Metasurface broadband antenna based on characteristic mode analysis

Abstract

The invention discloses a metasurface broadband wide antenna based on characteristic mode analysis, the upper surface of the antenna adopts a non-periodic square metasurface structure, and the overall modal significance and current distribution of the metasurface can be regulated and controlled by adjusting the sizes of square patches of different parts and the width of gaps, so that the metasurface broadband wide antenna is obtained. Therefore, a proper mode is screened out. After the overall size of the metasurface is determined, the optimal feed position is selected based on current distribution obtained through characteristic mode analysis, and the antenna is fed in a coaxial feed mode. Characteristic mode analysis is applied to the design of the aperiodic square metasurface structure, the square patches in different cutting modes are optimized, peripheral surface current is gathered on the central patch, and therefore the modal characteristics and current distribution of the metasurface structure can be observed conveniently, the proper modal and feed position can be determined rapidly, and the metasurface structure can be applied to the field of metasurface structure design. And the design process of the metasurface antenna is simplified.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave antennas, and in particular relates to a metasurface wide-bandwidth antenna based on characteristic mode analysis. Background Art

[0002] With the rapid development of wireless communication technologies such as 5G, Wi-Fi 6, and the Internet of Things, traditional narrowband antennas can no longer meet the requirements of multi-band, high data transmission rates, and complex communication environments. Wide-bandwidth antennas, through multi-resonance structures, tapered slot designs, metamaterials, and other technologies, can achieve good impedance matching and high radiation efficiency over a wide frequency range while supporting multiple frequency band operations, thereby reducing the number of antennas in the device and reducing costs. However, the design of wide-bandwidth antennas still faces many challenges, such as how to achieve broadband characteristics within a limited size, maintain high radiation efficiency within a wide frequency band, and optimize multi-band performance. Currently, wide-bandwidth antennas have been widely used in mobile communications, radar, satellite communications, the Internet of Things, military aerospace, and other fields.

[0003] Metasurfaces are two-dimensional planar arrays composed of subwavelength metallic units. They possess unique electromagnetic properties not found in nature, such as negative refractive index and negative magnetic permeability, offering new avenues for electromagnetic wave manipulation. Their deliberate electromagnetic wave manipulation properties lend themselves to a wide range of applications in improving antenna performance, broadening antenna design possibilities while effectively addressing many bottlenecks associated with traditional antennas. Applications of metasurfaces primarily include using antennas as feed sources to excite metasurfaces, directly enhancing antenna performance, and using metasurfaces as antenna radiating surfaces. Therefore, the rational use of metasurfaces is crucial for modern antenna design.

[0004] While traditional wide-bandwidth antennas offer significant advantages in extending frequency range, they also have significant drawbacks. Their typically large physical size makes them difficult to meet the miniaturization and integration requirements of modern communication equipment. With the advancement of technology, eigenmode theory has become widely used in antenna design. Its core principle is to solve the eigenvalues of the antenna structure to obtain a set of orthogonal eigencurrent modes and their corresponding eigenvalues. These modes reflect the natural resonant characteristics of the antenna at different frequencies. By analyzing these eigenmodes, designers can intuitively understand the radiation mechanism and bandwidth potential of the antenna structure, thereby optimizing antenna performance in a targeted manner.

[0005] In order to design a high-performance wide-bandwidth antenna, the present invention combines metasurface technology with characteristic mode analysis and applies it to the design of a non-periodic square metasurface wide-bandwidth antenna. Existing antenna technology has the following shortcomings: 1) Although wide-bandwidth antennas can cover a wide frequency range, their physical size is usually large, making it difficult to meet the miniaturization and integration requirements of modern communication equipment. Achieving broadband performance in a limited space remains a technical difficulty; 2) The feeding methods of existing wide-bandwidth antennas are often complex. The complex feeding structure not only increases the design difficulty and cost, but may also affect the stability of the antenna. Therefore, how to design an antenna with wide bandwidth, small size and simple feeding method in the smallest size has become the focus of current design. By combining metasurfaces with characteristic mode analysis, the present invention aims to solve the above problems and provide an efficient, compact and easy-to-implement wide-bandwidth antenna design solution. Summary of the Invention

[0006] The purpose of the present invention is to address the defects and shortcomings of the above-mentioned prior art and propose a metasurface wide-bandwidth antenna based on characteristic mode analysis. The wide-bandwidth antenna has wide bandwidth, low profile, simple feeding structure, etc., and is low profile and easy to design and process. The characteristic mode analysis is used to analyze the metal metasurface, and the appropriate mode and modal significance are found by controlling the side length of the square. The wide-bandwidth performance is achieved by finding the appropriate feeding position through the current distribution of the mode.

[0007] The technical solution adopted by the present invention to solve its technical problems is: from top to bottom, it includes an upper non-periodic square metasurface metal layer, a dielectric layer, and a bottom metal layer. The bottom metal layer is tightly fitted with the dielectric layer. The geometric centers of the dielectric layer, the bottom metal layer, and the metasurface metal layer are all on the same straight line. The bottom metal layer is used as the center for coaxial feeding of the metal ground plate, and the side length is consistent with the length of the dielectric layer. The grounded metal layer is tightly attached to the dielectric plate, and the feeding structure is coaxial feeding, and the position is located at the center of the bottom metal layer.

[0008] Furthermore, each metasurface unit of the upper non-periodic square metasurface metal layer of the present invention is a square and is composed only of squares, and the entire metasurface structure is also square. The side length of the dielectric layer is not less than 90 mm, the dielectric layer and the grounding metal layer are standard squares in top view, and the upper surface of the dielectric layer is a non-periodic square metasurface. The non-periodic square metasurface as a whole contains three types of metasurface units with different side lengths, totaling 232 metasurface units. Each individual metasurface unit is also a square, and the side lengths of the square metasurface units from the center to the outside are 14 mm, 6.5 mm, and 4.5 mm, respectively. The gaps between the square units with the same side lengths are 0.8 mm, 1 mm, and 0.25 mm from the center to the outside.

[0009] Furthermore, each layer of squares and gaps of the non-periodic square metasurface metal layer on the upper surface of the dielectric layer of the present invention can be adjusted. The mode significance and current distribution of the metasurface structure can be obtained by analyzing the metasurface structure using characteristic mode analysis. By adjusting the side lengths and gaps of the squares at different positions, the mode significance and current distribution can be changed, and the mode significance of the non-periodic square metasurface metal layer with different parameters can be analyzed using characteristic mode analysis to reduce the influence of high-order modes on the selected mode. By changing the side lengths and gaps of the squares, the side length of the outermost square is minimized and the side length of the center square is maximized. The maximum currents of the surface currents in multiple frequency bands can be distributed on the square patch in the center, thereby selecting the mode that is most suitable for forming wide-bandwidth performance.

[0010] The grounding metal layer is tightly fitted to the lower surface of the dielectric layer, and the upper super-surface metal layer is in contact with the bottom grounding metal layer through a copper column located in the center, and the height of the copper column is the thickness of the dielectric layer.

[0011] Furthermore, the entire antenna of the present invention is a single-layer dielectric structure, with a non-periodic square metal metasurface unit on the upper surface of the dielectric layer and a grounded metal layer on the lower surface. The feed structure at the bottom of the dielectric layer of the antenna is coaxial. To excite the selected mode, the feed position needs to be placed where the surface current is most concentrated. The use of coaxial feed ensures a simple and efficient feed structure.

[0012] The wide-bandwidth antenna's feed structure is located on the lower surface of the dielectric layer. The antenna uses coaxial feeding, with a copper post connecting the non-periodic square metasurface metal units. Radiated energy is conducted to the metasurface metal layer via the copper post.

[0013] Compared with the prior art, the present invention has the following technical advantages: (1) The present invention uses a method of realizing a wide-bandwidth antenna using a non-periodic square metasurface with characteristic mode analysis, which fills the gap in realizing wide-bandwidth performance using non-periodic metasurfaces. Compared with traditional wide-bandwidth antennas, this non-periodic square metasurface wide-bandwidth antenna innovatively designs the metasurface into a square structure that is cut and reorganized in different ways. The characteristic mode analysis method is used to analyze the overall structure of the metasurface to find the mode and current distribution that are most suitable for achieving wide-bandwidth performance. The side length and gap of each layer of squares can be adjusted to control the overall mode and current distribution of the metasurface. At the same time, the arrangement of the squares enhances the surface coupling and reduces the cross-section of the antenna. This antenna adopts a coaxial feeding method. The characteristic mode analysis is used to analyze the current distribution of the metasurface to find the feeding position suitable for achieving wide bandwidth, which simplifies the feeding design of the wide-bandwidth antenna. The feeding structure of this antenna is simple and easy to manufacture, which greatly reduces the cost. The smaller size, wider bandwidth, and simpler feeding method make the present invention have a larger application space in the Internet of Things.

[0014] (2) The upper surface of the antenna of the present invention is a non-periodic square metasurface structure. The square structure has a stronger coupling effect due to the presence of multiple units, which can reduce the cross-section of the antenna.

[0015] (3) The present invention uses the method of characteristic mode analysis to analyze the non-periodic square metasurface on the upper surface to find the appropriate mode, and analyzes its surface current to find the appropriate feeding position. Since the square metasurface structure on the upper surface is non-periodic, by adjusting the square side length and gap of each layer, the appropriate feeding position can be found based on the overall modal significance and current distribution of the metasurface. This antenna is fed by coaxial feeding. Coaxial feeding excites the mode with the widest bandwidth, thereby achieving wide-bandwidth performance.

[0016] (4) This invention applies characteristic mode analysis to a non-periodic square metasurface structure. The square structure enhances coupling between units and reduces the antenna profile. The non-periodicity allows the metasurface structure to have controllable modes to find the most suitable mode, simplifying the metasurface design process. The wide bandwidth and simple structure make this invention have important application scenarios in the field of Internet of Things. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structural decomposition of the non-periodic square metasurface wide-bandwidth antenna using characteristic mode analysis of the present invention.

[0018] Figure 2 These are top and bottom views of the non-periodic square metasurface wide-bandwidth antenna using characteristic mode analysis of the present invention.

[0019] Figure 31 is a side view of the non-periodic square metasurface wide bandwidth antenna using characteristic mode analysis of the present invention.

[0020] Figure 4 Mode saliency map of the metasurface for a non-periodic square metasurface wide bandwidth antenna using eigenmode analysis.

[0021] Figure 5 Figure 2 is the S11 parameter diagram of the metasurface for the aperiodic square metasurface wide bandwidth antenna using eigenmode analysis. DETAILED DESCRIPTION

[0022] In order to more specifically explain the purpose, technical solutions, etc. of the present invention, the technical solutions of the present invention are further described below in conjunction with the accompanying drawings.

[0023] like Figure 1 As shown, the present invention utilizes a non-periodic square metasurface with wide bandwidth, using characteristic mode analysis. It primarily consists of a non-periodic metal metasurface on the upper surface of a dielectric layer, a dielectric layer, a grounded metal layer below the dielectric layer, and copper pillars. The dielectric layer utilizes Rogers RO4003 dielectric material, which has a dielectric constant of 3.55 and a dielectric loss factor of 0.0027. Both the metal metasurface and the grounded metal layer are tightly bonded to the dielectric layer. The dielectric layer has a square structure with a side length of 90 mm and no slots or cut corners.

[0024] like Figure 2 As shown, the non-periodic square metasurface on the upper surface of the dielectric layer of the present invention has gaps between each metasurface unit of 0.8mm, 1mm, and 0.35mm from the center outward, and the side lengths of the square patches from the center outward are 14mm, 6.5mm, and 4.5mm, respectively. The metal ground plate is a square with a side length of 90mm.

[0025] like Figure 2 As shown, the coaxial feeding method in the present invention is to place a copper column with a height consistent with the thickness of the dielectric layer starting from the center of the grounded metal layer, and the radius of the copper column is 0.65 mm.

[0026] like Figure 3 As shown, the height of the dielectric layer of the present invention is 8 mm. The non-periodic metasurface on the upper surface of the dielectric layer, the dielectric layer, the grounding metal layer on the lower surface of the dielectric layer, and the copper pillars embedded in the dielectric layer are all tightly fitted.

[0027] like Figure 4As shown in the figure, the present invention obtains the first four modes of the metasurface structure obtained by the characteristic mode analysis of the non-periodic square metasurface. It can be seen from the figure that the bandwidth of mode three with a mode significance of >0.707 is the widest. By adjusting the structural parameters of the non-periodic metasurface, the modal significance of the entire metasurface can be controlled. In order to avoid exciting other modes, the structural parameters of the non-periodic metasurface should be regulated to achieve the excitation of the same mode within the required frequency band. Finally, by observing the surface current, it can be found that only the surface current of mode three is concentrated on the central patch, so using coaxial feeding and placing it on the center of the patch can achieve the excitation of only mode three, thereby achieving wide bandwidth performance.

[0028] Mode 1 (black line) is the fundamental mode (lowest-order mode), which may correspond to electric dipole radiation.

[0029] It is more significant in the low-frequency band, contributing to the basic radiation pattern and determining the main lobe direction and initial bandwidth of the antenna.

[0030] Mode 2 (red line) is a magnetic dipole mode or a higher-order electric mode.

[0031] It plays a leading role in the intermediate frequency band, supplementing the radiation of the fundamental mode, and may optimize impedance matching or extend bandwidth.

[0032] Mode 3 (blue line) is a higher-order mode (such as a quadrupole mode).

[0033] It is significantly enhanced in the high frequency band, providing additional radiation paths and further widening the operating frequency band.

[0034] Mode 4 (green line) is a higher-order mode or complex coupled mode.

[0035] It is superimposed with other modes in a specific frequency band to optimize the directivity pattern or gain through phase interference.

[0036] like Figure 5 As shown in the figure, the present invention uses the S11 parameters of the non-periodic square metasurface wide-bandwidth antenna using characteristic mode analysis. It can be seen from the figure that the -10dB bandwidth of this antenna is 59% (6.5-13.52GHz), and the minimum return loss within the working bandwidth is -24dB.

[0037] The upper surface of the antenna of the present invention is a non-periodic square metasurface structure. The square structure can ensure a stronger coupling effect between patches and reduce the antenna profile. The non-periodic square metasurface of the upper surface is analyzed using the characteristic mode analysis method to find a suitable mode, and the current distribution on its surface is analyzed to find a suitable feeding position. Since the square structure of the upper surface is non-periodic, the modal significance and current distribution of the entire metasurface can be controlled by adjusting the side length and gap of each layer of squares to find a suitable mode. After determining the overall size of the metasurface, the current distribution is obtained by characteristic mode analysis to find a suitable feeding position. This antenna is fed by coaxial feeding. The wide bandwidth performance of the antenna is achieved. The present invention applies characteristic mode analysis to the non-periodic square metasurface structure. The square structure enhances the coupling between units and reduces the cross-section of the antenna. The non-periodicity can make the mode of the metasurface structure controllable to find the most suitable mode, simplifying the design process of the metasurface. The low cross-section and wide bandwidth make the present invention have important application prospects in the field of the Internet of Things.

[0038] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A metasurface wide-bandwidth antenna based on characteristic mode analysis is characterized by comprising, from top to bottom, an upper non-periodic square metasurface metal layer, a dielectric layer, and a bottom metal layer, wherein the bottom metal layer is tightly fitted to the dielectric layer, and the geometric centers of the dielectric layer, bottom metal layer, and metasurface metal layer are all on the same straight line.

2. The metasurface wide bandwidth antenna based on characteristic mode analysis according to claim 1, characterized in that: The bottom metal layer is a metal ground plate for coaxial feeding at the center, and the side length is consistent with the length of the dielectric layer.

3. The metasurface wide bandwidth antenna based on characteristic mode analysis according to claim 1, characterized in that: The bottom metal layer is in close contact with the dielectric layer.

4. The metasurface wide bandwidth antenna based on characteristic mode analysis according to claim 1, characterized in that: The upper surface of the dielectric layer is a non-periodic square metasurface metal layer with three layers arranged in a square pattern. The three layers of square metasurface units cut into different specifications have side lengths of 14 mm, 6.5 mm, and 4.5 mm from the center to the outside, respectively.

5. The metasurface wide bandwidth antenna based on characteristic mode analysis according to claim 4, characterized in that: The gaps between square units with the same side length are 0.8 mm, 1 mm, and 0.25 mm from the center outward.

6. The metasurface wide bandwidth antenna based on characteristic mode analysis according to claim 1, characterized in that: Each supersurface unit of the upper non-periodic square supersurface metal layer is a square and is only composed of squares, and the structure of the entire supersurface is also square.

7. The metasurface wide bandwidth antenna based on characteristic mode analysis according to claim 1 or 2, characterized in that: The entire antenna of the non-periodic square metasurface metal layer is a single-layer dielectric layer structure, the upper surface of the dielectric layer is the non-periodic square metasurface metal layer, the lower surface of the dielectric layer is the grounded metal layer, and the feeding position is at the center of the bottom of the antenna dielectric layer.

8. The metasurface wide bandwidth antenna based on characteristic mode analysis according to claim 1, characterized in that: The non-periodic square metasurface metal layers are all arranged in a square and subjected to cutting and reassembly operations.

9. The metasurface wide bandwidth antenna based on characteristic mode analysis according to claim 7, characterized in that: The feeding structure on the grounded metal layer at the bottom of the antenna dielectric layer is coaxial feeding. In the center of the entire antenna, a metasurface unit is placed that coaxially contacts the grounded metal layer to the surface of the dielectric layer. Coaxial feeding can ensure that the feeding current and the surface current after characteristic mode analysis are in the same direction.

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