Single-frequency millimeter wave imaging system based on cylindrical reconfigurable electromagnetic surface reflectarray
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING INST OF TECH
- Filing Date
- 2023-11-10
- Publication Date
- 2026-07-14
Smart Images
Figure CN117554959B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of millimeter-wave imaging technology, and in particular to a single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array. Background Technology
[0002] Millimeter-wave imaging technology, as a novel imaging method, has become a major development direction in human security inspection due to its advantages such as suitable imaging resolution for security checks, good penetration of clothing and packaging, and high safety for the human body. However, existing millimeter-wave 3D imaging security inspection systems have some shortcomings. Existing millimeter-wave imaging systems using planar reconfigurable electromagnetic surface arrays have poor focusing performance in the range direction, making it difficult to obtain high-quality 3D images of targets and thus unsuitable for security analysis. Furthermore, some existing imaging systems have extremely high hardware costs and long signal processing times, making them unsuitable for rapid, high-throughput security inspections with large crowds.
[0003] Therefore, a millimeter-wave imaging system that can quickly acquire a three-dimensional image of the target under high traffic conditions is worth studying. Summary of the Invention
[0004] The present invention aims to at least partially solve one of the technical problems in the related art.
[0005] To address the problems of high cost of phased arrays, high complexity of broadband arrays, long post-processing time of MIMO arrays, and poor range resolution of planar arrays in existing technologies, this invention proposes a single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable reflective electromagnetic surface array. This system can rapidly acquire high-quality 3D images of targets with low cost and low system complexity. Furthermore, to address the sidelobe lift problem of the cylindrical array radiation pattern, an amplitude adjustment module is added to the electromagnetic surface unit to improve the radiation pattern of the cylindrical array, further enhancing the imaging quality.
[0006] To achieve the above objectives, this invention proposes a single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array, comprising:
[0007] Millimeter-wave signal generation unit, used to generate millimeter-wave excitation signals;
[0008] Transceiver feed, used to transmit millimeter-wave signals to a cylindrical reconfigurable electromagnetic surface array, or to receive signals transmitted by the cylindrical reconfigurable electromagnetic surface array;
[0009] A cylindrical reconfigurable electromagnetic surface reflector array is composed of reconfigurable electromagnetic surface units uniformly arranged on a cylindrical or elliptical cylindrical surface. By adjusting the phase of each reconfigurable electromagnetic surface unit, the cylindrical reconfigurable electromagnetic surface array can transmit a narrow beam of millimeter-wave signal to the corresponding area of the imaging target.
[0010] Wide-beam horn antennas are used to transmit millimeter-wave signals to the imaging target area or to receive echo signals scattered from the imaging target area.
[0011] The pattern optimization control unit is used to control the amplitude adjustment modules of each unit in the cylindrical reconfigurable electromagnetic surface array to reduce the sidelobes of the pattern.
[0012] The beam scanning control unit is used to control the phase of each reconfigurable electromagnetic surface unit in the cylindrical reconfigurable electromagnetic surface array, so that the narrow beam millimeter wave signal emitted by the cylindrical reconfigurable electromagnetic surface array can scan through all positions of the imaging area.
[0013] The data processing unit is used to store millimeter-wave echo signals and process the signals to obtain a three-dimensional image of the target area.
[0014] Optionally, the transceiver feed is a transmitting feed; the transmitting feed is used to illuminate the millimeter-wave excitation signal generated by the millimeter-wave signal generation unit onto the cylindrical reconfigurable electromagnetic surface array; the reconfigurable electromagnetic surface array modulates the millimeter-wave excitation signal and focuses it onto a corresponding position in the target area; the wide-beam horn antenna is used to receive the echo signal scattered from the imaging target area;
[0015] or,
[0016] The transceiver feed is a receiving feed; the receiving feed is used to receive the echo signal transmitted by the cylindrical reconfigurable electromagnetic surface array and transmit the echo signal with target characteristics to the data processing unit; the cylindrical reconfigurable electromagnetic surface array is used to receive and modulate the echo signal scattered by the imaging target area, and the wide-beam horn antenna is used to transmit the millimeter-wave excitation signal emitted by the millimeter-wave generation unit to the imaging target area.
[0017] Optionally, the cylindrical reconfigurable electromagnetic surface array is composed of N*M reconfigurable electromagnetic surface units with identical structures, where N and M are both positive integers, N is the number of rows in the array, and M is the number of columns in the array. The reconfigurable electromagnetic surface units are uniformly arranged on a cylindrical surface to form a cylindrical reconfigurable electromagnetic surface array.
[0018] Optionally, the reconfigurable electromagnetic surface unit adopts a transceiver reflector unit structure. The reconfigurable electromagnetic surface unit includes a receiving antenna, a phase control section, an amplitude adjustment module, and a radiating antenna. A millimeter-wave generating unit emits a millimeter-wave excitation signal, which is transmitted via a transmitting feed to the receiving antennas of each reconfigurable electromagnetic surface unit in the reconfigurable electromagnetic surface array. The receiving antenna is used to receive the electromagnetic wave emitted by the transmitting feed. The phase control section is used to adjust the phase of the electromagnetic wave received by the receiving antenna. The amplitude adjustment module is used to adjust the amplitude value of the radiated signal of each unit. The radiating antenna is used to radiate the phase-changed millimeter-wave signal.
[0019] Optionally, the phase control section is a 1-bit, multi-bit, or continuously adjustable phase shifter composed of lumped elements, functional materials, or microelectromechanical system switches; the reflection phase of each reconfigurable electromagnetic surface unit is adjusted according to the state of the lumped elements or functional materials.
[0020] Optionally, the amplitude adjustment module consists of a lumped amplifier or an adjustable load; the amplitude of the reflected energy of each unit is adjusted according to the operating state of the lumped amplifier or the load.
[0021] Optionally, the beam scanning control unit sends instructions to the phase control portion of each unit in the cylindrical reconfigurable array to control the cylindrical reconfigurable array to transmit millimeter-wave signals to a specific location in the imaging target area or to receive echo signals scattered from a specific location in the imaging target area; the beam scanning control unit is composed of an FPGA, a microcontroller or other controllers.
[0022] Optionally, the data processing unit includes: a signal preprocessing module, a data acquisition and recording module, an imaging processor module, and an image display module;
[0023] The signal preprocessing module is used to preprocess the echo signal carrying the three-dimensional scattering intensity data of the imaging target. The preprocessing steps include amplification, mixing and matched filtering to obtain an intermediate frequency signal with the three-dimensional scattering intensity of the target and a signal-to-noise ratio reaching a preset threshold.
[0024] The data acquisition and recording module is used to acquire and store mid-frequency signals containing target three-dimensional scattering intensity data;
[0025] The imaging processor module is used to process the intermediate frequency signal with the target three-dimensional scattering intensity data, and obtain a three-dimensional image of the target area based on the three-dimensional scattering intensity data of the detected target area;
[0026] The image display module is used to display a three-dimensional image of the target area.
[0027] This invention discloses a single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array, comprising: a millimeter-wave signal generation unit for generating a millimeter-wave excitation signal; a cylindrical reconfigurable electromagnetic surface array for transmitting modulated millimeter-wave signals, which can be converged to various positions in the imaging target area; and a data processing unit for processing echo signals and obtaining a three-dimensional image of the target area. Compared to planar single-frequency electromagnetic surface arrays, the cylindrical single-frequency reconfigurable electromagnetic surface array disclosed in this invention has better range resolution; the amplitude modulation of the reconfigurable electromagnetic surface unit effectively reduces the sidelobes of the cylindrical array pattern, improving imaging quality; and compared to broadband imaging systems, the single-frequency system greatly simplifies system design complexity, reduces costs, and increases the speed of imaging data processing, making it suitable for rapid-passage security checks in densely populated areas. Attached Figure Description
[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0029] Figure 1 A system structure diagram of a single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array is provided for an embodiment of the present invention.
[0030] Figure 2 A flowchart illustrating a working mode for millimeter-wave imaging provided in an embodiment of the present invention;
[0031] Figure 3 A flowchart illustrating another working mode for millimeter-wave imaging provided in this embodiment of the invention;
[0032] Figure 4 This is a schematic diagram of a specific example of a single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array, provided as an embodiment of the present invention.
[0033] Figure 5 is a schematic diagram comparing the simulation imaging results of the cylindrical reconfigurable array of the present invention and the traditional planar reconfigurable array;
[0034] Figure 6 This is a schematic diagram of the electromagnetic surface unit of the present invention;
[0035] Figure 7 This is a comparison diagram of the radiation patterns of cylindrical reconfigurable arrays and planar reconfigurable arrays before and after amplitude weighting optimization according to the present invention. Detailed Implementation
[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0037] Reference Figure 1 This invention provides a single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array, comprising:
[0038] Millimeter-wave signal generation unit, used to generate millimeter-wave excitation signals.
[0039] Transceiver feeds are used to transmit millimeter-wave signals to a cylindrical reconfigurable electromagnetic surface array (CRASA) or to receive signals transmitted by the CRASA.
[0040] A cylindrical reconfigurable electromagnetic surface array can be composed of reconfigurable electromagnetic surface units uniformly arranged on a cylindrical or elliptical cylindrical surface. By adjusting the phase of each reconfigurable electromagnetic surface unit, the cylindrical reconfigurable electromagnetic surface array can transmit millimeter-wave signals to the corresponding region of the imaging target.
[0041] The pattern optimization control unit is used to control the amplitude adjustment modules of each unit in the cylindrical reconfigurable electromagnetic surface array to reduce the sidelobes of the pattern.
[0042] The beam scanning control unit is used to control the phase of each reconfigurable electromagnetic surface unit in the cylindrical reconfigurable electromagnetic surface array, so that the narrow beam millimeter wave signal emitted by the array can scan through all positions of the imaging area.
[0043] The data processing unit is used to store millimeter-wave echo signals and process the signals to obtain a three-dimensional image of the target area.
[0044] Optionally, the cylindrical reconfigurable electromagnetic surface array is composed of N*M reconfigurable electromagnetic surface units with identical structures, where N and M are both positive integers, N is the number of rows in the array, and M is the number of columns in the array. These reconfigurable electromagnetic surface units are uniformly arranged on a cylindrical surface to form a cylindrical reconfigurable electromagnetic surface array.
[0045] The cylindrical reconfigurable electromagnetic surface reflector array consists of N*M reconfigurable electromagnetic surface units with identical structures.
[0046] In one implementation, the reconfigurable electromagnetic surface unit adopts a transceiver reflective unit structure, including a receiving antenna, a phase control section, an amplitude adjustment module, and a radiating antenna.
[0047] Reference Figure 2 The present invention provides a flowchart of a working mode for realizing millimeter-wave imaging.
[0048] The millimeter-wave generating unit emits a millimeter-wave excitation signal, which is then transmitted to the receiving antenna of each reconfigurable electromagnetic surface unit in the reconfigurable electromagnetic surface array via a transmitting feed.
[0049] The receiving antenna portion of the reconfigurable electromagnetic surface unit can receive millimeter-wave signals emitted by the transmitting feed.
[0050] The phase control section of the reconfigurable electromagnetic surface unit can adjust the phase of the millimeter-wave signal received by the receiving antenna.
[0051] The amplitude adjustment module of the reconfigurable electromagnetic surface unit is used to adjust the amplitude value of the radiation signal of each unit.
[0052] The radiating antenna portion of the reconfigurable electromagnetic surface unit can radiate millimeter-wave signals with altered phase.
[0053] In one feasible implementation, the phase control section comprises a lumped element (including but not limited to PIN diodes and varactor diodes), functional materials (including but not limited to liquid crystals and graphene), or microelectromechanical system (MEMS) switches, forming a 1-bit, multi-bit, or continuously adjustable phase shifter. By controlling the state of the aforementioned elements or materials (e.g., the on / off state of the PIN diodes, the bias voltage of the varactor diodes), the phase difference between the receiving antenna and the radiating antenna in each unit can be adjusted.
[0054] In one possible implementation, the amplitude adjustment module consists of a lumped amplifier. The amplitude of the reflected energy from each unit can be adjusted by controlling the operating state of the lumped amplifier.
[0055] In one feasible approach, the beam scanning control unit can consist of a controller such as an FPGA (Field Programmable Gate Array) or a microcontroller, which sends instructions to the phase control module of each cell in the reconfigurable electromagnetic surface array, causing the phase control module to make corresponding adjustments.
[0056] The electromagnetic waves emitted by the reconfigurable electromagnetic surface array illuminate the imaging target area and are scattered. The resulting echo signal is received by a wide-beam horn that can cover the entire imaging target area. After receiving the signal, the wide-beam horn transmits the signal to the data processing unit.
[0057] Reference Figure 3 The flowchart of another working mode for achieving millimeter-wave imaging provided by the embodiments of the present invention.
[0058] In another example, a millimeter-wave signal generation unit generates a millimeter-wave excitation signal, which is transmitted as an electromagnetic wave to the imaging target area via a wide-beam horn antenna. When the electromagnetic wave emitted by the wide-beam horn illuminates the imaging target, it is scattered. The scattered echo signal carrying the imaging target data is received by a reconfigurable electromagnetic surface array. The phase control module of each unit in the array adjusts the reflection phase of each unit, allowing the array beam to converge at the corresponding position in the imaging target area. The beam scanning control unit continuously sends commands to the phase control module to continuously adjust the reflection phase of each unit, enabling the array beam to scan across the entire imaging target area. After scanning is completed, the cylindrical reconfigurable reflective array receives the echo signal from the entire target imaging area and transmits the echo signal to the receiving feed. The receiving feed then transmits the echo signal with target characteristics to the data processing unit. In the data processing unit, the echo signal carrying the imaging target data is amplified, mixed, and matched filtered to become an intermediate frequency signal carrying the target's three-dimensional scattering intensity data. The intermediate frequency signal is processed by various modules of the data processing unit, such as the data acquisition unit and the imaging processor, and finally a three-dimensional image of the target area is realized on the imaging display module.
[0059] Optionally, the data processing unit includes: a signal preprocessing module, a data acquisition and recording module, an imaging processor module, and an image display module.
[0060] The signal preprocessing module is used to amplify, mix, and match filter the echo signal with the three-dimensional scattering intensity data of the imaging target to obtain an intermediate frequency signal with the three-dimensional scattering intensity of the target and a high signal-to-noise ratio.
[0061] The data acquisition and recording module is used to acquire and store the mid-frequency signal containing the target three-dimensional scattering intensity data.
[0062] The imaging processor is used to process the aforementioned intermediate frequency signal and obtain a three-dimensional image of the target area based on the three-dimensional scattering intensity data of the target area.
[0063] The image display module is used to display a three-dimensional image of the target area. Based on the three-dimensional image displayed by the image display module, inspectors can easily identify whether the target being inspected is carrying hazardous materials. Based on the imaging results, hazardous material characteristic parameters can also be further extracted to establish a database of typical hazardous material target characteristics, which can be used as a reference for future computer software to automatically identify hazardous materials.
[0064] Figure 4 This is a schematic diagram of a specific example of a single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array, provided as an embodiment of the present invention.
[0065] Figure 5 shows the radiation patterns of a planar reconfigurable array, an unoptimized cylindrical reconfigurable array, and a beam-optimized cylindrical reconfigurable array. It can be seen that the unoptimized cylindrical array has higher sidelobes than the planar array, exhibiting a problem of high sidelobes. After amplitude-weighted beam optimization, the sidelobes of the cylindrical array are significantly reduced, falling below those of the traditional planar array.
[0066] Figure 6 This is a schematic diagram of a reconfigurable electromagnetic surface unit. The unit includes an amplitude control module, a phase control module, a receiving patch, and a radiating patch. The amplitude control module includes a 3-1 amplifier. The phase control module includes a 3-2 phase shifter. The receiving patch consists of a top 1-1 square metal patch, 4 and 5 intermediate dielectric substrates, and a 2-2 metal ground. An H-shaped groove is etched on the 2-2 metal ground as a feeding structure. The radiating patch antenna includes 1-2 square metal patches, 4 and 5 intermediate dielectric layers, and a 2-2 bottom metal ground.
[0067] Figure 7 This is the result of imaging point targets using cylindrical and planar reconfigurable arrays. It can be seen that the range resolution of the cylindrical array is much greater than that of a planar array of the same size.
[0068] This invention provides a single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array. This system can achieve rapid scanning and imaging of the human body at a lower cost, making it suitable for rapid-passage security checks in high-traffic areas. The cost of the reconfigurable electromagnetic surface reflector array is far lower than that of a phased array antenna; the hardware complexity and imaging signal processing complexity of the single-frequency system are both lower than those of broadband systems; the single-frequency cylindrical array has good resolution in the range direction, solving the problem of single-frequency planar arrays being unable to focus in the range direction; the beam optimization control unit manipulates the amplitude changes of the reconfigurable electromagnetic surface elements, which can effectively reduce the sidelobes of the cylindrical array pattern, further improving the imaging quality. In summary, this invention can meet the requirements of rapid-passage security check systems in high-traffic areas such as subways, airports, and train stations.
[0069] In some alternative embodiments, the functions / operations mentioned in the block diagrams may not occur in the order shown in the operation diagrams. For example, depending on the functions / operations involved, two consecutively shown blocks may actually be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order. Furthermore, the embodiments presented and described in the flowcharts of this invention are provided by way of example to provide a more comprehensive understanding of the technology. The disclosed methods are not limited to the operations and logic flows presented herein. Alternative embodiments are contemplated in which the order of various operations is altered and sub-operations described as part of a larger operation are executed independently.
[0070] Furthermore, although the invention has been described in the context of functional modules, it should be understood that, unless otherwise stated, one or more of the described functions and / or features may be integrated into a single physical device and / or software module, or one or more functions and / or features may be implemented in a separate physical device or software module. It is also understood that a detailed discussion of the actual implementation of each module is unnecessary for understanding the invention. Rather, given the properties, functions, and internal relationships of the various functional modules in the apparatus disclosed herein, the actual implementation of the module will be understood within the scope of conventional skill of an engineer. Therefore, those skilled in the art can implement the invention as set forth in the claims using ordinary techniques without excessive experimentation. It is also understood that the specific concepts disclosed are merely illustrative and not intended to limit the scope of the invention, which is determined by the full scope of the appended claims and their equivalents.
[0071] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.
[0072] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.
[0073] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.
[0074] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.
[0075] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0076] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
[0077] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of the present invention.
Claims
1. A single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array, characterized in that, include: Millimeter-wave signal generation unit, used to generate millimeter-wave excitation signals; Transceiver feed, used to transmit millimeter-wave signals to a cylindrical reconfigurable electromagnetic surface array, or to receive signals transmitted by the cylindrical reconfigurable electromagnetic surface array; A cylindrical reconfigurable electromagnetic surface reflector array is composed of reconfigurable electromagnetic surface units uniformly arranged on a cylindrical or elliptical cylindrical surface. By adjusting the phase of each reconfigurable electromagnetic surface unit, the cylindrical reconfigurable electromagnetic surface array can transmit a narrow beam of millimeter-wave signal to the corresponding area of the imaging target. Wide-beam horn antennas are used to transmit millimeter-wave signals to the imaging target area or to receive echo signals scattered from the imaging target area. The beam optimization control unit is used to control the amplitude adjustment module of each unit in the cylindrical reconfigurable electromagnetic surface array to reduce the sidelobes of the cylindrical pattern. The beam scanning control unit is used to control the phase of each reconfigurable electromagnetic surface unit in the cylindrical reconfigurable electromagnetic surface array, so that the narrow beam millimeter wave signal emitted by the cylindrical reconfigurable electromagnetic surface array can scan through all positions of the imaging area. The data processing unit is used to store millimeter-wave echo signals and process the signals to obtain a three-dimensional image of the target area. The reconfigurable electromagnetic surface unit adopts a transceiver reflector unit structure. The reconfigurable electromagnetic surface unit includes a receiving antenna, a phase control section, and a radiating antenna. A millimeter-wave generating unit emits a millimeter-wave excitation signal, which is transmitted to the receiving antenna of each reconfigurable electromagnetic surface unit in the reconfigurable electromagnetic surface array via a transmitting feed. The receiving antenna is used to receive the electromagnetic wave emitted by the transmitting feed. The phase control section is used to adjust the phase of the electromagnetic wave received by the receiving antenna. The radiating antenna is used to radiate millimeter-wave signals with altered phase. or, The reconfigurable electromagnetic surface unit includes a phase control section and a reflective surface; the millimeter wave generation unit emits a millimeter wave excitation signal, which is transmitted to the reflective surface of each reconfigurable electromagnetic surface unit in the reconfigurable electromagnetic surface array through a transmission feed source; the phase control section is used to adjust the reflection phase of the reflective surface on each reconfigurable electromagnetic surface unit. The beam optimization control unit sends instructions to the amplitude control module of each unit of the cylindrical reconfigurable array to adjust the amplitude of the reflected energy of each unit, optimize the array pattern, and reduce the sidelobe level; the beam optimization control unit is composed of FPGA, microcontroller or other controllers.
2. The single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array according to claim 1, characterized in that, The transceiver feed is a transmitting feed; the transmitting feed is used to illuminate the millimeter-wave excitation signal generated by the millimeter-wave signal generation unit onto the cylindrical reconfigurable electromagnetic surface array; the reconfigurable electromagnetic surface array modulates the millimeter-wave excitation signal and focuses it onto a corresponding position in the target area; the wide-beam horn antenna is used to receive the echo signal scattered from the imaging target area. or, The transceiver feed is a receiving feed; the receiving feed is used to receive the echo signal transmitted by the cylindrical reconfigurable electromagnetic surface array and transmit the echo signal with target characteristics to the data processing unit; the cylindrical reconfigurable electromagnetic surface array is used to receive and modulate the echo signal scattered by the imaging target area, and the wide-beam horn antenna is used to transmit the millimeter-wave excitation signal emitted by the millimeter-wave generation unit to the imaging target area.
3. The single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array according to claim 2, characterized in that, The cylindrical reconfigurable electromagnetic surface array consists of N*M reconfigurable electromagnetic surface units with identical structures, where N and M are both positive integers, N is the number of rows in the array, and M is the number of columns in the array. The reconfigurable electromagnetic surface units are uniformly arranged on a cylindrical surface to form the cylindrical reconfigurable electromagnetic surface array.
4. The single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array according to claim 1, characterized in that, The phase control section is a 1-bit, multi-bit, or continuously adjustable phase shifter composed of lumped elements, functional materials, or microelectromechanical system switches. The phase difference between the receiving antenna and the radiating antenna in each reconfigurable electromagnetic surface unit is adjusted according to the state of the lumped elements or functional materials.
5. The single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array according to claim 1, characterized in that, The beam scanning control unit sends commands to the phase control part of each unit in the cylindrical reconfigurable array to control the cylindrical reconfigurable array to transmit millimeter-wave signals to a specific position in the imaging target area or to receive echo signals scattered from a specific position in the imaging target area; the beam scanning control unit is composed of FPGA, microcontroller or other controllers.
6. The single-frequency millimeter-wave imaging system based on a cylindrical reconfigurable electromagnetic surface reflector array according to claim 2, characterized in that, The data processing unit includes: a signal preprocessing module, a data acquisition and recording module, an imaging processor module, and an image display module; The signal preprocessing module is used to preprocess the echo signal with three-dimensional scattering intensity data of the imaging target. The preprocessing steps include amplification, mixing and matched filtering to obtain an intermediate frequency signal with three-dimensional scattering intensity of the target and a signal-to-noise ratio reaching a preset threshold. The data acquisition and recording module is used to acquire and store mid-frequency signals containing target three-dimensional scattering intensity data; The imaging processor module is used to process the intermediate frequency signal with the target three-dimensional scattering intensity data, and obtain a three-dimensional image of the target area based on the three-dimensional scattering intensity data of the detected target area; The image display module is used to display a three-dimensional image of the target area.