Multi-mode reconfigurable unmanned aerial vehicle platform synthetic aperture radar system

Abstract

The invention provides a multi-mode reconfigurable unmanned aerial vehicle platform synthetic aperture radar system. The multi-mode reconfigurable unmanned aerial vehicle platform synthetic aperture radar system comprises a mounting structure, at least two antenna modules and an electronic unit. The mounting structure is arranged on an external unmanned aerial vehicle. The at least two antenna modules are detachably connected to the mounting structure, and each antenna module comprises an antenna sub-array. The electronic unit is connected to the mounting structure and is suitable for controlling the antenna module to receive and transmit signals. Wherein the radar system has at least two working modes: in the first mode, the two antenna sub-arrays are separately arranged, the electronic unit controls one of the two antenna modules to transmit signals, and the two antenna modules receive signals at the same time; and in the second mode, the two antenna sub-arrays cling to each other side by side, and the electronic unit controls the two antenna modules as a whole to simultaneously transmit and receive signals. According to the radar system, the antenna layout is physically reconstructed, the working modes are flexibly switched, diversified observation requirements are met through a single hardware platform, the task adaptability of the unmanned aerial vehicle load is improved, and the cost is reduced.

Description

Technical Field

[0001] This disclosure relates to the field of synthetic aperture radar technology, and more particularly to a multimodal reconfigurable synthetic aperture radar system for an unmanned aerial vehicle platform. Background Technology

[0002] In Synthetic Aperture Radar (SAR) remote sensing applications on UAV platforms, it is necessary to acquire image, elevation, deformation, and full polarization information, corresponding to multiple operating modes. This requires the SAR system to support multiple operating modes, such as multiple-track interferometry, cross-track interferometry, along-track interferometry, and full polarization observation. However, the hardware foundations for achieving these functions differ: interferometry requires dual antennas to form a specific baseline, while full polarization observation requires a specific polarization configuration, making the integration of multiple operating modes difficult. In addition, the payload capacity, space volume, and power supply conditions of UAV platforms are limited, further complicating the design.

[0003] Therefore, given the limited payload resources of UAVs, how to enable a single radar system to operate in multiple modes has become a pressing technical problem that needs to be solved. Summary of the Invention

[0004] To address at least one of the aforementioned and other technical problems in related technologies, this disclosure provides a multimodal reconfigurable synthetic aperture radar system for an unmanned aerial vehicle (UAV) platform, comprising a mounting structure, at least two antenna modules, and an electronic unit. The mounting structure is externally mounted on the UAV. At least two antenna modules are detachably connected to the mounting structure, and each antenna module includes an antenna subarray. The electronic unit is connected to the mounting structure and is used to control the antenna modules to receive and transmit signals. The radar system has at least two operating modes: a first mode in which the two antenna subarrays are separated, and the electronic unit controls one of the two antenna modules to transmit a signal while both simultaneously receive signals; and a second mode in which the two antenna subarrays are placed side-by-side, and the electronic unit controls the two antenna modules as a single unit to simultaneously transmit and receive signals.

[0005] According to embodiments of this disclosure, the mounting structure includes at least three mounting interfaces spaced apart along its length. When the radar system is in a first mode, at least two antenna modules are disposed on at least two spaced-apart mounting interfaces, and the antenna subarrays of the at least two antenna modules are spaced apart. When the radar system is in a second mode, at least two antenna modules are disposed on at least two adjacent mounting interfaces, and the antenna subarrays of the at least two antenna modules abut against each other.

[0006] According to embodiments of this disclosure, the antenna subarray includes a plurality of square radiating elements arranged with the same physical gap, and the thickness of the frame between at least two antenna subarrays is equal to half the physical gap.

[0007] According to embodiments of this disclosure, the antenna module further includes an antenna bracket, which comprises a first mounting portion, a second mounting portion, and a bracket body. The bracket body is disposed between the first mounting portion and the second mounting portion. The first mounting portion is connected to an antenna interface, and the antenna subarray is connected to the second mounting portion.

[0008] According to embodiments of this disclosure, the antenna module further includes a connector. The connector passes through the first mounting portion and the antenna interface, and / or, the connector passes through the second mounting portion and the antenna subarray.

[0009] According to embodiments of this disclosure, the first mode includes at least two sub-modes. When the synthetic aperture radar is in the first sub-mode, the output direction of the radiated beam of the antenna subarray is towards the flight direction of the UAV. When the synthetic aperture radar is in the second sub-mode, the output direction of the radiated beam of the antenna subarray is offset from the flight direction of the UAV.

[0010] According to embodiments of this disclosure, the mounting structure is configured as a plate-shaped structure. And / or, the extension direction of the second mounting portion is inclined to the horizontal direction.

[0011] According to embodiments of this disclosure, the support body is pivotally connected to the second mounting portion so that the output direction of the radiated beam of the antenna subarray is adjustable.

[0012] According to embodiments of this disclosure, in a first mode, the electronic unit performs interferometric processing on the signals received by the two antenna modules to obtain phase difference information of the target. In a second mode, the electronic unit performs synthetic aperture radar imaging processing on the signals received by the two antenna modules as a whole to obtain an image of the target.

[0013] According to embodiments of this disclosure, in the first sub-mode, the two antenna subarrays are configured to transmit and receive orthogonally polarized electromagnetic waves. Alternatively, the two antenna subarrays are configured to transmit and receive electromagnetic waves with the same polarization.

[0014] Through embodiments of this disclosure, the reconfigurability of the antenna physical layout is achieved by detachably connecting at least two antenna modules to the mounting structure, enabling the system to switch between at least two preset operating modes. In the first mode, where the two antenna subarrays are separated and operate in a single-transmit, dual-receive mode, the system constitutes a spatial baseline interferometry system, capable of acquiring interferometric information in a single flight. In the second mode, where the two antenna subarrays are side-by-side and operate as a whole, it is equivalent to a larger-aperture antenna, improving imaging performance. Thus, this scheme allows a single system to be flexibly configured as needed within the strict constraints of an UAV platform, acquiring two different advanced observation capabilities: interferometry and high-resolution imaging. This improves the adaptability and functional versatility of the radar system, reduces the cost of multi-mission observation, and increases imaging resolution. Attached Figure Description

[0015] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0016] Figure 1 This is a front view of the first sub-modality in an embodiment of this disclosure;

[0017] Figure 2 This is a front view of the second modality in an embodiment of this disclosure;

[0018] Figure 3 This is a front view of the second sub-modality in an embodiment of this disclosure;

[0019] Figure 4 This is a front view of the antenna subarray in an embodiment of the present disclosure.

[0020] Figure 5 This is a top view of the mounting structure in an embodiment of this disclosure;

[0021] Figure 6 This is a perspective view of the antenna module in the first sub-mode in an embodiment of this disclosure;

[0022] Figure 7 This is a perspective view of the antenna module in the second sub-mode in an embodiment of this disclosure;

[0023] Figure 8 This is a partial perspective view of the radar system in the second sub-mode in an embodiment of this disclosure;

[0024] Figure 9 This is a partial three-dimensional view of the radar system in the first sub-mode of an embodiment of this disclosure.

[0025] The meanings of the reference numerals in the attached figure are as follows:

[0026] 1. Installation structure; 11. First interface; 12. Second interface; 13. Third interface; 14. Fourth interface; 15. Fifth interface; 16. Heat dissipation interface; 2. Electronic unit; 3. Antenna module; 31. Antenna bracket; 32. Antenna subarray; 311. First mounting part; 312. Second mounting part; 313. Bracket body. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0029] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0030] When using expressions such as "at least one of A, B, and C," the meaning should generally be interpreted according to the understanding of someone skilled in the art. For example, "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C. Similarly, when using expressions such as "at least one of A, B, or C," the meaning should generally be interpreted according to the understanding of someone skilled in the art. For example, "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C.

[0031] In the field of synthetic aperture radar (SAR) technology for unmanned aerial vehicles (UAVs), existing solutions face systemic contradictions in meeting diverse remote sensing observation needs. UAV platforms impose strict limitations on payload weight, size, and power consumption, requiring airborne radar systems to possess high compactness and lightweight characteristics. However, scientific observation and engineering applications often require acquiring multiple information elements, such as high-resolution two-dimensional images, three-dimensional terrain elevation, minute surface deformations, and the fully polarimetric scattering characteristics of targets. These different observation elements correspond to different radar operating modes, including but not limited to multiple-track interferometry, cross-track interferometry, along-track interferometry, and fully polarimetric observation.

[0032] To adapt to UAV platforms, some related technologies have simplified system functions, meaning that a single radar is fixed to perform only one specific observation mode. To complete multi-element observation tasks, it is necessary to rely on multiple flights carrying radars with different functions. This approach not only significantly increases the time and economic costs of data acquisition, but also makes it difficult to completely reproduce the platform trajectory between multiple flights, introducing additional registration errors and thus affecting the accuracy of multi-source data fusion and quantitative analysis.

[0033] Other related technologies integrate multiple functional hardware components into a single system. However, the hardware requirements for interferometry, such as the dual-antenna spatial baseline, the dual-polarized antenna feed network for fully polarized observation, and the large-aperture antenna for high-resolution imaging, overlap and interfere with each other, leading to increased system complexity, physical size, and weight, exceeding the payload capacity of small and medium-sized UAVs.

[0034] Figure 1 This is a front view of the first sub-mode in the first mode of the embodiments of this disclosure. Figure 2 This is a front view of the second modality in an embodiment of this disclosure. Figure 3 This is a front view of the second sub-mode in the first mode of an embodiment of this disclosure.

[0035] Therefore, this disclosure provides a multimodal reconfigurable synthetic aperture radar system for an unmanned aerial vehicle platform, with reference to... Figures 1 to 3 The system includes an installation structure 1, at least two antenna modules 3, and an electronic unit 2. The installation structure 1 is mounted externally on the unmanned aerial vehicle (UAV). At least two antenna modules 3 are detachably connected to the installation structure 1, and each antenna module 3 includes an antenna subarray 32. The electronic unit 2 is connected to the installation structure 1 and is used to control the antenna modules 3 to receive and transmit signals. The radar system has at least two operating modes: a first mode in which the two antenna subarrays 32 are separated, and the electronic unit 2 controls one of the two antenna modules 3 to transmit signals while both receive signals simultaneously; and a second mode in which the two antenna subarrays 32 are placed side-by-side, and the electronic unit 2 controls the two antenna modules 3 as a single unit to simultaneously transmit and receive signals.

[0036] In this implementation, at least two detachable antenna modules 3 can be manually separated and arranged side-by-side, providing a physical structural basis for the radar system to switch between different modes. The electronic unit 2 controls the reception and transmission of signals from the antenna modules 3. By adjusting the control method of the electronic unit 2, the operating mode of the antenna modules 3 can be controlled, thereby controlling the operating mode of the radar system and providing a control basis for switching between different modes. Together, these two components enable the radar system to be reconfigured on an UAV platform without increasing the load or introducing other structures, allowing the radar system to operate in multiple modes. This improves the adaptability and functional versatility of the radar system, reduces the cost of multi-mission observation, and improves imaging resolution.

[0037] Understandably, when a reconfiguration is required, it is only necessary to disassemble and reinstall the antenna module 3, and then adjust the control mode of the electronic unit 2 to complete the switching of the radar system modes. The switching process is simple and quick.

[0038] In addition, in the second mode, the two antenna subarrays 32 are placed side by side, which can be equivalent to an antenna with a larger effective physical aperture, thereby improving the resolution and signal gain of the synthetic aperture radar.

[0039] In some illustrative embodiments of this disclosure, the mounting structure 1 is suspended below the drone and connected to the drone via one or more connecting rods. Furthermore, the drone platform mentioned in this disclosure broadly refers to all unmanned or manned aircraft with limited payload capacity, limited external installation space, and limited onboard power supply capability. Specific forms include, but are not limited to, multi-rotor aircraft, fixed-wing drones, vertical takeoff and landing (VTOL) drones, and other lightweight flying vehicles suitable for carrying mission payloads.

[0040] In some illustrative embodiments of this disclosure, the antenna subarray 32 of the antenna module 3 can be in the form of an active phased array antenna or a microstrip array antenna, which is suitable for radiating and receiving microwave signals.

[0041] Figure 4 This is a front view of the antenna subarray 32 in an embodiment of this disclosure.

[0042] According to embodiments of this disclosure, such as Figure 4 As shown, the antenna subarray 32 includes a plurality of square radiating elements arranged with the same physical gap, and the thickness of the frame where at least two antenna subarrays 32 abut each other is equal to half of the physical gap.

[0043] In some illustrative embodiments of this disclosure, the antenna subarray 32 includes a plurality of square radiating elements arranged with the same physical gap. The physical gap is the shortest distance between the edges of adjacent square radiating elements in a regularly arranged rectangular grid. Simultaneously, the antenna subarray 32 has a frame on one side for splicing with another identical subarray. The thickness of the frame is configured to be equal to half the physical gap to improve the electrical performance continuity of the two antenna subarrays 32 in the spliced ​​state. When the two antenna subarrays 32 are placed side-by-side along this frame, the total distance from the center of the outermost radiating element of the first subarray to the outer surface of its frame, then to the outer surface of the frame of the second subarray, and finally back to the center of the outermost radiating element of the second subarray, is exactly equal to the distance between the centers of two adjacent radiating elements within a single antenna subarray 32 (i.e., the element period). This geometric relationship ensures that after the two subarrays are physically spliced, the arrangement of radiating elements in their combined array across the entire aperture has a strict and continuous periodicity.

[0044] Specifically, refer to Figure 4The distance between the centers of the radiating elements of the two antenna subarrays 32 is D, and the side length of the radiating element is A. The physical gap is defined as the shortest distance between the edges of adjacent radiating elements, and its value is G=DA. The antenna subarray 32 has a mechanical frame on the side used for splicing, and this frame has a specific structural thickness. The thickness of the frame is configured to be equal to half the physical gap G, that is, the distance from the center of the outermost radiating element to the outer edge of the frame is equal to half D. After the two antenna subarrays 32 are physically spliced, the gap between the radiating elements between the edges of the splicing frame of the two antenna subarrays 32 is equal to G, that is, the distance between the centers of the radiating elements at the edges of the two antenna subarrays 32 after splicing is D. This ensures that the array period remains unchanged after the two antenna subarrays 32 are spliced.

[0045] This implementation avoids the element spacing variations introduced by mechanical splicing, as well as potential far-field pattern deterioration, such as increased higher-order grating lobes, main beam distortion, or gain loss. This allows the spliced ​​synthetic aperture to approach the key electrical performance of a single, integrated antenna of the same size, improving the system's imaging resolution and signal-to-noise ratio in the second mode.

[0046] According to embodiments of this disclosure, in a first mode, the electronic unit 2 performs interference processing on the signals received by the two antenna modules 3 to obtain phase difference information of the target. In a second mode, the electronic unit 2 performs synthetic aperture radar imaging processing on the signals received by the two antenna modules 3 as a whole to obtain an image of the target.

[0047] In some illustrative embodiments of this disclosure, in the first mode, electronic unit 2 performs a dual-channel synthetic aperture radar imaging and interferometric processing procedure on the received signals from two spatially separated antenna modules 3. The workflow of electronic unit 2 in obtaining target phase difference information through interferometric processing is as follows: Electronic unit 2 first performs independent synthetic aperture radar imaging processing on the two received signals to generate two complex images with precise spatial registration. Subsequently, by calculating the phase difference values ​​of corresponding pixels in the two complex images, an interferometric phase map is generated. This interferometric phase map contains phase information directly related to the three-dimensional geometry or motion state of the target, introduced by the spatial position difference between the two antennas. By unwrapping, correcting, and inverting this phase information, the elevation information of the target or the motion velocity information along the radar line of sight can be finally extracted, thereby realizing interferometric measurement.

[0048] In the second mode, electronic unit 2 treats the two closely joined antenna modules 3 as a single unit and performs single-channel synthetic aperture radar (SAR) imaging processing on their received signals. The workflow for electronic unit 2 to acquire target images through SAR imaging processing in the second mode is as follows: Since the two antenna subarrays 32 are joined into a large-aperture antenna, electronic unit 2 treats its receiving channel as equivalent to a signal from a single aperture at the signal processing level. Electronic unit 2 executes a standard SAR focusing algorithm (such as range-Doppler or frequency domain algorithms) on this uniform-aperture echo signal. By performing two-dimensional compression of the echo in the range and azimuth directions, the energy of the scattering points is focused, ultimately generating a high-resolution two-dimensional complex image. This image contains not only the intensity information of backscattered ground features but also the phase information recorded by the coherent radar system. The image can be directly used for terrain interpretation and target identification, and can also serve as the base image required for subsequent heavy-track interferometry.

[0049] In some illustrative embodiments of this disclosure, the electronic unit 2 includes circuit modules such as a waveform generator, an up-converter and power amplifier, a low-noise amplifier and down-converter, an analog-to-digital converter, and a digital signal processor. The electronic unit 2 is connected to the antenna module 3 via a cable. The electronic unit 2 generates the radar signal to be transmitted and sends it to the designated antenna module 3. Simultaneously, it receives and processes the echo signal from the antenna module 3. Through internally embedded timing and control logic, the electronic unit 2 can configure the operating modes of the radar system: in the first mode, it controls one designated antenna module 3 to transmit a signal and simultaneously acquires data from the receiving channels of two antenna modules 3; in the second mode, the two antenna modules 3 are logically treated as a single transmit / receive unit, and their collaborative operation is controlled to achieve signal reception and transmission.

[0050] Figure 5 This is a top view of the mounting structure 1 in an embodiment of this disclosure.

[0051] According to embodiments of this disclosure, such as Figure 5 As shown, the mounting structure 1 includes at least three mounting interfaces spaced apart along its length. When the radar system is in its first mode, at least two antenna modules 3 are positioned on the at least two spaced-apart mounting interfaces, and the antenna subarrays 32 of the at least two antenna modules 3 are spaced apart. When the radar system is in its second mode, at least two antenna modules 3 are positioned on at least two adjacent mounting interfaces, and the antenna subarrays 32 of the at least two antenna modules 3 abut against each other.

[0052] In some illustrative embodiments of this disclosure, such as Figure 5As shown, the mounting structure 1 is a rectangular plate structure. The mounting structure 1 has three mounting interfaces: a first interface 11, a second interface 12, and a third interface 13. All three interfaces are used for mounting the antenna modules 3. The first interface 11 and the second interface 12 are respectively located on opposite sides of the length of the mounting structure 1, and the third interface 13 is located on the side of the second interface 12 near the center. The distance between the second interface 12 and the third interface 13 is configured such that when two antenna modules 3 are mounted on the second interface 12 and the third interface 13 respectively, the edges of the antenna subarrays 32 of the two antenna modules 3 abut against each other. Therefore, in the second mode, it can be equivalent to an antenna with a larger effective physical aperture.

[0053] In some illustrative embodiments of this disclosure, such as Figure 5 As shown, the mounting structure 1 is also provided with a fourth interface 14 and a fifth interface 15 for mounting the electronic unit 2. The fifth interface 15 is located in the middle of the mounting structure 1, and the fourth interface 14 is located on the side of the fifth interface 15 away from the second interface 12. When the two antenna modules 3 are respectively mounted on the first interface 11 and the second interface 12, the electronic unit 2 is mounted on the fifth interface 15 in the middle to avoid mutual interference. Furthermore, when the two antenna modules 3 are respectively mounted on the second interface 12 and the third interface 13, due to the limited space of the mounting structure 1, if the electronic unit 2 is also mounted on the fifth interface 15, interference may occur. In this case, the electronic unit 2 can be mounted on the fourth interface 14 to avoid mutual interference.

[0054] In this implementation, the multiple interfaces provide definite and non-interfering physical installation locations for the hardware configuration of the system in two operating modes. Furthermore, by configuring two different installation interfaces for the electronic unit 2, it can select the appropriate installation location according to the different layouts of the antenna module 3, thereby effectively avoiding spatial and electromagnetic interference between modules in any mode and ensuring the system's structural compactness and operational reliability under various configurations.

[0055] In some illustrative embodiments of this disclosure, the mounting interface is configured to provide multiple mounting positions with different orientations, allowing the antenna module 3 to be selectively fixed at these positions, thereby enabling the switching of the radiated beam direction of the antenna subarray 32 between different directions. The multiple mounting positions include at least a mounting position where the radiated beam points towards the flight direction and a mounting position where the radiated beam points perpendicular to the flight direction.

[0056] As an example, the mounting interface is a set of connection holes evenly distributed along the circumference (e.g., four holes spaced 90 degrees apart). By rotating the antenna module 3 relative to the mounting interface by a certain angle (e.g., 0 degrees, 90 degrees) and aligning it using connectors passing through different sets of holes, the antenna module 3 can be locked in different orientations, thereby causing the radiation beam of the antenna subarray 32 to point parallel or perpendicular to the flight direction. The connectors can be quick-release locking mechanisms or screw sets with locating pins to ensure quick and accurate reinstallation of the antenna module after disassembly.

[0057] Alternatively, the mounting interface itself can be integrated into a rotatable and lockable mechanical component, such as a turntable base with indexing pins. Antenna module 3 is mounted on this turntable. By pulling out the indexing pins, rotating the turntable to the next indexing position (e.g., 90 degrees), and then reinserting and locking it, the overall orientation of antenna module 3 can be changed, thereby altering the beam direction.

[0058] Alternatively, the mating surface between antenna module 3 and the mounting interface can be designed as a nested structure of polygons (such as squares). By fitting this nested structure at different angles (such as every 90 degrees of rotation), the beam direction can be changed.

[0059] It is understandable that the installation interface can be set up in a way that is not limited to this. As long as at least two stable and definite installation positions can be provided for the antenna module 3, the radiation beam of the antenna subarray 32 can be configured to point to different preset directions (e.g., parallel or perpendicular to the flight direction of the platform).

[0060] According to embodiments of this disclosure, such as Figure 1 and Figure 3 As shown, the first mode includes at least two sub-modes. When the synthetic aperture radar is in the first sub-mode, the output direction of the radiation beam of the antenna subarray 32 is towards the flight direction of the UAV. When the synthetic aperture radar is in the second sub-mode, the output direction of the radiation beam of the antenna subarray 32 is offset from the flight direction of the UAV.

[0061] Figure 6 This is a perspective view of the antenna module 3 in the first sub-mode of an embodiment of this disclosure. Figure 7 This is a perspective view of the antenna module 3 in the second sub-mode of an embodiment of this disclosure. Figure 6 and Figure 7 The arrow in the image indicates the output direction of the radiated beam of antenna subarray 32.

[0062] In some illustrative embodiments of this disclosure, reference is made to Figure 5 and Figure 6The first submode is the in-orbit interferometry mode, where the radiation beam output direction of the antenna subarray 32 is oriented towards the flight direction of the UAV. In the in-orbit interferometry mode, the radiation beam output directions of the two spaced antenna subarrays 32 are parallel to the flight direction. By processing the phase difference of the simultaneously received signals, the velocity information of the moving target along the radar line of sight in the observation scene can be directly extracted, realizing moving target detection and velocity measurement.

[0063] Figure 8 This is a partial three-dimensional view of the radar system in the second sub-mode of an embodiment of this disclosure. Figure 9 This is a partial three-dimensional view of the radar system in the first sub-mode of an embodiment of this disclosure.

[0064] In some illustrative embodiments of this disclosure, reference is made to Figure 8 and Figure 9 The second submode is the cross-track interferometry mode, where the output direction of the radiated beam is offset from the UAV's flight direction. In this mode, two spaced antennas form a spatial baseline perpendicular to the flight direction. By processing the interferometric phase, the three-dimensional terrain information of the observed scene can be calculated, thereby generating a digital model.

[0065] In some illustrative embodiments of this disclosure, the second mode is a double-track interferometry mode, in which two antenna subarrays 32 are arranged side-by-side and operate as a single unit. In the double-track interferometry mode, the two antenna subarrays 32, as a whole, can synthesize a larger spatial area, improving the spatial resolution and signal-to-noise ratio of the radar image. The high-quality single-look complex images acquired in the double-track interferometry mode can be used for detailed mapping and can also serve as a data source for subsequent double-track interferometry measurements to monitor surface deformation.

[0066] According to embodiments of this disclosure, such as Figure 7 As shown, the antenna module 3 also includes an antenna bracket 31, which includes a first mounting part 311, a second mounting part 312, and a bracket body 313. The bracket body 313 is disposed between the first mounting part 311 and the second mounting part 312. The first mounting part 311 is connected to the antenna interface, and the antenna subarray 32 is connected to the second mounting part 312.

[0067] According to embodiments of this disclosure, the antenna module 3 further includes a connector. The connector passes through the first mounting portion 311 and the antenna interface, and / or, the connector passes through the second mounting portion 312 and the antenna subarray 32.

[0068] In some illustrative embodiments of this disclosure, the first mounting portion 311 of the antenna bracket 31 is configured to cooperate with the aforementioned various mounting interface settings to achieve the fixation and orientation adjustment of the antenna module 3 on the mounting structure 1.

[0069] When the mounting interface consists of a group of connecting holes evenly distributed along the circumference, the first mounting part 311 has multiple connecting holes evenly distributed along the circumference, and the diameter of the distribution circle of the first mounting part 311 is the same as the diameter of the distribution circle of the corresponding connecting hole group on the mounting interface. By rotating the first mounting part 311 about the center of the distribution circle relative to the mounting interface by a specific angle (e.g., 0°, 90°, 180°, or 270°), all the connecting holes on the first mounting part 311 can be aligned one by one with the corresponding connecting hole group on the mounting interface at the new angular position. At this time, the connector passes through the aligned holes, and the antenna module 3 can be stably locked in the corresponding angular position.

[0070] When the mounting interface is a lockable rotary dial, the first mounting part 311 is fixedly connected to the dial. By operating the dial to rotate to different divisions and locking it, the mounting orientation of the first mounting part 311 and the entire antenna module 3 can be changed.

[0071] When the mounting interface adopts a polygonal (such as a square) nested structure, the first mounting part 311 is constructed with a complementary polygonal mating structure. By embedding the mating structure into the mounting interface at different angles, the first mounting part 311 is fixedly mounted in a preset discrete direction.

[0072] In some illustrative embodiments of this disclosure, the bracket body 313 is used to connect the first mounting part 311 and the second mounting part 312. The bracket body 313 forms a relatively fixed rigid connection between the two, thereby ensuring that the second mounting part 312 and the antenna subarray 32 can stably maintain a relative spatial relationship with the first mounting part 311. The bracket body 313 can be integrally formed with the first mounting part 311 to enhance the overall structural rigidity and reliability. When the first mounting part 311 is matched with different mounting interfaces or with the same mounting interface in different orientations, that is, when the overall orientation of the antenna module 3 changes, the radiation beam direction of the antenna subarray 32 changes synchronously.

[0073] According to embodiments of the present disclosure, the mounting structure 1 is configured as a plate-shaped structure, and / or the extension direction of the second mounting portion 312 is inclined to the horizontal direction.

[0074] According to an embodiment of the present disclosure, the support body 313 is pivotally connected to the second mounting portion 312 so that the output direction of the radiation beam of the antenna subarray 32 is adjustable.

[0075] In some illustrative embodiments of this disclosure, the mounting structure 1 is a plate-shaped structure, such as a rectangular or elongated metal plate or composite material plate. This structure provides a flat, rigid mounting surface, facilitating the planning and fabrication of multiple mounting interfaces with precise relative positions. The extension direction of the second mounting portion 312 is configured to be inclined to the horizontal direction; for example, after being mounted to a UAV, the mounting plane for connecting the antenna subarray 32 forms a fixed acute angle with the horizontal plane.

[0076] In this implementation, by pre-setting the extension direction of the second mounting part 312 to be inclined to the horizontal direction, when the radar system is installed on a horizontally flying UAV, the radiation beam of the antenna subarray 32 can obtain a fixed, non-zero elevation angle. This allows the beam to illuminate the ground at a specific incident angle, optimizing the geometry of ground observation, and obtaining a beam pointing that meets the needs of specific remote sensing applications (such as imaging at a specific incident angle) without requiring the UAV to perform pitch maneuvers.

[0077] In other illustrative embodiments of this disclosure, the bracket body 313 and the second mounting portion 312 are pivotally connected. For example, a hinge axis is provided between them, and an angle locking mechanism (such as an arcuate plate with positioning holes and a pin) is provided. Alternatively, a friction rotary joint is used, and the relative angle is fixed by tightening screws.

[0078] In this implementation, by pivotally connecting the support body 313 to the second mounting portion 312, the elevation angle of the antenna subarray 32 can be adjusted within a certain range. For example, by releasing the angle locking mechanism and manually adjusting the elevation angle of the antenna subarray 32 about the hinge axis, and then relocking it, the direction of its radiated beam in the vertical plane can be changed. This allows the system to flexibly adjust the beam elevation angle (or equivalent incident angle) according to different flight altitudes, terrain slopes, or the needs of specific observation tasks, thereby optimizing illumination coverage and signal-to-noise ratio of the target area and enhancing the system's adaptability to different application scenarios.

[0079] In some illustrative embodiments of this disclosure, the second mounting portion 312 includes a central base and four connecting arms extending outward from the central base. The four connecting arms are evenly distributed around the central base, with an included angle of 90 degrees between adjacent connecting arms, and each connecting arm has a set of connecting holes at its end. The antenna subarray 32 has four sets of connecting holes at corresponding positions on its back side. By selecting different alignment combinations between the connecting holes on the back side of the antenna subarray 32 and the connecting holes at the ends of the four connecting arms for detachable fastening, the antenna subarray 32 can be fixed to the second mounting portion 312 at multiple discrete angles differing by 90 degrees, thereby changing the polarization direction of the antenna subarray.

[0080] In this implementation, the polarization direction of the antenna subarray 32 is adjustable through the cooperation of the second mounting part 312 and the antenna subarray 32. Specifically, the polarization direction of the antenna subarray 32 is determined by the arrangement direction of its internal radiating elements. By loosening the fasteners, disassembling the antenna subarray 32 from its current connection state, rotating it 90 degrees, selecting another set of connection holes for alignment, and then re-tightening it, the physical orientation of the antenna subarray 32 relative to the antenna bracket 31 and the UAV platform can be changed. This, in turn, changes the polarization direction of the electromagnetic waves radiated and received by the antenna subarray 32.

[0081] In this implementation, by rotating and fixing the two antenna subarrays 32 to orthogonal orientations, they can operate in horizontal and vertical polarization modes respectively, thereby enabling the radar system to support full polarization observation. This configuration allows for switching of polarization configurations solely through mechanical reconfiguration without replacing hardware or internal circuitry, improving the flexibility of system functionality.

[0082] According to embodiments of this disclosure, in the first sub-mode, the two antenna subarrays 32 are configured to transmit and receive orthogonally polarized electromagnetic waves, or the two antenna subarrays 32 are configured to transmit and receive electromagnetic waves of the same polarization.

[0083] In some illustrative embodiments of this disclosure, when the system operates in the fully polarized interferometry mode, one of the two antenna subarrays 32 is configured as horizontally polarized and the other as vertically polarized. During system operation, the horizontally polarized antenna subarray 32 is first controlled to transmit a pulse, and the echo is simultaneously received by both horizontally and vertically polarized antenna subarrays 32, acquiring two sets of scattering data: "horizontal transmission-horizontal reception" and "horizontal transmission-vertical reception." Subsequently, the vertically polarized antenna subarray 32 is controlled to transmit the next pulse, which is also simultaneously received by both antenna subarrays 32, acquiring two sets of data: "vertical transmission-horizontal reception" and "vertical transmission-vertical reception." By interferometric processing of the two resulting fully polarized complex images, while acquiring information on surface deformation or motion, the complete target polarization scattering characteristics can be preserved, thereby achieving fine classification and identification of the physical properties of ground objects and enhancing the information dimension and application value of the interferometric data.

[0084] In other illustrative embodiments of this disclosure, one antenna subarray 32 transmits a signal, and two antenna subarrays 32 with the same polarization simultaneously receive the echo. Since the polarization of the transmission and reception are the same (e.g., both are "horizontal transmission-horizontal reception"), the two acquired signals are polarized and matched. This configuration eliminates phase errors and crosstalk that may be introduced between different polarization channels due to hardware differences, making the subsequent interferometric phase extraction process more direct, the signal stability higher, and enabling higher accuracy and reliability of elevation or deformation measurement results.

[0085] According to embodiments of this disclosure, the electronic unit (2) can reconfigure the waveform. By changing the configuration of its internal signal generator, timing controller, and processing algorithm through software programming, the electronic unit (2) enables the radar system to switch between two basic signal forms: pulse waveforms and linear frequency modulated continuous wave waveforms, thereby optimizing performance under different observation tasks. This is another core aspect that further enhances the system's versatility and adaptability.

[0086] The pulse waveform is characterized by transmitting a radio frequency pulse with an extremely short duration (microseconds or nanoseconds) and high peak power, followed by receiving the echo during the pulse interval. Its working principle is based on measuring the time delay between transmission and reception to determine the target distance (ranging). In synthetic aperture radar (SAR) processing, a virtual large aperture is synthesized in the azimuth direction (along the flight direction) by coherently processing a series of pulse echoes, thereby obtaining a high-resolution image. The advantages of the pulse system are its mature technology, long operating range, and relatively low requirements for the system's instantaneous dynamic range due to its time-division multiplexing operation.

[0087] The characteristic of linear frequency modulated (LFM) continuous wave (LCW) waveforms is the continuous transmission of a signal whose frequency varies linearly with time, while simultaneously receiving echoes. Its working principle is based on demodulation: the received echo signal is mixed with the currently transmitted reference signal to generate a difference frequency signal. The frequency of this difference frequency signal is proportional to the target distance, while its phase contains information about the target's motion. LFM WCB waveforms have low average transmit power, facilitating system miniaturization and low power consumption. The continuous observation characteristic of LFM WCB waveforms makes them sensitive to phase changes, suitable for high-precision velocity and micro-deformation measurements; simultaneously, it directly achieves high range resolution through wide-bandwidth frequency sweeping without range ambiguity issues, making it suitable for medium-to-short-range observation scenarios using UAVs.

[0088] In the first submode of in-orbit interferometry (for velocity measurement), when the two antenna modules (3) are set apart to form a baseline along the flight direction, the waveform selection can be determined according to the requirements of velocity measurement accuracy and operating distance. For example, if high-precision (sub-millimeter) measurement of slow movement or small vibrations of ground objects (such as bridge deformation monitoring) is required, the electronic unit (2) can be configured as a linear frequency modulated continuous wave waveform. The system operates in continuous wave form, performs long-term phase continuous observation of the same target area, and retrieves the line-of-sight velocity change by processing the stable and high signal-to-noise ratio phase difference historical data between the two receiving channels.

[0089] If the mission requires high-resolution imaging and moving target indication at a long operating distance (such as wide-area maritime monitoring), the electronic unit (2) can be configured as a pulse waveform. The system transmits a pulse train and compares the instantaneous phase difference of the echo signals received by the two antennas within the same distance unit to detect and measure the velocity of the moving target, and simultaneously generate an image.

[0090] In the second submode of cross-track interferometry (for altimetry), when two antenna modules (3) are separated to form a baseline perpendicular to the heading, regardless of whether a pulse waveform or a linear frequency modulated continuous wave waveform is used, the elevation information is extracted by interferometric processing of two complex images, utilizing the viewing angle difference generated by the spatial baseline. When using a pulse waveform, the system acquires echo data of the scene through a series of pulses, and generates a digital elevation model after imaging and interferometric processing. When using a linear frequency modulated continuous wave waveform, the power consumption is low and the phase stability at close range is good, enabling efficient and high-precision generation of three-dimensional topographic maps of local areas.

[0091] In high-resolution imaging in the second mode, and / or as a data source for heavy-orbit interferometry, when two antenna subarrays (32) are placed side-by-side and are equivalent to a larger-aperture antenna. The waveform can be selected based on the operating distance, resolution, and system complexity.

[0092] On UAV platforms, the low peak power characteristics of linear frequency modulated continuous wave waveforms are well-suited to the limited power supply capabilities of UAVs. The frequency-modulated receiver mechanism reduces the sampling rate requirements, enabling the system to achieve excellent high-resolution imaging performance within compact size and weight constraints, providing high-quality foundational images for subsequent heavy-orbit interferometric deformation monitoring. If the mission requires a higher operating range (e.g., on large fixed-wing UAV platforms), it can also be configured as a pulse waveform, utilizing its high peak power to achieve a longer detection range. This, combined with an equivalent large-aperture antenna, further enhances azimuth resolution and gain.

[0093] In other illustrative embodiments of this disclosure, reference is made to Figure 5 The mounting structure 1 also has heat dissipation interfaces 16 on both sides of its edge. Optionally, a similar heat dissipation interface 16 may be provided next to the third interface 13. The heat dissipation interface 16 may be configured as a ventilation mesh, a heat sink fin mounting surface, or a mechanical and electrical interface for connecting an external active cooling device (such as a fan).

[0094] In this implementation, by placing heat dissipation interfaces 16 near the exposed edges of the mounting structure and in areas with concentrated high heat load modules (such as antenna modules), the effective surface area for heat exchange between the system and the external air is increased, and a structured airflow channel is provided. Through this active or passive heat dissipation design, the operating temperature of critical RF and processing components can be effectively controlled, avoiding performance degradation, signal drift, or device damage caused by overheating.

[0095] It should also be noted that the directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," and "right," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of this disclosure. Throughout the drawings, the same elements are identified by the same or similar reference numerals. Conventional structures or constructions will be omitted where they may cause confusion in understanding this disclosure.

[0096] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A multimodal reconfigurable synthetic aperture radar system for an unmanned aerial vehicle (UAV) platform, characterized in that, include: Installation structure for externally mounted drones; At least two antenna modules are detachably connected to the mounting structure, and each antenna module includes an antenna subarray. as well as An electronic unit, connected to the mounting structure, is adapted to control the antenna module to receive and transmit signals; The radar system has at least two operating modes: In the first mode, the two antenna subarrays are separated, and the electronic unit controls one of the two antenna modules to transmit a signal while both receive signals simultaneously. In the second mode, the two antenna subarrays are placed side by side and closely attached, and the electronic unit controls the two antenna modules to transmit and receive signals simultaneously as a whole.

2. The radar system according to claim 1, characterized in that, The mounting structure includes at least three mounting interfaces spaced apart along its length. When the radar system is in the first mode, at least two of the antenna modules are disposed at at least two mounting interfaces spaced apart from each other, and the antenna subarrays of the at least two antenna modules are spaced apart. When the radar system is in the second mode, at least two of the antenna modules are disposed at at least two adjacent mounting interfaces, and the antenna subarrays of at least two of the antenna modules abut against each other.

3. The radar system according to claim 2, characterized in that, The antenna subarray comprises a plurality of square radiating elements arranged with the same physical gap, and the thickness of the frame where at least two of the antenna subarrays abut each other is equal to half of the physical gap.

4. The radar system according to claim 2, characterized in that, The antenna module further includes an antenna bracket, which includes: First Installation Department; Second installation unit; and The main body of the bracket is disposed between the first mounting part and the second mounting part; The first mounting part is connected to the antenna interface, and the antenna subarray is connected to the second mounting part.

5. The radar system according to claim 4, characterized in that, The antenna module also includes connectors; The connector passes through the first mounting part and the antenna interface, and / or the connector passes through the second mounting part and the antenna subarray.

6. The radar system according to claim 5, characterized in that, The first mode includes at least two sub-modes; When the synthetic aperture radar is in the first sub-mode, the output direction of the radiation beam of the antenna subarray is toward the flight direction of the UAV; When the synthetic aperture radar is in the second sub-mode, the output direction of the radiation beam of the antenna subarray is offset from the flight direction of the UAV.

7. The radar system according to claim 6, characterized in that, The mounting structure is configured as a plate-shaped structure; And / or, the extension direction of the second mounting portion is inclined to the horizontal direction.

8. The radar system according to any one of claims 4 to 7, characterized in that, The main support body is pivotally connected to the second mounting part so that the output direction of the radiated beam of the antenna subarray is adjustable.

9. The radar system according to claim 6, characterized in that, In the first mode, the electronic unit performs interference processing on the signals received by the two antenna modules to obtain the phase difference information of the target; In the second mode, the electronic unit performs synthetic aperture radar imaging processing on the signals received by the two antenna modules as a whole to obtain an image of the target.

10. The radar system according to claim 9, characterized in that, In the first sub-mode, the two antenna subarrays are configured to transmit and receive orthogonally polarized electromagnetic waves; or, the two antenna subarrays are configured to transmit and receive electromagnetic waves with the same polarization.

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