Characteristic mode design system for broadband conformal antennas used in inspection

Abstract

This invention relates to the field of urban rail transit inspection technology, and particularly to a characteristic mode design system for broadband conformal antennas used in inspection. The system includes an inspection condition parameter input module for acquiring the condition parameters of the target inspection section, which at least include the section type, communication link requirements, and target operating frequency band; a multi-rotor UAV body modeling module for establishing a full-size three-dimensional electromagnetic model of the UAV based on its geometry and material properties; and a characteristic mode analysis module, signal-connected to the inspection condition parameter input module, for analyzing the characteristic modes based on the target operating frequency band. This invention deeply integrates inspection condition parameters into the entire process of characteristic mode selection, antenna element design, and beamforming. Based on the communication link requirements of different inspection sections, it selects matching dominant characteristic modes and implements targeted beamforming, ensuring that the antenna radiation characteristics are highly adapted to the complex inspection environment of rail transit and overcoming communication attenuation problems.

Description

Technical Field

[0001] This invention relates to the field of urban rail transit inspection technology, and in particular to a characteristic mode design system for broadband conformal antennas used in inspection. Background Technology

[0002] Routine inspections of urban rail transit lines, overhead contact lines, and track structures are crucial for ensuring operational safety. Multi-rotor drones equipped with multiple sensors have become the mainstream inspection equipment due to their maneuverability and high inspection efficiency. Communication antennas are the core components for data transmission and command issuance between drones and ground stations. As inspection tasks become more complex, drone antennas need to meet the requirements of broadband transmission, adaptability to complex rail transit conditions, and high integration with the drone body. However, existing design methods for communication antennas of inspection drones have the following technical shortcomings: Existing antenna design methods separate the antenna from the UAV platform and fail to consider the specific operating conditions of rail transit, resulting in a severe mismatch between antenna performance and the requirements of inspection scenarios. On the one hand, the antenna design process typically simplifies the UAV body as an ideal conductive plane or completely ignores its influence, failing to consider the electromagnetic characteristics of the body itself as part of the radiator. This leads to distortion of the radiation pattern and deterioration of impedance matching during actual antenna operation, making it difficult to achieve the expected performance. On the other hand, existing designs lack specific consideration for the operating conditions of rail transit inspection. For example, there is a severe multipath effect in tunnel environments, requiring the antenna to have enhanced radiation capability along the tunnel axis to overcome signal fading. Elevated sections require the antenna to provide directional coverage to the ground station to improve communication distance. Traditional design methods cannot directionally adjust the antenna radiation characteristics according to these operating parameters, resulting in poor communication quality and low reliability of the antenna in actual inspection scenarios, failing to meet the specific inspection requirements of rail transit.

[0003] Based on the above, we propose a characteristic mode design system for broadband conformal antennas used in inspection to solve the aforementioned problems. Summary of the Invention

[0004] This invention provides a characteristic mode design system for broadband conformal antennas used for inspection, in order to solve the problems existing in the prior art.

[0005] The technical problem solved by this invention is achieved by the following technical solution: A characteristic mode design system for a broadband conformal antenna used for inspection includes: The inspection condition parameter input module is used to obtain the condition parameters of the target inspection section. The condition parameters include at least the section type, communication link requirements and target operating frequency band. The multi-rotor UAV airframe modeling module is used to create a full-size three-dimensional electromagnetic model of the UAV based on the geometric structure and material properties of the target inspection UAV. The characteristic mode analysis module is signal-connected to the inspection condition parameter input module. It is used to solve the characteristic mode of the three-dimensional electromagnetic model according to the target operating frequency band, calculate multiple characteristic modes in the target operating frequency band, and obtain the characteristic current distribution, characteristic radiation pattern and modal saliency of each characteristic mode. The pattern filtering and beamforming module is signal-connected to the inspection condition parameter input module and the feature mode analysis module, respectively, and is used to filter at least one dominant feature mode that matches the communication link requirements from the plurality of feature modes according to the condition parameters. A broadband conformal antenna unit design module is signal-connected to the mode filtering and beamforming module. It is used to conformally fit and design a broadband conformal antenna unit that can couple and excite the dominant characteristic mode on the surface of the arm of the model built by the multi-rotor UAV body modeling module, based on the characteristic current distribution of the dominant characteristic mode. The feed network integration module is signal-connected to the broadband conformal antenna unit design module. It is used to design the feed structure and to perform weighted excitation on the dominant characteristic mode by adjusting the position, number, amplitude or phase of the feed points, so as to achieve broadband impedance matching and beamforming for the operating parameters.

[0006] Preferably, the broadband conformal antenna element is a broadband conformal helical antenna element.

[0007] Preferably, the section type obtained by the inspection condition parameter input module includes at least one of tunnel section, elevated section or ground section.

[0008] Preferably, the feature model analysis module solves for the feature model of a full UAV model including the arms, motor mounts, and central disk.

[0009] Preferably, the pattern screening and beamforming module is also used to assist in screening the dominant feature mode based on the feasibility condition that the strong distribution area of ​​the feature current is located on the surface of the arm.

[0010] Preferably, the broadband conformal spiral antenna element optimizes the number of turns, pitch, and linewidth to couple and excite the dominant characteristic mode within the target operating frequency band, and utilizes the multi-resonance characteristics of the spiral antenna to simultaneously couple and excite multiple adjacent characteristic modes, thereby expanding the impedance bandwidth of the antenna.

[0011] A characteristic mode design method for a broadband conformal antenna for inspection systems includes the following steps: S1: Obtain the operating condition parameters of the target inspection section through the inspection operating condition parameter input module. The operating condition parameters include at least the section type, communication link requirements and target operating frequency band. S2: Using the multi-rotor UAV body modeling module, a full-size three-dimensional electromagnetic model of the UAV is established based on the geometric structure and material properties of the target inspection UAV. S3: Through the characteristic mode analysis module, the characteristic modes of the three-dimensional electromagnetic model are solved according to the target operating frequency band, and multiple characteristic modes in the target operating frequency band, as well as their characteristic current distribution, characteristic radiation pattern and modal saliency are calculated. S4: Through the pattern filtering and beamforming module, based on the operating parameters and the feasibility of the layout condition that the strong distribution area of ​​the characteristic current is located on the surface of the machine arm, at least one dominant characteristic mode that matches the communication link requirements is selected from the multiple characteristic modes. S5: Using the broadband conformal antenna unit design module, based on the characteristic current distribution of the dominant characteristic mode, a broadband conformal antenna unit capable of coupling and exciting the dominant characteristic mode is conformally designed on the surface of the arm. S6: Through the power supply network integration module, design the power supply structure, and by adjusting the position, number, amplitude or phase of the power supply points, perform weighted excitation on the dominant characteristic mode to achieve broadband impedance matching and beamforming for the operating parameters.

[0012] The beneficial effects of this invention are as follows: by deeply integrating the inspection condition parameters into the entire process of feature mode selection, antenna unit design and beamforming, it can accurately select and match the dominant feature modes and achieve targeted beamforming according to the communication link requirements of different inspection sections such as tunnels, elevated roads and ground. This allows the antenna radiation characteristics to be highly adapted to the complex inspection environment of rail transit, overcomes the communication attenuation problem caused by tunnel multipath effect and contact network electromagnetic interference, improves the antenna's scene adaptability, and ensures the stability of inspection data transmission. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the feature pattern design method provided by the present invention; Figure 2 This is a schematic diagram of the module signal connection provided in this invention.

[0015] In the diagram, 1. Inspection condition parameter input module; 2. Multi-rotor UAV body modeling module; 3. Feature mode analysis module; 4. Mode selection and beamforming module; 5. Broadband conformal antenna unit design module; 6. Feed network integration module. Detailed Implementation

[0016] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0017] Reference Figures 1-2 As shown, the characteristic mode design system for a broadband conformal antenna used for inspection includes an inspection condition parameter input module 1, a multi-rotor UAV body modeling module 2, a characteristic mode analysis module 3, a mode selection and beamforming module 4, a broadband conformal antenna unit design module 5, and a feed network integration module 6. The inspection condition parameter input module 1 is connected to the characteristic mode analysis module 3 and the mode selection and beamforming module 4, respectively. The multi-rotor UAV body modeling module 2 is connected to the characteristic mode analysis module 3. The mode selection and beamforming module 4 is connected to the broadband conformal antenna unit design module 5. The broadband conformal antenna unit design module 5 is connected to the feed network integration module 6. Each module is a functional module combining hardware and software, which can be mounted on an electromagnetic simulation software platform to collaboratively complete the design of a broadband conformal antenna for a rail transit inspection UAV. The overall design process is driven by the inspection condition parameters, realizing an integrated design from condition input to feed optimization.

[0018] Furthermore, the inspection condition parameter input module 1 is used to acquire the condition parameters of the target inspection section. The condition parameters include at least the section type, communication link requirements, and target operating frequency band. The section type includes at least one of tunnel section, elevated section, or ground section. This module synchronously transmits the acquired condition parameters to the feature mode analysis module 3 and the mode screening and beamforming module 4, which serve as the core basis for subsequent feature mode solving, screening, and antenna design. In practical applications, the module can flexibly input the condition parameters of different sections according to the actual inspection needs of urban rail transit. For example, the tunnel cross-section dimensions can be input for tunnel sections, and the ground station communication distance requirements can be input for elevated sections, adapting to the design requirements of different inspection scenarios.

[0019] Among them, the function of the inspection condition parameter input module 1 is to realize the correlation between the inspection condition and the antenna design, and solve the technical defect of the existing antenna design without condition driving. The target working frequency band entered by it is the solution frequency range of the subsequent characteristic mode analysis module 3. The communication link requirements are the screening basis of the mode screening and beamforming module 4, ensuring that the antenna design is highly matched with the actual needs of rail transit inspection.

[0020] Furthermore, the multi-rotor UAV body modeling module 2 is used to establish a full-size three-dimensional electromagnetic model of the UAV based on the geometric structure and material properties of the target inspection UAV. This model is a complete UAV model including the arms, motor mounts, and central disk. During the modeling process, actual electromagnetic material properties are assigned to each structural component. For example, the carbon fiber central disk is given dielectric properties such as dielectric constant and loss tangent, while the aluminum alloy arms and metal motor mounts are given electrical properties such as conductivity. At the same time, the micro-structures of the UAV that are not affected by electromagnetic interference are simplified, improving computational efficiency while ensuring simulation accuracy. This module outputs the established full-size three-dimensional electromagnetic model to the feature mode analysis module 3, providing a basic model for solving the feature mode of the entire UAV. Among them, the multi-rotor UAV body modeling module 2 abandons the design method of simplifying the UAV body to an ideal conductive plane or ignoring the influence of the body in the existing technology. It fully restores the electromagnetic characteristics of the entire UAV, making the subsequent feature mode analysis results more in line with the actual application scenario, laying the foundation for making full use of the electromagnetic characteristics of the body and improving antenna radiation efficiency.

[0021] Furthermore, the characteristic mode analysis module 3 is signal-connected to the inspection condition parameter input module 1. It is used to solve the characteristic modes of the three-dimensional electromagnetic model according to the target operating frequency band, calculate multiple characteristic modes in the target operating frequency band, and obtain the characteristic current distribution, characteristic radiation pattern and modal saliency of each characteristic mode. This module uses the method of moments to solve the characteristic modes. The solution object is the whole UAV model. During the solution process, the effective characteristic modes with a modal saliency MS value greater than 0.5 are selected. Only the relevant parameters of the effective characteristic modes are output to the mode selection and beamforming module 4 to reduce the amount of calculation in subsequent selection.

[0022] Furthermore, the mode selection and beamforming module 4 is connected to the inspection condition parameter input module 1 and the characteristic mode analysis module 3, respectively. It is used to select at least one dominant characteristic mode that matches the communication link requirements from multiple characteristic modes according to the condition parameters. At the same time, this module also assists in the selection of dominant characteristic modes based on the feasibility condition that the strong distribution area of ​​the characteristic current is located on the surface of the arm. During the selection process, characteristic modes with a high degree of matching between the characteristic radiation pattern and the communication link requirements are given priority. Then, combined with the actual deployment requirements of the antenna unit, characteristic modes that have no deployment conditions in the strong current distribution area are excluded to ensure that the selected dominant characteristic mode is suitable for the communication requirements of the inspection condition.

[0023] Specifically, when the section type entered by the inspection condition parameter input module 1 is a tunnel section, the communication link requirement is to enhance coverage along the tunnel axis. The inspection condition parameter input module 1 will filter out the dominant characteristic mode with enhanced gain along the axial direction of the characteristic radiation pattern. When the section type is an elevated or ground section, the communication link requirement is to provide directional coverage to the ground station. The inspection condition parameter input module 1 will then filter out the dominant characteristic mode with a downward characteristic radiation pattern, thereby achieving precise adaptation of the antenna radiation characteristics to different inspection sections.

[0024] Furthermore, the broadband conformal antenna unit design module 5 is signal-connected to the mode screening and beamforming module 4. Based on the characteristic current distribution of the dominant characteristic mode, it conformally designs a broadband conformal antenna unit on the surface of the arm of the model built by the multi-rotor UAV body modeling module 2, capable of coupling and exciting the dominant characteristic mode. The broadband conformal antenna unit is a broadband conformal helical antenna unit. By optimizing the number of turns, pitch, and linewidth of the helical antenna, the antenna accurately couples and excites the dominant characteristic mode within the target operating frequency band. It also utilizes the multi-resonance characteristics of the helical antenna to simultaneously couple and excite multiple adjacent characteristic modes, thereby expanding the antenna's impedance bandwidth. The broadband conformal helical antenna unit is completely conformally fitted to the surface of the UAV arm without any protruding structures. This solves the structural safety hazards of existing exposed antennas, such as high wind resistance and susceptibility to scratches, and achieves efficient coupling and excitation of the dominant characteristic mode through the close fit between the antenna and the body, fully utilizing the electromagnetic characteristics of the body to improve antenna radiation efficiency.

[0025] Furthermore, the feed network integration module 6 is signal-connected to the broadband conformal antenna unit design module 5 for designing the feed structure. By adjusting the position, number, amplitude, or phase of the feed points, the dominant characteristic modes are weighted and excited to achieve broadband impedance matching and beamforming for operating parameters. The feed structure is a microstrip feed or a coaxial feed structure. The position of the feed points coincides with the strong distribution area of ​​characteristic current on the surface of the UAV arm. By adjusting the feed amplitude and phase, the dominant characteristic modes are precisely excited while suppressing the excitation of irrelevant characteristic modes, ensuring that the return loss S11 of the antenna in the target operating frequency band is < -10dB, which meets the design requirements of broadband impedance matching.

[0026] In addition, based on the aforementioned characteristic mode design system for broadband conformal antennas used for inspection, this invention also discloses a corresponding characteristic mode design method, including the following steps: S1: Obtain the operating parameters of the target inspection section through the inspection operating condition parameter input module 1. The operating parameters include at least the section type, communication link requirements and target operating frequency band. S2: Using the multi-rotor UAV body modeling module 2, a full-size three-dimensional electromagnetic model of the UAV is established based on the geometric structure and material properties of the target inspection UAV. S3: Through the characteristic mode analysis module 3, the characteristic modes of the three-dimensional electromagnetic model are solved according to the target operating frequency band, and multiple characteristic modes, their characteristic current distribution, characteristic radiation pattern and modal saliency are calculated in the target operating frequency band. S4: Through the pattern filtering and beamforming module 4, based on the working parameters and the feasibility of the layout condition that the strong distribution area of ​​the characteristic current is located on the surface of the arm, at least one dominant characteristic mode that matches the communication link requirements is selected from multiple characteristic modes. S5: Through the broadband conformal antenna unit design module 5, based on the characteristic current distribution of the dominant characteristic mode, a broadband conformal antenna unit capable of coupling and exciting the dominant characteristic mode is designed on the surface of the arm in a conformal fit. S6: Through the feed network integration module 6, the feed structure is designed, and the dominant characteristic mode is weighted and excited by adjusting the position, number, amplitude or phase of the feed points to achieve broadband impedance matching and beamforming for operating parameters.

[0027] The above steps are executed sequentially, with each step corresponding to a specific module of the system, forming a complete design process from operating condition input to power supply optimization. This transforms antenna design from a traditional experience-based trial-and-error model to a condition-driven, theory-guided model, shortening the antenna development cycle, increasing the design success rate, and enabling rapid adaptation to different types of multi-rotor inspection drones and different operating conditions in urban rail transit inspection sections. In practical applications, taking the antenna design of an inspection drone in the 2.4~2.5GHz ISM band of urban rail transit as an example, the broadband conformal helical antenna designed using the above system and method achieves a radiation efficiency ≥80% and a return loss S11 <-10dB throughout the target operating frequency band, meeting the broadband requirements for simultaneous transmission of multiple types of inspection data such as high-definition video, infrared thermal imaging, and lidar. Furthermore, because the antenna conformally fits the arm without protrusion, it reduces the drone's wind resistance, avoiding the risk of scraping in confined environments such as tunnels and overhead contact lines. The antenna's radiation characteristics are highly adaptable to different inspection sections of rail transit, effectively overcoming communication attenuation caused by tunnel multipath effects and resulting in better signal stability for inspection data transmission.

[0028] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A characteristic mode design system for a broadband conformal antenna used for inspection, characterized in that, include: The inspection condition parameter input module (1) is used to obtain the condition parameters of the target inspection section. The condition parameters include at least the section type, communication link requirements and target operating frequency band. Multi-rotor UAV body modeling module (2) is used to establish a full-size three-dimensional electromagnetic model of the UAV based on the geometric structure and material properties of the target inspection UAV; The characteristic mode analysis module (3) is connected to the inspection working condition parameter input module (1) by signal. It is used to solve the characteristic mode of the three-dimensional electromagnetic model according to the target working frequency band, calculate multiple characteristic modes in the target working frequency band, and obtain the characteristic current distribution, characteristic radiation pattern and modal saliency of each characteristic mode. The pattern filtering and beamforming module (4) is connected to the inspection working condition parameter input module (1) and the feature mode analysis module (3) respectively, and is used to filter out at least one dominant feature mode that matches the communication link requirements from the multiple feature modes according to the working condition parameters. The broadband conformal antenna unit design module (5) is signal-connected to the mode filtering and beamforming module (4) and is used to conformally fit the broadband conformal antenna unit that can couple and excite the dominant characteristic mode on the surface of the arm of the model built by the multi-rotor UAV body modeling module (2) according to the characteristic current distribution of the dominant characteristic mode. The feed network integration module (6) is signal-connected to the broadband conformal antenna unit design module (5) and is used to design the feed structure. By adjusting the position, number, amplitude or phase of the feed point, the dominant characteristic mode is weighted and excited to achieve broadband impedance matching and beamforming for the operating parameters.

2. The characteristic mode design system for a broadband conformal antenna for inspection according to claim 1, characterized in that, The broadband conformal antenna element is a broadband conformal helical antenna element.

3. The characteristic mode design system for a broadband conformal antenna for inspection according to claim 1, characterized in that, The section type obtained by the inspection condition parameter input module (1) includes at least one of the following: tunnel section, elevated section or ground section.

4. The characteristic mode design system for a broadband conformal antenna for inspection according to claim 1, characterized in that, The feature model analysis module (3) solves the feature model for the entire UAV model, which includes the arms, motor mounts and the central disk.

5. The characteristic mode design system for a broadband conformal antenna for inspection according to claim 1, characterized in that, The pattern selection and beamforming module (4) is also used to assist in selecting the dominant feature mode based on the feasibility condition that the strong distribution area of ​​the feature current is located on the surface of the arm.

6. The characteristic mode design system for a broadband conformal antenna for inspection according to claim 1, characterized in that, The broadband conformal spiral antenna element optimizes the number of turns, pitch, and linewidth to couple and excite the dominant characteristic mode within the target operating frequency band, and utilizes the multi-resonance characteristics of the spiral antenna to simultaneously couple and excite multiple adjacent characteristic modes, thereby expanding the impedance bandwidth of the antenna.

7. A characteristic mode design method for a characteristic mode design system based on any one of claims 1 to 6 for a broadband conformal antenna for inspection, characterized in that, Includes the following steps: S1: Obtain the working condition parameters of the target inspection section through the inspection working condition parameter input module (1). The working condition parameters include at least the section type, communication link requirements and target operating frequency band. S2: Using the multi-rotor UAV body modeling module (2), a full-size three-dimensional electromagnetic model of the UAV is established based on the geometric structure and material properties of the target inspection UAV; S3: Through the characteristic mode analysis module (3), the characteristic mode of the three-dimensional electromagnetic model is solved according to the target working frequency band, and multiple characteristic modes in the target working frequency band and their characteristic current distribution, characteristic radiation pattern and modal saliency are calculated. S4: Through the mode filtering and beamforming module (4), based on the working condition parameters and combined with the deployment feasibility condition that the strong distribution area of ​​the characteristic current is located on the surface of the arm, at least one dominant characteristic mode that matches the communication link requirements is selected from the multiple characteristic modes. S5: Through the broadband conformal antenna unit design module (5), based on the characteristic current distribution of the dominant characteristic mode, a broadband conformal antenna unit capable of coupling and exciting the dominant characteristic mode is designed in conformal bonding on the surface of the arm; S6: Design the feeding structure through the feeding network integration module (6), and perform weighted excitation on the dominant characteristic mode by adjusting the position, number, amplitude or phase of the feeding point to achieve wideband impedance matching and beamforming for the operating parameters.

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