Tourist inspection device based on distributed dual-polarization millimeter wave radar

Abstract

The invention discloses a tour inspection device based on a distributed dual-polarization millimeter wave radar, and relates to the field of tour inspection devices and radar imaging detection, and the tour inspection device comprises a detection device body and an upper computer device. The detection device body comprises an electromagnetic wave shielding box and a wave-absorbing material conveying belt; the front side and the rear side of the electromagnetic wave shielding box are respectively provided with an inlet and an outlet to form a transmission channel; the wave-absorbing material conveying belt penetrates through the transmission channel and is fixed at the bottom of the electromagnetic wave shielding box through a transmission bracket; electromagnetic shielding curtains are arranged at the inlet and the outlet of the electromagnetic wave shielding box; the vertical polarization detection radar and the horizontal polarization detection radar are symmetrically installed on the left and right inner walls of the electromagnetic wave shielding box. The dual-polarization MIMO imaging radar is installed in the center area of the inner wall of the top of the electromagnetic wave shielding box. According to the device, distributed dual-polarization millimeter-wave radar cooperative detection and multi-modal information fusion are utilized, the contradiction between the coverage range and the recognition precision in tour inspection and the difficulty in vital sign detection are solved, and the security inspection efficiency and accuracy are improved.

Description

Technical Field

[0001] This invention relates to the fields of passenger inspection equipment and radar imaging detection, and more specifically to a passenger inspection equipment based on distributed dual-polarization millimeter-wave radar. Background Technology

[0002] At airports, customs, and other ports of entry and exit, efficient and accurate non-contact security checks on prohibited items hidden in luggage and parcels are crucial. Millimeter-wave radar imaging technology, due to its penetrating power, non-ionizing properties, and sensitivity to micro-motion, has become an important detection method in this field, aiming to achieve non-destructive detection of the shape and vital signs of items inside parcels.

[0003] Existing millimeter-wave passenger inspection devices often employ a single or limited number of radar units. To meet the coverage requirements of large packages or high-throughput scenarios, it is often necessary to widen the beamwidth or use mechanical scanning. This directly leads to a significant decrease in spatial resolution, making it difficult to clearly identify the outlines of small or structurally complex objects within the package. Conversely, if high-resolution imaging is desired, a focused narrow beam or complex array is usually required, with a limited field of view, which cannot effectively cover multiple target areas on large packages or conveyor belts, creating a technical bottleneck where detection range and imaging accuracy are difficult to balance.

[0004] For detecting living individuals inside packages, current technologies primarily rely on extracting micro-Doppler or phase information from radar echoes to sense vital signs such as breathing and heartbeat. However, in complex passenger inspection environments, the material of the package, the stacking of internal items, and environmental interference can significantly attenuate or distort these subtle signals. Single-angle, single-polarization detection methods have weak anti-interference capabilities, making it difficult to extract and untangle weak vital signs, easily leading to missed detections or false alarms, and compromising the accuracy and reliability of the detection.

[0005] Existing systems have shortcomings in dealing with complex electromagnetic environments and suppressing their own clutter. Furthermore, the detection capabilities and resolution of these systems are often fixed at the time of hardware deployment, lacking flexibility and scalability. For example, improving imaging resolution typically requires replacing the entire radar array, which is costly and inconvenient to implement. In addition, the data collaborative processing capabilities of different functional modules are weak, failing to effectively integrate multi-angle and multi-polarization information to improve overall recognition confidence.

[0006] Therefore, how to design a passenger inspection device based on distributed dual-polarization millimeter-wave radar that can effectively overcome the contradiction between coverage and high resolution, and improve the robustness and accuracy of vital sign detection in complex package environments, so as to meet the urgent needs of efficient and accurate security inspection at ports, is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, the present invention provides a passenger inspection device based on distributed dual-polarization millimeter-wave radar, which aims to overcome the problems in the prior art of simultaneously achieving large-area coverage and high-resolution identification, as well as the difficulty in detecting vital signs in complex package environments, thereby enabling rapid and reliable non-contact detection and identification of live persons and contraband in transit cargo at airports, customs and other locations.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A passenger inspection device based on distributed dual-polarization millimeter-wave radar includes: a detection device body and a host computer device communicatively connected to the device body;

[0010] The detection device body includes an electromagnetic wave shielding box and a wave-absorbing material conveyor belt; the electromagnetic wave shielding box has an inlet and an outlet on its front and rear sides, respectively, to form a transmission channel; the wave-absorbing material conveyor belt passes through the transmission channel and is fixed to the bottom of the electromagnetic wave shielding box by a conveyor bracket.

[0011] The electromagnetic wave shielding box is equipped with electromagnetic shielding curtains at both the inlet and outlet.

[0012] The electromagnetic wave shielding box is equipped with a start button on the right outer wall and an alarm device on the top outer wall.

[0013] The electromagnetic wave shielding box is symmetrically equipped with vertical polarization detection radar and horizontal polarization detection radar on the left and right inner walls, and a dual polarization MIMO imaging radar is installed in the central area of ​​the top inner wall of the electromagnetic wave shielding box.

[0014] The electromagnetic wave shielding box is also equipped with a camera device on the inner rear wall.

[0015] Preferably, the host computer device includes:

[0016] The signal preprocessing module is used to preprocess the raw signals acquired by the vertical polarization detection radar, the horizontal polarization detection radar, and the dual polarization MIMO imaging radar.

[0017] The object imaging detection module is used to receive dual-polarization MIMO imaging radar data output by the signal preprocessing module, perform target imaging and contraband identification, and output imaging classification results.

[0018] The vital signs information extraction module is used to receive data from the vertical polarization detection radar and horizontal polarization detection radar output by the signal preprocessing module, extract vital signs information, and output vital signs classification results.

[0019] The information fusion module is used to receive imaging classification results, vital sign classification results, and visual images from camera devices, perform multimodal information fusion, and generate the final classification result.

[0020] The visualization module is used to display the detection results and trigger an alarm when prohibited items are detected.

[0021] Preferably, the object imaging detection module includes:

[0022] The pulse compression unit is used to perform range-direction matched filtering on the I / Q signals preprocessed by the dual-polarization MIMO imaging radar and output a range-slow time matrix to improve range resolution.

[0023] The virtual aperture synthesis unit calculates the spatial path difference of the matrix output by the pulse compression unit based on the MIMO virtual array principle, and generates an equivalent large aperture spatial sampling signal.

[0024] The image reconstruction unit uses a back projection algorithm to interpolate the polarization scattering matrix of the spatial sampling data output by the virtual aperture synthesis unit, and reconstructs the target HH / VV / HV three-channel contour image.

[0025] The feature classification unit uses a lightweight YOLOv5 network to extract polarization image features from the image reconstruction unit and outputs the contraband classification results.

[0026] Preferably, the vital signs information extraction module includes:

[0027] The micro-motion signal separation unit performs preset respiratory and heartbeat frequency bandpass filtering on the I / Q signals preprocessed by the vertical polarization detection radar and the horizontal polarization detection radar to separate the time-domain micro-motion signals;

[0028] The phase unwrapping unit eliminates the 2π phase jump in the output signal of the micro-motion signal separation unit based on the Itoh conditional algorithm, and reconstructs the continuous phase sequence;

[0029] The feature extraction unit performs peak detection and phase difference calculation on the continuous phase sequence output by the phase unwrapping unit, and outputs respiratory rate (BR), heart rate (HR), and coefficient of variation.

[0030] The existence determination unit inputs the vital sign parameters output by the feature extraction unit into the SVM classifier, combines the phase variance to determine the type of living organism, and outputs the classification result.

[0031] Preferably, the vertical polarization detection radar and the horizontal polarization detection radar are used for micro-motion detection, and each includes a transmitting antenna, a receiving antenna, an FMCW waveform generator, a power divider, a control circuit, a beamforming unit, a combiner, and an ADC data storage device.

[0032] Among them, the vertically polarized one-dimensional phased array micro-motion detection radar and the horizontally polarized one-dimensional phased array micro-motion detection radar are both installed symmetrically with an angle θ tilted downwards. In the vertical direction, beamforming technology is used to achieve a wide beam coverage, and in the horizontal direction, one-dimensional phased scanning technology is used to achieve high-precision scanning and micro-motion detection.

[0033] Preferably, the dual-polarization MIMO imaging radar is used for high-resolution imaging detection and recognition, and includes a transmitting antenna array, a receiving antenna array, a frequency-modulated continuous wave waveform generator, a control circuit, and an ADC data storage device.

[0034] Both the transmitting and receiving antenna arrays are linear arrays and are placed perpendicular to each other, forming a MIMO antenna array with an apex shape.

[0035] Preferably, the dual-polarization MIMO imaging radar consists of at least one MIMO antenna array, with the distance between the transmitting antenna element and the receiving antenna element being d, and the number of each being 2N. Multiple MIMO antenna arrays are distributed at equal intervals, with a distance of 2Nd between them.

[0036] To meet the detection resolution requirements, the number of MIMO antenna arrays is increased based on 2Nd equal spacing. The MIMO antenna arrays achieve polarization switching by rotating their installation position by 90 degrees, supporting dual-polarization detection.

[0037] Preferably, each MIMO antenna array includes 2N transmit antenna elements and 2N receive antenna elements; for M MIMO antenna arrays, combined with the MIMO virtual aperture principle, it is equivalent to 2N×2N×M virtual antenna elements, which are used to perform coherent imaging and identification of the dual-polarized detection echo signal reflected by the target through the MIMO imaging algorithm.

[0038] Preferably, the electromagnetic shielding curtain is woven from nickel-plated metal wire and is fixed to the edge of the electromagnetic wave shielding box along the circumference of the inlet and outlet, with the bottom of the curtain being ≤5cm from the surface of the wave-absorbing material conveyor belt.

[0039] The start button features an IP65 waterproof and dustproof design; it is connected to the control circuit of the passenger inspection device via a shielded wire, supporting single-trigger start and emergency stop with a 3-second long press.

[0040] Preferably, the alarm device includes a red LED warning light and a buzzer, and is connected to the host computer via an RVV cable for communication.

[0041] The camera device is a high-definition industrial camera with its lens facing the transmission direction of the absorbing material conveyor belt. It communicates with the host computer device via a USB 3.0 interface.

[0042] As can be seen from the above technical solution, compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0043] 1. By combining a distributed radar architecture with beamforming and phased scanning, the left-side vertically polarized radar and the right-side horizontally polarized radar form a wide-area coverage beam in the vertical direction, achieving high-precision scanning in the horizontal direction; the top MIMO imaging radar improves resolution through virtual aperture expansion. The three work in a time-sharing and coordinated manner, resolving the contradiction between detection range and imaging accuracy that traditional passenger inspection devices cannot balance.

[0044] 2. Utilizing dual-polarization detection and multi-angle data fusion: The micro-motion detection radars on both sides extract the phase information of vital signs, guiding the top MIMO radar to perform dual-polarization high-resolution imaging of suspicious targets. Through the information fusion module of the host computer, the vital sign classification results and the imaging contour recognition results are weighted and fused, significantly improving the detection accuracy of live bodies, dangerous goods, and other contraband, especially suitable for the identification of concealed targets inside packages.

[0045] 3. The dual-polarization MIMO imaging radar consists of multiple "U"-shaped antenna arrays. Resolution is improved by increasing the number of arrays with equal spacing of 2Nd, and dual-polarization detection is achieved by rotating the arrays 90°. An electromagnetic shielding box and nickel-plated metal wire shielding curtain effectively isolate external interference; a conveyor belt made of absorbing material reduces clutter. It supports time-division multiplexing and multi-modal data collaborative processing, maintaining strong anti-interference capabilities and scalability in complex passenger inspection scenarios. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0047] Figure 1 A schematic diagram of a passenger inspection device based on a distributed dual-polarization millimeter-wave radar is provided for an embodiment of the present invention;

[0048] Figure 2 This is a schematic diagram of an electromagnetic wave shielding box structure provided in an embodiment of the present invention;

[0049] Figure 3 This is a schematic diagram of the upper computer device structure provided in an embodiment of the present invention;

[0050] Figure 4 This is a schematic diagram of the vertical polarization detection radar and the horizontal polarization detection radar provided in an embodiment of the present invention;

[0051] Figure 5 This is a schematic diagram of the transceiver beam of a vertical polarization detection radar provided in an embodiment of the present invention;

[0052] Figure 6 This is a schematic diagram of the transceiver beam of a horizontal polarization detection radar provided in an embodiment of the present invention;

[0053] Figure 7 This is a schematic diagram of a MIMO antenna array structure provided in an embodiment of the present invention;

[0054] Figure 8 This is a schematic diagram of the transmit and receive beams of a dual-polarization MIMO imaging radar provided in an embodiment of the present invention;

[0055] Figure 9 A schematic diagram illustrating the distributed collaborative operation of a vertical polarization detection radar, a horizontal polarization detection radar, and a dual-polarization MIMO imaging radar provided in an embodiment of the present invention.

[0056] Figure 10 The image shows the expected imaging and detection effect of the dual-polarization MIMO imaging radar provided in this embodiment of the invention. Detailed Implementation

[0057] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] like Figure 1 As shown, this embodiment provides a passenger inspection device based on distributed dual-polarization millimeter-wave radar, including: a detection device body 1 and a host computer device 2 that is communicatively connected to the device body 1;

[0059] The detection device body 1 includes an electromagnetic wave shielding box 3 and a wave-absorbing material conveyor belt 4;

[0060] like Figure 2 As shown, the electromagnetic wave shielding box 3 has an inlet and an outlet on the front and rear sides respectively to form a transmission channel; the wave-absorbing material conveyor belt 4 passes through the transmission channel and is fixed to the bottom of the electromagnetic wave shielding box 3 through the conveyor bracket 5;

[0061] Electromagnetic shielding box 3 is equipped with electromagnetic shielding curtains 6 at both the inlet and outlet.

[0062] An alarm device 8 is provided on the top outer wall of the electromagnetic wave shielding box 3, with a start button 7 on the right outer wall and an alarm device 8 on the top outer wall.

[0063] A vertical polarization detection radar 9 and a horizontal polarization detection radar 10 are symmetrically installed on the left and right inner walls of the electromagnetic wave shielding box 3. A dual polarization MIMO imaging radar 11 is installed in the central area of ​​the top inner wall of the electromagnetic wave shielding box 3.

[0064] A camera device 12 is also installed on the inner rear wall of the electromagnetic wave shielding box 3.

[0065] This passenger inspection device, through the coordinated operation of distributed dual-polarized millimeter-wave radar, combined with beamforming, phased scanning, dual-polarization detection, and multi-modal information fusion technologies, effectively solves the contradiction between the detection coverage and high-resolution identification of traditional devices. It significantly improves the reliability of detecting live vital signs signals in packages and the accuracy of imaging contour recognition of prohibited items, thereby improving security inspection efficiency and accuracy.

[0066] The following provides a further detailed description of each structure of the aforementioned passenger inspection device;

[0067] In this embodiment, the electromagnetic wave shielding box 3 is U-shaped and inverted on the wave-absorbing material conveyor belt 4. It can be fixed by bolts. The material is a high conductivity metal, which can effectively shield external electromagnetic wave interference. The width of the transmission channel formed by the inlet and outlet matches the wave-absorbing material conveyor belt 4. The edge is protected by an electromagnetic shielding curtain 6 to ensure the stability of the electromagnetic environment in the detection area.

[0068] like Figure 3 As shown, the host computer device 2 includes:

[0069] The signal preprocessing module is used to preprocess the raw signals acquired by the vertical polarization detection radar, the horizontal polarization detection radar, and the dual polarization MIMO imaging radar.

[0070] The object imaging detection module is used to receive dual-polarization MIMO imaging radar data output by the signal preprocessing module, perform target imaging and contraband identification, and output imaging classification results.

[0071] The vital signs information extraction module is used to receive data from the vertical polarization detection radar and horizontal polarization detection radar output by the signal preprocessing module, extract vital signs information, and output vital signs classification results.

[0072] The information fusion module is used to receive imaging classification results, vital sign classification results, and visual images from camera devices, perform multimodal information fusion, and generate the final classification result.

[0073] The visualization module is used to display the detection results and trigger an alarm when prohibited items are detected.

[0074] Specifically, the object imaging and detection module includes:

[0075] The pulse compression unit is used to perform range-direction matched filtering on the I / Q signals preprocessed by the dual-polarization MIMO imaging radar and output a range-slow time matrix. It utilizes the time-domain correlation of the linear frequency modulated signal to compress the wide pulse echo into a narrow pulse, clearly distinguishing target echoes at different distances in the range-slow time matrix, significantly improving range resolution, and providing high-resolution range dimension data support for subsequent imaging.

[0076] The virtual aperture synthesis unit calculates the spatial path difference of the matrix output by the pulse compression unit based on the MIMO virtual array principle, and generates an equivalent large aperture spatial sampling signal. By calculating the spatial path difference of the received signals of different antenna elements in the pulse-compressed matrix, it synthesizes physically dispersed small-aperture antenna arrays into an equivalent ultra-large aperture array, thereby expanding the spatial sampling range.

[0077] The image reconstruction unit uses a back projection algorithm to interpolate the polarization scattering matrix of the spatial sampling data output by the virtual aperture synthesis unit, reconstructing the target's HH / VV / HV three-channel contour image; among which, the dual polarization information (such as the amplitude ratio of HH / VV and the cross-polarization characteristics of HV) can effectively distinguish contraband of different materials such as metal, liquid, and plastic.

[0078] The feature classification unit uses a lightweight YOLOv5 network to extract polarization image features from the image reconstruction unit, outputting the contraband classification results. It performs matching and classification using a pre-trained contraband sample database, improving computational efficiency while ensuring detection accuracy, thus meeting real-time detection requirements.

[0079] The vital signs information extraction module includes:

[0080] The micro-motion signal separation unit performs pre-processed I / Q signals from the vertical polarization detection radar and the horizontal polarization detection radar with preset respiratory and heartbeat bandpass filtering to separate time-domain micro-motion signals. The filtering parameters for the respiratory band (0.1-0.5Hz) and the heartbeat band (0.8-2Hz) are optimized through a large amount of live experimental data, which can effectively suppress interference such as conveyor belt vibration (low frequency) and environmental noise (wideband) while retaining the micro-displacement signals related to life activities.

[0081] The phase unwrapping unit eliminates the 2π phase jump in the output signal of the micro-motion signal separation unit based on the Itoh conditional algorithm, and reconstructs a continuous phase sequence. Specifically, based on the Itoh conditional algorithm, the discrete phase sequence is corrected by judging whether the phase difference between adjacent sampling points exceeds π (i.e., the 2π jump threshold). The discrete phase sequence is then accumulating or subtracting integer multiples of 2π to eliminate the phase jump caused by the target micro-motion amplitude exceeding 1 / 4 of the radar wavelength, and a continuous and smooth phase curve is reconstructed to ensure the integrity of the respiratory / heartbeat cycle characteristics.

[0082] The feature extraction unit performs peak detection and phase difference calculation on the continuous phase sequence output by the phase unwrapping unit, and outputs respiratory rate (BR), heart rate (HR), and coefficient of variation. Specifically, peak detection identifies the periodic peaks of breathing / heartbeat, and the values ​​of respiratory rate (BR) and heart rate (HR) are obtained by combining phase difference calculation. At the same time, the coefficient of variation of the phase sequence is calculated to reflect the stability of vital signs, such as the difference in the regularity of micro-movements between living and non-living organisms.

[0083] The existence determination unit inputs the vital sign parameters output by the feature extraction unit into the SVM classifier, combines the phase variance to determine the type of living organism and outputs the classification result; it can distinguish different types of living organisms such as humans and animals, and the output classification result has both numerical features and category labels, providing accurate vital sign basis for multimodal information fusion.

[0084] In this embodiment, the specific working process of the host computer device 2 includes:

[0085] The signal preprocessing module performs orthogonal demodulation, wavelet denoising, and bandpass filtering on the raw ADC data from the three radars to remove environmental clutter and hardware noise, and separate the I / Q orthogonal signals.

[0086] The processed dual-polarization MIMO imaging radar I / Q signal is input to the object imaging detection module. The pulse compression unit performs range-direction matched filtering on the signal and outputs a range-slow time matrix. The virtual aperture synthesis unit calculates the spatial path difference of the matrix based on the MIMO virtual array principle and generates an equivalent large-aperture spatial sampling signal. The image reconstruction unit performs polarization scattering matrix interpolation on the spatial sampling data using a back projection algorithm to reconstruct the target's HH / VV / HV three-channel contour image. The feature classification unit uses a lightweight YOLOv5 network to extract polarization image features and finally outputs the contraband imaging classification result.

[0087] The vertical polarization detection radar and horizontal polarization detection radar I / Q signals output from the signal preprocessing module enter the vital signs information extraction module: the micro-motion signal separation unit first performs bandpass filtering on the signals in the preset respiratory frequency band (0.1-0.5Hz) and heart rate frequency band (0.8-2Hz) to separate the time-domain micro-motion signals; the phase unwrapping unit eliminates the 2π phase jump in the signal based on the Itoh conditional algorithm and reconstructs the continuous phase sequence; the feature extraction unit performs peak detection and phase difference calculation on the continuous phase sequence and outputs the respiratory rate (BR), heart rate (HR), and coefficient of variation; the existence determination unit inputs these vital signs parameters into the SVM classifier, combines the phase variance to determine the type of living organism, and outputs the vital signs classification results.

[0088] The information fusion module receives the imaging classification results from the object imaging detection module, the vital signs classification results from the vital signs information extraction module, and the visual images captured by the camera device, and performs multimodal information fusion: first, it automatically calculates the weight ratio based on the imaging signal energy and the vital signs signal energy, and then performs Bayesian probability fusion on the imaging classification confidence, the vital signs classification confidence, and the camera visual features to generate the final classification result.

[0089] The visualization module simultaneously renders vital sign waveforms, target contour images, and fusion results. When the final classification confidence exceeds the threshold and the item is identified as a contraband, the alarm device is immediately triggered via the GPIO interface to provide an audible and visual warning, thus completing the detection process.

[0090] In this embodiment, a vertically polarized detection radar 9 and a horizontally polarized detection radar 10 are symmetrically installed on the left and right inner walls of the electromagnetic wave shielding box 3, and a dual-polarized MIMO imaging radar 11 is installed in the central area of ​​the top inner wall of the electromagnetic wave shielding box 3; as shown in Table 1 below:

[0091] Table 1

[0092]

[0093] like Figure 4 As shown, the vertical polarization detection radar 9 and the horizontal polarization detection radar 10 are used for micro-motion detection. Both include a transmitting antenna, a receiving antenna, an FMCW waveform generator, a power divider, a control circuit, a beamforming unit, a combiner, and an ADC data memory.

[0094] Among them, the vertically polarized one-dimensional phased array micro-motion detection radar 9 and the horizontally polarized one-dimensional phased array micro-motion detection radar 10 are both installed symmetrically with an angle θ tilted downwards. In the vertical direction, beamforming technology is used to achieve a wide beam coverage, and in the horizontal direction, one-dimensional phased array scanning technology is used to achieve high-precision scanning and micro-motion detection.

[0095] Specifically, both the vertically polarized radar 9 and the horizontally polarized radar 10 adopt a one-dimensional phased array antenna architecture; the transmitting and receiving antenna arrays of the vertically polarized radar 9 are designed to generate and receive vertically polarized electromagnetic waves, while the horizontally polarized radar 10 generates and receives horizontally polarized electromagnetic waves.

[0096] The core components of both systems include: an FMCW waveform generator that produces a wide-bandwidth linear frequency modulated signal; a power divider that distributes the signal to the transmitting antenna units; a control circuit that precisely manages the transmission timing, receiving channel switching, and beam pointing; a beamforming unit that adjusts the excitation amplitude / phase of each antenna unit to form a fixed wide beam in the vertical dimension to cover the entire height range of the conveyor belt; a combiner that merges the signals from each receiving channel; and an ADC data memory that samples and stores echo data at high speed. A symmetrical tilt installation angle θ (θ range 15-30 degrees) ensures that the beam center effectively covers the wrapped area on the conveyor belt.

[0097] like Figure 5 and Figure 6 As shown, the two radars transmit in a time-division manner under the coordination of the control circuit. The FMCW signal is fed into their respective polarized antenna arrays via a power divider. In the vertical direction, the shaped beam covers the entire height in one go. In the horizontal direction, the control circuit controls the phase of each antenna element through a precision phase shifter, achieving high-precision electronic scanning of the beam across the conveyor belt width in sequence. The echo reflected from the target is captured by the receiving antenna array, combined by a combiner, and then digitized at high speed by an ADC. The minute Doppler frequency shifts and phase changes caused by the target's micro-movements carried in the echo signal are recorded and transmitted to the host computer for subsequent vital sign extraction.

[0098] In this embodiment, the dual-polarization MIMO imaging radar 11 is used for high-resolution imaging detection and recognition, and includes a transmitting antenna array, a receiving antenna array, a frequency-modulated continuous wave waveform generator, a control circuit and an ADC data memory.

[0099] The transmitting antenna array and the receiving antenna array are both linear arrays and are placed perpendicular to each other, forming a MIMO antenna array 13 with an apex shape.

[0100] like Figure 7 As shown, the dual-polarization MIMO imaging radar 11 consists of at least one MIMO antenna array 13. The distance between the transmitting antenna element and the receiving antenna element is d, and the number of each element is 2N. The multiple MIMO antenna arrays 13 are evenly distributed with a distance of 2Nd.

[0101] To meet the detection resolution requirements, the number of MIMO antenna arrays 13 is increased based on a 2Nd equal spacing. The MIMO antenna arrays 13 achieve polarization switching by rotating their installation positions by 90 degrees, supporting dual-polarization detection.

[0102] Furthermore, each MIMO antenna array 13 includes 2N transmitting antenna elements and 2N receiving antenna elements; for M MIMO antenna arrays 13, combined with the MIMO virtual aperture principle, they are equivalent to 2N×2N×M virtual antenna elements, which are used to perform coherent imaging and identification of the dual-polarized detection echo signal reflected by the target through the MIMO imaging algorithm.

[0103] like Figure 8 As shown, the dual-polarization MIMO imaging radar 11 transmits dual-polarization frequency-modulated continuous waves through an acetylene array, and receives the echo signals reflected from the target through a receiving antenna array. It utilizes the MIMO virtual aperture principle to construct an equivalent large-aperture array, and combines this with a high-resolution imaging algorithm to generate a target contour image. The control circuit coordinates the time-division multiple arrays to avoid signal interference. The echo signals are stored by an ADC and then transmitted to the host computer's object imaging detection module, where they are compared with the training set to identify contraband. Dual-polarization detection can distinguish the polarization characteristics of different objects, improving recognition accuracy in complex scenes.

[0104] like Figure 9 As shown, the three radars work in concert, employing a coordinated strategy of first guiding micro-motion and then performing precise imaging. First, radar A (vertical polarization) and radar B (horizontal polarization) work alternately in a time-sharing manner under the control circuit scheduling. Through their wide vertical beam coverage and high-precision horizontal electronic scanning, they quickly scan the packages on the conveyor belt, extract micro-motion signals of vital signs and preliminary location information, and transmit the coordinates of the suspicious target area to the host computer in real time.

[0105] like Figure 10 As shown, the host computer immediately activates radar C, focusing on the suspicious area provided by radars A / B, and controls its apex array to emit orthogonally coded dual-polarized FMCW signals. It then utilizes an equivalent ultra-large virtual aperture to perform high-density, dual-polarized coherent imaging of the area. The high-resolution contours and material reflection characteristics acquired by radar C, combined with the micro-motion features of radars A / B and camera visual information, are subjected to multi-modal fusion analysis by the host computer, ultimately achieving high-precision and high-efficiency identification and classification of contraband within packages. This collaborative mechanism effectively resolves the contradiction between large-area coverage and high-resolution identification, significantly improving detection accuracy.

[0106] Furthermore, the electromagnetic shielding curtain 6 is woven from nickel-plated metal wire and is fixed to the edge of the electromagnetic wave shielding box 3 along the circumference of the inlet and outlet, with the bottom of the curtain 6 being ≤5cm away from the surface of the wave-absorbing material conveyor belt 4.

[0107] The start button 7 features an IP65 waterproof and dustproof design; it is connected to the control circuit of the passenger inspection device via a shielded wire, supporting single-trigger start and emergency stop with a 3-second long press.

[0108] Furthermore, the alarm device 8 includes a red LED warning light and a buzzer, and is connected to the host computer device 2 via an RVV wire.

[0109] The camera device 13 is a high-definition industrial camera with its lens facing the transmission direction of the absorbing material conveyor belt 4. It communicates with the host computer device 2 via a USB 3.0 interface.

[0110] The working process of the passenger inspection device in this embodiment includes:

[0111] 1) Start-up preparation phase;

[0112] At the airport or customs security checkpoint, the operator presses the start button 7 on the right side of the electromagnetic wave shielding box. The device automatically completes a self-test, including checking the circuit connections of the vertically polarized radar 9, the horizontally polarized radar 10, and the dual-polarized MIMO imaging radar 11, the transmission function of the absorbing material conveyor belt 4, and the image clarity of the camera device 13. After the self-test is passed, the conveyor belt starts at a preset speed, and the electromagnetic shielding curtains 6 at the entrance and exit naturally fall, forming a closed electromagnetic detection environment. The upper computer device 2 displays the status of being tested, waiting for the package to enter.

[0113] 2) Package entry stage;

[0114] Passengers or staff place their suitcases and parcels on the wave-absorbing material conveyor belt 4. The parcels are carried by the conveyor belt through the electromagnetic shielding curtain 6 at the entrance and into the transmission channel of the electromagnetic wave shielding box 3. At this time, a high-definition industrial camera at the rear of the shielding box immediately takes a picture of the parcel and generates a unique tag containing time and location information for subsequent data association.

[0115] 3) Radar cooperative detection phase;

[0116] After the package enters the detection area, the left vertical polarization radar 9 and the right horizontal polarization radar 10 work in a time-division manner under the coordination of the control circuit. They emit corresponding polarization waves at an angle θ of 15-30 degrees downward. In the vertical direction, the beamforming covers the entire height of the package, and in the horizontal direction, the phased scanning covers the width of the conveyor belt. This accurately captures the micro-motion signals of any living organisms that may exist inside the package. The data is stored by the ADC and then transmitted to the host computer in real time.

[0117] Meanwhile, the top dual-polarization MIMO imaging radar 11 transmits dual-polarization signals through an ace antenna array based on the suspicious area provided by the A / B radar, and uses virtual aperture technology to generate a high-resolution contour image of the object inside the package. The echo data is also transmitted to the host computer.

[0118] 4) Data processing and fusion stage;

[0119] The host computer first denoises and filters the radar data to separate the effective signals; the object imaging detection module processes the C radar data to reconstruct the outlines of contraband such as knives and liquid bottles, classifies them using the YOLOv5 algorithm, and labels the confidence level; the vital signs information extraction module processes the A / B radar data to identify breathing and heartbeat signals, and uses the SVM algorithm to determine whether the person is alive; the information fusion module combines the above results with the appearance of the package captured by the camera, dynamically weights the signals according to the signal energy, and finally determines the results such as knives + no live people or insects + no contraband.

[0120] 5) Result output and alarm stage;

[0121] The host computer screen displays the package label, vital sign waveform, object outline image, and final classification result in real time. If the result is a contraband item with a confidence level of ≥90%, the top alarm device 8 will immediately trigger, with the red LED light flashing and the buzzer sounding an alarm to remind security personnel to manually verify the item; if the item is normal, it will only display "No abnormality".

[0122] 6) Package departure stage;

[0123] After inspection, the package passes through the electromagnetic shielding curtain 6 at the exit on the conveyor belt and leaves the electromagnetic wave shielding box. The whole process takes about 5-10 seconds. The device automatically resets and waits for the next package to enter the inspection process.

[0124] This embodiment provides a collaborative system combining vertically polarized radar, horizontally polarized radar, and dual-polarized MIMO imaging radar. Through beamforming, phased scanning, dual-polarization detection, and multimodal information fusion, it achieves precise linkage from micro-motion detection to high-resolution imaging. The host computer efficiently fuses radar signals and visual information through multi-module collaborative processing, ultimately outputting the results in a visualized manner and triggering alarms. This effectively resolves the contradictions in coverage and resolution, as well as the reliability of vital sign detection, inherent in traditional passenger inspection devices. This device can be widely applied in airports, customs, and other locations, significantly improving the efficiency and accuracy of transit cargo security checks and providing reliable technical support for preventing invasive species and the flow of contraband.

[0125] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0126] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A passenger inspection device based on distributed dual-polarization millimeter-wave radar, characterized in that, include: The detection device body (1) and the host computer device (2) which is communicatively connected to the device body (1); The detection device body (1) includes an electromagnetic wave shielding box (3) and a wave-absorbing material conveyor belt (4); the electromagnetic wave shielding box (3) has an inlet and an outlet on its front and rear sides respectively to form a transmission channel; the wave-absorbing material conveyor belt (4) passes through the transmission channel and is fixed to the bottom of the electromagnetic wave shielding box (3) through a conveyor bracket (5); The electromagnetic wave shielding box (3) is equipped with electromagnetic shielding curtains (6) at both the entrance and the exit. The electromagnetic wave shielding box (3) has a start button (7) on the right outer wall and an alarm device (8) on the top outer wall; The electromagnetic wave shielding box (3) is symmetrically equipped with a vertical polarization detection radar (9) and a horizontal polarization detection radar (10) on the left and right inner walls. The electromagnetic wave shielding box (3) is equipped with a dual polarization MIMO imaging radar (11) in the central area of ​​the top inner wall. The electromagnetic wave shielding box (3) is also equipped with a camera device (12) on the inner rear wall.

2. The passenger inspection device based on distributed dual-polarization millimeter-wave radar according to claim 1, characterized in that, The host computer device (2) includes: The signal preprocessing module is used to preprocess the raw signals acquired by the vertical polarization detection radar, the horizontal polarization detection radar, and the dual polarization MIMO imaging radar. The object imaging detection module is used to receive dual-polarization MIMO imaging radar data output by the signal preprocessing module, perform target imaging and contraband identification, and output imaging classification results. The vital signs information extraction module is used to receive data from the vertical polarization detection radar and horizontal polarization detection radar output by the signal preprocessing module, extract vital signs information, and output vital signs classification results. The information fusion module is used to receive imaging classification results, vital sign classification results, and visual images from camera devices, perform multimodal information fusion, and generate the final classification result. The visualization module is used to display the detection results and trigger an alarm when prohibited items are detected.

3. A passenger inspection device based on distributed dual-polarization millimeter-wave radar according to claim 1, characterized in that, The object imaging detection module includes: The pulse compression unit is used to perform range-direction matched filtering on the I / Q signals preprocessed by the dual-polarization MIMO imaging radar and output a range-slow time matrix to improve range resolution. The virtual aperture synthesis unit calculates the spatial path difference of the matrix output by the pulse compression unit based on the MIMO virtual array principle, and generates an equivalent large aperture spatial sampling signal. The image reconstruction unit uses a back projection algorithm to interpolate the polarization scattering matrix of the spatial sampling data output by the virtual aperture synthesis unit, and reconstructs the target HH / VV / HV three-channel contour image. The feature classification unit uses a lightweight YOLOv5 network to extract polarization image features from the image reconstruction unit and outputs the contraband classification results.

4. A passenger inspection device based on distributed dual-polarization millimeter-wave radar according to claim 1, characterized in that, The vital signs information extraction module includes: The micro-motion signal separation unit performs preset respiratory and heartbeat frequency bandpass filtering on the I / Q signals preprocessed by the vertical polarization detection radar and the horizontal polarization detection radar to separate the time-domain micro-motion signals; The phase unwrapping unit eliminates the 2π phase jump in the output signal of the micro-motion signal separation unit based on the Itoh conditional algorithm, and reconstructs the continuous phase sequence; The feature extraction unit performs peak detection and phase difference calculation on the continuous phase sequence output by the phase unwrapping unit, and outputs respiratory rate (BR), heart rate (HR), and coefficient of variation. The existence determination unit inputs the vital sign parameters output by the feature extraction unit into the SVM classifier, combines the phase variance to determine the type of living organism, and outputs the classification result.

5. A passenger inspection device based on distributed dual-polarization millimeter-wave radar according to claim 1, characterized in that, The vertical polarization detection radar (9) and the horizontal polarization detection radar (10) are used for micro-motion detection. Both include a transmitting antenna, a receiving antenna, an FMCW waveform generator, a power divider, a control circuit, a beamforming unit, a combiner, and an ADC data storage. Among them, the vertically polarized one-dimensional phased array micro-motion detection radar (9) and the horizontally polarized one-dimensional phased array micro-motion detection radar (10) are both installed symmetrically with an angle θ tilted downwards. In the vertical direction, beamforming technology is used to achieve a wide beam coverage, and in the horizontal direction, one-dimensional phased array scanning technology is used to achieve high-precision scanning and micro-motion detection.

6. A passenger inspection device based on distributed dual-polarization millimeter-wave radar according to claim 1, characterized in that, The dual-polarization MIMO imaging radar (11) is used for high-resolution imaging detection and recognition, including a transmitting antenna array, a receiving antenna array, a frequency-modulated continuous wave waveform generator, a control circuit and an ADC data storage; The transmitting antenna array and the receiving antenna array are both linear arrays and are placed perpendicular to each other to form a MIMO antenna array with an apex shape (13).

7. A passenger inspection device based on a distributed dual-polarization millimeter-wave radar according to claim 4, characterized in that, The dual-polarization MIMO imaging radar (11) consists of at least one MIMO antenna array (13), with the distance between the transmitting antenna unit and the receiving antenna unit being d and the number being 2N. Multiple MIMO antenna arrays (13) are distributed at equal intervals with a distance of 2Nd. In accordance with the detection resolution requirements, the number of MIMO antenna arrays (13) is increased based on 2Nd equal spacing. The MIMO antenna arrays (13) achieve polarization conversion by rotating the installation position by 90 degrees, supporting dual polarization detection.

8. A passenger inspection device based on a distributed dual-polarization millimeter-wave radar according to claim 4, characterized in that, Each MIMO antenna array (13) includes 2N transmitting antenna elements and 2N receiving antenna elements; for M MIMO antenna arrays (13), combined with the MIMO virtual aperture principle, they are equivalent to 2N×2N×M virtual antenna elements, which are used to perform coherent imaging and identification of the dual-polarized detection echo signal reflected by the target through the MIMO imaging algorithm.

9. A passenger inspection device based on distributed dual-polarization millimeter-wave radar according to claim 1, characterized in that, The electromagnetic shielding curtain (6) is woven from nickel-plated metal wire and is fixed to the edge of the electromagnetic wave shielding box (3) along the circumference of the inlet and outlet. The bottom of the curtain is ≤5cm away from the surface of the wave-absorbing material conveyor belt (4). The start button (7) adopts an IP65 waterproof and dustproof design; it is connected to the control circuit of the passenger inspection device through a shielded wire, and supports single-trigger start and long-press for 3 seconds emergency stop.

10. A passenger inspection device based on a distributed dual-polarization millimeter-wave radar according to claim 1, characterized in that, The alarm device (8) includes a red LED warning light and a buzzer, and is connected to the host computer device (2) via an RVV wire; The camera device (13) is a high-definition industrial camera with its lens facing the transmission direction of the wave-absorbing material conveyor belt (4). It is connected to the host computer device (2) via a USB 3.0 interface.

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