Metal truss antenna housing and design method thereof

Abstract

The invention discloses a metal truss antenna housing and a design method thereof, and belongs to the field of radar antennas. In order to solve the problem that an antenna radiation pattern of an existing antenna housing is seriously distorted, the metal truss antenna housing comprises a metal framework and a skin arranged on the surface of the metal framework, the metal framework is of a truss structure, and a first section of at least part of rod pieces in the metal framework comprises a connecting part. The reflecting part is connected with the connecting part; the reflecting part is used for realizing non-mirror scattering between a reflected wave and the first cross section of the partial rod piece; the connecting part is used for realizing the connection between the rod pieces, and the first cross section is the cross section of one side, facing the antenna, of the rod piece. According to the metal truss, mirror reflection is converted into non-mirror scattering through the arrangement of the reflection part, so that distortion of an antenna pattern is effectively suppressed, particularly, raising of a far-region minor lobe level and loss of main lobe gain are reduced, and meanwhile, the original high-strength advantage of the metal truss is completely reserved through the arrangement of the connection part.

Description

Technical Field

[0001] This invention belongs to the field of radar antenna technology, and more specifically, relates to a metal truss radome and its design method. Background Technology

[0002] Large ground-based radar metal truss radomes are widely used in radar systems for radio astronomy, satellite communications, meteorological observation, and national defense surveillance due to their superior structural strength and stability. However, traditional metal truss structures can obstruct and scatter the radiated electromagnetic waves of the antenna, causing distortion in the antenna pattern. This is mainly manifested as mainlobe gain loss and sidelobe level elevation, severely degrading the detection performance of the radar system. Current research focuses on using non-metallic composite materials (such as basalt fiber) to replace metallic materials to reduce electromagnetic scattering. However, this approach often sacrifices the structural mechanical properties of the radome and is costly.

[0003] To address the aforementioned issues, corresponding improvements have been made. For example, Chinese patent application CN202111214142.4, published on January 4, 2022, discloses a method for improving the operational performance of an antenna system and a simulation method for antenna system operational performance. A metal truss electromagnetic window serves as the antenna system's protective cover, employing a variable cross-section electromagnetic window structure. This structure utilizes trusses of varying widths to create an irregular pseudo-random distribution truss. The pseudo-random distribution truss of the electromagnetic window counteracts the scattering effects between the trusses, thereby reducing the impact on the electromagnetic performance of the antenna system and improving its operational performance. The variable cross-section electromagnetic window structure also optimizes the mechanical properties of the electromagnetic window. However, this patent has limitations: the pseudo-random distribution truss requires complex algorithms for generation and optimization, resulting in high computational costs and complexity, making large-scale application difficult.

[0004] For example, Chinese patent application CN201210247390.3, published on November 28, 2012, discloses a method for predicting the electrical performance of a metal truss radome considering scattering and transmission. The technical solution involves: calculating the far field of the antenna based on the antenna aperture field, plotting the radiation pattern, and extracting electrical performance indicators; calculating the far field generated by the aperture field after passing through the skin; calculating the scattering field of the ribs, adding the scattering field of the ribs to the far field generated by the aperture field after passing through the skin to obtain the far field of the antenna after adding the radome, plotting the radiation pattern, and extracting electrical performance indicators; comparing the far field radiation pattern and electrical performance indicators before and after adding the radome; if the requirements are met, outputting the far field radiation pattern before and after adding the radome, the change in electrical performance after adding the radome, and the structural parameters of the radome; otherwise, modifying the structural parameters of the radome and repeating the above process until the electrical performance meets the requirements. The shortcoming of this patent is that it relies on a simplified physical model, resulting in limited prediction accuracy and restricted use. Summary of the Invention

[0005] 1. The problem to be solved To address the problem of severe antenna radiation pattern distortion in existing radomes, this invention provides a metal truss radome and its design method. This invention converts specular reflection into non-spectral scattering through the placement of reflective elements, thereby effectively suppressing antenna pattern distortion, particularly reducing the rise in far-field sidelobe levels and the loss of main lobe gain. Simultaneously, the design of the connecting parts fully preserves the high strength advantage of the original metal truss.

[0006] 2. Technical Solution To solve the above problems, the present invention adopts the following technical solution.

[0007] A metal truss radome includes a metal frame and a skin disposed on the surface of the metal frame. The metal frame is a truss structure, wherein at least some of the members in the metal frame have a first cross-section including a connecting portion and a reflective portion connected to the connecting portion. The reflective portion is used to achieve non-speculative scattering between the reflected wave and the first cross-section of the member. The connecting portion is used to connect the members, and the first cross-section is the side of the member facing the antenna.

[0008] Furthermore, the connecting part is rectangular, the reflective part is conical, and the connection between the reflective part and the connecting part presents a smooth and continuous transition.

[0009] Furthermore, the cone angle in the reflective part is 55°~65°.

[0010] Furthermore, the height of the cone in the reflective part accounts for 50-70% of the total height of the first cross section.

[0011] Furthermore, at least some of the rods are the rods in the metal frame that face the antenna radiating port.

[0012] Furthermore, the metal frame is a spherical metal mesh frame, and the skin is tightened and fixed to the outer surface of the spherical metal mesh frame by fasteners.

[0013] Furthermore, the fastener has a viscoelastic adhesive on the side closest to the skin.

[0014] A design method for a metal truss radome as described in any of the above claims includes the following steps: S1: Determine the structural parameters of the metal skeleton and the material parameters of the skin; S2: Establish a model of the antenna array and metal frame, and set variables for the reflector, including at least one of the following: cone shape, cutting depth, and transition radius; S3: Set simulation tasks and performance metrics; S4: Result analysis and iterative optimization, finally obtaining the optimal solution for the reflector.

[0015] 3. Beneficial effects (1) This invention sets the first section of some rods as a connection between the connecting part and the reflective part. The presence of the reflective part transforms the original strong specular reflection into scattering in all directions, making it difficult for the reflected wave energy to return directly to the antenna aperture, thereby greatly reducing the interference to the antenna pattern and significantly reducing the impact on the antenna far-field sidelobes. At the same time, since the reflected energy is dispersed, the energy returning to the antenna direction and ultimately being lost is greatly reduced, and more energy is used for effective radiation and reception, thereby reducing the loss of main lobe gain. The presence of the connecting part ensures the stability of the structural strength. The entire metal truss radome structure has practical significance for the design of metal truss dome for large ground radars, especially suitable for high-frequency radar systems such as X-band, Ku-band and above. The overall structure is simple and easy to implement. (2) The design of the connecting part and the reflecting part in this invention realizes that the overall cross-sectional shape of the rod is rectangular, and only the local geometry of one side is optimized to form the reflecting part. The material and main structure size of the rod are not changed. While reducing the impact on the far-field sidelobe of the antenna, it maintains the high strength, high rigidity and excellent mechanical properties of the traditional metal truss structure. Moreover, the processing of the conical surface can be achieved by mature machining or profile pultrusion process, without complicated manufacturing process, simple process and controllable cost. (3) The present invention limits the cone angle of the reflector to provide a just right slope for electromagnetic waves of a specific frequency band, effectively guiding the incident wave to propagate along the slope and forming a strong traveling wave current instead of being immediately reflected, thus minimizing the energy back scattered to the antenna direction; at the same time, within the cone angle range, the waves scattered back from different depths can cancel each other in phase in the direction of returning to the antenna, thus having excellent scattering suppression effect; limiting the height of the reflector ensures that there is a sufficient non-mirror scattering area, which not only effectively suppresses the distortion of the antenna pattern, especially reducing the rise of the far-field sidelobe level and the loss of the main lobe gain, but also ensures that the stability of the original structure is not lost due to the presence of the reflector. (4) The present invention sets the first section of the rod facing the antenna radiating surface. The antenna radiating surface is the core area. Any interference in this area will directly and significantly affect the main lobe gain and beam shape. Therefore, setting the rod in this part can most effectively suppress the main lobe distortion and gain loss, ensuring the core performance indicators of the antenna from the source, and avoiding the cost increase and time consumption caused by setting all the rods. In addition, the skin is tightened and then fixed to the outer surface of the spherical metal mesh frame with fasteners, avoiding the additional vibration noise and structural fatigue damage caused by the skin vibration, and also ensuring the stability of electromagnetic wave transmission. The setting of viscoelastic glue plays a buffering role, prolongs the service life of the skin, and also plays a good sealing and waterproof role, and further suppresses vibration and noise. (5) This invention uses systematic simulation-driven design to accurately determine the optimal shape and size of the reflector, thereby achieving the optimal electromagnetic performance of the radome while ensuring structural strength. Ultimately, it converts specular reflection into non-spectral scattering, thereby effectively suppressing the distortion of the antenna pattern, especially reducing the rise of the far-field sidelobe level and the loss of the main lobe gain, while fully retaining the original high strength advantage of the metal truss. Attached Figure Description

[0016] Figure 1 A schematic diagram of a structure where the cross-section of a member is rectangular; Figure 2 This is a structural schematic diagram of the first cross-section of the rod in this application; Figure 3 A schematic diagram of the antenna array and metal frame; Figure 4 The XOZ principal sectional radiation pattern of a rod antenna with a rectangular cross-section at a frequency of 500MHz; Figure 5 The YOZ principal tangential radiation pattern of the rod antenna with the first cross section at a frequency of 500MHz; Figure 6 The XOZ principal sectional radiation pattern of a rod antenna with a rectangular cross-section at a frequency of 10 GHz; Figure 7 The YOZ principal sectional radiation pattern of the rod antenna with the first cross section at a frequency of 10 GHz is shown. Detailed Implementation

[0017] The present invention will now be further described with reference to specific embodiments and accompanying drawings.

[0018] like Figure 2As shown, a metal truss radome includes a metal frame and a skin disposed on the surface of the metal frame. The metal frame is a truss structure, wherein at least some of the members in the metal frame have a first cross-section including a connecting portion and a reflective portion connected to the connecting portion. The reflective portion is used to achieve non-speculative scattering between the reflected wave and the first cross-section of the member. The connecting portion is used to connect the members, and the first cross-section is the side of the member facing the antenna.

[0019] In this embodiment, the core principle is to transform the original strong specular reflection into scattering in all directions, making it difficult for reflected wave energy to directly return to the antenna aperture, thereby greatly reducing interference with the antenna pattern. Simulation results show that in the 10GHz band, compared to traditional rectangular cross-section rods, this embodiment can reduce the degradation of the average sidelobe level in the far-field of the antenna from 7.17dB to 5.87dB, and reduce the main lobe gain loss by 0.06dB. Simultaneously, the presence of the connecting parts ensures the stability of the structural strength, preventing the structural mechanical properties of the radome from being sacrificed to reduce electromagnetic scattering.

[0020] In one specific embodiment, the connecting part is rectangular, the reflective part is conical, and the connection between the reflective part and the connecting part has a smooth and continuous transition. Since the cross-section of the rod itself is rectangular, this embodiment only partially processes the cross-section of the rod facing the antenna to form a conical surface. This conical surface faces the antenna array during installation, that is, the narrow side of the rod faces the antenna; that is, in this embodiment, at least part of the rod's cross-section is rectangular in shape, but one side is processed into the conical surface. The processing of the conical surface can be achieved through mature machining (such as milling, grinding) or profile pultrusion processes, without complex manufacturing processes, making the process simple and cost-controllable. At the same time, only the local geometry of the rod is optimized, without changing the material of the rod (still metal) and the main structural dimensions, thus fully inheriting the high strength, high rigidity, and excellent mechanical properties of traditional metal truss radomes. Therefore, this design is simple to manufacture and has good results.

[0021] In one specific embodiment, the cone angle in the reflector is 55°~65°. Preferably, in this embodiment, the cone angle of the reflector's conical surface is 60°. Through continuous simulation verification by the inventors, this angle exhibits excellent scattering suppression effect in the X-band (10GHz). By continuously adjusting the angle, the inventors discovered that if the cone angle of the conical surface is too small, the conical surface becomes very steep, closer to a vertical plane. Although still better than a right angle, its impedance gradient effect is insufficient, and a significant amount of energy is still directly reflected back, resulting in an unsatisfactory scattering suppression effect. If the cone angle is too large, the conical surface becomes too flat. Although the impedance gradient is smooth, it leads to an increase in the electrical dimensions of the wave-facing surface of the member, which may begin to exhibit planar characteristics, also detrimental to suppressing reflection.

[0022] In one specific embodiment, the height of the cone in the reflector accounts for 50-70% of the total height of the first cross-section. This proportion is set in this embodiment because the reflector needs sufficient non-mirror scattering area while also ensuring sufficient connection space for the connecting part; this avoids the inability to achieve both connection strength and maximize electromagnetic scattering suppression. With the cone's height within this range, sufficient non-mirror scattering area is ensured, thus effectively protecting the antenna pattern overall; while also ensuring sufficient cross-sectional dimensions for the connecting part, allowing for a secure connection with the node plate and maintaining sufficient moment of inertia to withstand loads, ensuring the structural reliability and stability of the radome in harsh environments such as strong winds and snow.

[0023] In one specific embodiment, the at least some of the rods are the rods in the metal frame that face the antenna's radiating aperture. In this embodiment, considering that the antenna's radiating aperture is the core area, any interference in this region will directly and significantly affect the main lobe gain and beamform. Therefore, setting the antenna-facing side cross-section of all rods facing the antenna's radiating aperture as the first cross-section can most effectively suppress main lobe distortion and gain loss, ensuring the antenna's core performance indicators from the source and avoiding the increased cost and time consumption associated with setting all rods.

[0024] In one specific embodiment, the metal frame is a spherical metal mesh frame, and the skin is tightened and fixed to the outer surface of the spherical metal mesh frame with fasteners. The skin is tightened before being fixed to the outer surface of the spherical metal mesh frame with fasteners, which avoids additional vibration noise and structural fatigue damage caused by skin vibration, while also ensuring the stability of electromagnetic wave transmission. Furthermore, a viscoelastic adhesive is provided on the side of the fastener near the skin. The viscoelastic adhesive acts as a buffer, extending the service life of the skin, and also provides good sealing and waterproofing, further suppressing vibration and noise.

[0025] In one specific embodiment, a method for designing a metal truss radome as described in any of the above embodiments includes the following steps: S1: Determine the structural parameters of the metal skeleton and the material parameters of the skin; S2: Establish a model of the antenna array and metal frame, and set variables for the reflector, including at least one of the following: cone shape, cutting depth, and transition radius; S3: Set simulation tasks and performance metrics; S4: Result analysis and iterative optimization, finally obtaining the optimal solution for the reflector.

[0026] This embodiment presents a design method for a metal truss radome. Several core parameters of the first cross-section of at least some of the members in the metal frame are used as variables, and clear performance indicators (such as gain loss ≤ a certain set value) are set to improve design accuracy and success rate. In S1, the structural parameters of the metal frame are determined first, which ensures that the optimized boundary conditions always meet the structural safety requirements. Then, in the iterative optimization in S4, the optimal solution that can simultaneously satisfy electromagnetic performance (S3 indicator) and structural constraints (S1 parameters) is found, which greatly shortens the R&D cycle and reduces R&D costs.

[0027] To further verify the effectiveness of the metal truss radome of this application, the following comparative tests were conducted: This application uses an elliptical array antenna as the radiating aperture, with operating frequencies of 500MHz and 10GHz compared. The radiating elements employ a half-wave spacing. The radome adopts a spherical metal mesh structure with a diameter of 20m, and the length of the rods is 1–3m, with a cross-sectional dimension of 20mm × 70mm, and the narrow side faces the antenna.

[0028] Establish a structural model of the antenna array and metal frame, such as Figure 3 As shown, the software was imported using Altair Feko - FEKOVersion 2025.1. Figure 3 The model shown was used for electrical performance simulation, with a mesh size of 50 million. The MLFMM algorithm used 964GB of memory. At a frequency of 500MHz, the antenna and its truss with rectangular cross-section members (such as...) were simulated. Figure 1 The XOZ section of the member truss (as shown) and the section of the member truss in this application (as shown) Figure 2 The YOZ cross-sectional orientation patterns (as shown) are respectively as follows: Figure 4 and Figure 5 As shown. At a frequency of 10 GHz, the radiation patterns of the antenna and its XOZ cross-section with rectangular cross-section rod truss and the YOZ cross-section with cross-section rod truss of this application are respectively shown in the figures. Figure 6 and Figure 7 As shown in Table 1, the radiation pattern distortion characteristics are obtained by simulating the effects of two different cross-sectional shapes of metal truss radomes on the antenna pattern.

[0029] Table 1. Antenna pattern distortion characteristics at low and high frequencies.

[0030] As shown in Table 1, the influence of metal truss radomes with different cross-sections of the same size on antenna pattern distortion is significant. At 500MHz and 10GHz, the conical cross-section members (i.e., those in this application) have a significantly smaller impact on the far-field sidelobe level than the metal truss radomes with rectangular cross-section members. This is mainly because the rectangular cross-section members cause the reflected waves to coherently interact with the direct waves, significantly affecting the radiation pattern. In contrast, the conical cross-section metal truss members prevent the reflected waves from returning to the antenna through their inclined surfaces, thus reducing the impact on the antenna pattern. This also indicates that the shape of the members plays a role at high frequencies. Therefore, the metal truss radome of this application can significantly reduce the impact on the far-field sidelobes of the antenna, which has practical significance for the design of metal truss domes for large ground radars.

[0031] The examples described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. A metal truss radome comprising a metal framework and a skin arranged on a surface of the metal framework, characterized in that: The metal framework is a truss structure, wherein a first section of at least part of the bars in the metal framework comprises a connecting portion and a reflecting portion connected to the connecting portion; the reflecting portion is used to realize non-specular scattering between the reflected wave and the first section of the part of the bars; the connecting portion is used to realize the connection between the bars, and the first section is a section of the bar towards the antenna.

2. A metal truss radome according to claim 1, wherein: The connecting portion is in a rectangular shape, the reflecting portion is in a conical shape, and the connection between the reflecting portion and the connecting portion presents a smooth and continuous transition.

3. A metal truss radome according to claim 2, wherein: The taper angle in the reflecting portion is 55°-65°.

4. A metal truss radome according to claim 1 or 2, wherein: The height of the conical shape in the reflecting portion accounts for 50-70% of the height of the entire first section.

5. The metal truss radome according to claim 1, wherein: The at least part of the bars is a bar in the metal framework directly opposite the radiation surface of the antenna.

6. A metal truss radome according to claim 1, wherein: The metal framework is a spherical metal net framework, and the skin is fixed on the outer surface of the spherical metal net framework through fasteners after being tightened.

7. A metal truss radome according to claim 6 wherein: The side of the fastener close to the skin is provided with viscoelastic glue.

8. A method of designing a metal truss radome according to any one of claims 1 to 7, characterised by: The method comprises the following steps: S1: determining the structure parameters of the metal framework and the material parameters of the skin; S2: establishing a model of the antenna array and the metal framework, and setting variables for the reflecting portion, the variables including at least one of the conical shape, the cutting depth and the transition radius; S3: setting a simulation task and performance indicators; S4: result analysis and iterative optimization, and finally obtaining the optimal solution about the reflecting portion.

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