A method for generating target and environmental measurement situation based on multipath signals

Abstract

This invention discloses a target and environment measurement situation generation method based on multipath signals, applicable to non-line-of-sight detection. Addressing the limitations of existing technologies that rely on prior building layout information and are applicable to relatively simple and regular scenarios, this invention proposes a target and environment measurement situation generation method based on multipath signals using elliptical envelope approximation. First, the arrival delays of multipath signals with different periods are robustly and continuously correlated using a nearest neighbor algorithm. Second, the arrival delays corresponding to diffraction, primary reflection, and secondary reflection are identified and completed using a least-squares-based strategy. Then, based on the circular cross-location method, the arrival delays of diffraction and primary reflection are used to locate the obscured target, while the arrival delay corresponding to secondary reflection is used for elliptical envelope approximation to reconstruct the obscured building layout. This invention's method can estimate and reconstruct irregular, continuous obscured walls based on the obtained target location.

Description

Technical Field

[0001] This invention relates to the field of radar situational awareness technology, and in particular to a method for generating target and environmental situational awareness based on multipath signals. Background Technology

[0002] Non-line-of-sight (NLOS) detection, as a technique that can overcome the limitations of line-of-sight (LOS) detection, has significant research and application value. NLOS detection methods fully utilize the multipath propagation characteristics of electromagnetic waves for target detection, and numerous studies have demonstrated the feasibility of using multipath propagation for target detection.

[0003] The Technical University of Ilmanau in Germany tracked the detected multipath arrival time delay (ToA) based on the global nearest neighbor algorithm, and obtained the two-dimensional position of non-line-of-sight targets by intersecting the multipath trajectories corresponding to the diffraction path and the first-order reflection (R. Zetik, M. Eschrich, S. Jovanoska, et al., “Looking behind a corner using multipath-exploiting UWB radar,” IEEE Trans. Aerosp. Electron. Syst., vol. 51, no. 3, pp. 1916–1926, Jul. 2015). Using only ToA information undoubtedly ignores the phase characteristics carried by the signal. To address this, the University of Electronic Science and Technology of China used the Minimum Variance Distortionless Response (MVDR) algorithm to estimate the Direction of Arrivals (DoA) of multipath echoes and proposed a multipath identification strategy that combines ToA and DoA information (J. Chen, S. Guo, H. Luo, et al., “Non-line-of-sight multi-target localization algorithm for driver-assistance radar system,” IEEE Trans. Veh. Technol., vol. 72, no. 4, pp. 5332-5337, Dec. 2022). Furthermore, the literature (Z.Xu, S.Guo, J.Chen, et al., “Multi-domain features-based NLOS target localization method for MIMO UWB Radar,” IEEE Sensors J., vol.23, no.23, pp.29314-29322, Oct.2023) also makes full use of Doppler information and proposes a multipath identification strategy based on the range-Doppler (RD) topology. Based on the multipath sorting results and combined with DoA information, target localization is achieved.To better address the impact of rough walls and noise on ToA estimation, the University of Electronic Science and Technology of China (UESTC) used a back projection (BP) imaging algorithm to identify the ghost image corresponding to a single multipath event through matching, and then derived the target position through mirror symmetry (S.Li, S.Guo, J.Chen, et al., “Multiple targets lofcalization behind L-shaped corner via UWB radar,” IEEE Trans. Veh. Technol., vol.70, no.4, pp.3087–3100, Apr.2021).

[0004] However, the above methods all assume that the two-dimensional detection scene is known, which is impractical in practice. Without loss of generality, based on whether the radar direct signal is reachable, the building layout walls are divided into line-of-sight reflective surfaces and non-line-of-sight reflective surfaces. The estimation of line-of-sight reflective surfaces is relatively simple and can be achieved based on radar direct-line echoes and other auxiliary means. The University of Electronic Science and Technology of China used Hough transform to extract the shape and position of the line-of-sight walls (Z. Zhu, S. Guo, J. Chen, et al., “Non-line-of-sight targets localization algorithm via joint estimation of DoD and DoA,” IEEE Trans. Instrum. Meas., vol. 72, pp. 1-11, Oct. 2023). The National University of Defense Technology has achieved line-of-sight building layout information acquisition using lidar (H.Du, C.Fan, C.Cao, et al., “A novel NLOS target localization method with a synthetic bistatic MMW radar,” in Proc. IEEE 11th Sensor Array Multichannel Signal Process. Workshop (SAM), Hangzhou, China, Jun. 2020, pp. 1-5).

[0005] Estimating non-line-of-sight reflective surfaces is more complex and requires the assistance of multipath signals. The University of Electronic Science and Technology of China, assuming a straight non-line-of-sight corridor, proposed a joint estimation algorithm for non-line-of-sight channel width and non-line-of-sight target position based on the geometric distribution characteristics of multipath ghosting, the true target position, and the building layout (P.Wu, J.Chen, S.Guo, et al., “NLOS positioning for building layout and target based on association and hypothesis method,” IEEE Trans. Geosci. Remote Sens., vol.61, pp.1-13, Mar.2023). Furthermore, the literature (J. Chen, Y. Zhang, S. Guo, et al., “Joint estimation of NLOS building layout and targets via sparsity-driven approach,” IEEE Trans. Geosci. RemoteSens., vol. 60, pp. 1-13, Jun. 2022) presents a joint estimation of the tilt angle of the non-line-of-sight reflector and the target position based on the shape reconstruction group sparse algorithm and the particle swarm optimization algorithm.

[0006] In summary, existing non-line-of-sight reflective surface estimation algorithms only consider linear scenes, assuming the scene is a straight line. However, in real-world complex urban environments, building outlines are often complex and variable. Therefore, researching a target and environmental measurement situation generation method based on multipath signal utilization, capable of estimating and reconstructing unknown non-line-of-sight wall surfaces, is of significant research importance. Summary of the Invention

[0007] To address the issues of existing technologies that rely on prior building layout information and are applicable to relatively simple and rule-based scenarios, this invention proposes a target and environment measurement situation generation method based on multipath signals to achieve estimation and reconstruction of unknown non-line-of-sight walls.

[0008] The technical solution adopted in this invention is as follows:

[0009] A target and environment measurement situation generation method based on multipath signals is applied to a scenario with continuously moving non-line-of-sight targets. The scenario includes: two buildings, a concealed target, and a single-transmitter single-receiver radar. One building is an L-shaped wall, with the horizontal wall defined as the first wall and the vertical wall as the second wall. The other building is a linear wall, with its wall defined as the third wall. The second wall and the third wall are opposite each other, and the single-transmitter single-receiver radar is located on the same side of the first wall. The second wall is a concealed wall of unknown shape with non-line-of-sight, while the third wall is a line-of-sight wall. The concealed target (i.e., the non-line-of-sight target) is a moving single target located in the non-line-of-sight area formed by the second and third walls.

[0010] Perform the following target localization and building layout estimation in scenarios with continuously moving non-line-of-sight targets:

[0011] Step S1, Data Acquisition: Use a single-transmitter, single-receiver radar to acquire K (K≥2) cycles of echo data for a scene with continuously moving non-line-of-sight targets;

[0012] Step S2, Multipath Tracking: Extract the arrival delay (ToA) of the echo data collected in step S1, and correlate the multipath arrival delays of K cycles based on the nearest neighbor algorithm to obtain the multipath arrival delays of several multipaths in each cycle.

[0013] Step S3, Multipath Sorting: Based on the least squares method, the arrival delays τ of the multiple multipath paths obtained in step S2 are processed. n (k) Perform multipath sorting to identify or complete the arrival time delays corresponding to diffraction, primary reflection, and secondary reflection;

[0014] Step S4, Target Localization: Based on the arrival delay corresponding to the diffraction and first reflection obtained in step S3, the target localization is performed to obtain the position of the occluded target;

[0015] Step S5, Layout estimation: Based on the arrival delay corresponding to the secondary reflection obtained in step S3 and the position of the occlusion target obtained in step S4, the elliptical envelope approximation method is used to estimate the position of the secondary reflection point in order to reconstruct the shape of the occlusion wall.

[0016] This invention firstly and robustly correlates the arrival delays of multipath paths with different periods based on the nearest neighbor algorithm; secondly, the arrival delays corresponding to diffraction, primary reflection, and secondary reflection are identified and completed through a least squares-based strategy; then, based on the circular cross-location method, the arrival delays of multipath paths corresponding to diffraction and primary reflection are used to locate the occluded target, while the arrival delay corresponding to secondary reflection is used to approximate the elliptical envelope to reconstruct the layout of the occluded building.

[0017] Furthermore, step S2 specifically includes the following steps:

[0018] Step S201: Use a moving target indicator to eliminate the effects of static background echo and antenna coupling in the echo data;

[0019] Step S202: Extract the arrival delay from the echo data based on the constant false alarm rate detector, and store the arrival delay of the echo data for each cycle in ascending order in vector p. (k) In, that is This represents the arrival delay of the nth time obtained in the kth period, where n = 1, ..., N. k N k This represents the total arrival delay extracted in the k-th cycle;

[0020] Step S203: The multipath arrival delay of K cycles is equivalent to the one-dimensional motion of multiple targets, and the target is tracked based on the nearest neighbor algorithm to obtain the measurement associated with the track.

[0021] During tracking processing, for the j-th arrival delay observed in the k-th period... Its information regarding the i-th multipath track is as follows:

[0022]

[0023] Where H = [1, 0] T For the measurement matrix, State prediction for the i-th multipath track;

[0024] Step S204: Perform multipath tracking filtering on the multipath signal based on the specified track length threshold, and then obtain the time delay matrix M based on the multipath arrival time delay of the multipath signal at all time points after multipath tracking filtering. A :

[0025]

[0026] in, Let N be the arrival delay of the nth multipath in the kth period, N be the total arrival delay in each period after multipath tracking filtering (i.e., the number of tracks after multipath tracking filtering), k be the period index, and the multipath index n = 1, ..., N be the multipath delay vector of the nth multipath.

[0027] Furthermore, in step S3, based on the specific linear relationship between the multipaths, a specific strategy is formulated using the least squares method to identify or complete the ToA of diffraction, primary reflection, and secondary reflection paths. This specifically includes the following steps:

[0028] Step S301: Check if N / 3≥1. If not, building layout estimation cannot be achieved, and multipath sorting ends directly. If yes, initialize the number of multipath combinations χ that meets the conditions. S =0, and set σ T After obtaining the value, proceed to step S302;

[0029] Step S302, from the time delay matrix M A Three multipath delay vectors were repeatedly selected from the Chinese and African samples and arranged in ascending order as p. n1 p n2 p n3 And arrange them into a matrix A = [p n1 p n3 ] and vector b = p n2 ;

[0030] Step S303: Calculate the least squares solution x = (A) based on the least squares method. T A) -1 A T b, Determine whether ||x-α|| < σ T Check if the condition is met. If it is met, proceed to step S304; otherwise, return to step S302. Where the auxiliary quantity α = [1 / 2, 1 / 2] T ;

[0031] Step S304, the currently selected multipath delay vector p n1 and p n3 Treat them as basis vectors and store them in matrix M B In the middle, the multipath combination number χ S Increment by 1;

[0032] Detect whether χ S =2 or all If all filtering combinations have been traversed, proceed to step S305; otherwise, return to step S302.

[0033] Step S305, if χ S =2, then matrix M B The column vectors in the image are arranged in ascending order to obtain the arrival time delay vectors corresponding to the diffraction path, the first reflection path, and the second reflection path;

[0034] If χ S =1, then there are at least 4 multipaths corresponding to two-way multipaths. The arrival delay vector corresponding to the secondary reflection path is derived based on the arrival delay relationship between the base multipath and the combined multipath.

[0035] If χ S =0, then it is considered that there are at least 3 corresponding multipaths. Based on the arrival time delay relationship between the base multipath and combined multipath, the arrival time delay vectors corresponding to the diffraction and secondary reflection paths are derived; where... This represents the two-way multipath propagation captured by the receiving antenna of a single-transmitter, single-receiver radar, with propagation path indices i,j∈{0,1,2}. Propagation path 0 refers to the electromagnetic wave being diffracted at the corner of an L-shaped wall before propagating to the concealed target; propagation path 1 refers to the electromagnetic wave being reflected once on a third wall before propagating to the concealed target; propagation path 2 refers to the electromagnetic wave being reflected once on a third wall and then reflected a second time on a second wall before propagating to the concealed target, and the two-way multipath propagation where i=j. This is called a two-way multipath with i ≠ j, also known as a base multipath. This is called a combined multipath.

[0036] Furthermore, step S4 specifically includes:

[0037] Define R1 as the radar mirror point and C as the corner of the L-shaped wall. Then, the concealed target Q is located on both a circle with the corner C as the center and ||CQ|| as the radius and a circle with R1 as the center and ||R1Q|| as the radius. Here, the radar mirror point R1 is the mirror symmetric position of the single-transmitter single-receiver radar about the third wall. The position of the concealed target Q is obtained based on the circular intersection algorithm.

[0038] Furthermore, in step S5, based on the coupling relationship between the target and the building layout contained in the multipath signal, the shape of the occluding wall (second wall) is dynamically reconstructed by sensing the moving occluding target.

[0039] Furthermore, step S5 specifically includes:

[0040] Let S represent the secondary reflection point on the shielding wall, which lies on an ellipse with the concealed target Q and the radar mirror point R1 as foci and the secondary reflection path length (||R1S||+||SQ||) as the major axis; where the radar mirror point R1 is the mirror symmetric position of the single-transmitter single-receiver radar about the third wall.

[0041] The outline shape of the occlusion wall is reconstructed from the elliptical family envelope generated by the continuously moving occlusion target.

[0042] Furthermore, by discretizing the envelope of the elliptic family into the common tangent of two adjacent ellipses, the two corresponding tangent points can be approximated as the positions of the secondary reflection points S. The outline shape of the shielding wall can be reconstructed using the elliptic envelope approximation method.

[0043] The technical solution provided by this invention brings at least the following beneficial effects:

[0044] (1) The multipath sorting strategy based on least squares can identify or even complete the arrival delay ToA corresponding to diffraction, primary reflection and secondary reflection paths;

[0045] (2) Based on the elliptical envelope approximation, the reflection point located on the non-line-of-sight wall is approximately estimated, and then the non-line-of-sight wall is reconstructed;

[0046] (3) This invention can be applied to fields such as disaster relief and environmental sensing. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram illustrating the process of a target and environment measurement situation generation method based on multipath signals proposed in an embodiment of the present invention;

[0049] Figure 2 A diagram illustrating the multipath propagation model under irregular wall conditions;

[0050] Figure 3 Schematic diagram of target localization principle for masking;

[0051] Figure 4 The results show the target localization and building layout estimation in three different non-line-of-sight wall environments.

[0052] in, Figure 4 (4-a) is a straight wall scene; (4-b) is a curved concave wall; (4-c) is a sudden concave wall.

[0053] Figure 5 Estimate lateral deviation of walls in three different non-visual-range wall environments;

[0054] Figure 6 This is a diagram of a mutational concavity experiment.

[0055] Figure 7 for Figure 6 Multipath tracking results in the experimental scenario shown;

[0056] Figure 8 for Figure 7 The results of target localization and building layout estimation in the experimental scenario shown;

[0057] in, Figure 8 (8-a) represents the experimental results; (8-b) represents the numerical simulation results; and (8-c) represents the estimated lateral bias. Detailed Implementation

[0058] 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 described in detail and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Generally, the components of the embodiments of the present invention described and shown in the accompanying drawings can be arranged and designed using different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of the present invention.

[0059] See Figure 1 This invention proposes a method for generating target and environmental measurement situations based on multipath signals, which includes the following steps:

[0060] Step 1: Signal Analysis

[0061] A scene with an irregular, non-line-of-sight reflective wall, such as Figure 2 As shown in the diagram, Wall-3 of Building 2 and Wall-1 of Building 1 are located within line-of-sight, and their positions and shapes can be obtained through direct reflected echoes from the walls. However, continuously moving targets and Wall-2 of Building 1 are located outside line-of-sight, and their relevant information cannot be obtained using traditional line-of-sight-based radar detection methods.

[0062] A portable single-transmitter, single-receiver radar R = [x R ,y R ] T Placed on one side of Wall-1, the target and radar are not visible to each other. In this configuration, the radar detects the target through multipath propagation of electromagnetic waves rather than through direct line-of-sight signals. Based on the ray tracing model, the one-way electromagnetic propagation path from the transmitting antenna to the target can be classified into three types, see [link to relevant documentation]. Figure 2 Specifically, it is as follows:

[0063] 1) Path-0: The electromagnetic wave first diffracts at the corner and then propagates to the target, denoted as Path-0.

[0064] 2) Path-1: The electromagnetic wave propagates to the target location after being reflected once on Wall-3, denoted as Path-1.

[0065] 3) Path-2: After the electromagnetic wave is reflected once on Wall-3, it is reflected a second time on Wall-2 and propagates to the target. This is denoted as Path-2.

[0066] Electromagnetic waves experience significant signal attenuation after multiple reflections; therefore, multipath propagation beyond secondary reflections is ignored. If the building surface provides sufficiently strong specular reflection in the considered frequency band (1–3 GHz), then the mirror-symmetric position of the radar is:

[0067] R1 = [x R1 ,y R1 ] T =[2x w3 -x R ,y R ] T (1)

[0068] Where, x w3 Let x be the x-coordinate of Wall-3. The relationship between the arrival delays for the three types of one-way multipath routes is as follows:

[0069]

[0070] Where c is the speed of light, and R1 is the mirror-symmetric position of the radar about wall 3. In the above formula, the value on the left side of the equation can be obtained through signal processing, while the coordinates of the target Q and the secondary reflection point S are unknown and need to be solved. Since the problem under consideration is two-dimensional, the coordinates of Q can be obtained by solving the formula related to τ0 and τ1. Geometrically, the target Q is located simultaneously in a circle with corner C as the center and ||CQ|| as the radius and a circle with R1 as the center and ||R1Q|| as the radius. The sum of ||R1S|| and ||SQ|| is a constant value τ2c. Therefore, the secondary reflection point S is located on an ellipse with Q and R1 as foci and the secondary reflection path length (||R1S|| + ||SQ||) as the major axis. Therefore, this embodiment of the invention can estimate the shielding wall by fully utilizing the target and building layout information contained in the multipath.

[0071] The two-way multipath captured by the receiving antenna is a pairwise combination of the three types of multipath mentioned above. The corresponding multipath arrival delay is τ. ij The following relationship exists:

[0072]

[0073] It is easy to see from the above equation that the received multipath paths all exist in the space spanned by the diffraction, primary reflection, and secondary reflection paths. Therefore, it is reasonable to consider... i=j is called the basis multipath, and For i ≠ j, it is a combined multipath. Correspondingly, the arrival delay τ of a two-way multipath for i = j is... ij This is called the base course multipath arrival delay, such as τ. 00 τ 11 τ 22 The arrival delay τ of two-way multipath propagation with i ≠ jij This is called the combined multipath arrival delay, such as τ. 01 τ 02 τ 12 It is worth mentioning that, because the propagation attenuation of the primary reflection path is greater than that of diffraction and secondary reflection paths, the energy contained in the primary reflection multipath is greater, for example... and

[0074] Step 2: Multipath Tracking

[0075] 2.1 The effects of static background echo and antenna coupling in the received echo signal are eliminated by using Moving Target Indicator (MTI) technology.

[0076] 2.2 Extracting the Time of Arrival (ToA) from the echoes using a Constant False Alarm Rate (CFAR) detector. Considering that the radar acquires echoes for K cycles, the ToA of the echo data in the k-th cycle is stored in ascending order in vector p. (k) middle:

[0077]

[0078] in, This represents the arrival delay of the nth time extracted in the kth period, while N... k This represents the total arrival delay extracted in the k-th cycle;

[0079] 2.3 The multipath ToA changes of all K cycles are equivalent to the one-dimensional motion of multiple targets. The nearest neighbor algorithm is used to track them. As a result, residual clutter will be further filtered out, and prediction of some missing multipaths can be achieved.

[0080] Specifically, the multi-radial quantity p extracted from the k-th frame (k) Since the measurement vector is denoted as , the information about the observed j-th multipath delay value and the i-th multipath track is:

[0081]

[0082] Where H = [1, 0] T For the measurement matrix, This is the state prediction for the i-th multipath track.

[0083] Define S(k) as the new information covariance matrix, then the Mahalanobis distance can be calculated as:

[0084]

[0085] The basic idea of ​​the nearest neighbor algorithm is to calculate the Mahalanobis distance and select the measurement with the smallest Mahalanobis distance as the measurement associated with the track.

[0086] 2.4 Since noise-generated measurements do not occur in every cycle, their corresponding tracking results often present short tracks, while multipath measurements will exist for most of the time, and missing parts can be predicted and filled in by the multipath tracking algorithm. Therefore, tracks with a length less than K will be discarded, and the number of remaining tracks is represented by N;

[0087] 2.5 The multipath signals obtained after multipath tracking filtering at all time points are stored in a matrix:

[0088]

[0089] in, This represents the arrival delay of the nth multipath in the kth period.

[0090] Step 3: Multipath sorting:

[0091] As can be seen from equation (3), there is a definite linear relationship between the time delay values ​​of the base multipath and the combined multipath:

[0092]

[0093] Where the auxiliary quantity α = [1 / 2, 1 / 2] T .

[0094] Define p n1 p n2 p n3 For three from M A The selected non-repeating column vectors, i.e., the selected multi-radial quantities, arranged in ascending order, then have a total of There are several combinations, where C represents the combination. Then, matrix A = [p] n1 p n3 ] and vector b = p n2 .

[0095] Equation (8) can be transformed into the form Ax = b. Theoretically, if x = α holds, then p n1 and p n3 It happens to be a multipath base, while p n2 This is a combination of multipaths. The closer x and α are, the higher the probability that the two vectors in the corresponding matrix A form a basis multipath. In the case of multiple periods, the number of equations (the number of rows in matrix A) exceeds the number of unknowns (the number of columns in matrix A), making the solution to x an overdetermined problem. Using the least squares method, x is obtained as follows:

[0096] x=(A T A) -1 A T b (9)

[0097] However, due to target expansion and measurement errors, the solved x is close to, but not strictly equal to, α. Therefore, this embodiment of the invention considers that ||x-α||<σ T In multipath combinations, p n1 and p n3 This represents the base multipath. Where σ T In this embodiment, a relatively small empirical threshold σ is determined by analyzing simulation and measured data. T The value is set to 0.05, typically the threshold σ. T The magnitude can be set to 10. -1 ~10 -2 Therefore, theoretically, all basis multipaths can be obtained by finding only two sets of x that satisfy the conditions.

[0098] However, in real-world environments, radar echoes often fail to contain all six multipath types mentioned above. In such cases, the missing multipath types can be supplemented using the following steps:

[0099] 3.1 Initialize parameter χ S =0, which means that ||x-α||<σ T The number of multipath combinations. If N / 3≥1, then proceed to step 3.2; otherwise, if the number of multipaths is too small to achieve building layout estimation, the multipath completion step ends directly.

[0100] 3.2 From M A Three non-repeating multi-radial quantities are selected and arranged in ascending order as p. n1 p n2 p n3 And arrange them into a matrix A = [p n1 p n3 ] and vector b = p n2 ;

[0101] 3.3 Calculation of x = (A) based on the least squares method T A) -1 A T b, Determine whether ||x-α|| < σ T Check if the condition is met. If it is, proceed to step 3.4; otherwise, proceed to step 3.2.

[0102] 3.4 It is believed that the selected p n1 and p n3 Generate basis vectors and store them in matrix M B In the middle, χ S =χ S +1, if χ S =2 or all If all possible cases have been traversed, proceed to step 3.5; otherwise, proceed to step 3.2.

[0103] 3.5 If χ S =2, then the arrival time delay vectors corresponding to the diffraction path, the first reflection path, and the second reflection path can be obtained by changing matrix M. B The column vectors in the array are obtained by arranging them in ascending order;

[0104] If χ S =1, then it is considered that there are at least 4 corresponding multipaths. Based on the relationship between the base multipath and the combined multipath, the arrival delay vector corresponding to the secondary reflection path can be derived.

[0105] If χ S =0, then it is considered that there are at least 3 corresponding multipaths. Based on the relationship between the base multipath and the combined multipath, the arrival time delay vectors corresponding to the diffraction and secondary reflection paths can be derived.

[0106] Step 4: Target Positioning:

[0107] like Figure 3 As shown, the target's position can be determined by two circles: the target is located at the intersection of a circle with corner C as its center and ||CQ|| as its radius, and a circle with R1 as its center and ||R1Q|| as its radius.

[0108] Let the length of line segment CR1 be L, and its slope be l. CR The slope of line segment QE (the perpendicular line from target Q to line segment CR1) is l. QE Then we have:

[0109]

[0110] By the Pythagorean theorem, we can obtain the following relationship:

[0111]

[0112] Therefore, the length of line segment CE can be calculated as follows:

[0113]

[0114] The coordinates of the perpendicular point E can be expressed as:

[0115]

[0116] Based on geometric relationships, we obtain:

[0117]

[0118] The length of line segment EF can then be expressed as:

[0119]

[0120] The position of target Q is:

[0121]

[0122] Step 5: Layout estimation:

[0123] The principle of building layout estimation is as follows: the reflection point S lies on an ellipse with foci Q and R1 and the secondary reflection path length (||R1S|| + ||SQ||) as its major axis. The building layout can be obtained by inverting the reflection point on Wall-2. However, an ellipse has an optical property: light emitted from one focus and incident on the ellipse will be reflected through the other focus. Therefore, directly solving for the position of the reflection point S is impractical.

[0124] Consider a moving target; the envelope of the family of ellipses it forms can outline the contour of Wall-2. However, due to the uncertainty of the target's motion, the envelope of the family of ellipses is difficult to solve. The envelope of the family of ellipses can be discretized into the common tangent of adjacent ellipses. Therefore, the position of the reflection point can be approximately equivalent to the position of the tangent point. The specific calculation method is as follows:

[0125] Let *a* represent the semi-major axis of the ellipse, and *b* represent the semi-minor axis, which can be calculated from the arrival time delays corresponding to the first and second reflection paths, respectively. Let (x0, y0) represent the center coordinates of the ellipse, and θ represent the inclination angle of the major axis (counterclockwise is positive), then the coefficients of the general equation of the ellipse are:

[0126]

[0127] in,

[0128] Then two adjacent ellipses can be represented as

[0129]

[0130] In this context, the subscripts 1 and 2 of the coefficients of each ellipse equation serve as separators between two adjacent ellipses.

[0131] Consider two cases. First, when the slope of the common tangent exists, its equation is y = lx + m, which can be simplified to:

[0132]

[0133] in,

[0134] When the above equation has multiple roots, it means that the common tangent is tangent to both ellipses simultaneously. Therefore, according to the discriminant for multiple roots, we get:

[0135]

[0136] Solving the above equation yields the slope l and the intercept m. Therefore, the x-coordinates of the two tangent points are:

[0137]

[0138] Substituting the x-coordinate into the equation y = lx + m, we can obtain its corresponding y-coordinate.

[0139] In the second case, considering that the slope of the common tangent is infinite, i.e., its equation is x = h, then the equations of the two adjacent ellipses are:

[0140]

[0141] Similarly, the discriminant of the above equation is:

[0142]

[0143] Solving the above equation yields h, which represents the x-coordinate of the two tangent points. Therefore, its y-coordinate is:

[0144]

[0145] The (x1, y1) and (x2, y2) obtained through the above steps are the coordinates of the tangent point, which are then equivalent to the positions of the reflection points. After estimating all reflection points, a Hamper filter is used to remove obvious outliers from the results, and a Kalman filter is used to smooth the results, thereby obtaining the target location and building layout estimation results.

[0146] The effectiveness of the embodiments of the present invention is further illustrated by the following simulation and experimental verification:

[0147] Simulation results:

[0148] Without loss of generality, consider a scenario with three L-shaped building corners, such as... Figure 4 As shown. Among them, Figure 4In scenario (4-a), Wall-2 is a conventional straight wall, used to test the applicability of the algorithm in a typical scenario. In scenario (4-b), Wall-2 is a curved, concave wall, used to demonstrate the universality of the proposed algorithm in the case of any continuous wall. In scenario (4-c), Wall-2 is concave by 0.2m at a position between 5 and 7m on the vertical axis, used to simulate door frames / windows in a real-world corridor. In the non-line-of-sight channel, a cylinder with a radius of 0.1m is used to simulate a target that moves along a curve. To detect non-line-of-sight targets and perform scenario estimation, a single-transmitter, single-receiver radar is placed on the same side as Wall-1, at coordinates (1,1)m. The above scenarios are simulated using gprMax electromagnetic simulation software, with the transmitted waveform having a center frequency of 1.5GHz and a bandwidth of 1GHz in stepped frequencies.

[0149] Figure 4 The results of target localization and building layout estimation obtained by the method proposed in the embodiments of the present invention in the above three scenarios are shown. As can be seen from the figures, the estimated positions of non-line-of-sight targets match the actual positions well. Most of the estimated secondary reflection points are distributed on Wall-2, effectively outlining the contour of Wall-2. However, for the concave-convex wall scenario, such as... Figure 4 As shown in (4-c), the estimated reflection point position is significantly deviated at the abrupt concavity in the wall. This is because the multipath propagation is more complex in the abrupt change area of ​​the building, and the abrupt change in the multipath signal delay leads to correlation errors in the multipath tracking process.

[0150] Considering the target is a cylinder with a radius of 0.1m, which allows for some expansion, and that electromagnetic propagation in real-world environments often does not strictly follow ray tracing, the theoretical location of the secondary reflection point is often difficult to determine. To evaluate the performance of the building layout estimation, the lateral deviation between the estimated reflection point and the actual wall is used to measure the performance. Figure 5 As shown, the estimation deviations are all less than 0.25m, which is within an acceptable range.

[0151] Actual test results:

[0152] Experiments containing concave structures, such as Figure 6 As shown. Corner C is located at (2.0, 2.0)m, and the x-coordinate of Wall-3 is 4.38m. There is a recessed door on Wall-2, 0.14m inward, 1.85m from the corner, with a width of 1.15m. The selected ultra-wideband radar has its transmitting antenna positioned at (1.05, 0.94)m and its receiving antenna positioned at (1.3, 0.66)m. A non-line-of-sight target moves along a straight line from (2.85, 3.4)m to (2.85, 5.9)m.

[0153] The method proposed in this embodiment of the invention is used to track multipath in multi-period range images, and the results are as follows: Figure 7 The figure is shown by the black dashed line. The white box indicates the multipath fluctuations caused by the indentation of the wall. As can be seen from the figure, the method proposed in this embodiment can effectively correlate the arrival delays of multiple cycles of multipaths and, to a certain extent, complete the multipaths missing in some cycles.

[0154] The target location and building layout estimation results obtained by the method proposed in the embodiments of the present invention are as follows: Figure 8 As shown in (8-a), it is clear that the target localization results all revolve around the actual trajectory, and the inverted reflection points roughly outline the shape of the wall. Based on the experimental parameters, the numerical simulation inversion results are shown in (8-b). Comparing the experimental results with the numerical simulation results, it can be seen that the estimated reflection points and the theoretical reflection points are basically consistent in their distribution locations.

[0155] To measure the deviation between the estimated building layout and the actual wall, the calculated deviation between the abscissa of the second-order reflection point and the abscissa of the actual wall is shown in (8-c). The maximum deviation is approximately 0.16m, which is within an acceptable range. Furthermore, the maximum error occurs at a concave area within the wall, consistent with the simulation results. This corroborates the accuracy of the wall inversion.

[0156] 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.

[0157] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for generating a target and environment measurement situation based on multipath signals, applied to a scenario with a continuously moving non-line-of-sight target, the scenario comprising: Two building bodies, a concealed target and a single-transmitting single-receiving radar, one of the building bodies is a L-shaped wall, the horizontal wall of the L-shaped wall is defined as a first wall, and the vertical wall is defined as a second wall; the other building body is a linear wall, and the wall is defined as a third wall, wherein the second wall is opposite to the third wall, the single-transmitting single-receiving radar is arranged on the same side of the first wall, the second wall is a non-line-of-sight shielding wall with an unknown shape, and the third wall is a line-of-sight wall, and the concealed target is a moving single target, which is located in a non-line-of-sight area formed by the second wall and the third wall; and the method comprises the following steps: Step S1, collecting K periods of echo data of the scene with the continuous motion non-line-of-sight target by using the single-transmitting single-receiving radar; Step S2, multi-path tracking: extracting the arrival time delay of the echo data collected in step S1, and associating the multi-path arrival time delay in each period based on a nearest neighbor algorithm to obtain a plurality of multi-path arrival time delays in each period; Step S3, multipath sorting: based on the least square method, the multiple multipath arrival time delays obtained in step S2 The multipath sorting is performed, and the arrival time delays corresponding to the diffraction, the first reflection and the second reflection are identified or completed. Step S4, target positioning: performing target positioning on the arrival time delays corresponding to the diffraction and the first reflection obtained in step S3 based on a circle intersection algorithm, and obtaining the position of the shielding target; Step S5, layout estimation: based on the arrival time delay corresponding to the second reflection obtained in step S3 and the position of the shielding target obtained in step S4, an elliptical envelope approximation solving method is used to estimate the position of the second reflection point to reconstruct the shape of the shielding wall; Step S3 specifically comprises the following steps: Step S301, detecting whether , if not, the building layout estimation cannot be realized, and the multipath sorting is directly ended; if yes, the number of multipath combinations satisfying the condition is initialized , and the value of is set, and then step S302 is executed; wherein, N is the total number of arrival time delays of each period after multipath tracking filtering. Step S302, from the delay matrix Three multipath delay vectors are screened out from the non-repeated delay matrix, and arranged in ascending order as , , , and the matrix and the vector are composed. Step S303: Calculate the least squares solution based on the least squares method. ,judge If the condition is met, proceed to step S304; otherwise, return to step S302. (The auxiliary quantity is not specified in the original text.) ; Step S304, the current screened multipath delay vector and is regarded as a base vector and stored in a matrix , and the multipath combination number is increased by 1; detecting whether or all the screening combinations have been traversed, and if so, executing step S305; otherwise, returning to step S302; Step S305, if , the column vectors in matrix are arranged in ascending order to obtain the arrival time delay vectors corresponding to the diffraction path, the first reflection path and the second reflection path. If , there are at least 4 multipath corresponding double-path multipath , , , , the arrival time delay vector corresponding to the secondary reflection path is derived based on the relationship between the arrival time delay of the base multipath and the combined multipath. If , it is considered that at least 3 multipath paths correspond to , , , the arrival time delay vectors corresponding to the diffraction and secondary reflection paths are derived based on the relationship between the base multipath and the combined multipath; wherein, represents the two-way multipath captured by the receiving antenna of the single-transmit-single-receive radar, and the propagation path index , wherein the propagation path 0 refers to the diffraction of the electromagnetic wave at the corner of the L-shaped wall and then propagating to the hidden target; the propagation path 1 refers to the first reflection of the electromagnetic wave on the third wall and then propagating to the hidden target; the propagation path 2 refers to the first reflection of the electromagnetic wave on the third wall, and then the second reflection on the second wall to propagate to the hidden target, and the two-way multipath is called the base multipath, the two-way multipath is called the combined multipath.

2. The method of claim 1, wherein, Step S2 specifically comprises the following steps: Step S201, using a moving target indicator to eliminate the influence of static background echoes and antenna coupling in the echo data; Step S202, extracting the arrival time delay in the echo data based on the constant false alarm detector, and storing the arrival time delay of each period of echo data in ascending order in a vector , that is , , wherein n represents the n th arrival time delay extracted in the k th period, and , , wherein k represents the total number of arrival time delays extracted in the k th period. Step S203, equivalent the multi-path arrival time delays in K periods to one-dimensional motion of a plurality of targets, and track the targets based on a nearest neighbor algorithm to obtain measurements associated with the tracks; In the tracking process, for the jth observed arrival time delay in the kth period The innovation with the ith multipath track is: wherein, is a measurement matrix, is a state prediction for the i-th multipath track; Step S204, performing multipath tracking filtering on the multipath signals based on the specified track length threshold, and obtaining a time delay matrix based on the multipath arrival time delays of the multipath signals at all time points after multipath tracking filtering : wherein is the multipath delay of the nth multipath in the kth period, k is the period index, and n is the multipath index , the multipath delay vector of the nth multipath .

3. The method of claim 2, wherein, In step S203, the tracking based on the nearest neighbor algorithm is specifically: Definitions is the innovation covariance matrix according to the i-th multipath track The Mahalanobis distance is calculated as: ; Selecting the measurement with the smallest Mahalanobis distance as the measurement associated with the track.

4. The method of claim 1, wherein, Threshold value Magnitude is set to .

5. The method of claim 1, wherein, Step S4 specifically comprises: Definitions R is a radar mirror point, C is a corner of a L-shaped wall, and the hidden target Q is located on a circle with the corner C as the center and R1 as the radius and on a circle with R1 as the center and R2 as the radius; wherein the radar mirror point R1 is a mirror symmetric position of a single-transmitting single-receiving radar relative to the third wall. Obtaining the position of the concealed target Q based on the circle intersection algorithm.

6. The method of claim 5, wherein, In step S4, the position of the concealed target Q is specifically: Definition of a line segment of length L and slope l CR with two circle radii ; Definition E is the hidden target Q on the line segment The upper vertical point, then the line segment QE slope ; Based on the length of the line segment CE , the position coordinates of the corner C , the position coordinates of the radar mirror point R1 Calculate the position coordinates of the perpendicular point E: where, ; According to the coordinates of the vertical point E, the length of the segment QE and the slope the coordinates of the position of the hidden target Q are calculated: .

7. The method of claim 1, wherein, In step S5, based on the coupling relationship between the target and the building layout contained in the multi-path signal, the shielding wall shape is dynamically reconstructed by perceiving the moving shielding target.

8. The method of claim 1, wherein, Step S5 specifically comprises: S represents a secondary reflection point on the shielding wall, which is located on an ellipse with the hidden target Q and the radar mirror point R1 as the foci, and the length of the secondary reflection path is the length of the major axis of the ellipse; wherein the radar mirror point R1 is the mirror symmetric position of the single-transmitting and single-receiving radar with respect to the third wall. Based on the elliptical envelope of the shielding target with continuous motion, the contour shape of the shielding wall is reconstructed.

9. The method of claim 8, wherein, In step S5, the elliptical envelope is discretized into the common tangent line of two adjacent ellipses, and the two tangent points corresponding to the common tangent line are approximately equivalent to the positions of the second reflection points S, and the elliptical envelope approximation solving method is used to reconstruct the contour shape of the shielding wall.

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