Metasurface broadband antenna based on eigenmode analysis

Abstract

The application discloses a kind of super surface broadband antennas based on eigenmode analysis, the upper surface of the antenna adopts non-periodic square super surface structure, by adjusting the size of different parts square patch and gap width, the modality significance and current distribution of super surface whole can be regulated, to filter out suitable mode.Determine the size of super surface whole, based on the current distribution obtained by eigenmode analysis, select the optimal feeding position, and adopt coaxial feeding mode to feed the antenna.The application applies eigenmode analysis to the design of non-periodic square super surface structure, by optimizing square patch of different cutting modes, the peripheral surface current is gathered on the center patch, so as to facilitate the observation of the modal characteristics and current distribution of super surface structure, quickly determine the appropriate mode and feeding position, simplify the design process of super surface antenna.

Description

Technical Field

[0001] This invention belongs to the field of microwave antenna technology, specifically relating to a metasurface wideband antenna based on characteristic mode analysis. Background Technology

[0002] With the rapid development of wireless communication technologies such as 5G, Wi-Fi 6, and the Internet of Things (IoT), traditional narrowband antennas can no longer meet the demands of multi-band operation, high data transmission rates, and complex communication environments. Wideband antennas, through technologies such as multi-resonant structures, tapered groove designs, and metamaterials, 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 devices and lowering costs. However, the design of wideband antennas still faces many challenges, such as how to achieve broadband characteristics within a limited size, maintain high radiation efficiency over a wide frequency band, and optimize multi-band performance. Currently, wideband antennas are widely used in mobile communications, radar, satellite communications, IoT, and military aerospace 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 permeability, providing new directions for electromagnetic wave manipulation. Their intentional electromagnetic wave manipulation characteristics make them widely applicable in improving antenna performance, not only broadening antenna design ideas but also effectively solving many bottleneck problems of traditional antennas. The main applications of metasurfaces include: using antennas as feed sources to excite metasurfaces, directly improving antenna performance using metasurfaces, or using metasurfaces as the radiating surface of antennas. Therefore, the rational utilization of metasurfaces is of great significance to modern antenna design.

[0004] While traditional wideband antennas offer significant advantages in extending the frequency range, they also have notable drawbacks. Their physical size is typically large, making it difficult to meet the miniaturization and integration requirements of modern communication equipment. With technological advancements, characteristic mode theory has been widely applied in antenna design guidance. Its core principle involves solving the intrinsic equations of the antenna structure to obtain a set of orthogonal characteristic current modes and their corresponding eigenvalues. These modes reflect the natural resonance characteristics of the antenna at different frequencies. By analyzing these characteristic modes, designers can intuitively understand the radiation mechanism and bandwidth potential of the antenna structure, thereby enabling targeted optimization of antenna performance.

[0005] To design a high-performance widebandwidth antenna, this invention combines metasurface technology with characteristic mode analysis and applies it to the design of a non-periodic square metasurface widebandwidth antenna. Existing antenna technologies have the following shortcomings: 1) Although widebandwidth 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 within a limited space remains a technical challenge; 2) The feeding methods of existing widebandwidth antennas are often complex. Complex feeding structures not only increase design difficulty and cost but may also affect antenna stability. Therefore, how to design a widebandwidth, small-size antenna with a simple feeding method in the smallest possible size has become a current design focus. This invention, by combining metasurfaces and characteristic mode analysis, aims to solve the above problems and provide an efficient, compact, and easily implemented widebandwidth antenna design scheme. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings and deficiencies of the existing technology by proposing a wide-bandwidth metasurface antenna based on eigenmode analysis. This wide-bandwidth antenna features wide bandwidth, low profile, and simple feeding structure. Furthermore, the low profile makes it easy to design and manufacture. Eigenmode analysis is used to analyze the metallic metasurface. By controlling the side length of the square, suitable modes and mode saliency are found. By analyzing the current distribution of the modes, a suitable feeding position is found to achieve wide-bandwidth performance.

[0007] The technical solution adopted by the present invention to solve its technical problem is as follows: 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 closely attached to 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 a metal grounding plate that is coaxially fed from the center, and its side length is the same as that of the dielectric layer. The grounding metal layer is closely attached to the dielectric plate, and the feeding structure is coaxial feeding, with its position located at the center of the bottom metal layer.

[0008] Furthermore, in this invention, each metasurface unit of the upper aperiodic square metasurface metal layer is a square, and consists only of squares, resulting in a square metasurface structure as well. The side length of the dielectric layer is not less than 90 mm. The top view of the dielectric layer and the grounding metal layer is a standard square, and the upper surface of the dielectric layer is an aperiodic square metasurface. The aperiodic square metasurface as a whole comprises three types of metasurface units with different side lengths, totaling 232 metasurface units. Each individual metasurface unit is also a square, with side lengths of 14 mm, 6.5 mm, and 4.5 mm respectively from the center outwards. The gaps between square units of the same side length from the center outwards are 0.8 mm, 1 mm, and 0.25 mm respectively.

[0009] Furthermore, in this invention, the squares and gaps of each layer of the aperiodic square metasurface metal layer on the upper surface of the dielectric layer are adjustable. Characteristic mode analysis (EMA) can be used to analyze the metasurface structure to obtain the mode saliency and current distribution. By adjusting the side length and gaps of the squares at different positions, the mode saliency and current distribution can be changed. EEM can also be used to analyze the mode saliency of aperiodic square metasurface metal layers with different parameters, reducing the influence of higher-order modes on the selected mode. By changing the side length and gaps of the squares, the outermost square has the smallest side length, and the central square has the largest side length. This allows the maximum surface current in multiple frequency bands to be distributed on the central square patch, thereby selecting the mode most suitable for forming a wide bandwidth performance.

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

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

[0012] The wideband antenna of this invention has a feeding structure on the lower surface of the dielectric layer. The antenna uses a coaxial feeding method and employs a copper pillar to contact the non-periodic square metasurface metal element. The radiated energy is conducted to the metasurface metal layer through the copper pillar.

[0013] Compared with the prior art, the present invention has the following technical advantages:

[0014] (1) This invention fills the gap in achieving wide bandwidth antennas using aperiodic square metasurfaces with characteristic mode analysis. Compared with traditional wide bandwidth antennas, this aperiodic square metasurface wide bandwidth antenna innovatively designs the metasurface as a square structure that has been cut and reassembled in different ways. The characteristic mode analysis method is used to analyze the overall structure of the metasurface to find the most suitable modes and current distribution for achieving wide bandwidth performance. The side length and gaps of each square can be adjusted to control the overall mode and current distribution of the metasurface. At the same time, the arrangement of squares enhances the surface coupling and reduces the antenna profile. This antenna adopts a coaxial feeding method. The current distribution of the metasurface is analyzed through characteristic mode analysis to find the feeding position suitable for achieving wide bandwidth, simplifying the feeding design of wide bandwidth antennas. The simple feeding structure of this antenna is easy to manufacture and greatly reduces the cost. The smaller size, wider bandwidth, and simpler feeding method make this invention have greater application potential in the Internet of Things.

[0015] (2) The upper surface of the antenna of the present invention is a non-periodic square metasurface structure. Since there are multiple units in the square structure, it has a stronger coupling effect and can reduce the cross-section of the antenna.

[0016] (3) This invention uses characteristic mode analysis to analyze the aperiodic square metasurface on the upper surface to find suitable modes, and analyzes its surface current to find suitable feed positions. Since the square metasurface structure on the upper surface is aperiodic, by adjusting the square side length and gaps of each layer, suitable feed positions can be found for the overall modal saliency and current distribution of the metasurface. This antenna uses coaxial feeding. Coaxial feeding excites the mode with the widest bandwidth, thereby obtaining wide bandwidth performance.

[0017] (4) This invention applies characteristic mode analysis to aperiodic square metasurface structures. The square structure enhances the coupling between units and reduces the antenna profile. The aperiodicity allows for modal control of the metasurface structure to find the most suitable mode, simplifying the metasurface design process. The wide bandwidth and simple structure make this invention suitable for important applications in the Internet of Things (IoT) field. Attached Figure Description

[0018] Figure 1 This is a structural decomposition diagram of a non-periodic square metasurface wideband antenna using characteristic mode analysis in this invention.

[0019] Figure 2 These are top and bottom views of the non-periodic square metasurface wideband antenna using characteristic mode analysis according to this invention.

[0020] Figure 3This is a side view of the non-periodic square metasurface wideband antenna using characteristic mode analysis according to the present invention.

[0021] Figure 4 This is a mode saliency plot of the metasurface of a wide-bandwidth, non-periodic square metasurface antenna using eigenmode analysis.

[0022] Figure 5 This is a diagram of the S11 parameters of the metasurface of a non-periodic square metasurface wideband antenna using characteristic mode analysis. Detailed Implementation

[0023] To more specifically explain the purpose and technical solutions of this invention, the technical solutions of this invention will be further described below with reference to the accompanying drawings.

[0024] like Figure 1 As shown, this invention utilizes a non-periodic square metasurface wideband antenna based on characteristic mode analysis. It primarily consists of a non-periodic metallic metasurface on the upper surface of a dielectric layer, a dielectric layer, a grounded metallic layer on the lower surface of the dielectric layer, and copper pillars. Specifically, the dielectric layer uses Rogers RO4003 dielectric material with a dielectric constant of 3.55 and a dielectric loss angle of 0.0027. Both the metallic metasurface and the grounded metallic layer are tightly bonded to the dielectric layer. The 90mm square structure of the dielectric layer contains no slots or chamfers.

[0025] like Figure 2 As shown, the non-periodic square metasurface on the upper surface of the dielectric layer of this invention has gaps of 0.8 mm, 1 mm, and 0.35 mm between each metasurface unit from the center outwards, and side lengths of the square patches from the center outwards are 14 mm, 6.5 mm, and 4.5 mm, respectively. The metal ground plane is a square with a side length of 90 mm.

[0026] like Figure 2 As shown, the coaxial power supply method in this invention starts from the center of the grounding metal layer and places a copper pillar with the same height as the dielectric layer and a radius of 0.65mm.

[0027] like Figure 3 As shown, the dielectric layer height of this 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 bonded together.

[0028] like Figure 4As shown in the figure, this invention presents the first four modes of the metasurface structure obtained from the characteristic mode analysis of an aperiodic square metasurface. As can be seen from the figure, mode three, with a mode significance >0.707, has the widest bandwidth. The overall modal significance of the metasurface can be controlled by adjusting its structural parameters. To avoid exciting other modes, the structural parameters of the aperiodic metasurface should be adjusted to ensure that all modes within the desired frequency band are excited by the same mode. Finally, observing the surface current reveals that only the surface current of mode three is concentrated on the central patch. Therefore, using coaxial feeding and placing it at the center of the patch can ensure that only mode three is excited, thus achieving wide bandwidth performance.

[0029] Mode 1 (black line) is the fundamental mode (lowest order mode), which may correspond to electric dipole radiation.

[0030] It has a higher significance in the low-frequency band, contributes to the basic radiation pattern, and determines the main lobe direction and initial bandwidth of the antenna.

[0031] Mode 2 (red line) is the magnetic dipole mode or higher-order electric mode.

[0032] It plays a dominant role in the mid-frequency band, supplements the radiation of the fundamental mode, and may optimize impedance matching or extend bandwidth.

[0033] Mode 3 (blue line) is a higher-order mode (such as the quadrupole mode).

[0034] It significantly enhances performance in the high-frequency band, provides additional radiation paths, and further widens the operating frequency band.

[0035] Mode 4 (green line) is a higher-order mode or a complex coupling mode.

[0036] By superimposing it with other modes in a specific frequency band, the radiation pattern or gain can be optimized through phase interference.

[0037] like Figure 5 As shown, the present invention provides the S11 parameters of a non-periodic square metasurface wideband 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 backoff loss within the operating bandwidth is -24dB.

[0038] The antenna of this invention features an aperiodic square metasurface structure on its upper surface. The square structure ensures stronger coupling between patches, reducing the antenna profile. Characteristic mode analysis (EMA) is used to analyze the aperiodic square metasurface to find suitable modes, and the current distribution on its surface is analyzed to determine the appropriate feed location. Because the square structure of the upper surface is aperiodic, the overall modal significance and current distribution of the metasurface can be controlled by adjusting the side length and gaps of each square layer to find suitable modes. After determining the overall dimensions of the metasurface, EMA is used to obtain the current distribution and find the appropriate feed location. This antenna uses coaxial feeding, achieving wide bandwidth performance. This invention applies EMA to an aperiodic square metasurface structure. The square structure enhances the coupling between elements, reducing the antenna profile. The aperiodicity allows for controllable modes of the metasurface structure to find the most suitable modes, simplifying the metasurface design process. The low profile and wide bandwidth make this invention promising for applications in the Internet of Things (IoT) field.

[0039] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment 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 within the scope of protection of the present invention.

Claims

1. A metasurface wideband antenna based on characteristic mode analysis, characterized in that: from top to bottom, it includes an upper non-periodic square metasurface metal layer, a dielectric layer, and a bottom metal layer, wherein the bottom metal layer is closely attached to the dielectric layer, and the geometric centers of the dielectric layer, the bottom metal layer, and the metasurface metal layer are all on the same straight line. The upper surface of the dielectric layer is a non-periodic metasurface with three layers of squares arranged in a specific pattern. The three layers of square metasurface units cut to different specifications have side lengths of 14mm, 6.5mm, and 4.5mm from the center outwards, respectively. The gaps between square units of the same side length, from the center outwards, are 0.8mm, 1mm, and 0.25mm respectively; The entire antenna of the aforementioned metasurface bandwidth antenna is a single-layer dielectric layer structure. The upper surface of the dielectric layer is a non-periodic square metasurface unit, the lower surface of the dielectric layer is a grounded metal layer, and the feed position is at the center of the bottom of the antenna dielectric layer. The feeding structure on the ground metal layer at the bottom of the antenna dielectric layer is coaxial feeding. At the center of the entire antenna, a metasurface unit is placed coaxially from the ground metal layer to the surface of the dielectric layer. Using coaxial feeding can make the feeding current and the surface current after characteristic mode analysis in the same direction, thereby exciting the desired mode.

2. The metasurface wideband antenna based on characteristic mode analysis according to claim 1, characterized in that: The bottom metal layer is a metal ground plane that is coaxially fed from the center, and its side length is the same as that of the dielectric layer.

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

4. The metasurface wideband antenna based on characteristic mode analysis according to claim 1, characterized in that: The power supply structure is coaxial and located at the center of the bottom metal layer.

5. The metasurface wideband antenna based on characteristic mode analysis according to claim 1, characterized in that: Each metasurface unit of the upper aperiodic square metasurface metal layer is a square and consists only of squares, and the entire metasurface structure is also square.

6. The metasurface wideband antenna based on characteristic mode analysis according to claim 1, characterized in that: The metasurface units are all arranged in a square shape and are cut and reassembled to enhance the coupling between the patches and reduce the antenna profile.

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