Object imaging method, system, medium, and computing device based on diffraction of RF signals

Abstract

The application relates to an object imaging method, system, medium and computing device based on RF signal diffraction, which comprises the following steps: establishing a relationship model of diffraction signals between RF signal transceiving devices and a target object contour, determining a forward relationship from a contour function and a displacement function of the target object to the diffraction signals; based on the relationship model and by using inverse Fresnel transformation, giving an analytical solution of the contour function of the target object under the condition that the diffraction signals and the displacement function are known; collecting CSI by the arranged RF signal transceiving devices with transceiving separation, performing signal processing on the collected CSI, and extracting dynamic components; substituting the dynamic components and the displacement function into the analytical solution of the contour function to obtain the amplitude of the contour function and the contour of the target object. By measuring channel state information of a moving target at different positions on a straight motion track, the application can realize fine-grained object imaging, the median error of the reconstructed object contour is small, and the application can be applied in the technical field of object imaging.

Description

Technical Field

[0001] This invention relates to the field of object imaging technology based on radio frequency (RF) systems, and in particular to an object imaging method, system, medium, and computing device based on RF signal diffraction. Background Technology

[0002] Existing RF signal imaging methods are all based on signal reflection. The basic principle is to project a narrow beam signal at the target and obtain the accurate time of flight, angle of arrival, and Doppler shift of the reflected signal, thereby reconstructing the target's point cloud. Forming a narrow beam signal requires a high signal frequency and a large antenna array. Obtaining an accurate time of flight requires a large bandwidth. However, commercial communication equipment suffers from hardware limitations such as low signal frequency (several GHz), narrow bandwidth (tens of MHz), and a small number of antennas, making it difficult to achieve fine-grained object imaging using existing methods. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide an object imaging method, system, medium, and computing device based on RF signal diffraction. By measuring the Channel State Information (CSI) of a moving target at different positions on its linear trajectory, fine-grained object imaging can be achieved, and the median error of the reconstructed object contour is relatively small.

[0004] To achieve the above objectives, in a first aspect, the technical solution adopted by the present invention is as follows: an object imaging method based on RF signal diffraction, comprising: establishing a relationship model between diffraction signals and the contour of a target object between RF signal transceivers, and determining the positive relationship from the contour function and displacement function of the target object to the diffraction signal; based on the relationship model and using inverse Fresnel transform, providing an analytical solution for the contour function of the target object given the diffraction signal and displacement function; acquiring CSI by arranged RF signal transceivers with separate transceivers, performing signal processing on the acquired CSI, and extracting dynamic components; substituting the dynamic components and displacement function into the analytical solution of the contour function to obtain the amplitude of the contour function, thereby obtaining the contour of the target object.

[0005] Furthermore, the relationship model between the diffraction signal and the contour of the target object is as follows:

[0006]

[0007] In the formula, H S (d t ) represents the dynamic component of the diffraction signal, P(x) represents the contour function of the target object, and D(x+d) represents the contour function of the target object. t Let d be the displacement function of any point x on the contour of the target object. tThis represents the displacement of the target object along the X-axis.

[0008] Furthermore, given the diffraction signal and displacement function, the analytical solution of the contour function of the target object is provided, including:

[0009] Estimate and eliminate the static component of the diffraction signal to obtain the dynamic component of the diffraction signal;

[0010] The profile function is solved by substituting the dynamic components and displacement functions into the analytical solution of the profile function.

[0011] Furthermore, the analytical solution of the contour function is:

[0012]

[0013] In the formula, L is the total length of displacement, k is the RF signal wavenumber, and π is pi. Where y T The distance from the transmitting device's antenna to the X-axis is represented by y. R H represents the distance from the receiving device's antenna to the X-axis. S (d t ) represents the dynamic component of the diffraction signal, D(d) t Let d be the displacement function of the target object. t This represents the displacement of the target object along the X-axis.

[0014] Furthermore, the arrangement of the RF signal transceiver equipment with separate transmit and receive functions includes:

[0015] At least one pair of RF signal transceivers should be deployed, serving as both the transmitting device and the receiving device for acquiring CSI data.

[0016] Each transmitting device is equipped with a transmitting antenna Tx to transmit RF signals;

[0017] Each receiving device is equipped with two antennas to measure channel state information; the two antennas are the main receiving antennas Rx. pri and reference antenna Rx ref ;

[0018] Main receiving antenna Rx pri The transmitting antenna Tx is placed on both sides of the motion trajectory, and the reference antenna Rx is placed on the other side. ref The transmitting antenna Tx is placed on the same side of the trajectory.

[0019] Transmitting antenna Tx and reference antenna Rx ref There is a gap between them, and the line connecting them is parallel to the trajectory of motion;

[0020] Both the transmitting and receiving antennas are vertically polarized omnidirectional antennas, placed vertically to the ground.

[0021] Furthermore, the acquired CSI signals are processed to extract dynamic components, including:

[0022] Eliminate random phase shifts caused by clock asynchrony between transceiver devices;

[0023] Static elimination is performed on the phase-division signal to extract the dynamic component;

[0024] Amplitude calibration is performed on the dynamic components to eliminate amplitude deviations caused by the phase division operation.

[0025] Furthermore, by substituting the dynamic components and displacement function into the analytical solution of the contour function, the amplitude of the contour function is obtained, thus yielding the contour of the target object, including:

[0026] Substitute the trajectory of the target object into the definition of the displacement function to calculate the displacement function of the target object;

[0027] Substitute the dynamic components and displacement function of the diffraction signal into the analytical solution of the profile function to obtain the amplitude of the profile function and thus the difference between the upper and lower boundary functions of the profile region.

[0028] For objects with a wide and flat bottom, the lower boundary is constant, and the difference between the upper and lower boundary functions is the desired object contour, thus obtaining the imaging result;

[0029] Median filtering was used to smooth the imaging results.

[0030] Secondly, the technical solution adopted by the present invention is as follows: an object imaging system based on RF signal diffraction, comprising: a relational model construction module, which establishes a relational model between the diffraction signal and the contour of the target object between the RF signal transceiver devices, and determines the positive relationship from the contour function and displacement function of the target object to the diffraction signal; a contour function solution module, which, based on the relational model and using inverse Fresnel transform, provides an analytical solution for the contour function of the target object given the diffraction signal and displacement function; a dynamic component extraction module, which acquires CSI from the separately arranged RF signal transceiver devices, performs signal processing on the acquired CSI, and extracts the dynamic component; and a target contour acquisition module, which substitutes the dynamic component and displacement function into the analytical solution of the contour function, obtains the amplitude of the contour function, and obtains the contour of the target object.

[0031] Thirdly, the technical solution adopted by the present invention is: a computer-readable storage medium for storing one or more programs, wherein the one or more programs include instructions, which, when executed by a computing device, cause the computing device to perform any of the methods described above.

[0032] Fourthly, the technical solution adopted by the present invention is: a computing device comprising: one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include instructions for performing any of the methods described above.

[0033] The present invention has the following advantages due to the adoption of the above technical solutions:

[0034] 1. The object imaging method based on RF signal diffraction of the present invention can realize fine-grained object imaging, the median error of the reconstructed object contour is less than 1cm, and it is robust to the surrounding environment, equipment placement and signal sampling rate.

[0035] 2. This invention establishes a relationship model between diffraction signals between transceivers and the contour of the target object, providing a theoretical basis for object imaging based on RF signal diffraction.

[0036] 3. This invention proposes using inverse Fresnel transform to analytically solve for object contours, thereby improving the efficiency of imaging algorithms.

[0037] 4. This invention proposes a novel antenna placement strategy to eliminate random phase shifts in the CSI of commercial communication equipment, thereby improving imaging accuracy. Attached Figure Description

[0038] Figure 1 This is a flowchart of an object imaging method based on RF signal diffraction in an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the diffraction scene in an embodiment of the present invention;

[0040] Figure 3a This is a schematic diagram of the three-dimensional spatial relationship between the antenna of the transceiver device and the outline of the target object in an embodiment of the present invention;

[0041] Figure 3b This is a schematic diagram illustrating the mathematical description of the outline of the target object in an embodiment of the present invention;

[0042] Figure 4 This is a schematic diagram of the target object moving along the perpendicular bisector of the transceiver device in an embodiment of the present invention;

[0043] Figure 5a This is the amplitude diagram of the displacement function when the target object moves from -0.3m to 0.3m along the perpendicular bisector of the transceiver device in an embodiment of the present invention.

[0044] Figure 5b This is the IQ diagram of the displacement function when the target object moves from -0.3m to 0.3m along the perpendicular bisector of the transceiver device in an embodiment of the present invention.

[0045] Figure 6a This is the amplitude diagram of the diffraction signal when the target object moves from -0.3m to 0.3m along the perpendicular bisector of the transceiver device in an embodiment of the present invention.

[0046] Figure 6b This is the IQ diagram of the diffraction signal when the target object moves from -0.3m to 0.3m along the perpendicular bisector of the transceiver in an embodiment of the present invention.

[0047] Figure 7 This is a schematic diagram of the arrangement of transceiver equipment and antenna placement in an embodiment of the present invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0049] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0050] In recent years, with the widespread adoption of wireless communication infrastructure, the field of wireless sensing has attracted extensive attention from both academia and industry. Existing work has enabled various valuable applications by reusing RF signals from existing commercial communication devices in the environment, including intrusion detection, indoor tracking, activity recognition, gesture recognition, and vital sign monitoring. However, compared to dedicated radar equipment, the RF signals from commercial communication devices have lower frequencies, narrower bandwidths, and fewer antennas. Therefore, achieving fine-grained object imaging (determining the shape and size information of objects) using the RF signals of commercial communication devices remains a key challenge in the field of wireless sensing.

[0051] Compared to optical imaging, RF signal imaging is less affected by environmental factors such as light, smoke, and dust. Furthermore, because RF signals can penetrate opaque materials such as foam and paper, RF signal imaging allows for the inspection of internal objects without removing the packaging. Therefore, RF signal imaging has significant application value in various fields such as industrial automation, robotics, healthcare, and security.

[0052] Therefore, achieving fine-grained object imaging (determining the shape and size information of objects) using RF signals from commercial communication devices is a key problem in the field of wireless sensing. This invention proposes a method, system, medium, and computing device for object imaging based on RF signal diffraction. This invention establishes a relationship model between the diffraction signal between the transceiver and the contour (shape and size) of the target object. Guided by this model, this invention designs and implements an object imaging system based on RF signal diffraction. This system can achieve fine-grained object imaging, with a median error of less than 1 cm for the reconstructed object contour, and is robust to the surrounding environment, device placement, and signal sampling rate. This work explores an important missing part of the wireless sensing field and lays the theoretical foundation for object imaging based on RF signal diffraction. The proposed method can be applied to any transceiver-separated wireless RF device, including but not limited to Wi-Fi devices, 4G / 5G devices, UWB devices, LoRa devices, etc., to achieve new applications.

[0053] The basic principle of this invention is to establish a relationship model between the diffraction signal between RF signal transceivers and the contour (shape and size) of the target object. When the target object is placed on a line-of-sight (LoS) path between the transceivers, diffraction dominates, and the RF signal emitted by the transmitting device bypasses the target boundary and reaches the receiving device through diffraction. According to the Huygens-Fresnel principle, the received diffraction signal carries the contour information of the target object. Furthermore, when controlling the target object to move along a straight trajectory between the transceivers, the contour of the target object can be solved by performing an inverse Fresnel transform on the acquired diffraction signal.

[0054] In this invention, the specific terms are as follows: RF represents radio frequency signal, CSI represents channel state information, Tx represents transmitting device antenna, Rx represents receiving device antenna, and LoS (Line of Sight) represents the distance between the transmitting and receiving devices.

[0055] In one embodiment of the present invention, an object imaging method based on RF signal diffraction is provided. This embodiment is applicable to any wireless radio frequency device with separate transmit and receive, including but not limited to Wi-Fi devices, 4G / 5G devices, UWB devices, LoRa devices, etc. Specifically, as shown... Figure 1 As shown, the method includes the following steps:

[0056] 1) Establish a relationship model between the diffraction signal and the contour of the target object between the RF signal transceiver devices, and determine the relationship between the contour function P(x) and displacement function D(x) of the target object and the diffraction signal. Positive relationship;

[0057] 2) Based on the relational model and utilizing the inverse Fresnel transform, given the diffraction signal... Given the displacement function D(x), provide the analytical solution for the contour function P(x) of the target object;

[0058] 3) The CSI is acquired by the deployed RF signal transceiver equipment with separate transmit and receive functions, and the acquired CSI is processed to extract the dynamic components;

[0059] 4) Substitute the dynamic components and displacement function into the analytical solution of the profile function. Obtain the magnitude of the contour function Obtain the outline of the target object.

[0060] In step 1) above, if Figure 2 As shown, when a target object is placed in the line of sight (LoS) path between the transmitting and receiving devices, diffraction dominates. The RF signal emitted by the transmitting device bypasses the target boundary and reaches the receiving device through diffraction. According to the Huygens-Fresnel principle, the received diffracted signal carries the contour information of the target object. Figure 3a As shown, a coordinate system (X, Y, Z) is defined to represent the diffraction correlation parameters, and Tx is located at (0, -y). T Rx is located at (0, y). R ,0),y T The distance from the transmitting device's antenna to the X-axis is represented by y. R This represents the distance from the receiving device's antenna to the X-axis. When the thickness of the target object is much smaller than the distance from Tx to Rx, the diffraction effect of the target object on the signal can be approximated by the diffraction effect of its projection region on the XZ plane. This projection region is denoted as the contour region S, such as... Figure 3b As shown, the contour region S can be represented using two functions u S (x) and l S (x) characterization, i.e.:

[0061] S={(x,z)∣x∈[W L W R ],z∈[l S (x),u S (x)]}, (1)

[0062] Among them, W L and W R These are the left and right boundaries of the contour region S on the X-axis, respectively. S (x) and l S (x) are the upper and lower boundary functions of the contour region, respectively.

[0063] According to the Fresnel-Kirchhoff diffraction law, a diffraction signal emitted from Tx and reaching Rx can be represented as bypassing the contour region S (or equivalently passing through the region S). (Signal)

[0064]

[0065] Where f(x,z) is the fundamental function that characterizes the diffraction signal at a single point in space;

[0066]

[0067] Where A is the signal amplitude, j is the imaginary unit, λ is the signal wavelength, and k is the signal wavenumber. r T (x,z) is the distance between Tx and the point (x,0,z), r R (x,z) is the distance between Rx and the point (x,0,z), α T (x, z) is the angle between the Y-axis and the line connecting point Tx (x, 0, z), α R (x,z) is the angle between the Y-axis and the line connecting the Rx-point (x, 0, z).

[0068] Based on the Babiné principle, this invention transforms formula (2) into... Where H wo =∫∫f(x,z)dxdz,H S =∫∫ S f(x,z)dxdz。 H wo This is the signal without objects, calculated as the infinite integral of f(x,z) over the entire XZ plane. Given positions Tx and Rx, H... wo It does not change with the position of the target object. H S It is a region The signal passing through the contour region S when occluded is calculated as the integral of f(x,z) over the contour region S. S It changes as the position of the target object changes.

[0069] Next, consider the target object, such as... Figure 4 The diagram shows the change in diffraction signal as the target object moves along a straight line along the X-axis. Let d be the displacement of the target object along the X-axis. t The contour region at time is S(d) t From formula (1), we can obtain:

[0070] S(d t )={(x,z)∣x∈[W L +d t W R +d t ],z∈[l S (xd t ),u S (xd t )]}.

[0071] Without loss of generality, Where W is the width of the contour region. Definition

[0072]

[0073] and

[0074]

[0075] H S =∫∫ S In f(x,z)dxdz, S is represented by S(d t Substitution yields

[0076]

[0077] at this time, It is the static component H wo and dynamic component H S (d t The superposition of )

[0078]

[0079] When the height of the contour region is much smaller than the distance from Tx to Rx, the following approximate relationship exists.

[0080]

[0081] in Substituting formula (6) into formula (4) yields

[0082]

[0083] Note f(x+d) t The expression ,0) is independent of the integration variable z, therefore it can be extracted outside the integral, resulting in

[0084]

[0085] Formula (8) is the integral of the product of terms ① and ②.

[0086] The value of term ① is determined by the upper and lower limits of integration u(x) and l(x). Therefore, in this embodiment, ① is called the "profile function" and denoted as .

[0087]

[0088] By the properties of P(x), |P(x)| = u(x) - l(x). Therefore, the amplitude of the contour function represents the difference between the upper and lower boundary functions u(x) and l(x) of the contour region. For an object with a constant lower boundary l(x), the amplitude of the contour function gives the change in the upper boundary function u(x), thus characterizing the contour of the target object.

[0089] The value of term ② is determined by the integration limits u(x) and l(x). Therefore, in this embodiment, ② is referred to as the "displacement function", denoted as .

[0090] D(x+d t )=f(x+d t ,0). (10)

[0091] Without loss of generality, the displacement function D(x+d) of different points on the target object can be expressed as... t The displacement function D(d) is unified as the center of the target object (x = 0). t This invention is based on... Figure 4 The following example illustrates the displacement function, which describes the motion of a target object moving along the X-axis from -0.3m to 0.3m. Figure 5a The amplitude of the displacement function is shown, which is symmetric about d2 = 0m and reaches its maximum value at d2, corresponding to the case where the target object is exactly between Tx and Rx. Figure 5b The IQ plot of the displacement function is shown. When the target object moves from d2 = 0m to d4 = 0.3m, the diffraction path lengthens, causing a decrease in the amplitude and phase of the displacement function, resulting in a counterclockwise spiral in the IQ plot. The displacement function carries the relative position information between the target object and the transceiver.

[0092] Let P(x) and D(x+d) be the bases of the two arrays. t Substituting into formula (8), the relationship model between the diffraction signal and the contour of the target object is obtained as follows:

[0093]

[0094] In the formula, H S (d t ) represents the dynamic component of the diffraction signal, P(x) represents the contour function of the target object, and D(x+d) represents the contour function of the target object. t Let dt be the displacement function of any point x on the contour of the target object, and let dt be the displacement of the target object along the X-axis.

[0095] Therefore, H S (d t In fact, it is the convolution of P(-x) and D(x). Figure 6a and Figure 6b The dynamic component H of the diffraction signal is shown. S (d t The amplitude and IQ plot of ). From Figure 6a As can be seen, unlike the amplitude of the displacement function, the amplitude of the dynamic component of the diffraction signal is no longer symmetrical. This is due to the asymmetry of the target object's contour. As the target object approaches the LoS, its occlusion of the signal increases, and the amplitude of the dynamic component also increases accordingly. Figure 6b This indicates that minute movements of the target object can cause significant phase changes in the IQ plot.

[0096] In step 2) above, after establishing the relationship between the profile function P(x) and the displacement function D(x) and the diffraction signal... Based on the positive relationship, when performing imaging, it is necessary to know the diffraction signal. Solve for the profile function P(x) given the displacement function D(x).

[0097] Therefore, in this embodiment, given the diffraction signal and displacement function, an analytical solution for the contour function of the target object is provided. Includes the following steps:

[0098] 2.1) Estimate and eliminate the static component of the diffraction signal to obtain the dynamic component of the diffraction signal;

[0099] Specifically, the diffraction signal can be obtained through formula (5). From static component H wo and dynamic component H S (d t Therefore, in this embodiment, the static component H is first estimated and eliminated. wo The dynamic component H is obtained. S (d t ).

[0100] 2.2) Utilizing dynamic component H S (d t Substitute the displacement function D(x) and the analytical solution of the profile function to solve for the profile function P(x).

[0101] Formula (10) shows that H S (d t P(-x) is the convolution of P(-x) and D(x). Therefore, theoretically, P(x) can be solved by deconvolution. However, this solution method is extremely sensitive to noise in practical use, resulting in very low imaging accuracy. Therefore, formula (11) is further rewritten in the form of Fresnel transform.

[0102]

[0103] Therefore, the analytical solution of the contour function Through dynamic component H S (d t The inverse Fresnel transform of ) gives

[0104]

[0105] The right side of formula (13) is the integration variable d. t The infinite integral of . In the actual imaging process, the displacement d t The solution to the contour function is always finite, therefore, under this constraint, the analytical solution is... Formula (13) can be rewritten as follows:

[0106]

[0107] In the formula, L is the total length of displacement, k is the RF signal wavenumber, and π is pi. Where y T The distance from the transmitting device's antenna to the X-axis is represented by y. R H represents the distance from the receiving device's antenna to the X-axis. S (d t ) represents the dynamic component of the diffraction signal, D(d) t Let d be the displacement function of the target object. t This represents the displacement of the target object along the X-axis.

[0108] Finally, the magnitude of the contour function This represents the difference between the upper and lower boundary functions u(x) and l(x) of the contour region. For objects with a wide and flat bottom (such as cuboids, cylinders, cones, etc.), the lower boundary l(x) is constant, and the difference between the upper and lower boundary functions changes in the same way as the change in the upper boundary function u(x), which is the contour of the target object.

[0109] In step 3) above, the arrangement of the RF signal transceiver equipment with separate transmission and reception is as follows:

[0110] At least one pair of RF signal transceiver devices (such as Wi-Fi devices, 4G / 5G devices, LoRa devices, etc.) should be deployed, serving as the transmitting device and the receiving device for collecting CSI, respectively.

[0111] Each transmitting device is equipped with a transmitting antenna Tx to transmit RF signals, such as Figure 7 As shown;

[0112] Each receiving device is equipped with two antennas to measure channel state information; the two antennas are the main receiving antennas Rx. pri and reference antenna Rx ref ;

[0113] Main receiving antenna Rx pri The transmitting antenna Tx is placed on both sides of the motion trajectory, and the reference antenna Rx is placed on the other side. ref The transmitting antenna Tx is placed on the same side of the trajectory.

[0114] Transmitting antenna Tx and reference antenna Rx ref There is a gap between them, and the line connecting them is parallel to the trajectory of motion;

[0115] Both the transmitting and receiving antennas are vertically polarized omnidirectional antennas, placed vertically to the ground.

[0116] In this embodiment, preferably, the transmitting antenna Tx and the reference antenna Rxref The spacing between them is 10cm.

[0117] In this embodiment, the RF signal transceiver can be a laptop, a MiniPC, or any device that supports RF signal transmission and reception. Preferably, a Wi-Fi signal with a center frequency of 5.32 GHz and a bandwidth of 20 MHz is used as the RF signal, and a MiniPC equipped with an 8 dB omnidirectional antenna and an Intel 5300 network card is used as the RF signal transceiver.

[0118] In step 3) above, the acquired CSI signal is processed to extract the dynamic components, including the following steps:

[0119] 3.1) Eliminate random phase shifts caused by clock asynchrony between transceiver devices;

[0120] In this embodiment, the receiving device is configured with two antennas (main receiving antenna Rx). pri and reference antenna Rx ref Measure Channel State Information (CSI). Divide the CSI data collected by the two antennas at the same time to eliminate random phase shifts caused by clock asynchrony between the transceivers. For example, consider a subcarrier of a Wi-Fi signal; at time t, the main receiving antenna Rx pri The CSI is Reference antenna Rx ref The CSI is The phase division signal obtained after eliminating random phase shift is:

[0121]

[0122] 3.2) Static elimination is performed on the phase division signal to extract the dynamic component;

[0123] In this embodiment, by dividing the signal... In |d t The static component is obtained by taking the mean of the part where (t)|>0.2m. Eliminating static components yields dynamic component Q. S (f,t).

[0124] 3.3) Perform amplitude calibration on the dynamic components to eliminate amplitude deviation caused by the phase division operation.

[0125] In step 4) above, the dynamic components and displacement function are substituted into the analytical solution of the contour function to obtain the amplitude of the contour function and thus the contour of the target object. This includes the following steps:

[0126] 4.1) Substitute the trajectory of the target object (displacement at different times) into the definition of the displacement function (formula (10)) to calculate the displacement function of the target object;

[0127] 4.2) Substitute the dynamic components and displacement function of the diffraction signal into the analytical solution of the contour function (formula (14)) to obtain the amplitude of the contour function and the difference between the upper and lower boundary functions of the contour region.

[0128] 4.3) For objects with a wide and flat bottom (such as cuboids, cylinders, cones, etc.), the lower boundary is constant, and the difference between the upper and lower boundary functions is the outline of the target object, thus obtaining the imaging result;

[0129] 4.4) Median filtering is used to smooth the imaging results.

[0130] It should be noted that in order to achieve high-precision imaging based on RF signal diffraction using this invention, the target object needs to meet the following pre-defined limitations regarding material, size, and contour shape:

[0131] First, there are material requirements. The target object's material needs to significantly block the propagation of RF signals. In other words, the target object's material needs to be either metallic or a non-metallic material with a high dielectric constant in the RF band. When a significant transmitted signal exists, the signal received by the receiving device is a superposition of the diffracted and transmitted signals. The received signal is affected not only by the shape of the object's profile but also by the dielectric constant and thickness of the target object.

[0132] Secondly, there are size requirements. The target object size needs to be within an appropriate range—neither too small nor too large. Specifically, the lower limit of the size is half the wavelength of the RF signal (3cm for a 5GHz Wi-Fi signal). When the target object size is smaller than half the wavelength of the RF signal, the diffraction effect weakens, and the imaging accuracy decreases. The upper limit of the size requires considering the width and height separately. The maximum width is half the Tx-Rx distance, and the maximum height is:

[0133]

[0134] When the size of the target object exceeds the upper limit, some key approximation errors in the model derivation increase, leading to a decrease in imaging accuracy.

[0135] Finally, there are requirements for the contour shape. The contour of the target object needs to be flat-bottomed, and there cannot be any holes inside the contour. This is because the imaging result of this invention is the difference between the upper and lower boundary functions of the contour region. For contour shapes that do not meet this condition, the imaging result may deviate from the actual contour.

[0136] In one embodiment of the present invention, an object imaging system based on RF signal diffraction is provided, comprising:

[0137] The relational model construction module establishes a relational model between the diffraction signal and the contour of the target object between the transceiver devices, and determines the positive relationship from the contour function and displacement function of the target object to the diffraction signal;

[0138] The contour function solution module, based on the relational model and utilizing the inverse Fresnel transform, provides an analytical solution for the contour function of the target object given the diffraction signal and displacement function.

[0139] The dynamic component extraction module uses a set of separate RF signal transceiver devices to collect CSI, performs signal processing on the collected CSI, and extracts the dynamic components.

[0140] The target contour acquisition module substitutes the dynamic components and displacement function into the analytical solution of the contour function to obtain the amplitude of the contour function and thus the contour of the target object.

[0141] In the above embodiments, the relationship model between the diffraction signal and the contour of the target object is as follows:

[0142]

[0143] In the formula, H S (d t ) represents the dynamic component of the diffraction signal, P(x) represents the contour function of the target object, and D(x+d) represents the contour function of the target object. t Let d be the displacement function of any point x on the contour of the target object. t This represents the displacement of the target object along the X-axis.

[0144] In the above embodiments, given the diffraction signal and displacement function, an analytical solution for the contour function of the target object is provided, including:

[0145] Estimate and eliminate the static component of the diffraction signal to obtain the dynamic component of the diffraction signal;

[0146] The profile function is solved using dynamic components and displacement functions.

[0147] The analytical solution of the contour function is:

[0148]

[0149] In the formula, L is the total length of displacement, k is the RF signal wavenumber, and π is pi. Where y T The distance from the transmitting device's antenna to the X-axis is represented by y. R H represents the distance from the receiving device's antenna to the X-axis. S (d t ) represents the dynamic component of the diffraction signal, D(d) t Let d be the displacement function of the target object. t This represents the displacement of the target object along the X-axis.

[0150] In the above embodiments, the arrangement of the RF signal transceiver equipment includes:

[0151] At least one pair of RF signal transceivers should be deployed, serving as both the transmitting device and the receiving device for acquiring CSI data.

[0152] Each transmitting device is equipped with a transmitting antenna Tx to transmit RF signals;

[0153] Each receiving device is equipped with two antennas to measure channel state information; the two antennas are the main receiving antennas Rx. pri and reference antenna Rx ref ;

[0154] Main receiving antenna Rx pri The transmitting antenna Tx is placed on both sides of the motion trajectory, and the reference antenna Rx is placed on the other side. ref The transmitting antenna Tx is placed on the same side of the trajectory.

[0155] Transmitting antenna Tx and reference antenna Rx ref There is a gap between them, and the line connecting them is parallel to the trajectory of motion;

[0156] Both the transmitting and receiving antennas are vertically polarized omnidirectional antennas, placed vertically to the ground.

[0157] In the above embodiments, signal processing is performed on the acquired CSI data to extract dynamic components, including:

[0158] Eliminate random phase shifts caused by clock asynchrony between transceiver devices;

[0159] Static elimination is performed on the phase-division signal to extract the dynamic component;

[0160] Amplitude calibration is performed on the dynamic components to eliminate amplitude deviations caused by the phase division operation.

[0161] In the above embodiments, the dynamic components and displacement function are substituted into the analytical solution of the contour function to obtain the amplitude of the contour function, thereby obtaining the contour of the target object, including:

[0162] Substitute the trajectory of the target object (displacement at different times) into the definition of the displacement function to calculate the displacement function of the target object;

[0163] Substitute the dynamic components and displacement function of the diffraction signal into the analytical solution of the profile function to obtain the amplitude of the profile function and thus the difference between the upper and lower boundary functions of the profile region.

[0164] For objects with a wide and flat bottom, the lower boundary is constant, and the difference between the upper and lower boundary functions is the desired object contour, thus obtaining the imaging result;

[0165] Median filtering was used to smooth the imaging results.

[0166] The system provided in this embodiment is used to execute the above-described method embodiments. For specific processes and details, please refer to the above embodiments, which will not be repeated here.

[0167] In one embodiment of the present invention, a computing device is provided, which can be a terminal and may include: a processor, a communication interface, memory, a display screen, and an input device. The processor, communication interface, and memory communicate with each other via a communication bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system and computer programs, which, when executed by the processor, implement the methods described in the above embodiments. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The communication interface is used for wired or wireless communication with external terminals. Wireless communication can be achieved through Wi-Fi, a management network, NFC (Near Field Communication), or other technologies. The display screen can be a liquid crystal display or an e-ink display. The input device can be a touch layer covering the display screen, or buttons, a trackball, or a touchpad mounted on the casing of the computing device, or an external keyboard, touchpad, or mouse. The processor can call logical instructions stored in the memory.

[0168] Furthermore, the logical instructions in the aforementioned memory can be implemented as software functional units and sold or used as independent products, and can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part 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 the present 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.

[0169] In one embodiment of the present invention, a computer program product is provided, the computer program product including a computer program stored on a non-transitory computer-readable storage medium, the computer program including program instructions, and when the program instructions are executed by a computer, the computer is able to perform the methods provided in the above-described method embodiments.

[0170] In one embodiment of the present invention, a non-transitory computer-readable storage medium is provided, which stores server instructions that cause a computer to perform the methods provided in the above embodiments.

[0171] The computer-readable storage medium provided in the above embodiments has a similar implementation principle and technical effect to the above method embodiments, and will not be described again here.

[0172] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0173] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0174] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0175] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for object imaging based on RF signal diffraction, characterized in that, include: Establish a model relating the diffraction signal between RF signal transceivers and the contour of the target object, and determine the positive relationship from the contour function and displacement function of the target object to the diffraction signal; Based on the relational model and using the inverse Fresnel transform, an analytical solution for the contour function of the target object is given given the diffraction signal and displacement function; CSI is acquired by RF signal transceiver equipment with separate transmit and receive settings, and the acquired CSI is processed to extract dynamic components. Substitute the dynamic components and displacement function into the analytical solution of the contour function to obtain the amplitude of the contour function and thus the contour of the target object. The relationship model between the diffraction signal and the contour of the target object is as follows: In the formula, For the dynamic components of the diffraction signal, This is the contour function of the target object. For any point on the outline of the target object displacement function, This represents the displacement of the target object along the X-axis. Given the diffraction signal and displacement function, provide an analytical solution for the contour function of the target object, including: estimating and eliminating the static component of the diffraction signal, obtaining the dynamic component of the diffraction signal, and using the dynamic component and displacement function to solve the contour function analytically. The analytical solution of the contour function is: In the formula, The total length of the displacement. For RF signal wavenumber, Pi ,in This represents the distance from the transmitting device's antenna to the X-axis. This represents the distance from the receiving device's antenna to the X-axis. For the dynamic components of the diffraction signal, Center of the target object The displacement function; The target object contour is obtained by substituting the dynamic components and displacement function into the analytical solution of the contour function to obtain the amplitude of the contour function. This includes: substituting the motion trajectory of the target object into the definition of the displacement function to calculate the displacement function of the target object; substituting the dynamic components of the diffraction signal and the displacement function into the analytical solution of the contour function to obtain the amplitude of the contour function and obtain the difference between the upper and lower boundary functions of the contour region; for objects with a wide and flat bottom, the lower boundary is constant, and the difference between the upper and lower boundary functions is the target object contour to obtain the imaging result; and median filtering is used to smooth the imaging result.

2. The object imaging method based on RF signal diffraction as described in claim 1, characterized in that, The arrangement of separate RF signal transceiver equipment includes: At least one pair of RF signal transceiver devices should be deployed, one as the transmitting device and the other as the receiving device for acquiring CSI. Each transmitting device is equipped with a transmitting antenna Tx to transmit RF signals; Each receiving device is equipped with two antennas to measure channel state information; the two antennas are the main receiving antennas Rx. pri and reference antenna Rx ref ; Main receiving antenna Rx pri The transmitting antenna Tx is placed on both sides of the motion trajectory, and the reference antenna Rx is placed on the other side. ref The transmitting antenna Tx is placed on the same side of the trajectory. Transmitting antenna Tx and reference antenna Rx ref There is a gap between them, and the line connecting them is parallel to the trajectory of motion; Both the transmitting and receiving antennas are vertically polarized omnidirectional antennas, placed vertically to the ground.

3. The object imaging method based on RF signal diffraction as described in claim 1, characterized in that, The acquired CSI signals are processed to extract dynamic components, including: Eliminate random phase shifts caused by clock asynchrony between transceiver devices; Static elimination is performed on the phase-division signal to extract the dynamic component; Amplitude calibration is performed on the dynamic components to eliminate amplitude deviations caused by the phase division operation.

4. An object imaging system based on RF signal diffraction, used to implement the object imaging method based on RF signal diffraction as described in any one of claims 1 to 3, characterized in that, include: The relational model construction module establishes a relational model between the diffraction signal and the contour of the target object between RF signal transceivers, and determines the positive relationship from the contour function and displacement function of the target object to the diffraction signal; The contour function solution module, based on the relational model and utilizing the inverse Fresnel transform, provides an analytical solution for the contour function of the target object given the diffraction signal and displacement function. The dynamic component extraction module uses a set of separate RF signal transceiver devices to collect CSI, performs signal processing on the collected CSI, and extracts the dynamic components. The target contour acquisition module substitutes the dynamic components and displacement function into the analytical solution of the contour function to obtain the amplitude of the contour function and thus the contour of the target object.

5. A computer-readable storage medium for storing one or more programs, characterized in that, The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform any of the methods described in claims 1 to 3.

6. A computing device, characterized in that, include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including instructions for performing any of the methods described in claims 1 to 3.

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