Unmanned aerial vehicle-mounted dual-frequency millimeter wave radiation imaging system and imaging method

Abstract

The invention provides an unmanned aerial vehicle-mounted dual-frequency millimeter wave radiation imaging system and imaging method, and belongs to the technical field of passive millimeter wave radiation imaging, and the system comprises an antenna feeder network system, a W-band receiver, a D-band receiver, a stepping motor turntable, a calibration structure and a main control board card. The system is mainly used in the application fields of sea target detection, passive imaging to the ground, forest fire early warning and monitoring and the like, and can provide a new solution for the requirements of sea-to-ground target detection and imaging, forest fire early warning and the like under low visibility. Therefore, the application of the passive millimeter wave radiation remote sensing technology in the target detection field is further promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of passive millimeter wave radiation imaging, and in particular to an unmanned aerial vehicle-borne dual-frequency millimeter wave radiation imaging system and an imaging method. Background Art

[0002] Remote sensing technology is a technology that detects and identifies targets by sensing electromagnetic waves reflected or radiated by targets from a long distance. Remote sensing technology can be applied to meteorological observation, earth resource survey, environmental pollution monitoring, earthquake monitoring, ocean monitoring, land use planning, vegetation classification, crop yield survey and crop pest and disease monitoring. At present, the main remote sensing technologies include visible light, infrared and active radar. Visible light imaging technology has the advantage of high resolution, but generally has a narrow field of view and is easily affected by low-visibility weather such as clouds, fog, haze, smoke, and rain; infrared detection technology also has a high spatial resolution, but also has a narrow field of view and is greatly affected by the earth's background. Although it has stronger penetration than optics, it is also unable to penetrate clouds and rainy areas and is greatly affected by low-visibility weather such as clouds and rain. Active radar imaging technology has all-day and quasi-all-weather imaging capabilities, but it requires active signal transmission, high power consumption, poor concealment, and is easily interfered by factors such as ground and sea clutter.

[0003] At present, millimeter wave radiation passive imaging has attracted much attention due to its many advantages, such as being all-day, quasi-all-weather, not emitting any signals, strong concealment, little interference from ground and sea clutter, and good detection capabilities for stealth targets and electromagnetically silent targets. Microwave radiation imaging technology can penetrate the surface, vegetation, and human body to a certain depth, and can provide information that infrared and visible light methods cannot provide. It has strong application value in the fields of passive earth remote sensing, security inspection, transportation, guidance, and target detection. In the application research of millimeter wave radiation passive imaging, there are a large number of representative companies abroad, such as Millivision, TRW, Andrew, and QinetiQ, etc. They have all developed millimeter wave imaging systems that can be used in civil fields such as human body scanning, security inspection, and traffic monitoring. Although domestic research in the field of millimeter wave radiation imaging started late, there are also many research representatives. In 1998, Nanjing University of Science and Technology first proposed a method of using millimeter-wave radiation imaging technology to detect coated stealth aircraft in the air. In 2005, Huazhong University of Science and Technology developed an 8mm 16-unit one-dimensional parabolic cylindrical comprehensive aperture millimeter-wave radiation imaging system. In 2008, Lang Liang and others from Huazhong University of Science and Technology proposed the application of airborne comprehensive aperture microwave radiation imaging technology to target detection. In 2016, the Xi'an Institute of Space Radio Technology proposed the use of airborne / satellite-borne high-resolution comprehensive aperture microwave radiation imaging technology for sea surface target detection. In 2018, the first airborne comprehensive aperture microwave radiation passive detection verification experiment of sea surface targets was carried out at home and abroad, verifying the good performance of airborne comprehensive aperture microwave radiation passive detection for ground imaging and detection. It is one of the important progress made in the field of microwave / millimeter-wave radiation detection and imaging in China in the past decade. It has very important practical significance for promoting the application of microwave / millimeter-wave radiation imaging technology in the field of ground imaging and detection.

[0004] Specifically, millimeter wave radiation imaging technology mainly includes synthetic aperture millimeter wave radiation imaging system and real aperture millimeter wave radiation imaging system. Compared with the traditional real aperture millimeter wave radiation imaging system, the synthetic aperture millimeter wave radiation imaging system has higher spatial resolution and wider instantaneous field of view, but it is a large-scale imaging system composed of multiple receiver channels and antenna arrays, which increases the complexity of the system and signal processing while greatly increasing the hardware cost of the system. The traditional real aperture millimeter wave radiation imaging system has the disadvantages of large size and heavy weight, but its hardware cost is relatively low, which is especially suitable for the civilian field that is very sensitive to price. At the same time, various types of drone technology are developing rapidly, which has the advantages of flexible operation, low cost, long hovering time, and less affected by human physiological conditions. UAVs have shown great value in both civilian and military fields. Millimeter wave radiation imaging technology has the advantages of all-day, quasi-all-weather, and little interference from ground and sea clutter. It has a very broad application prospect in ground imaging, environmental monitoring, forest fire warning, landing guidance and target detection. Currently, products that combine the advantages of drones and millimeter-wave radiation imaging systems have not yet been proposed. Summary of the invention

[0005] The present invention provides an unmanned aerial vehicle-mounted dual-frequency millimeter wave radiation imaging system and imaging method, which are used to solve the defects of millimeter wave radiation imaging products in the prior art, such as high cost and complex system, and the failure to effectively combine with unmanned aerial vehicle technology, and unable to give full play to the advantages of remote sensing system imaging.

[0006] In a first aspect, the present invention provides an unmanned aerial vehicle-mounted dual-frequency millimeter wave radiation imaging system, comprising: Antenna network system, W-band receiver, D-band receiver, stepper motor turntable, calibration structure and main control board; The antenna feed network system receives millimeter wave radiation signals from the environment; The W-band receiver converts the W-band radiation signal in the millimeter wave radiation signal into a first voltage signal and a first signal parameter; The D-band receiver converts the D-band radiation signal in the millimeter wave radiation signal into a second voltage signal and a second signal parameter; The calibration structure is connected to the antenna feeder network system to provide an operating space for two-point calibration; The stepper motor turntable is connected to the antenna feeder network system to drive the antenna feeder network system with a preset scanning mode and stepping accuracy; The main control board is connected to the antenna network system, the W-band receiver, the D-band receiver and the stepper motor turntable respectively, and is used for system analog-to-digital conversion, data processing, signal transmission and control system operation.

[0007] According to a dual-frequency millimeter-wave radiation imaging system on a drone provided by the present invention, the antenna feed network system includes an offset-fed parabolic antenna and a polarization grid; The offset-fed parabolic antenna comprises a rotating parabola and two feed lines, wherein the two feed lines are placed at the focus of the rotating parabola and are respectively located on both sides of the polarization grid; The polarization grid is connected to the W-band receiver and the D-band receiver respectively. The W-band receiver receives the W-band radiation signal that is parallel to the polarization grid and reflected and propagated on the polarization grid, and the D-band receiver receives the D-band radiation signal that is perpendicular to the polarization grid and penetrates and propagates on the polarization grid.

[0008] According to an unmanned aerial vehicle dual-frequency millimeter wave radiation imaging system provided by the present invention, the W-band receiver comprises a W-band low noise amplifier, a W-band radio frequency filter, a W-band power amplifier and a W-band detector connected in sequence; The W-band receiver receives the W-band radiation signal and outputs the first voltage signal and the first signal parameter.

[0009] According to an unmanned aerial vehicle dual-frequency millimeter wave radiation imaging system provided by the present invention, the D-band receiver comprises a D-band low noise amplifier, a D-band radio frequency filter, a D-band power amplifier and a D-band detector connected in sequence; The D-band receiver receives the D-band radiation signal and outputs the second voltage signal and the second signal parameter.

[0010] According to a dual-frequency millimeter-wave radiation imaging system on an unmanned aerial vehicle provided by the present invention, the calibration structure comprises a room-temperature black body and a liquid nitrogen box, the room-temperature black body is a heat source, and the liquid nitrogen box is a cold source; The rotating parabola in the antenna feed network system collects observation data on the heat source and the cold source in a single observation cycle to obtain a calibration equation.

[0011] According to the dual-frequency millimeter-wave radiation imaging system for unmanned aerial vehicles provided by the present invention, the stepper motor turntable adopts a permanent magnet synchronous motor as a driving body, and the rotation angle of the output shaft in the permanent magnet synchronous motor is controlled by a pulse signal; The output shaft is connected to the rotating parabola, and the output shaft drives the rotating parabola to perform scanning motion.

[0012] According to an unmanned aerial vehicle dual-frequency millimeter wave radiation imaging system provided by the present invention, the main control board transmits the received radiation digital information to the host computer and the external storage device, and receives the control command of the host computer to control the scanning state of the stepper motor turntable.

[0013] According to the present invention, a dual-frequency millimeter-wave radiation imaging system on a drone also includes a power supply, which is connected to the main control board; The power source is a rechargeable power source or a direct-supply power source.

[0014] In a second aspect, the present invention further provides a dual-frequency millimeter wave radiation imaging method for an unmanned aerial vehicle, comprising: The dual-frequency millimeter-wave radiation imaging system is mounted under the drone to obtain the flight direction of the drone; The dual-frequency millimeter wave radiation imaging system adopts a circular scanning imaging method perpendicular to the flight direction to achieve scanning imaging perpendicular to the flight direction; The dual-frequency millimeter wave radiation imaging system uses a push-scan method with the help of the UAV in the flight direction to achieve two-dimensional millimeter wave radiation imaging of the target.

[0015] According to a dual-frequency millimeter wave radiation imaging method on a drone provided by the present invention, the scanning imaging includes a fixed-point uniform-speed scanning mode, a fixed-point variable-speed scanning mode, a fixed-point swing scanning mode, and a fixed-point spiral scanning mode; The fixed-point uniform scanning mode is that the UAV hovers and rotates at a uniform speed, and the dual-frequency millimeter wave radiation imaging system performs uniform circular scanning. The uniform circular scanning speed of the dual-frequency millimeter wave radiation imaging system is much faster than the uniform rotation speed of the UAV, and the target imaging projection is in the shape of a close spider web; The fixed-point variable-speed scanning mode is that the UAV hovers and rotates at a uniform speed, and the dual-frequency millimeter-wave radiation imaging system rotates at a uniform speed. The uniform circular scanning speed of the dual-frequency millimeter-wave radiation imaging system is much greater than the uniform rotation speed of the UAV. It scans at a uniform speed within the target imaging observation angle range and scans quickly within other angle ranges. The fixed-point swing scanning mode is that the UAV hovers and rotates at a uniform speed, and the dual-frequency millimeter wave radiation imaging system rotates at a uniform speed. The uniform circular scanning speed of the dual-frequency millimeter wave radiation imaging system is much faster than the uniform rotation speed of the UAV. The system swings back and forth within the target imaging observation angle range and does not scan within other angle ranges. The fixed-point spiral scanning mode is that the UAV hovers and rotates at a uniform speed, and the dual-frequency millimeter wave radiation imaging system performs uniform circular scanning. The uniform circular scanning speed of the dual-frequency millimeter wave radiation imaging system is much lower than the uniform rotation speed of the UAV, and the target imaging projection is spiral.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The UAV-mounted dual-frequency millimeter-wave radiation imaging system and imaging method provided by the present invention provide a new structural solution for the passive millimeter-wave radiation remote sensing system by combining the dual-frequency millimeter-wave radiation imaging system with a UAV, and provide real-time millimeter-wave radiation images and data by connecting to a host computer. In various adverse environmental scenarios, it can also provide technicians with all-day and all-weather work detection and obtain real-time radiation information of the detection target. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a schematic structural diagram of the dual-frequency millimeter wave radiation imaging system onboard an unmanned aerial vehicle provided by the present invention; Figure 2 It is a schematic diagram of the composition of a W-band millimeter wave receiver provided by the present invention; Figure 3 It is a schematic diagram of the composition of a D-band millimeter wave receiver provided by the present invention; Figure 4 It is a schematic diagram of the operation of the two-point calibration function of the calibration structure provided by the present invention; Figure 5 It is a schematic diagram of the process of the dual-frequency millimeter wave radiation imaging method onboard an unmanned aerial vehicle provided by the present invention; Figure 6 It is a schematic diagram of the route of the multi-purpose dual-frequency millimeter wave radiation measurement method onboard an unmanned aerial vehicle provided by the present invention; Figure 7 It is a schematic diagram of various scanning modes of the millimeter wave radiation imaging system provided by the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] In view of the limitations of millimeter-wave radiation imaging technology in existing solutions and considering the rapid development of drone technology, it is of great significance and broad market prospects to propose a product that combines the drone platform and the millimeter-wave radiation imaging system.

[0021] Figure 1 FIG. 1 is a schematic diagram of the structure of a dual-frequency millimeter wave radiation imaging system for an unmanned aerial vehicle provided by an embodiment of the present invention. Figure 1 As shown, including: Antenna network system, W-band receiver, D-band receiver, stepper motor turntable, calibration structure and main control board; The antenna feed network system receives the millimeter wave radiation signal from the environment; The W-band receiver converts the W-band radiation signal in the millimeter wave radiation signal into a first voltage signal and a first signal parameter; The D-band receiver converts the D-band radiation signal in the millimeter wave radiation signal into a second voltage signal and a second signal parameter; The calibration structure is connected to the antenna and feeder network system to provide operating space for two-point calibration; The stepper motor turntable is connected to the antenna feeder network system to drive the antenna feeder network system with a preset scanning mode and stepping accuracy; The main control board is connected to the antenna network system, W-band receiver, D-band receiver and stepper motor turntable respectively, and is used for system analog-to-digital conversion, data processing, signal transmission and control system operation.

[0022] Specifically, the antenna feed network system consists of an offset-feed parabolic antenna and a polarization grid, and the system receives millimeter-wave radiation signals from the environment; The W-band receiver (90-98GHz) processes the received ambient radiation brightness temperature signal and outputs a digital signal and provides parameters (voltage information, brightness temperature information, etc.). The signal noise coefficient after processing by the W-band receiver is less than 3.5dB, and the linearity index of the receiver is 0.999; The D-band receiver (138-142GHz) processes the received ambient radiation brightness temperature signal and outputs a digital signal and provides parameters (voltage information, brightness temperature information, etc.). The noise coefficient of the signal processed by the D-band receiver is less than 6.5dB, and the linearity index of the receiver is 0.999; The stepper motor turntable uses a permanent magnet synchronous motor as the driving body, and controls the rotation angle of the rotor through a pulse signal. The output shaft of the motor is connected to the rotating parabola in the offset-fed parabola antenna, where the motor output shaft and the rotation center of the offset-fed parabola antenna are perpendicular to each other, and under the control of the motor drive control system, the rotating parabola is driven to perform omnidirectional circular motion on a plane. The stepper motor turntable can realize two modes: circular scanning and swing scanning, with a stepping accuracy of 0.2°; The calibration structure consists of a room temperature black body and a liquid nitrogen box, providing operating space for two-point calibration; The main control board is the central structure of the system for analog-to-digital conversion, data processing, signal transmission and system operation. It can transmit the real-time digital radiation information converted by the receiver to the host computer and external storage device, and display the real-time brightness temperature radiation voltage image and ambient radiation brightness temperature curve. The integration time is adjustable from 10 to 1000ms. At the same time, the main control board also receives the control command from the host computer to control the stepper motor turntable to change the scanning state; The power supply is a rechargeable power supply and can also be a 220V direct power supply.

[0023] The UAV-mounted dual-frequency millimeter-wave radiation imaging system proposed in the present invention provides an effective means for measuring the millimeter-wave radiation characteristics of various types of scenes and targets and verifying the correctness of relevant detection theories and methods. It can also provide new solutions for the needs of ground imaging, sea target detection, environmental monitoring, and forest fire warning under low visibility, thereby further promoting the application of passive millimeter-wave radiation remote sensing technology in the field of target detection.

[0024] In one embodiment, the antenna feed network system includes an offset-fed parabolic antenna and a polarization grid; The offset-fed parabolic antenna includes a rotating parabola and two feed lines, and the two feed lines are placed at the focus of the rotating parabola and on both sides of the polarization grid respectively; The polarization grid is connected to a W-band receiver and a D-band receiver respectively. The W-band receiver receives the W-band radiation signal reflected and propagated parallel to the polarization grid, and the D-band receiver receives the D-band radiation signal penetrated and propagated perpendicular to the polarization grid.

[0025] Specifically, the rotating parabola antenna of the offset-fed parabola antenna has an aperture of 160 mm. Two horn antennas are placed at the focus of the parabola as feeders. The feeders are distributed on both sides of the polarization grid. The electromagnetic waves that pass through the polarization reflection of the polarization grid and reach the feeder are received by the W-band receiver, while the electromagnetic waves that penetrate the polarization grid and reach the feeder are received by the D-band receiver.

[0026] The polarization grid here is mainly used for polarization separation of electromagnetic waves in passive remote sensing. It is composed of a group of equally spaced metal wires and has a frequency selective surface with wide-band characteristics. When the polarization direction of the incident electromagnetic wave is perpendicular to the direction of the polarization grid wire, the electromagnetic wave can be fully transmitted, and when the polarization direction of the incident electromagnetic wave is parallel to the direction of the polarization grid wire, the electromagnetic wave is fully reflected.

[0027] In one embodiment, the W-band millimeter wave receiver includes a W-band low noise amplifier, a W-band radio frequency filter, a W-band power amplifier and a W-band detector connected in sequence; The W-band receiver receives the W-band radiation signal and outputs a first voltage signal and a first signal parameter.

[0028] Specifically, Figure 2 As shown, the millimeter wave signal received by the W-band feed source enters the W-band low noise amplifier for amplification, and then enters the W-band RF filter, W-band power amplifier, and W-band detector, and finally outputs a voltage signal related to the millimeter wave radiation signal strength. The voltage signal is converted into digital by the acquisition module in the main control panel, and the output digital signal is saved in the memory card or computer for subsequent imaging and data analysis.

[0029] In one embodiment, the D-band receiver includes a D-band low noise amplifier, a D-band radio frequency filter, a D-band power amplifier and a D-band detector connected in sequence; The D-band receiver receives the D-band radiation signal and outputs the second voltage signal and the second signal parameter.

[0030] Specifically, Figure 3 As shown, the millimeter wave signal received by the D-band feed source enters the D-band low noise amplifier for amplification, and then enters the D-band RF filter, D-band power amplifier, and D-band detector, and finally outputs a voltage signal related to the millimeter wave radiation signal strength. The voltage signal is converted into digital by the acquisition module in the main control panel, and the output digital signal is saved in the memory card or computer for subsequent imaging and data analysis.

[0031] In one embodiment, the calibration structure includes a room temperature black body and a liquid nitrogen box, the room temperature black body is a heat source, and the liquid nitrogen box is a cold source; The rotating parabola in the antenna network system collects observation data of the heat source and the cold source in a single observation period to obtain the calibration equation.

[0032] Specifically, Figure 4As shown, the calibration structure consists of a room-temperature blackbody and a liquid nitrogen box. The room-temperature blackbody is placed directly below the rotating parabolic antenna. The nitrogen box has built-in absorbing materials and foam boards, and is designed to be easily loaded and unloaded. When equipped, it is placed directly below the rotating parabolic antenna. The rotating parabolic antenna scans the two to achieve two-point calibration. When calibrating, liquid nitrogen should be poured into the liquid nitrogen box first until the liquid nitrogen completely immerses the absorbing material in the box.

[0033] The rotating parabola observes the heat source (normal temperature black body) and the cold source (liquid nitrogen) once each in one cycle. The calibration factor can be calculated based on the voltage and temperature values ​​output from these two observations to generate a calibration equation. The voltage values ​​or voltage count values ​​(Vobservation) and observed temperatures (Tobservation) of the two observation sources can be substituted into the formula Vobservation=k0+k1Tobservation to obtain the calibration factors (k0, k1), thereby establishing a two-point calibration equation.

[0034] In one embodiment, the stepper motor turntable uses a permanent magnet synchronous motor as a driving body, and the rotation angle of the output shaft in the permanent magnet synchronous motor is controlled by a pulse signal; The output shaft is connected to the rotating parabola, and the output shaft drives the rotating parabola to perform scanning motion.

[0035] Specifically, the stepper motor turntable in the embodiment of the present invention uses a permanent magnet synchronous motor as the driving body. The output shaft of the motor is connected to the rotating parabola in the offset-fed parabola antenna, and drives the rotating parabola to perform omnidirectional circular motion on a plane under the control of the motor drive control system.

[0036] Figure 5 FIG. 1 is a flow chart of a dual-frequency millimeter wave radiation imaging method for an unmanned aerial vehicle provided by an embodiment of the present invention. Figure 5 As shown, including: Step 100: Mount the dual-frequency millimeter wave radiation imaging system under the drone to obtain the flight direction of the drone; Step 200: the dual-frequency millimeter wave radiation imaging system adopts a circular scanning imaging method perpendicular to the flight direction to achieve scanning imaging perpendicular to the flight direction; Step 300: The dual-frequency millimeter wave radiation imaging system uses a push-scan method with the help of the UAV in the flight direction to achieve two-dimensional millimeter wave radiation imaging of the target.

[0037] Specifically, Figure 6 As shown, the dual-frequency millimeter-wave radiation imaging system is mounted under the UAV, and adopts a circular scanning imaging method in the vertical flight direction (cross-track direction), that is, the scanning rotation axis is perpendicular to the flight direction, so as to realize scanning imaging in the cross-track direction, and a push-broom method is adopted in the flight direction (along-track direction) with the help of the UAV flight, so as to finally realize two-dimensional millimeter-wave radiation imaging of the ground.

[0038] The unmanned aerial vehicle dual-band millimeter wave radiation imaging system in the embodiment of the present invention has multiple scanning modes, including a push-broom model, a fixed-point uniform-speed scanning mode, a fixed-point variable-speed scanning mode, a fixed-point swing scanning mode, and a fixed-point spiral scanning mode.

[0039] It is understandable that during the scanning process, the turntable of the dual-band millimeter wave radiation imaging system drives the parabolic antenna to rotate and scan accordingly, and the corresponding millimeter wave radiation observation beam realizes multiple working modes with the turntable axis as the center. When the drone flies in a straight line, the radiation imaging system moves in a circle, and the imaging system works in the push-broom imaging mode. Specifically, it includes: The fixed-point uniform scanning imaging mode is that the UAV hovers and rotates at a uniform speed, and the dual-band millimeter wave radiation imaging system performs uniform circular scanning. The uniform circular scanning speed of the dual-band millimeter wave radiation imaging system is much faster than the uniform rotation speed of the UAV, and the imaging projection on the ground is in the shape of a close spider web; The fixed-point variable-speed scanning imaging mode is a variation of the fixed-point uniform-speed scanning mode. The UAV also hovers and rotates at a uniform speed, and the uniform circular scanning speed of the radiation imaging system is much greater than the uniform rotation speed of the UAV. The main difference is that the dual-band millimeter-wave radiation imaging system scans at a uniform speed within the ground imaging observation angle range and quickly scans in other angle ranges, so as to effectively improve the ground observation imaging time of the millimeter-wave radiation imaging system. The fixed-point swing scanning imaging mode is a variation of the fixed-point uniform scanning mode. The UAV also hovers and rotates at a uniform speed, and the uniform circular scanning speed of the radiation imaging system is much greater than the uniform rotation speed of the UAV. The main difference is that the dual-band millimeter-wave radiation imaging system swings back and forth within the ground imaging observation angle range, and does not scan other observation angle scanning areas, so as to effectively improve the ground observation imaging time of the millimeter-wave radiation imaging coefficient; The fixed-point spiral scanning imaging mode is that the UAV hovers and rotates at a uniform speed, and the dual-band millimeter-wave radiation imaging system performs uniform circular scanning. The uniform circular scanning speed of the dual-band millimeter-wave radiation imaging system is much lower than the uniform rotation speed of the UAV, and the imaging projection on the ground is spiral.

[0040] It should be noted that when the system is in circular motion, the imaging system works in push-broom imaging mode. When the drone is hovering and rotating, the imaging system works in other modes, such as Figure 7As shown, specifically, 1. When the scanning speed of the radiation imaging system is much faster than the rotation speed of the drone, if the radiation imaging system performs uniform scanning in the entire 0~360° range, this is a fixed-point uniform scanning imaging mode; 2. If the radiation imaging system performs uniform scanning in the earth observation area (assuming ±70°, 290°~0°~70°) and performs variable acceleration motion in other areas, this is a fixed-point variable speed scanning imaging mode; 3. If the radiation imaging system only scans back and forth in the earth observation area (assuming ±70°, 290°~0°~70°), this is called a fixed-point swing scanning imaging mode; 4. When the drone is hovering and rotating, the radiation imaging system performs uniform scanning in the entire 0~360° range, and the drone rotation speed is much faster than the circular scanning speed of the radiation imaging system, this is a calibrated spiral scanning imaging mode. According to actual needs, the dual-band millimeter-wave radiation imaging system on drones can provide a variety of scanning imaging modes.

[0041] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0042] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dual-frequency millimeter wave radiation imaging system for unmanned aerial vehicles, characterized in that: include: Antenna network system, W-band receiver, D-band receiver, stepper motor turntable, calibration structure and main control board; The antenna feed network system receives millimeter wave radiation signals from the environment; The W-band receiver converts the W-band radiation signal in the millimeter wave radiation signal into a first voltage signal and a first signal parameter; The D-band receiver converts the D-band radiation signal in the millimeter wave radiation signal into a second voltage signal and a second signal parameter; The calibration structure is connected to the antenna feeder network system to provide an operating space for two-point calibration; The stepper motor turntable is connected to the antenna feeder network system to drive the antenna feeder network system with a preset scanning mode and stepping accuracy; The main control board is connected to the antenna network system, the W-band receiver, the D-band receiver and the stepper motor turntable respectively, and is used for system analog-to-digital conversion, data processing, signal transmission and control system operation.

2. The dual-frequency millimeter-wave radiation imaging system for unmanned aerial vehicles according to claim 1, characterized in that: The antenna feed network system includes an offset-feed parabolic antenna and a polarization grid; The offset-fed parabolic antenna comprises a rotating parabola and two feed lines, wherein the two feed lines are placed at the focus of the rotating parabola and are respectively located on both sides of the polarization grid; The polarization grid is connected to the W-band receiver and the D-band receiver respectively. The W-band receiver receives the W-band radiation signal that is parallel to the polarization grid and reflected and propagated on the polarization grid, and the D-band receiver receives the D-band radiation signal that is perpendicular to the polarization grid and penetrates and propagates on the polarization grid.

3. The dual-frequency millimeter-wave radiation imaging system for unmanned aerial vehicles according to claim 1, characterized in that: The W-band receiver comprises a W-band low noise amplifier, a W-band radio frequency filter, a W-band power amplifier and a W-band detector which are connected in sequence; The W-band receiver receives the W-band radiation signal and outputs the first voltage signal and the first signal parameter.

4. The dual-frequency millimeter-wave radiation imaging system for unmanned aerial vehicles according to claim 1, characterized in that: The D-band receiver comprises a D-band low noise amplifier, a D-band radio frequency filter, a D-band power amplifier and a D-band detector connected in sequence; The D-band receiver receives the D-band radiation signal and outputs the second voltage signal and the second signal parameter.

5. The dual-frequency millimeter-wave radiation imaging system carried by an unmanned aerial vehicle according to claim 1, characterized in that: The calibration structure includes a room temperature black body and a liquid nitrogen box, wherein the room temperature black body is a heat source and the liquid nitrogen box is a cold source; The rotating parabola in the antenna feed network system collects observation data on the heat source and the cold source in a single observation cycle to obtain a calibration equation.

6. The dual-frequency millimeter wave radiation imaging system for unmanned aerial vehicles according to claim 2, characterized in that: The stepper motor turntable adopts a permanent magnet synchronous motor as the driving body, and the rotation angle of the output shaft in the permanent magnet synchronous motor is controlled by a pulse signal; The output shaft is connected to the rotating parabola, and the output shaft drives the rotating parabola to perform scanning motion.

7. The dual-frequency millimeter-wave radiation imaging system carried by an unmanned aerial vehicle according to claim 1, characterized in that: The main control board transmits the received radiation digital information to the host computer and the external storage device, and receives the control command of the host computer to control the scanning state of the stepper motor turntable.

8. The dual-frequency millimeter-wave radiation imaging system for unmanned aerial vehicles according to claim 1, characterized in that: Also includes a power supply, the power supply is connected to the main control board; The power source is a rechargeable power source or a direct-supply power source.

9. A method for dual-frequency millimeter wave radiation imaging on an unmanned aerial vehicle, used to implement the dual-frequency millimeter wave radiation imaging system on an unmanned aerial vehicle as claimed in any one of claims 1 to 8, characterized in that: include: The dual-frequency millimeter-wave radiation imaging system is mounted under the drone to obtain the flight direction of the drone; The dual-frequency millimeter wave radiation imaging system adopts a circular scanning imaging method perpendicular to the flight direction to achieve scanning imaging perpendicular to the flight direction; The dual-frequency millimeter wave radiation imaging system uses a push-scan method with the help of the UAV in the flight direction to achieve two-dimensional millimeter wave radiation imaging of the target.

10. The dual-frequency millimeter wave radiation imaging method for unmanned aerial vehicles according to claim 9, characterized in that: The scanning imaging includes a fixed-point uniform-speed scanning mode, a fixed-point variable-speed scanning mode, a fixed-point swing scanning mode and a fixed-point spiral scanning mode; The fixed-point uniform scanning mode is that the UAV hovers and rotates at a uniform speed, and the dual-frequency millimeter wave radiation imaging system performs uniform circular scanning. The uniform circular scanning speed of the dual-frequency millimeter wave radiation imaging system is much faster than the uniform rotation speed of the UAV, and the target imaging projection is in the shape of a close spider web; The fixed-point variable-speed scanning mode is that the UAV hovers and rotates at a uniform speed, and the dual-frequency millimeter-wave radiation imaging system rotates at a uniform speed. The uniform circular scanning speed of the dual-frequency millimeter-wave radiation imaging system is much greater than the uniform rotation speed of the UAV. It scans at a uniform speed within the target imaging observation angle range and scans quickly within other angle ranges. The fixed-point swing scanning mode is that the UAV hovers and rotates at a uniform speed, and the dual-frequency millimeter wave radiation imaging system rotates at a uniform speed. The uniform circular scanning speed of the dual-frequency millimeter wave radiation imaging system is much faster than the uniform rotation speed of the UAV. The system swings back and forth within the target imaging observation angle range and does not scan within other angle ranges. The fixed-point spiral scanning mode is that the UAV hovers and rotates at a uniform speed, and the dual-frequency millimeter wave radiation imaging system performs uniform circular scanning. The uniform circular scanning speed of the dual-frequency millimeter wave radiation imaging system is much lower than the uniform rotation speed of the UAV, and the target imaging projection is spiral.

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