One-dimensional microstrip array antenna loaded with electromagnetic metasurface

Abstract

The invention discloses a one-dimensional microstrip array antenna loaded with an electromagnetic metasurface, which comprises a transmission type electromagnetic metasurface layer and a one-dimensional microstrip antenna array, and is characterized in that the transmission type electromagnetic metasurface layer is arranged right above the phase center of the one-dimensional microstrip antenna array. The transmission type electromagnetic metasurface layer adopts a one-dimensional phase modulation mode, and phase modulation is only carried out on a y-axis plane perpendicular to the arrangement direction of the one-dimensional microstrip antenna array. According to the invention, high-gain, low-sidelobe and wide-angle stable scanning in a wide frequency band is realized, and batch application requirements of airborne platforms are met.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, specifically relating to a one-dimensional microstrip array antenna loaded with an electromagnetic metasurface. Background Technology

[0002] Airborne fire control radar and surveillance systems are core components of aircraft target detection, tracking, guidance, and airspace surveillance. As a key component for electromagnetic signal transmission and reception in this system, the antenna's performance directly determines the system's detection range, target resolution accuracy, surveillance range, and anti-interference capability. In high-dynamic airborne operating environments, antennas must simultaneously meet excellent electromagnetic performance and stringent airborne environmental adaptability requirements: Electromagnetically, the antenna must possess high gain, wide bandwidth, wide-angle scanning, low sidelobes, and high radiation efficiency to ensure accurate long-range detection and wide-range airspace surveillance; In terms of airborne adaptability, the antenna must have a low profile, be lightweight, and small in size to fit the aerodynamic layout of the fuselage and reduce flight drag, while also possessing physical characteristics such as vibration resistance, resistance to extreme temperature changes, and high structural strength to adapt to the harsh environment of high-speed flight, vibration, shock, and high-altitude temperature variations. Furthermore, the structure must be simple, easy to manufacture and integrate, and adaptable to the mass application requirements of airborne platforms.

[0003] One-dimensional microstrip array antennas have become one of the preferred antenna forms for airborne microwave radio frequency systems due to their advantages of compact structure, light weight, low processing cost, and easy integration with planar circuits. However, their traditional structure has problems such as low gain, severe gain attenuation during wide-angle scanning, and high sidelobe level, which make it difficult to meet the high-performance application requirements of airborne fire control radar and surveillance systems.

[0004] Electromagnetic metasurfaces are two-dimensional artificial electromagnetic structures composed of subwavelength units. By designing the geometric parameters and arrangement of these units, the amplitude, phase, and polarization characteristics of electromagnetic waves can be flexibly controlled, providing a novel solution for antenna performance optimization. Transmissive electromagnetic metasurfaces possess the core advantages of beam focusing and phase compensation. Combining them with one-dimensional microstrip array antennas allows for the conversion of spherical waves radiated by the array into plane waves through lens focusing, achieving antenna gain enhancement and beam control. This has become a core technological path to overcome the performance bottlenecks of traditional airborne microstrip array antennas. Integrating transmissive electromagnetic metasurfaces with one-dimensional microstrip array antennas, utilizing the synergistic effect of small-scale antenna arrays and metasurfaces to replace traditional large-scale arrays, retains the compactness and lightweight advantages of microstrip arrays while achieving high gain and narrow beam through metasurface beam control. Simultaneously, it increases the antenna's power capacity, meeting the application requirements of airborne fire control radar and surveillance systems, and has become a research hotspot in this field.

[0005] Currently, various implementation schemes have been developed for microstrip array antennas loaded with electromagnetic metasurfaces. However, existing technologies still face numerous technical bottlenecks when adapting to airborne fire control radar and surveillance systems. Specifically: 1) Existing metasurface loading schemes are mostly designed for single antennas or general-purpose arrays, failing to adapt to the high-dynamic environment of airborne systems. The antenna profiles are too high, the structures are redundant, they cannot conform to the aerodynamic layout of the fuselage, and their vibration resistance and temperature adaptability are poor, making it difficult to meet the physical environment requirements of airborne platforms; 2) Traditional metasurface gain enhancement schemes are mostly single-band designs with fixed metasurface unit parameters. Within the wide bandwidth required by airborne radar, this easily leads to gains in some bands and performance degradation in others, making it difficult to balance bandwidth and gain; 3) Existing metasurface loading schemes are mostly single-band designs with fixed metasurface unit parameters. 4) Microstrip arrays have insufficient phase modulation capability, severe gain attenuation during wide-angle scanning, and poor sidelobe suppression, failing to meet the beam scanning requirements of airborne fire control radar for accurate target detection and wide-range surveillance; 5) Traditional high-gain antenna arrays require large-scale element arrangement, resulting in complex structure, heavy weight, high processing and integration costs, and high feed network loss, which contradicts the requirements of miniaturization, low cost, and high integration of airborne platforms; 6) Existing transmissive metasurface feeds are mostly single-channel structures with low power capacity, failing to meet the application requirements of high-power transmission of airborne fire control radar; 7) Existing metasurface and microstrip arrays are separate designs without integrated phase modulation and structural design, easily introducing additional mutual coupling and loss, leading to reduced radiation efficiency.

[0006] Existing related patents have also failed to solve the above-mentioned technical problems. For example, in the 24GHz high-gain metamaterial microstrip antenna based on topology optimization published in CN110098481A, the proposed 24GHz high-gain metamaterial microstrip antenna design based on topology optimization is only for a single antenna design and does not involve array antennas. The gain improvement is limited and there is no wide-angle scanning capability. Therefore, there is an urgent need to develop a one-dimensional microstrip array antenna with a loaded electromagnetic metasurface specifically for airborne fire control radar and surveillance systems. While meeting the airborne physical characteristics such as low profile, lightweight, vibration and temperature resistance, it should achieve wide-bandwidth, wide-angle scanning, high gain, and low sidelobe electromagnetic performance, while also taking into account high power capacity and ease of fabrication, thus solving many of the shortcomings of existing technologies. Summary of the Invention

[0007] To overcome the shortcomings of the existing technology, the present invention aims to provide a one-dimensional microstrip array antenna loaded with an electromagnetic metasurface. This antenna has the characteristics of strong adaptability to airborne environments, excellent wideband and wide-angle scanning performance, high gain and compact structure, high radiation efficiency, large power capacity, convenient processing and integration, and high standardization. It can be used in airborne fire control radar and surveillance systems. While meeting the stringent physical requirements of airborne applications such as low profile, lightweight, vibration resistance and extreme temperature change resistance, it achieves high gain, low sidelobe, and wide-angle stable scanning in a wide bandwidth, adapting to the batch application needs of airborne platforms.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A one-dimensional microstrip array antenna with an electromagnetic metasurface layer includes a transmissive electromagnetic metasurface layer and a one-dimensional microstrip antenna array, wherein the transmissive electromagnetic metasurface layer is disposed directly above the phase center of the one-dimensional microstrip antenna array.

[0009] The transmissive electromagnetic metasurface layer adopts a one-dimensional phase modulation method, and phase modulation is only performed in the y-axis plane perpendicular to the arrangement direction of the one-dimensional microstrip antenna array. The metasurface unit structure along the x-direction of the one-dimensional microstrip antenna array is the same, and the metasurface unit along the y-direction is phase compensated according to the spatial distance difference, and is symmetrically arranged on both sides of the y-axis.

[0010] The specific phase compensation rule is as follows: taking the phase center of the one-dimensional microstrip antenna array as the reference origin, precise phase compensation is performed based on the principle of path difference phase compensation from spherical wave to plane wave. The phase offset is calculated through the path difference, and then the corresponding metasurface unit is matched (six types of side length units achieve full phase coverage from 0° to 360°). The compensation is symmetrical along both sides of the y-axis to ensure the symmetry and accuracy of beam control.

[0011] The one-dimensional microstrip array antenna achieves gain enhancement and sidelobe suppression within the 30.5GHz~32.5GHz frequency band and a wide-angle scanning range of -30°~30°, with a gain enhancement of 6.3dB~8.1dB and a sidelobe level below -22.4dB.

[0012] The transmissive electromagnetic metasurface layer is composed of multiple airborne dedicated transmissive electromagnetic metasurface units. The metasurface units are arranged in a symmetrical array with one-dimensional phase modulation, and the whole is arranged around the phase center of the one-dimensional microstrip antenna array. The arrangement rule of the units is strongly related to the arrangement direction of the one-dimensional microstrip antenna array. The specific arrangement method is divided into two parts: the overall array logic and the unit arrangement details. The core is to perform phase compensation arrangement only in the direction perpendicular to the one-dimensional microstrip antenna array, and to uniformly replicate the airborne dedicated transmissive electromagnetic metasurface along the direction of the one-dimensional microstrip antenna array.

[0013] The metasurface unit has a regular hexagonal basic structure and includes a dielectric substrate, an upper surface metal layer, a lower surface metal layer, and metal pillars. The upper and lower surface metal layers have the same structure and are symmetrically arranged on the upper and lower surfaces of the dielectric substrate. Both are regular hexagonal base structures. Six symmetrical trapezoidal regions and six symmetrical diagonal slot regions are removed from the regular hexagonal base structures. There are six metal pillars 4 symmetrically arranged on the dielectric substrate 2, which are the six vertex projection positions of the regular hexagonal base structure. They penetrate the dielectric substrate and are connected to the corresponding vertices of the upper and lower surface metal layers 3 at their upper and lower ends, respectively, to enhance the vibration resistance of the structure.

[0014] The upper and lower surface metal layers are used to adjust the side lengths of the regular hexagonal base structure to achieve phase control. The diagonal slit regions are not connected to the center of the regular hexagon, and a trapezoid is set between adjacent diagonal slit regions.

[0015] The trapezoid is a congruent isosceles trapezoid. All dimensions of the trapezoid are linearly related to the side length w of the regular hexagon. The upper base length is 0.2w, the lower base length is 0.4w, the leg length is 0.3w, and the height is 0.25w. All gaps are straight gaps of equal width, with a uniform width of g, which is linearly related to the side length w of the regular hexagon and is 0.1w.

[0016] The phase compensation of the transmissive electromagnetic metasurface layer adopts an optimization strategy focused on a 0° scanning angle, so that the angle between the beam normal and the metasurface normal is 0°, which ensures the highest gain at a 0° scanning angle while reducing the gain attenuation in the -30° to 30° scanning range.

[0017] The transmissive electromagnetic metasurface layer and the one-dimensional microstrip antenna array are connected by lightweight insulating support pillars. The connection position is designed with an array-style symmetrical layout principle, with the phase center of the one-dimensional microstrip antenna array as the core of symmetry. This avoids the antenna radiation area and the key area for metasurface phase control, while ensuring the structural stability and uniform stress of the connection, adapting to the high dynamic vibration environment of airborne systems. The specific connection position is clearly defined in two parts: the core positioning reference and the specific placement position, and meets the design requirements of an integrated low profile. Furthermore, the connection part is treated with a reinforced welding process and is encapsulated with thermally conductive silicone to improve the overall vibration resistance and heat dissipation capabilities of the antenna.

[0018] The phase compensation parameters of the transmissive electromagnetic metasurface layer satisfy the following relationship: in, For free space wavenumber, F Focal length for and The included angle, for and The included angle, , n For along y The direction of the first n One electromagnetic metasurface unit p The period of the electromagnetic metasurface unit cell; Point O: The phase center (also the geometric center) of the one-dimensional microstrip antenna array, is the equivalent source point of the spherical wave radiated by the antenna, and is also the reference origin for metasurface phase compensation. Point A: The far-field observation point in the target scanning direction, representing the direction in which the main lobe is expected to point, and the corresponding beam scanning angle is α (the angle between the beam and the z-axis normal). Point B: The spatial location of a phase compensation unit on the metasurface layer, located on the phase modulation column in the y-axis direction, corresponding to the spherical wave propagation path O→B, which is the key unit location that needs to be phase compensated; Point C: The location of the central reference unit on the metasurface layer that is coaxial with point O (i.e., the unit in the z-axis normal direction). Its propagation path is O→C, serving as the reference path for phase compensation, with a corresponding angle of 0°.

[0019] The dielectric substrate is made of a heat-resistant, high-strength, lightweight insulating material. The upper surface metal layer, the lower surface metal layer, and the metal pillars are all made of high-conductivity, high-strength metal materials, such as oxygen-free copper (T2 / T3) and copper-beryllium alloy (BeCu).

[0020] The one-dimensional microstrip antenna array uses a 1×8 microstrip antenna array as the feed source and adopts a multi-channel structure with a total of 8 independent RF channels, each corresponding to one of the 8 microstrip radiating patches of the 1×8 microstrip antenna array. Each channel is responsible for the signal excitation and phase control of one array element. Channel functions: Each channel can be independently configured with phase offset (0°~360°) and amplitude weight, providing a basic feed phase distribution for subsequent metasurface phase compensation, realizing beam scanning and low sidelobe pattern optimization. This improves the overall power capacity of the antenna and meets the application requirements of high-power transmission for airborne fire control radar.

[0021] The transmissive electromagnetic metasurface layer and the one-dimensional microstrip antenna array adopt an integrated structural design with an overall low profile structure that fits the aerodynamic layout of the airborne fuselage. The overall structure is lightweight and meets the weight requirements of the airborne platform.

[0022] The feed source is a one-dimensional linear microstrip array, and the number of its array elements can be flexibly configured according to the detection aperture and scanning requirements of the airborne radar, including but not limited to one-dimensional linear arrangement forms of 1×4, 1×8, 1×16, etc. All specifications adopt a multi-channel parallel feeding structure, and each array element corresponds to an independent radio frequency channel, which can realize independent phase modulation and amplitude weighting, providing a reconfigurable spherical wave feed source for the upper transmissive electromagnetic metasurface layer, and collaboratively completing the beam modulation of wideband and wide-angle scanning. The transmissive electromagnetic metasurface layer undergoes corresponding phase compensation parameter adjustments and array structure adjustments based on the size and phase center of the replaced array; or, for the operating frequency bands of airborne fire control radars at 24GHz and 77GHz, the side length values ​​of the regular hexagons of the airborne dedicated transmissive electromagnetic metasurface unit are adjusted, and six side length parameters adapted to the corresponding frequency bands are designed to achieve 0°~360° full phase coverage of the corresponding frequency bands; or, according to the scanning requirements of airborne radar, the one-dimensional phase modulation direction is adjusted from the y-axis to the x-axis, the unit structure of the transmissive electromagnetic metasurface layer is the same along the y-direction, and phase compensation is performed along the x-direction; or, for the wide scanning priority requirements of airborne surveillance systems, the focal length F parameter of the transmissive electromagnetic metasurface layer is adjusted to increase the angle between the beam normal and the metasurface normal, reducing gain attenuation during wide-angle scanning.

[0023] The antenna is suitable for airborne fire control radar and surveillance systems.

[0024] The beneficial effects of this invention are: 1. This invention is tailored for airborne fire control radar and surveillance systems. The metasurface unit is equipped with metal pillars to improve vibration resistance. The dielectric substrate and metal components are made of heat-resistant, high-strength, and lightweight materials to adapt to high-altitude temperature changes and weight requirements. The low-profile integrated structure fits the aerodynamic layout of the fuselage. At the same time, the process design of reinforced welding + potting thermally conductive silicone ensures that the antenna works stably in the high dynamic environment of airborne flight and vibration impact, solving the core problem of lack of airborne adaptability in existing technologies.

[0025] 2. The metasurface unit of this invention achieves 0°~360° full phase coverage in the 30.5GHz~32.5GHz airborne core frequency band with transmission amplitudes all above -2dB, without frequency band performance degradation issues; through one-dimensional phase modulation and 0° focusing optimization strategies, it achieves a significant gain improvement of 6.3dB~8.1dB in the -30°~30° wide-angle scanning range, and the sidelobe level is as low as below -22.4dB, fully meeting the beam scanning requirements of long-range detection and wide-range surveillance of airborne fire control radar.

[0026] 3. This invention adopts a synergistic structure of a small-scale one-dimensional 1×8 microstrip array and a transmissive metasurface to replace the traditional large-scale array element array. While achieving a gain improvement of up to 8.1dB, it maintains a compact antenna structure, low profile, and lightweight design, significantly reducing the overall weight and volume of the antenna. This not only meets the requirements of airborne aerodynamic layout but also reduces processing and integration costs.

[0027] 4. This invention integrates the metasurface layer with a one-dimensional microstrip array for phase control and structural design. The units along the y-direction of the metasurface are precisely phase compensated according to the spatial distance difference of the array, avoiding the additional mutual coupling and loss of the split design, and greatly improving the radiation efficiency. At the same time, the design of the same units along the x-direction of the metasurface simplifies the array layout rules, reduces the processing accuracy requirements, and is easy to standardize production.

[0028] 5. This invention uses a one-dimensional 1×8 microstrip array multi-channel structure as the feed source, replacing the traditional single-channel feed source, which greatly improves the power capacity and meets the high-power transmission requirements of airborne fire control radar; the metasurface unit structure is simple, consisting of only two metal layers, one dielectric substrate and six metal pillars, and the six specifications of unit design are easy to standardize and process, and the integrated structure of array and metasurface is easy to integrate with airborne planar circuits, resulting in low processing cost and good batch adaptability.

[0029] 6. This invention is designed for array antennas, with a greater gain improvement and wide-angle scanning capability; compared with the metamaterial radome patent, this invention achieves integrated phase control of metasurface and array, with better beam control and sidelobe suppression effects; this invention adds dedicated optimizations for airborne vibration resistance, temperature variation, and aerodynamics, making it fully adaptable to high-dynamic airborne environments. Attached Figure Description

[0030] Figure 1 Schematic diagram of the metal layer structure on the upper surface of a transmission-type electromagnetic metasurface unit.

[0031] Figure 2 Side view of the overall structure of the transmission-type electromagnetic metasurface unit.

[0032] Figure 3 A detailed schematic diagram of the grooved structure of the metal layer on the upper surface of a transmission-type electromagnetic metasurface unit.

[0033] Figure 4 Schematic diagrams of six different specifications of transmission-type electromagnetic metasurface unit structures.

[0034] Figure 5 The transmission amplitude of the transmissive electromagnetic metasurface unit varies with the side length of the regular hexagon in the 30.5 GHz, 31.5 GHz, and 32.5 GHz frequency bands.

[0035] Figure 6The transmission phase of the transmissive electromagnetic metasurface unit varies with the side length of the regular hexagon in the 30.5 GHz, 31.5 GHz, and 32.5 GHz frequency bands.

[0036] Figure 7 A schematic diagram of the overall structure of a one-dimensional microstrip array antenna with an electromagnetic metasurface.

[0037] Figure 8 Performance test diagram of a one-dimensional 1×8 microstrip antenna array without a transmissive electromagnetic metasurface layer.

[0038] Figure 9 Performance test diagram of a one-dimensional 1×8 microstrip antenna array loaded with a transmissive electromagnetic metasurface layer. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings.

[0040] Reference Figure 1 , Figure 2 and Figure 3 An electromagnetic metasurface unit includes an upper surface metal layer 1 and a lower surface metal layer 3 printed on a dielectric substrate 2. The upper and lower metal layers are identical, and there are six identical metal pillars 4 at six symmetrical positions. The metal layer 1 is a regular hexagon with a side length of w. A groove is cut into the hexagon to remove six symmetrical trapezoids 111 and six symmetrical diagonal slots 112, resulting in metal layer 1. The dimensions of the entire regular hexagon are proportional to its side length. The six symmetrical trapezoids 111 removed from the regular hexagonal metal layer are congruent isosceles trapezoids. All dimensions of the trapezoids are linearly related to the side length w of the regular hexagon. Specifically, the upper base length is 0.2w, the lower base length b is 0.4w, the leg length is 0.3w, and the height is 0.25w. All slots are straight slots of equal width, with a uniform width g, which is linearly related to the side length w of the regular hexagon, being 0.1w.

[0041] Reference Figure 4 The airborne dedicated transmission-type electromagnetic metasurface unit is provided with six different specifications. The side lengths of the regular hexagons of the six specifications are 1.59mm, 1.73mm, 1.81mm, 1.88mm, 1.99mm and 2.37mm, respectively. The six side lengths of the hexagons are required to cover 360° of phase. The selected six specifications of metasurface units are used together to achieve 0°~360° full phase coverage in the 30.5GHz~32.5GHz frequency band, and the transmission amplitude of each specification of unit in this frequency band is above -2dB.

[0042] Electromagnetic metasurface units, employing a centrosymmetric structure, exhibit different phases depending on the side length w of the regular hexagon. By taking different values ​​for the side length w of the regular hexagon, six electromagnetic metasurface units are obtained, which can essentially cover the entire phase space from 0° to 360°: The first type of electromagnetic metasurface unit w =1.59mm; The second type of electromagnetic metasurface unit w =1.73mm; The third type of electromagnetic metasurface unit w =1.81mm; The fourth type of electromagnetic metasurface unit w =1.88mm; The fifth type of electromagnetic metasurface unit, w =1.99mm; The sixth type of electromagnetic metasurface unit, w =2.37mm; Reference Figure 5 and Figure 6 The metasurface unit exhibits good transmission amplitude variation with side length w within the corresponding frequency band, consistently remaining above -2dB, indicating excellent transmission performance. Furthermore, the metasurface unit achieves 360° phase coverage with varying w within the corresponding frequency band. In summary, this metasurface unit possesses excellent transmission amplitude and phase, meeting the design requirements of electromagnetic metasurfaces. Reference Figure 7 Antenna element along x In directional alignment, the electromagnetic metasurface performs one-dimensional phase modulation only on a plane perpendicular to the antenna alignment direction. The electromagnetic metasurface units are arranged in a column, and then this column of electromagnetic metasurface units is copied... y By observing both sides of the axis, the entire electromagnetic metasurface is obtained, that is, the electromagnetic metasurface along the axis. x The units in the same direction are identical, along... y The directional elements perform phase compensation based on spatial distance differences. A one-dimensional phase-modulated transmission array lens along... x The direction is uniform, which has almost no effect on the phase compensation of the linear array.

[0043] The electromagnetic metasurface is located directly above the phase center of the array antenna, so the phase shift of different elements on the electromagnetic metasurface can be expressed as: in, For free space wavenumber, F Focal length for and The included angle, for and The included angle, , n For along y The direction of the first n One electromagnetic metasurface unit pThe period of the electromagnetic metasurface unit is denoted as .

[0044] When the array antenna performs beam scanning, The phase compensation of the electromagnetic metasurface needs to be recalculated due to the change in beam direction. However, for electromagnetic metasurfaces, F and It is a fixed set of design parameters and cannot be applied to all incident angles. The corresponding phase requirements necessitate proper setting. The value of is used to improve scan coverage. At this time, focusing on beam modulation at a scanning angle of 0° can achieve higher gain and improve performance. This method focuses on beam modulation at other scanning angles, which can reduce gain drop during beam scanning. This method uses the first method, letting... .

[0045] Figure 7 The number of microstrip antenna arrays is determined according to the size and performance requirements of the applicable radar, and the transmissive electromagnetic metasurface layer 5 is located directly above the phase center of the one-dimensional microstrip antenna array 6.

[0046] The transmissive electromagnetic metasurface layer 5 employs a one-dimensional phase modulation method, performing phase modulation only in the y-axis plane perpendicular to the arrangement direction of the antenna array 6. The metasurface unit structures along the x-direction of the antenna array 6 are identical, while the metasurface units along the y-direction undergo phase compensation based on spatial distance differences, and are symmetrically arranged on both sides of the y-axis. Figure 8 This is a one-dimensional microstrip antenna array without a metasurface layer. Figure 9For a one-dimensional microstrip antenna array with a metasurface layer, analyze the two figures: When the scan angle is -30°, the maximum gain is 21.4dB, an increase of 6.4dB, and the sidelobe level is -22.7dB; when the scan angle is -20°, the maximum gain is 21.9dB, an increase of 6.6dB, and the sidelobe level is -26.1dB; when the scan angle is -10°, the maximum gain is 22.7dB, an increase of 7.3dB, and the sidelobe level is -28.4dB; when the scan angle is 0°, the maximum... The gain is 23.6 dB, an increase of 8.1 dB, with a sidelobe level of -31.88 dB. At a scan angle of 10°, the maximum gain is 22.6 dB, an increase of 7.2 dB, with a sidelobe level of -27.9 dB. At a scan angle of 20°, the maximum gain is 21.8 dB, an increase of 6.5 dB, with a sidelobe level of -25.9 dB. At a scan angle of 30°, the maximum gain is 21.3 dB, an increase of 6.3 dB, with a sidelobe level of -22.4 dB. This demonstrates that the gain of the antenna array after applying the novel metasurface layer is significantly improved across scan angles from -30° to 30°.

[0047] Simulation experimental conditions.

[0048] The simulation experiments of this invention utilize the Ansys Electronics Desktop software platform installed on computer hardware to simulate Ka-band electromagnetic metasurface units and beam scanning antennas.

[0049] Simulation content and result analysis.

[0050] like Figures 1-9 As shown, the present invention provides a one-dimensional microstrip array antenna loaded with an electromagnetic metasurface, specifically designed for airborne fire control radar and surveillance systems. The core is an integrated collaborative structure of a transmissive electromagnetic metasurface layer 5 and a one-dimensional 1×8 microstrip antenna array 6. The transmissive electromagnetic metasurface layer 5 is located directly above the phase center of the one-dimensional 1×8 microstrip antenna array. The overall structure is a low profile structure, which fits the aerodynamic layout of the airborne fuselage. It is also made of lightweight materials to meet the weight requirements of the airborne platform.

[0051] Airborne dedicated transmission electromagnetic metasurface unit design The transmissive electromagnetic metasurface layer 5 is composed of multiple airborne dedicated transmissive electromagnetic metasurface units. Each metasurface unit includes a dielectric substrate 2, an upper surface metal layer 1, a lower surface metal layer 3, and six metal pillars 4. The upper surface metal layer 1 and the lower surface metal layer 3 have the same structure and are symmetrically arranged on the upper and lower surfaces of the dielectric substrate 2. The six metal pillars 4 are symmetrically arranged at six positions on the dielectric substrate 2 to enhance the structural strength of the unit, improve its vibration resistance, and adapt to the working environment of airborne vibration and shock.

[0052] Both the upper surface metal layer 1 and the lower surface metal layer 3 are based on a regular hexagonal structure. A groove operation is performed on the regular hexagon to remove six symmetrical trapezoidal regions 111 and six symmetrical diagonal regions. The size of the entire regular hexagon changes proportionally with its side length. Phase modulation is achieved by adjusting the side length w of the regular hexagon. This invention designs six different specifications of metasurface units. The side lengths of the six specifications of regular hexagons are 1.59mm, 1.73mm, 1.81mm, 1.88mm, 1.99mm, and 2.37mm, respectively. These six specifications of units work together to achieve 0°~360° full phase coverage in the 30.5GHz~32.5GHz airborne core frequency band, and the transmission amplitude of each specification of unit in this frequency band is above -2dB, demonstrating excellent transmission performance.

[0053] The dielectric substrate 2 is made of a heat-resistant, high-strength, lightweight insulating material. The upper surface metal layer 1, the lower surface metal layer 3, and the metal pillars 4 are made of high-conductivity, high-strength metal materials, which not only ensures electromagnetic performance but also meets the physical requirements of airborne resistance to extreme temperature changes and lightweight design.

[0054] Transmissive Electromagnetic Metasurface Layer Array and Phase Modulation The transmissive electromagnetic metasurface layer 5 adopts a one-dimensional phase modulation method, which modulates the phase only in the y-axis plane perpendicular to the antenna array arrangement direction. The designed metasurface units are arranged in a column, and then the column of metasurface units is copied to both sides of the y-axis to form a complete metasurface layer. That is, the unit structure of the metasurface layer along the x-direction of the antenna array arrangement is the same, and the units along the y-direction are phase compensated according to the spatial distance difference.

[0055] The electromagnetic metasurface is located directly above the phase center of the array antenna, so the phase shift of different elements on the electromagnetic metasurface can be expressed as: in, For free space wavenumber, F Focal length for and The included angle, for and The included angle, , n For along y The direction of the first n One electromagnetic metasurface unit p The period of the electromagnetic metasurface unit is denoted as .

[0056] To meet the detection requirements of airborne fire control radar, this invention adopts a phase compensation optimization strategy focused on a 0° scanning angle, making the angle between the beam normal and the metasurface normal 0°. While ensuring the highest gain at a 0° scanning angle, it effectively reduces gain attenuation in the -30° to 30° scanning range and improves scanning coverage.

[0057] Antenna integrated structure optimization: The transmissive electromagnetic metasurface layer 5 is connected to the one-dimensional 1×8 microstrip antenna array by a lightweight insulating support column. The connection part is treated with a reinforced welding process and is also potted with thermally conductive silicone, which not only improves the overall vibration resistance of the antenna, but also enhances the heat dissipation effect, ensuring the structural stability and operational stability of the antenna in the high dynamic environment of airborne operation.

[0058] The one-dimensional 1×8 microstrip antenna array, used as a feed source, adopts a multi-channel structure, replacing the traditional single-channel feed source, which greatly improves the power capacity and meets the application requirements of high-power transmission of airborne fire control radar. The integrated design of the array and the transmissive electromagnetic metasurface layer 5 avoids the additional mutual coupling and loss of the split design, and greatly improves the radiation efficiency of the antenna.

[0059] Antenna performance testing: Performance tests were conducted on the antenna of this invention, comparing it with a one-dimensional 1×8 microstrip antenna array 6 without the transmissive electromagnetic metasurface layer 5. The results show that the antenna of this invention achieves a significant gain improvement within the 30.5GHz~32.5GHz frequency band and a wide-angle scanning range of -30°~30°. At a scanning angle of -30°, the maximum gain is 21.4dB, an increase of 6.4dB, and the sidelobe level is -22.7dB; at a scanning angle of -20°, the maximum gain is 21.9dB, an increase of 6.6dB, and the sidelobe level is -26.1dB; at a scanning angle of -10°, the maximum gain is 22... The maximum gain is 23.6 dB, with a gain improvement of 8.1 dB and a sidelobe level of -28.4 dB, achieved at a scan angle of 0°. At a scan angle of 10°, the maximum gain is 22.6 dB, with a gain improvement of 7.2 dB and a sidelobe level of -27.9 dB. At a scan angle of 20°, the maximum gain is 21.8 dB, with a gain improvement of 6.5 dB and a sidelobe level of -25.9 dB. At a scan angle of 30°, the maximum gain is 21.3 dB, with a gain improvement of 6.3 dB and a sidelobe level of -22.4 dB. Test results show that the antenna of this invention achieves significant gain improvement and effective sidelobe suppression within a wide-angle scan range over a wide bandwidth, and possesses excellent adaptability to airborne environments.

[0060] After understanding the content and principles of this invention, those skilled in the art can make substitutions without departing from the core inventive concept, all of which fall within the protection scope of this invention. For example, replacing the one-dimensional 1×8 microstrip antenna array with other sizes such as 1×4 or 1×16 one-dimensional linear microstrip arrays, and adjusting the metasurface layer according to the array size and phase center for corresponding phase compensation and array adjustment; adjusting the side length of the metasurface unit hexagon for other airborne fire control radar operating frequency bands such as 24GHz and 77GHz, designing six side length parameters adapted to the frequency band to achieve full phase coverage; replacing the materials of the dielectric substrate 2, metal layer, and metal pillar 4 while meeting airborne requirements; adjusting the one-dimensional phase modulation direction from the y-axis to the x-axis according to the airborne radar scanning requirements; adjusting the metasurface layer focal length F parameter to appropriately increase the angle between the beam normal and the metasurface normal to reduce gain attenuation during wide-angle scanning, etc., in response to the wide-scan priority requirements of the airborne surveillance system.

Claims

1. A one-dimensional microstrip array antenna loaded with an electromagnetic metasurface, characterized in that, It includes a transmissive electromagnetic metasurface layer (5) and a one-dimensional microstrip antenna array (6), wherein the transmissive electromagnetic metasurface layer (5) is disposed directly above the phase center of the one-dimensional microstrip antenna array (6); The transmissive electromagnetic metasurface layer (5) adopts a one-dimensional phase modulation method, and the phase modulation is performed only on the y-axis plane perpendicular to the arrangement direction of the one-dimensional microstrip antenna array (6).

2. The one-dimensional microstrip array antenna with a loaded electromagnetic metasurface according to claim 1, characterized in that, The transmissive electromagnetic metasurface layer (5) is composed of multiple airborne dedicated transmissive electromagnetic metasurface units. The metasurface units arranged along the x-direction of the one-dimensional microstrip antenna array (6) have the same structure. The metasurface units along the y-direction are phase-compensated according to the spatial distance difference and are arranged symmetrically on both sides of the y-axis. The specific phase compensation rule is as follows: take the phase center of the one-dimensional microstrip antenna array (6) as the reference origin, perform precise phase compensation based on the principle of path difference phase compensation from spherical wave to plane wave, calculate the phase offset through the path difference, match the corresponding metasurface unit, and compensate symmetrically on both sides of the y-axis to ensure the symmetry and accuracy of beam control.

3. A one-dimensional microstrip array antenna with a loaded electromagnetic metasurface according to claim 2, characterized in that, The metasurface unit is a regular hexagonal basic structure, and the metasurface unit includes a dielectric substrate (2), an upper surface metal layer (1), a lower surface metal layer (3), and metal pillars (4). The upper surface metal layer (1) and the lower surface metal layer (3) have the same structure and are symmetrically arranged on the upper and lower surfaces of the dielectric substrate (2). They are both regular hexagonal basic structures. Six symmetrical trapezoidal (111) regions and six symmetrical diagonal slot (112) regions are cut out from the regular hexagonal basic structure. There are six metal pillars (4). The six metal pillars (4) are symmetrically arranged on the dielectric substrate (2) and are the six vertex projection positions of the regular hexagonal basic structure. They penetrate the dielectric substrate (2) and are connected to the corresponding vertices of the upper surface metal layer (1) and the lower surface metal layer (3) at their upper and lower ends, respectively.

4. A one-dimensional microstrip array antenna with a loaded electromagnetic metasurface according to claim 3, characterized in that, The upper surface metal layer (1) and the lower surface metal layer (3) achieve phase control by adjusting the side length of the regular hexagonal base structure; The diagonal gap (112) region is not connected to the center of the regular hexagon, and a trapezoid (111) is set between adjacent diagonal gap (112) regions.

5. A one-dimensional microstrip array antenna with a loaded electromagnetic metasurface according to claim 4, characterized in that, The trapezoid (111) is a congruent isosceles trapezoid with a side length of w. The upper base of the trapezoid (111) is 0.2w, the lower base is 0.4w, the leg is 0.3w, and the height is 0.25w. All gaps are straight seams of equal width, with a uniform width of g=0.1w.

6. A one-dimensional microstrip array antenna with a loaded electromagnetic metasurface as described in claim 1, characterized in that, The phase compensation of the transmissive electromagnetic metasurface layer (5) adopts an optimization strategy focused on a 0° scanning angle, so that the angle between the beam normal and the metasurface normal is 0°. The transmissive electromagnetic metasurface layer (5) and the one-dimensional microstrip antenna array (6) are connected by a lightweight insulating support column. The connection position is designed according to the principle of array-type symmetrical placement, with the phase center of the one-dimensional microstrip antenna array (6) as the symmetry.

7. A one-dimensional microstrip array antenna with a loaded electromagnetic metasurface according to claim 6, characterized in that, The phase compensation parameters of the transmissive electromagnetic metasurface layer (5) satisfy the following relationship: in, For free space wavenumber, F Focal length for and The included angle, for and The included angle, , n For along y The direction of the first n One electromagnetic metasurface unit p The period of the electromagnetic metasurface unit cell is denoted as . Point O: The phase center of the one-dimensional microstrip antenna array 6, which is the equivalent source point of the spherical wave radiated by the antenna, and also the reference origin for metasurface phase compensation. Point A: The far-field observation point in the target scanning direction, representing the direction in which the desired main lobe points, corresponding to a beam scanning angle of α; Point B: The spatial location of a phase compensation unit on the metasurface layer, located on the phase modulation column in the y-axis direction, corresponding to the spherical wave propagation path O→B; Point C: The location of the central reference unit on the metasurface layer, coaxial with point O. Its propagation path is O→C, serving as the reference path for phase compensation, with a corresponding angle of 0°.

8. A one-dimensional microstrip array antenna with a loaded electromagnetic metasurface according to claim 3, characterized in that, The dielectric substrate (2) is made of a heat-resistant, high-strength, lightweight insulating material, and the upper surface metal layer (1), lower surface metal layer (3) and metal pillar (4) are all made of high-conductivity, high-strength metal materials.

9. A one-dimensional microstrip array antenna with a loaded electromagnetic metasurface according to claim 3, characterized in that, The one-dimensional microstrip antenna array (6) is a one-dimensional 1×8 microstrip antenna array with a multi-channel structure as the feed source. It has a total of 8 independent radio frequency channels, which correspond one-to-one with the 8 microstrip radiating patches of the one-dimensional 1×8 microstrip antenna array. Each channel is responsible for the signal excitation and phase control of one array element.

10. A one-dimensional microstrip array antenna with a loaded electromagnetic metasurface according to claim 1, characterized in that, The one-dimensional microstrip array antenna achieves gain enhancement and sidelobe suppression within the 30.5GHz~32.5GHz frequency band and a wide-angle scanning range of -30°~30°, with a gain enhancement of 6.3dB~8.1dB and a sidelobe level below -22.4dB.

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