MS) and mode characteristic angle (CA) of the first six modes are given. From Figure 5 and Figure 6 It can be seen that the polarization directions of Mode 1 and Mode 2 are orthogonal, and they have the same MS and a CA phase difference of about 90° at a frequency of 4.62 GHz. This frequency point is similar to... Figure 8 The first axial ratio dip point is located at a frequency close to the given frequency. Modes 2 and 5 have the same MS and a CA phase difference of about 90° at 6.4 GHz, which is consistent with... Figure 8 The second axial ratio dip point is located at a frequency close to the given frequency. Modes 5 and 6 show similar patterns at 7 GHz, which are close to the frequency of the third axial ratio dip point.

[0012] The beneficial effects of this invention are:

[0013] By loading L-shaped stubs onto a truncated square patch and designing a non-uniform metasurface, additional resonant points and minimum axial ratio points are generated at high frequencies, thereby achieving a wider impedance bandwidth and axial ratio bandwidth. This invention exhibits good left-hand circularly polarized radiation within its operating bandwidth, with an impedance bandwidth of 90.37% (4.07-10.78GHz) and an axial ratio bandwidth of 45.16% (4.68-7.41GHz), representing a significant improvement over other similar antennas and effectively addressing the drawback of narrow antenna bandwidth. Attached Figure Description

[0014] Figure 1 This is a side view diagram of the present invention.

[0015] Figure 2 This is a schematic diagram of the upper surface of the first dielectric substrate in this invention.

[0016] Figure 3 This is a schematic diagram of the upper surface of the second dielectric substrate in this invention.

[0017] Figure 4 This is a schematic diagram of the lower surface of the second dielectric substrate in this invention.

[0018] Figure 5 This is the current distribution and radiation pattern of the first six modes of the non-uniform metasurface in an embodiment of the present invention. They are Mode 1 at a frequency of 4.18 GHz, Mode 2 at a frequency of 5.45 GHz, Mode 3 at a frequency of 6.26 GHz, Mode 4 at a frequency of 6.76 GHz, Mode 5 at a frequency of 7 GHz, and Mode 6 at a frequency of 7.62 GHz.

[0019] Figure 6 These are (a) Mode Significance (MS) and (b) Mode Characteristic Angle (CA) in the embodiments of this invention.

[0020] Figure 7 The simulated reflection coefficient (|S) of this embodiment of the invention 11 |) Image.

[0021] Figure 8 This is a simulation axis ratio (AR) and gain graph of an embodiment of the present invention.

[0022] Figure 9 This is a simulated far-field radiation pattern at a frequency of 4.93 GHz according to an embodiment of the present invention.

[0023] Figure 10 This is a simulated far-field radiation pattern at a frequency of 6.36 GHz according to an embodiment of the present invention.

[0024] Figure 11 This is a simulated far-field radiation pattern at a frequency of 7.24 GHz according to an embodiment of the present invention.

[0025] Figure description: 1-First metal layer, 2-First dielectric substrate, 3-Air layer, 4-Second metal layer, 5-Second dielectric substrate, 6-Third metal layer. Detailed Implementation

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0027] This invention provides a bandwidth circularly polarized patch antenna based on a non-uniform metasurface, the structure of which is shown in the figure. Figures 1 to 4 As stated, in which Figure 1 This is a side view of the structure, from top to bottom: the first metal layer, the first dielectric substrate, the air layer, the second metal layer, the second dielectric substrate, and the third metal layer. Figure 2 The diagram illustrates the first metal layer, which consists of 4×4 non-uniform metasurface units, comprising eight square metasurface units and eight rectangular metasurface units. Figure 3 The diagram illustrates the second metal layer, which consists of L-shaped branches, diagonally truncated square patches, and extended trapezoidal strips. Figure 4 The diagram illustrates the third metal layer, which is a metal ground plane.

[0028] The first and second dielectric substrates are both made of FR-4 material and have a side length of 36mm. The first dielectric substrate has a thickness of 1mm, and the second dielectric substrate has a thickness of 3mm. The air layer has a thickness of 1mm.

[0029] In the first metal layer, the square metasurface unit has a side length of 7mm, the rectangular metasurface unit has a length of 7mm and a width of 5.8mm, and the spacing between each unit is 1mm.

[0030] In the second metal layer, the long branch of the L-shaped branch is 15.5 mm long and 0.5 mm wide, and the short branch is 4.5 mm long and 2.5 mm wide; the diagonally truncated square patch has a side length of 11.8 mm and the truncated diagonal side length is 6.8 mm; the trapezoidal extension has a length of 2 mm and a width of 2.5 mm, and the side lengths of the triangles on both sides are 2.5 mm and 1.5 mm respectively.

[0031] The third metal layer has a side length of 36 mm.

[0032] The simulation results of the embodiments are as follows Figures 7 to 11 As shown, |S 11 The bandwidth of |<-10dB is 4.07-10.78GHz (90.37%), the 3dB axial ratio bandwidth is 4.68-7.41 (45.16%), and the peak gain is 6.95dBi. The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A broadband circularly polarized patch antenna based on a non-uniform metasurface, characterized in that: It includes two dielectric substrates, one air layer, and three metal layers, which are, from top to bottom, the first metal layer, the first dielectric substrate, the air layer, the second metal layer, the second dielectric substrate, and the third metal layer; The first metal layer is a 4×4 non-uniform metasurface unit array, the center of which coincides with the center of the first dielectric substrate. The lower surface of the first metal layer is the first dielectric substrate that coincides with its center; The lower surface of the first dielectric substrate is the air layer; the lower surface of the air layer is the second metal layer, the center of the second metal layer is a diagonally truncated square patch, and an L-shaped branch and an extended trapezoid are connected to the truncated square patch; the lower surface of the second dielectric substrate is the third metal layer. The first metal layer consists of eight square metasurface units and eight rectangular metasurface units. The four central units and four corner units in the 4×4 non-uniform metasurface unit array are square metasurface units with a side length of 7 mm. The eight central units in the outer ring of the 4×4 non-uniform metasurface unit array are rectangular metasurface units with a length of 7 mm and a width of 5.8 mm. The spacing between each metasurface unit is the same, which is 1 mm.

2. The broadband circularly polarized patch antenna based on a non-uniform metasurface according to claim 1, characterized in that: The center of the truncated square patch in the second metal layer coincides with the center of the second dielectric substrate. An L-shaped branch is added in front of the truncated square patch, and an extended trapezoid is added behind the truncated square patch.

3. The broadband circularly polarized patch antenna based on a non-uniform metasurface according to claim 1, characterized in that: The third metal layer is the same size as the second dielectric substrate, so that the third metal layer can serve as the metal ground of the coaxial power supply structure.

4. The broadband circularly polarized patch antenna based on a non-uniform metasurface according to claim 1, characterized in that: The first dielectric substrate, the air layer, and the second dielectric substrate are of the same size, and the center of the first dielectric substrate, the center of the air layer, and the center of the second dielectric substrate coincide.

5. The broadband circularly polarized patch antenna based on a non-uniform metasurface according to claim 1, characterized in that: Both the first and second dielectric substrates are made of FR-4 material, with thicknesses of 1 mm and 3 mm, respectively. The air layer located between the first and second dielectric substrates has a thickness of 1 mm.

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