A broadband high-gain metasurface antenna and array for millimeter-wave vehicular radar

Abstract

The application provides a broadband high-gain metasurface antenna and array for a millimeter wave vehicle-mounted radar, comprising, from top to bottom, an air cavity dielectric substrate, a metasurface layer, a substrate patch, an upper layer dielectric substrate, a ground layer, a lower layer dielectric substrate and a feed line layer, wherein the metasurface layer is a metasurface patch group composed of 3*3 square patches, a center square patch located at the center position of the metasurface patch group is provided with a slot at the center, corner square patches located at the four corner positions of the metasurface patch group are provided with cut corners at the corners, and peripheral square patches located at the upper, lower, left and right positions of the center square patch are provided with grooves at the outer periphery; wherein the substrate patch is a substrate patch group composed of two rectangular patches arranged at intervals, the substrate patch group is arranged opposite to the metasurface patch group, has a super wideband performance of more than 650 MHz, a maximum gain greater than 6 dBi, and a radiation efficiency of more than 75%.

Description

Technical Field

[0001] This invention relates to the field of antenna design, and in particular to a broadband high-gain metasurface antenna and array for millimeter-wave vehicle-mounted radar. Background Technology

[0002] As modern radar systems continue to evolve towards multi-functionality, high resolution, miniaturization, and intelligence, increasingly stringent requirements are being placed on the core radiating component—the antenna. In particular, with the rapid development of intelligent driving, vehicle-to-everything (V2X) communication, and millimeter-wave radar detection systems towards high resolution, long-range detection, multi-target identification, and all-weather operation, antennas, as the core component of radar systems, face increasingly stringent performance requirements. Antennas often need to simultaneously achieve comprehensive performance indicators such as ultra-wide bandwidth, high gain, high radiation efficiency, low profile, miniaturization, and low coupling in the millimeter-wave band (12–14 GHz), while also meeting the requirements of compact structure, conformal design, and high reliability in vehicle environments.

[0003] Traditional millimeter-wave antennas mainly employ microstrip antennas, horn antennas, parabolic antennas, or conventional phased array antennas. While these antennas have proven mature in specific fields, they face inherent limitations in achieving a comprehensive balance between wide-bandwidth operation, high gain performance, low profile, lightweight design, and conformal characteristics. For example, parabolic antennas, although offering high gain, are typically bulky and have limited bandwidth; traditional phased arrays are expensive, complex in design, and prone to gain degradation and beam distortion during high-frequency wide-angle scanning. Therefore, exploring new antenna technologies to overcome these bottlenecks has become a cutting-edge issue in the radar field.

[0004] Against this backdrop, metasurface technology offers a new approach to overcoming the aforementioned bottlenecks. A metasurface is a two-dimensional artificial electromagnetic structure composed of subwavelength-scale units arranged in a specific sequence. It can flexibly control the amplitude, phase, and polarization of electromagnetic waves with a layer thickness much smaller than the operating wavelength. Loading a metasurface onto an antenna can effectively improve impedance matching, extend the operating bandwidth, and enhance radiation gain. However, existing metasurface antennas still suffer from the following key technical bottlenecks: 1. Most metasurfaces only support single-mode or weakly coupled multi-mode operation, making it difficult to maintain stable high gain over a wide bandwidth; 2. A lack of precise mode design based on physical mechanisms leads to poor mode matching between metasurface units and the feeding structure, resulting in low energy coupling efficiency; 3. Significant substrate loss, surface wave loss, and feed loss at high frequencies result in low radiation efficiency.

[0005] Characteristic Mode Analysis (CMA) is an efficient analytical method that can analyze the intrinsic modes, mode saliency, current distribution, and radiation characteristics of antenna structures from a physical perspective. It can accurately identify the optimal radiation mode of an antenna, suppress unwanted clutter modes, and guide key design aspects such as slotting / cutting / loading of the structure, significantly improving the mode utilization, bandwidth, and gain of metasurface antennas. However, there is still a lack of systematic solutions that combine characteristic mode analysis with metasurface multimode resonance, air cavity impedance matching, and array low-coupling design.

[0006] In summary, the existing technology still lacks an antenna design scheme that combines theoretical guidance and engineering practicality, which can effectively overcome the bottleneck of bandwidth and gain constraints, and meet the urgent needs of millimeter-wave vehicle radar for wide bandwidth, high gain and high radiation efficiency while achieving low profile. Summary of the Invention

[0007] The purpose of this invention is to provide a broadband high-gain metasurface antenna and array for millimeter-wave vehicle-mounted radar, which has an ultra-wideband performance of over 650 MHz, a maximum gain of over 6 dBi, and a radiation efficiency of over 75%, in order to meet the requirements of radar systems for high-performance antennas and provide new ideas and methods for radar antenna design.

[0008] To achieve the above objectives, this technical solution provides a broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar, comprising: an air cavity dielectric substrate, a metasurface layer, a substrate patch, an upper dielectric substrate, a ground layer, a lower dielectric substrate, and a feed line layer arranged sequentially from top to bottom. The metasurface layer is a metasurface patch group composed of 3×3 square patches. The center square patch located at the center of the metasurface patch group has a slot at its center, the corner square patches located at the four corners of the metasurface patch group have chamfered corners, and the peripheral square patches located above, below, left, and right of the center square patch have grooves on their outer peripheries. The substrate patch is a substrate patch group composed of two rectangular patches arranged at intervals, with the substrate patch group facing the metasurface patch group.

[0009] Secondly, this solution provides a broadband high-gain metasurface antenna array for millimeter-wave vehicle-mounted radar, including the broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar mentioned in the first aspect.

[0010] Compared with existing technologies, this technical solution has the following characteristics and beneficial effects: This design presents a broadband, high-gain metasurface microstrip patch antenna with a center frequency of 13.1 GHz. The metasurface unit structure is optimized using Characteristic Mode Analysis (CMA), employing a design scheme of loading periodic slots onto a square patch to effectively control the antenna's operating modes. Combining microstrip line rectangular coupling feed with ground plane slotting technology, and introducing an air cavity layer between the metasurface and the feed structure, impedance matching and energy transfer efficiency are further improved. Modeling and simulation using CST software show that the antenna achieves an impedance bandwidth of 2100 MHz with |S11| < -10 dB in the 12.1–14.2 GHz band, exhibiting excellent impedance matching, a peak gain of 8 dBi, and a radiation efficiency exceeding 90%. The simulation data effectively validates the feasibility of this design, providing new insights for the miniaturization and high-performance design of millimeter-wave radar antennas. Furthermore, based on this, a 2×2 antenna array is constructed to further enhance its gain, and CST simulations are performed. Experimental results show that the antenna array operates with a bandwidth of 12.1–14.2 GHz and a peak gain of 13.6 dBi. This antenna array not only possesses excellent bandwidth and gain characteristics but also exhibits superior directivity, meeting the stringent requirements of high-performance communication systems for signal transmission quality and coverage. Attached Figure Description

[0011] Figure 1 This is a side view of a broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar designed according to the present invention.

[0012] Figure 2 This is a schematic diagram of the metasurface layer of a broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar designed according to the present invention.

[0013] Figure 3 This is a schematic diagram of the substrate patch of a broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar designed according to the present invention.

[0014] Figure 4 This is a schematic diagram of the grounding layer of a broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar designed according to the present invention.

[0015] Figure 5 This is a schematic diagram of the structure of a broadband high-gain metasurface antenna feed layer for millimeter-wave vehicle-mounted radar designed according to the present invention.

[0016] Figure 6 This is a schematic diagram of the structure of a broadband high-gain metasurface antenna array for millimeter-wave vehicle-mounted radar designed according to the present invention.

[0017] Figure 7This is a modal significance (MS) curve of a broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar designed according to the present invention.

[0018] Figure 8 This invention relates to the surface current and radiation pattern of a broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar designed in this invention, under characteristic modes.

[0019] Figure 9 This is a schematic diagram of the return loss and gain of a broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar designed in this invention.

[0020] Figure 10 This is a schematic diagram of the electric field distribution of a broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar designed in this invention at 12.5 GHz and 13.5 GHz.

[0021] Figure 11 This invention relates to the radiation efficiency and overall efficiency of a broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar.

[0022] Figure 12 This invention describes the radiation pattern of a broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar with a phi of 0 at 13.1 GHz.

[0023] Figure 13 This invention presents a broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar with a phi of 90 at 13.1 GHz.

[0024] Figure 14 This is a schematic diagram of a metasurface structure for a broadband high-gain metasurface antenna array for millimeter-wave vehicle-mounted radar designed according to the present invention.

[0025] Figure 15 This is a schematic diagram of the feeding structure of a broadband high-gain metasurface antenna array for millimeter-wave vehicle-mounted radar designed according to the present invention.

[0026] Figure 16 This is a side view of a broadband high-gain metasurface antenna array for millimeter-wave vehicle-mounted radar designed according to the present invention.

[0027] Figure 17 This is a schematic diagram of the return loss and gain of a broadband high-gain metasurface antenna array for millimeter-wave vehicle-mounted radar designed in this invention.

[0028] Figure 18 This invention presents the radiation pattern of a broadband high-gain metasurface antenna array for millimeter-wave vehicle-mounted radar at 13.1 GHz, showing the E-plane main polarization and cross-polarization.

[0029] Figure descriptions: 10-Metasurface layer, 11-Square patch, 111-Center square patch, 112-Corner square patch, 113-Peripheral square patch, 20-Air cavity dielectric substrate, 30-Substrate patch, 31-Rectangular patch, 40-Upper dielectric substrate, 50-Lower dielectric substrate, 60-Feeder layer, 61-Long feeder, 62-Virtual short path stub, 70-Ground layer, 71-Rectangular gap. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0031] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0032] Example 1: This solution provides a broadband high-gain metasurface antenna, i.e., an antenna array, for millimeter-wave vehicle-mounted radar. The center frequency of this broadband high-gain metasurface antenna is 13.1 GHz, and it achieves an impedance bandwidth of 2100 MHz with |S11| < -10 dB in the 12.1-14.2 GHz band. It has very good impedance matching effect, a peak gain of 8 dBi, and a radiation efficiency of over 90%, providing a new approach for the miniaturization and high-performance design of millimeter-wave radar antennas.

[0033] Specifically, such as Figures 1-5 As shown, the broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar includes: The following layers are arranged sequentially from top to bottom: air cavity dielectric substrate 20, metasurface layer 10, substrate patch 30, upper dielectric substrate 40, ground layer 70, lower dielectric substrate 50, and feed line layer 60, wherein the metasurface layer 10 has 3 layers. The metasurface patch group consists of 3 square patches 11, wherein the center square patch 111 located at the center of the metasurface patch group has a groove in its center, the corner square patches 112 located at the four corners of the metasurface patch group have chamfered corners, and the outer periphery of the peripheral square patches 113 located at the top, bottom, left and right positions of the center square patch 111 has a groove; wherein the substrate patch 30 is a substrate patch group consisting of two rectangular patches 31 spaced apart, and the substrate patch group is positioned directly opposite the metasurface patch group.

[0034] Regarding the structure of metasurface layers, such as Figure 2 As shown, the metasurface layer 10 includes a central square patch 111 located at the center, four corner square patches 112 located at the corners, and four peripheral square patches 113 located above, below, left, and right of the central square patch 111. The central square patch 111, the corner square patches 112, and the peripheral square patches 113 are arranged at a 3:1 ratio. The three-dimensional array is arranged at intervals to form a metasurface patch group.

[0035] Furthermore, the central square patch 111, the corner square patches 112, and the peripheral square patches 113 are all the same size, and the spacing between them is also the same. This design allows the electromagnetic coupling strength between adjacent patches to remain completely consistent and predictable. The resonant frequency of each patch can be independently and precisely tuned simply by adjusting the size of the local microstructure, without the need for repeated iterations to optimize the coupling relationship between resonance and coupling. This significantly reduces the design difficulty and shortens the R&D cycle. At the same time, it allows 5 to 6 adjacent resonant peaks to smoothly merge into a continuous wide operating band with uniform coupling strength, avoiding the gain dip and performance fluctuation problems caused by uneven coupling strength under non-uniform arrangement. It also makes the surface current distribution of the entire metasurface layer more uniform, avoiding the additional loss and high sidelobes caused by current concentration, effectively improving radiation efficiency and antenna gain.

[0036] In some embodiments, a regular hexagonal slot is formed at the center of the central square patch 111, with the center of the regular hexagonal slot directly opposite the center of the central square patch 111. This can further improve the performance of the antenna. Compared with conventional rectangular or cross-shaped slots, this six-fold rotationally symmetric structure can achieve an omnidirectional consistent current path extension effect. It can reduce the main resonant frequency more efficiently and achieve miniaturization without increasing the patch size. At the same time, it can excite multiple polarization-independent degenerate resonant modes, which can be better coupled and integrated with the resonant modes of the surrounding patches, further expanding the operating bandwidth. It can also ensure the polarization stability of the antenna and avoid performance deviations under different polarization directions, thus adapting to the moving target detection requirements of vehicle radar in complex road conditions.

[0037] Preferably, the central square patch 111 is a centrally symmetrical shape.

[0038] As mentioned earlier, chamfers are formed at the corners of the four corner square patches 112 located at the four corners of the metasurface patch group. Specifically, chamfers are formed at the free corners of each corner square patch 112, where free corners are corners that are not close to the peripheral square patches or the central square patch. Correspondingly, chamfers are formed at the four corners of the metasurface patch group.

[0039] In some embodiments, the chamfers formed on each of the square patches 112 are the same, that is, the four corners of the metasurface patch group are the same.

[0040] As mentioned earlier, grooves are formed on the outer periphery of the peripheral square patches 113 located above, below, left, and right of the central square patch 111. Specifically, a groove is formed at the middle of the free edge of each peripheral square patch 113, wherein the free edge is the side edge of the square patch that is not near the corner or the central square patch. Correspondingly, grooves are formed at the middle of the four sides of the metasurface patch group.

[0041] In some embodiments, rectangular grooves are formed by indentation on the free edges of each peripheral square patch 113, and the rectangular grooves on each peripheral square patch 113 have the same shape and size.

[0042] It should be noted that the groove on each peripheral square patch 113 is a groove that is open on one side, that is, it is equivalent to opening a notch inward on the free edge of each peripheral square patch 113.

[0043] In this design, grooves are formed on the peripheral square patches 113, chamfers are formed on the corner square patches 112, and slots are formed on the central square patch 111. The three elements work together to ensure that the 5-6 adjacent resonance peaks of the 9 square patches exactly cover the target operating frequency band of the millimeter-wave vehicle radar. Combined with the uniform coupling strength between patches under a uniform base, the originally discrete narrow resonance peaks are smoothly merged into a continuous ultra-wide operating band, which completely solves the pain point of insufficient bandwidth of traditional metasurface antennas. At the same time, the three elements can also work together to optimize the surface current distribution of the entire metasurface layer, making the current distribution more uniform, suppressing local energy concentration and surface wave propagation, effectively improving radiation efficiency and antenna gain, and reducing sidelobes.

[0044] Preferably, the metasurface patch group is a centrally symmetrical pattern.

[0045] The structure of the substrate patch 30 in this solution is as follows: Figure 3 As shown, the substrate patch 30 is a substrate patch group consisting of two rectangular patches 31 spaced apart, wherein each rectangular patch 31 has the same shape and size, and the two rectangular patches are arranged in parallel and spaced apart to form a gap. That is, the substrate patch group 30 of this solution is a square patch structure with a gap in the middle.

[0046] It should be noted that introducing a rectangular gap on the substrate patch 30 in this solution is equivalent to introducing additional inductance and capacitance into the substrate patch, which will change the impedance distribution; it can achieve better matching at multiple frequency points, thereby expanding the bandwidth.

[0047] In some embodiments, each substrate patch group is positioned opposite each metasurface patch group.

[0048] The structure of the grounding layer in this scheme is as follows: Figure 4 As shown, in this design, a rectangular slot 71 is formed on the ground layer 70, directly opposite the slot of the substrate patch assembly. The length of the rectangular slot 71 is no longer than the length of the gap between the two substrate patches on the substrate patch assembly. The purpose of designing the rectangular slot on the ground layer 70 in this design is to effectively excite specific modes, which helps to improve the radiation characteristics and gain performance of the antenna.

[0049] The structure of the feeder layer in this solution is as follows: Figure 5 As shown, the feed line layer 60 includes a long feed line 61 and a virtual short path stub 62 located at the end of the long feed line 61. One end of the long feed line 61 is grounded, and the other end is connected to the virtual short path stub 62. The virtual short path stub 62 is positioned opposite the metasurface patch group and the substrate patch group.

[0050] In some embodiments, the virtual short path stub 62 is a fan with an opening angle of 90° and symmetrically arranged relative to the end of the long feed line 61 to ensure effective energy coupling between the antenna and the external circuit, thereby improving the overall system efficiency.

[0051] In addition, such as Figure 1 As shown, this scheme not only optimizes the shape of the metasurface layer 10, substrate patch 30, ground layer 70 and feed line layer 60, but also sets an air cavity dielectric substrate 20 above the metasurface layer 10, thereby realizing the collaborative design of the metasurface and the air cavity. This effectively breaks through the bottleneck of bandwidth and gain being mutually constrained in traditional antenna design and provides a reusable design paradigm for subsequent research.

[0052] In some embodiments, the air cavity dielectric substrate 20, the upper dielectric substrate 40, and the lower dielectric substrate 50 are all made of Rogers RO3003 material with a dielectric constant εr = 3; the metasurface layer, substrate patch 30, ground layer 70, and feed line layer 60 are made of copper, thereby improving the radiation performance and stability of the antenna.

[0053] In some embodiments, the air cavity dielectric substrate 20, the upper dielectric substrate 40, and the lower dielectric substrate 50 are 15 mm long, 15 mm wide, and 0.76 mm thick.

[0054] In some embodiments, the air cavity dielectric substrate 20 is 2.01 mm away from the ground layer, that is, the air cavity dielectric substrate 20 is disposed at a distance of 2.01 mm from the ground layer.

[0055] As described above, the broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar proposed in this scheme employs rectangular slots on the substrate patch 30 to improve impedance matching and bandwidth. The antenna performance is further optimized through the slotting and chamfering design of the metasurface patch on the metasurface layer 10. Verification shows that after introducing the metasurface structure, the antenna generates a new resonant point, effectively expanding the bandwidth and improving radiation efficiency and gain. Furthermore, combined with the design of the air cavity dielectric substrate 20, the antenna achieves excellent impedance matching.

[0056] Simulation results show that the antenna achieves good impedance matching within the 12.1–14.2 GHz band, with gains ranging from 7.2 to 8.2 dBi. Notably, the antenna achieves a gain of 7.7 dBi at 13.1 GHz, exhibiting high and stable overall gain, indicating good directivity and radiation capability. The impedance matching band covers 12.1–14.2 GHz, with a relative bandwidth of approximately 16%. The radiation efficiency exceeds 90%, consistent with the overall efficiency trend, demonstrating the outstanding radiation performance of the antenna element structure and low losses in the conductor and dielectric.

[0057] In some embodiments, after modeling, simulating and optimizing the antenna elements using CST, the dimensions of the broadband high-gain metasurface antenna for millimeter-wave vehicle radar are: 15 mm × 15 mm × 4.29 mm, wherein the size of the metasurface patch group of the metasurface layer is 2.0 mm, the height of the air cavity dielectric substrate 20 is 2.01 mm, the width of the rectangular slot on the ground layer is 0.2 mm, and the slot length is 9 mm.

[0058] Example 2: like Figure 6 , Figure 14 and Figure 16 As shown, this solution provides a broadband high-gain metasurface antenna array for millimeter-wave vehicle-mounted radar, including at least one broadband high-gain metasurface antenna as described above, arranged in an array.

[0059] Specifically, the broadband high-gain metasurface antenna array for millimeter-wave vehicle-mounted radar includes four broadband high-gain metasurface antennas as described in the first aspect, wherein the broadband high-gain metasurface antennas are arranged in a 2 Arranged in an array of 2.

[0060] Specifically, the broadband high-gain metasurface antenna array for millimeter-wave vehicle-mounted radar includes, from top to bottom, an air cavity dielectric substrate 20, a metasurface layer 10, a substrate patch 30, an upper dielectric substrate 40, a ground layer 70, a lower dielectric substrate 50, and a feed line layer 60. The metasurface layer 10 includes four metasurface patch groups, with each metasurface patch group consisting of 3... The metasurface patch group consists of three square patches 11. The center square patch 111 located at the center of the metasurface patch group has a slot. The corner square patches 112 located at the four corners of the metasurface patch group have chamfered corners. The outer periphery of the peripheral square patches 113 located at the top, bottom, left and right positions of the center square patch 111 has grooves. The substrate patch 30 includes four substrate patch groups. Each substrate patch group includes two rectangular patches 31 arranged at intervals. Each substrate patch group is positioned directly opposite the metasurface patch group.

[0061] At this time, as Figure 15 As shown, four rectangular slots are formed on the ground layer relative to the slots of the substrate patch group. The feed line layer 60 of the feed layer includes a T-shaped power divider, wherein four long feed lines 61 are provided in the four directions of the T-shaped power divider and virtual short path stubs 62 are placed at the ends of the long feed lines 61, wherein each virtual short path stub 62 is positioned directly opposite the metasurface patch group.

[0062] In some embodiments, the length of the elongated feed line 61 in this solution must also be greater than half the wavelength to satisfy the resonance condition, and the length of the elongated feed line 61 must be greater than the length of the rectangular slot 71 to ensure effective energy coupling between the antenna element feed line and the rectangular slot. In this invention, the length of the elongated feed line 61 is 11 mm.

[0063] In some embodiments, the spacing between broadband high-gain metasurface antennas in a broadband high-gain metasurface antenna array for millimeter-wave vehicle radar is greater than half a wavelength, which effectively avoids coupling between elements, reduces mutual interference, and thus improves the overall performance and radiation efficiency of the antenna array. The array arrangement enables spatial multiplexing and multipath propagation of signals, thereby effectively improving the system gain and anti-interference capability. The array is designed to improve antenna gain and directivity while maintaining a compact structure.

[0064] In some embodiments, the element spacing of each broadband high-gain metasurface antenna is set to 18 mm, the thickness of the upper dielectric substrate is 0.76 mm, the thickness of the lower dielectric substrate is 0.76 mm, the height of the dielectric substrate in the air cavity is 0.76 mm, and the rectangular slot of the ground layer has a length of 7 mm and a width of 0.25 mm.

[0065] Simulation results show that the broadband high-gain metasurface antenna array for millimeter-wave vehicle radar operates with a bandwidth of approximately 12.1–14.2 GHz and a peak gain of 13.6 dBi. This antenna array combines excellent bandwidth and gain performance with good directional radiation characteristics, fully meeting the stringent requirements of high-performance communication systems in terms of signal transmission quality and coverage.

[0066] Modal characteristic analysis of substrate patch in Example 3: To analyze the modal characteristics of the substrate patch of the broadband high-gain metasurface antenna for millimeter-wave vehicle radar in this scheme, a PEC (perfect electrical conductor) boundary condition in the -z direction is adopted, while other directions are open boundaries to simulate the radiation situation in free space. Through this boundary setting, the radiation characteristics of the antenna in the actual working environment can be accurately simulated, and the modes of the upper substrate patch can be analyzed.

[0067] The experimental process for modal saliency analysis was conducted using the eigenmode analysis function of CST software. First, a geometric model of the substrate patch was established in the CST simulation software, setting the substrate material, patch size, and boundary conditions. Then, the eigenmode solver was activated, the solution frequency range was set, and the number of modes to be calculated (4) was specified. After solving, the eigenvalue λ of each mode at each frequency point was extracted, and the MS value of each mode at each frequency point was calculated according to the definition of modal saliency: MS = 1 / |1+jλ|. Finally, the MS values ​​at different frequencies were summarized to obtain the modal saliency distribution of each mode of the substrate patch in the operating frequency band. For the patch structure of the substrate patch, mode 1 exhibits high modal saliency, indicating that the structure can effectively excite this mode in the operating frequency band, thus providing strong radiation capability and a wide operating bandwidth.

[0068] Figure 7 The results of modal significance analysis of the substrate patch in this scheme are presented. Figure 7 Modes 1 to 4 refer to the first four characteristic modes obtained from the analysis of the substrate patch structure based on Characteristic Mode Theory (CMA).

[0069] Figure 8 The surface current and radiation patterns of the antenna's four characteristic modes at 13.1 GHz are shown. Figure 8 In the diagram, (a), (b), (c), and (d) represent the surface current and radiation pattern of the antenna element in modes 1-4, respectively. Figure 8As shown in (a), under this feeding structure, the surface current of the substrate patch in mode 1 is vertically distributed. This vertical current distribution characteristic indicates that mode 1 of the substrate patch is effectively excited, demonstrating that the feeding structure can accurately excite the target mode, ensuring good radiation performance of the antenna in this operating frequency band. The vertical surface current distribution is ideal because it is highly consistent with the target mode in the metasurface design, which helps optimize the antenna's gain, directivity, and beamforming effect. Through this excitation mode, the antenna can achieve efficient energy transfer and radiation in the target frequency band, thereby improving the overall system performance and meeting the requirements of high gain and high directivity. Furthermore, from... Figure 8 As observed in (a), the antenna exhibits significant radiation directivity within the target frequency band, concentrating radiated energy in a specific direction. This radiation pattern validates the effectiveness of the metasurface design, demonstrating that the antenna achieves ideal beamforming and possesses high gain. At 13.1 GHz, the antenna's radiated energy is primarily concentrated in the main radiation direction, while radiation in other directions is relatively suppressed, further enhancing signal transmission efficiency and directivity. This optimized radiation pattern ensures superior antenna performance in high-performance communication and radar applications. The results indicate that this structure effectively concentrates radiated energy, improves beamforming, and thus further enhances the radiation performance of the antenna element in a specific direction.

[0070] from Figure 8 As can be seen in (b) of the diagram, under this feeding structure, the surface current of the substrate patch in mode 2 is horizontally distributed. This horizontal current distribution characteristic indicates that mode 2 of the substrate patch cannot be effectively excited within the operating frequency band.

[0071] like Figure 8 As shown in (c) and (d), the current distribution of modes 3 and 4 is odd-symmetric at the origin, resulting in a significant radiation blind zone in the main radiation direction of the z-axis. In actual antenna operation, modes 3 and 4 are modes that are not desired to be excited.

[0072] Example 4: Antenna return loss and gain test: The return loss and gain of the test antenna are shown in the diagram below. Figure 9 As shown, from Figure 9 As can be seen from the above, the impedance bandwidth of the metasurface antenna element of the present invention with a return loss of less than -10 dB is 12.1-14.2 GHz, the relative bandwidth reaches 16.1%, and the gain within the operating bandwidth is 7.2-8.2 dBi.

[0073] Example 5: Performance test of the grounding layer: The performance test was performed using CST simulation software: First, a three-dimensional simulation model of the metasurface antenna element was established. Then, an electric field monitor was used to monitor the frequencies at 12.5 GHz and 13.5 GHz. After the simulation was completed, the electric field distribution at the rectangular slot 71 was extracted. Schematic diagrams of the electric field distribution of the metasurface antenna element at 12.5 GHz and 13.5 GHz at the rectangular slot are shown below. Figure 10 As shown, the rectangular slot 71 of the feeder line 61 at 12.5 GHz and 13.5 GHz excites half-wavelength electric field distributions.

[0074] Example 6: Test on the effect of far-field conditions on antenna radiation performance: Antenna radiation pattern is a key electrical parameter characterizing the radiation intensity distribution of an antenna in space. To further investigate the influence of the metasurface on far-field radiation behavior, the radiation patterns of this metasurface antenna element at 13.1 GHz were plotted using CST software at two cross-sections: phi=0° and phi=90°. The results are shown in the figures below. Figure 12 and Figure 13 As can be seen in the phi=0° section, the main lobe gain of the antenna element is approximately 7.61 dBi, the 3dB beamwidth is 75.6°, and the sidelobe level is -14.7 dB, demonstrating strong radiation capability. In the phi=90° section, the main lobe gain is approximately 7.61 dBi, the 3dB beamwidth is 76.4°, and the sidelobe level is also -14.6 dB. Overall, the antenna element maintains good gain performance and low sidelobes at different azimuth angles, effectively concentrating radiated energy and meeting the design requirements.

[0075] Example 7: Return loss and gain test of antenna array: A schematic diagram of the return loss and gain of the test antenna array is shown below. Figure 17 As shown, the impedance bandwidth of the metasurface antenna array of the present invention with a return loss of less than -10 dB is 12.1-14.2 GHz, and the relative bandwidth is about 16.1%. The gain within the operating bandwidth is 12.6-13.7 dBi. Therefore, the metasurface antenna array of the present invention has a wide operating bandwidth and significantly high gain, which can meet the application requirements of wireless communication, radar systems and other high-performance signal transmission.

[0076] Example 8: Simulation Experiment Test of Antenna Array: In the CST simulation experiment, the overall length and width of the metasurface antenna array are 50 mm, and the spacing between the metasurface antenna elements is 18 mm. This layout not only achieves high gain, but also effectively realizes a MIMO (Multiple Input Multiple Output) antenna system. This combined design makes the antenna array more adaptable and flexible in modern wireless communication and radar applications, meeting the growing demand for high-performance antennas.

[0077] In the CST simulation experiment, the radiation patterns of the metasurface antenna array at 13.1 GHz with E-plane principal polarization and cross-polarization were measured as follows: Figure 18 As shown in the figure, the metasurface antenna array exhibits good radiation characteristics. The radiation patterns of both the main polarization and cross-polarization show relatively ideal beam shapes, with a high-gain and highly directive main lobe and a low sidelobe effect, indicating that the antenna array can effectively concentrate energy in a specific direction.

[0078] In summary, the antenna gain as a function of frequency, obtained through simulation and analysis using CST software (e.g., Figure 9 The relationship curves between (as shown) radiation efficiency and total efficiency (e.g.) Figure 11 As shown in the figure, analysis reveals that the antenna resonates at approximately 13.1 GHz, operating in the 12.1–14.2 GHz band. The gain curve indicates that the antenna element's gain remains stable above 7.2 dBi throughout the entire operating band, gradually increasing with frequency, reaching a peak gain of 8.2 dBi at 14.0 GHz. The radiation efficiency is close to 1 (100%), with a maximum overall efficiency of approximately 0.97 and a minimum of approximately 0.87. This antenna element exhibits wide bandwidth, high gain, low loss, and low profile characteristics. Based on this, CST software simulation shows that the corresponding antenna array has a bandwidth range of 12.1–14.2 GHz and a gain range of 12.6–13.7 dBi, demonstrating high gain and a wide operating band, meeting the application requirements of wireless communication, radar systems, and other high-performance signal transmission.

[0079] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar, characterized in that, include: The following components are arranged sequentially from top to bottom: an air cavity dielectric substrate (20), a metasurface layer (10), a substrate patch (30), an upper dielectric substrate (40), a ground layer (70), a lower dielectric substrate (50), and a feed line layer (60). The metasurface layer (10) is a metasurface patch group composed of 3×3 square patches (11). The center square patch (111) located at the center of the metasurface patch group has a slot in the center. The corner square patches (112) located at the four corners of the metasurface patch group have chamfered corners at their corners. The peripheral square patches (113) located at the top, bottom, left, and right of the center square patch (111) have grooves at their outer periphery. The substrate patch (30) is a substrate patch group composed of two rectangular patches (31) arranged at intervals. The substrate patch group is set directly opposite the metasurface patch group.

2. The broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar according to claim 1, characterized in that, A regular hexagonal slot is provided at the center of the central square patch (111), wherein the center of the regular hexagonal slot is directly opposite the center of the central square patch (111); a chamfer is formed at the free corner position on each corner square patch (112), wherein the free corner is not close to the corner of the peripheral square patch and the central square patch; a groove is formed at the middle position of the free edge of each peripheral square patch (113), wherein the free edge is not close to the side of the corner square patch and the central square patch.

3. The broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar according to claim 1, characterized in that, The central square patch (111), the corner square patches (112), and the peripheral square patches (113) are the same size, and the spacing between the central square patch (111), the corner square patches (112), and the peripheral square patches (113) is also the same.

4. The broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar according to claim 1, characterized in that, The metasurface patch group is a centrally symmetrical shape.

5. The broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar according to claim 1, characterized in that, A rectangular slot (71) is formed on the ground layer (70) facing the slot of the substrate patch assembly, wherein the length of the rectangular slot (71) is not longer than the length of the gap between two substrate patches on the substrate patch assembly.

6. The broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar according to claim 1, characterized in that, The feed line layer (60) includes a long feed line (61) and a virtual short path stub (62) located at the end of the long feed line (61). One end of the long feed line (61) is grounded and the other end is connected to the virtual short path stub (62). The virtual short path stub (62) is positioned opposite the metasurface patch group and the substrate patch group. The virtual short path stub (62) is a fan with an opening angle of 90° and is symmetrically arranged with respect to the end of the long feed line (61).

7. The broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar according to claim 1, characterized in that, The air cavity dielectric substrate (20), the upper dielectric substrate (40) and the lower dielectric substrate (50) are all made of Rogers RO3003 material, and the metasurface layer, substrate patch (30), ground layer (70) and feed line layer (60) are made of copper.

8. The broadband high-gain metasurface antenna for millimeter-wave vehicle-mounted radar according to claim 1, characterized in that, Good impedance matching was achieved in the range of 12.1–14.2 GHz, with in-band gains of 7.2–8.2 dBi.

9. A broadband high-gain metasurface antenna array for millimeter-wave vehicle-mounted radar, characterized in that, At least one broadband high-gain metasurface antenna according to any one of claims 1 to 5 is arranged in an array.

10. The broadband high-gain metasurface antenna array for millimeter-wave vehicle-mounted radar according to claim 9, characterized in that, The broadband high-gain metasurface antenna is arranged in a 2×2 array, wherein the metasurface layer (10) includes four metasurface patch groups, the substrate patch (30) includes four substrate patch groups, each substrate patch group is positioned opposite the metasurface patch group, and four rectangular slots are formed on the ground layer relative to the slots of the substrate patch groups. The feed line layer (60) of the feed layer includes a T-shaped power divider, wherein four long feed lines (61) are provided in the four directions of the T-shaped power divider and virtual short path stubs (62) are placed at the ends of the long feed lines (61), wherein each virtual short path stub (62) is positioned opposite the metasurface patch group.

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