An indoor multipath detection and positioning method of an external radiation source radar based on a 5G signal

Abstract

The present application relates to a kind of based on 5G signal's external radiation source radar indoor multipath detection and positioning method, 5G signal in indoor environment is used as the radiation source signal and reference signal of radar, specific indoor scene is abstracted, the length range of multipath in each case is obtained, then the target echo signal obtained in indoor scene is handled using signal processing mode such as clutter suppression, R-D processing, CFAR detection, then the peak value corresponding to first diffraction and first reflection in the result after CFAR processing is found, the position information of target is obtained by calculating the two-dimensional coordinates of target in combination with scene information, to realize the tracking and positioning of target.The indoor multipath detection and positioning method of the present application uses indoor 5G micro base station as radiation source to detect and locate target, simplifies design scheme, saves cost;And scene dependence is low, the required conditions for positioning can be measured on site, or calculated according to environment, scene adaptability is strong, and it is not necessary to transform due to the transformation of scene.

Description

Technical Field

[0001] This invention belongs to the field of radar technology, specifically relating to an indoor multipath detection and positioning method for external radiation sources based on 5G signals. Background Technology

[0002] External radiation sources possess advantages over active radars because they do not actively emit signals but instead utilize existing radiation signals in space to detect targets. Firstly, the lack of signal emission makes external radiation source radars difficult for enemy radars to detect, and the enemy cannot jam them after intercepting their signals, thus enhancing their stealth and anti-jamming capabilities. Secondly, passively receiving signals means that external radiation source radars lack a transmission system, resulting in lower system complexity and cost.

[0003] Currently, the main signal sources for external radiation source systems are digital television, radio, and LTE signals. However, with the widespread adoption of 5G signals, research on 5G signals as external radiation sources has attracted considerable attention within the industry. Due to its high frequency band (FR1 is the mainstream communication band, with a spectrum range of 410MHz to 7125MHz, and FR2 is the millimeter wave band, with a spectrum range of 24GHz to 52GHz), 5G signals experience significantly increased propagation loss and a reduced radiation range. Therefore, indoor applications of 5G signals are a research hotspot.

[0004] The complex indoor environment leads to frequent NLOS (Non-Line-of-Sight) situations, and multipath detection is the main method to solve the NLOS target problem. However, current research is basically based on integrated radar systems, where the radar transmitter emits a signal, which is then received by the receiver along the original path after multipath propagation and target reflection. Moreover, most methods require detailed prior environmental information, and the processing methods must be changed when the environment changes, resulting in poor system adaptability. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a method for indoor multipath detection and localization of external radiation sources using 5G signal-based radar. The technical problem to be solved by this invention is achieved through the following technical solution:

[0006] This invention provides a method for indoor multipath detection and localization of external radiation sources using radar based on 5G signals, comprising:

[0007] Step 1: Acquire 5G signals in the indoor environment and use them as the source and reference signals for radar radiation;

[0008] Step 2: Abstract the geometric configuration of the obstacles in the indoor environment, construct a coordinate system based on the positions of the base station and the receiver, divide the indoor environment into the line-of-sight range and non-line-of-sight range of the receiver, and obtain the length range of the multipath required for target localization in the line-of-sight range and non-line-of-sight range respectively.

[0009] Step 3: Obtain the target echo signal of the target, and perform static clutter suppression processing, coherent accumulation processing and constant false alarm rate detection on the target echo signal in sequence to obtain several multipath information;

[0010] Step 4: Based on the multipath information and the length range of the multipath required for target localization in both line-of-sight and non-line-of-sight situations, allocate the multipaths and extract the length of the first diffraction path and the length of the first reflection path containing the target information.

[0011] Step 5: Calculate the target's position information based on the constructed coordinate system, the length of the first diffraction path, and the length of the first reflection path, so as to achieve target tracking and positioning.

[0012] In one embodiment of the present invention, in step 2,

[0013] With the location of the base station as the origin, the straight line between the base station and the receiver is taken as the x-axis of the coordinate system;

[0014] For targets located in the indoor environment

[0015] r d ≤r r ;

[0016] r min ≥|TC|+|RC|;

[0017] In the formula, r d r represents the first diffraction path length of the target. r The length of the target's reflection path in one pass, r min The shortest multipath length carrying target information is represented by T, where T represents the base station location, C represents the diffraction point where the base station's transmitted signal is diffracted on the obstacle, |TC| represents the distance between the base station and the diffraction point, R represents the receiver location, and |RC| represents the distance between the receiver and the diffraction point.

[0018] When the target is within the line-of-sight range of the receiver,

[0019] r max ≤|TC|+2|CE|+|RD|;

[0020] When the target is within the non-line-of-sight range of the receiver.

[0021] r max ≤2(|tF|+|FR|);

[0022] In the formula, r max The longest multipath length carrying target information is represented by E, which represents the farthest reflection point of the base station's transmitted signal on the obstacle. |CE| represents the distance between the diffraction point and the farthest reflection point. D represents the intersection point of the base station's transmitted signal with the obstacle after reflection at the farthest reflection point E. |RD| represents the distance between the receiver and the intersection point. t represents the target position. F represents the reflection point of the echo signal reflected by the target on the obstacle. |tF| represents the distance between the target and the reflection point. |FR| represents the distance between the reflection point and the receiver.

[0023] In one embodiment of the present invention, step 3 includes:

[0024] Step 3.1: Obtain the target echo signal of the target, perform static clutter suppression processing on the target echo signal to filter out the static clutter reflected by the obstacle, and obtain the clutter suppression signal;

[0025] Step 3.2: Perform coherent accumulation processing on the clutter suppression signal and the reference signal to obtain the range-Doppler matrix;

[0026] Step 3.3: Use constant false alarm rate (CFAR) detection to filter out false targets in the range-Doppler matrix to obtain several multipath information.

[0027] In one embodiment of the present invention, step 4 includes:

[0028] Step 4.1: Based on several multipath information, obtain a range-Doppler spectrum, wherein the first peak in the range-Doppler spectrum represents a first diffraction path containing target information, and the peak with the highest amplitude after the first diffraction path represents a first reflection path containing target information.

[0029] Step 4.2: Obtain the first diffraction path length and the first reflection path length based on the peak information of the distance-Doppler spectrum.

[0030] In one embodiment of the present invention, step 5 includes:

[0031] Based on the first diffraction path length and the first reflection path length, the target's position information is calculated by solving the intersection equation of the ellipse. Kalman filtering is then used to correct the target's position information to obtain the final observation result, thereby achieving target tracking and localization.

[0032] When the target is within the line-of-sight range of the receiver, the equation of the intersection point of the ellipse is as follows:

[0033]

[0034]

[0035] When the target is located outside the line-of-sight range of the receiver, the equation of the intersection point of the ellipse is as follows:

[0036]

[0037]

[0038] In the formula, x C y C Let x and y represent the x and y coordinates of the diffraction point in the coordinate system, respectively. t y t These represent the x and y coordinates of the target in the coordinate system, respectively. R L1 represents the horizontal coordinate of the receiver in the coordinate system, and L2 represents the distance between the receiver and the obstacle from which the base station's transmitted signal is reflected.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] 1. The indoor multipath detection and positioning method of the external radiation source radar based on 5G signal of the present invention is a multipath detection method under the external radiation source system. That is, it does not require the design of an integrated 5G signal transmission and reception radar, but uses an indoor 5G micro base station as the radiation source detection and positioning target, which simplifies the design scheme and saves costs.

[0041] 2. The indoor multipath detection and positioning method for external radiation sources based on 5G signals of the present invention expands the multipath detection scenario of external radiation sources. Based on the characteristics of separate transmission and reception, it considers line-of-sight and non-line-of-sight situations based on the receiver, enriching the multipath detection system. Moreover, it has low scene dependence, and the positioning conditions can be measured on site or calculated based on the environment. It has strong scene adaptability and does not need to be converted due to scene changes.

[0042] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of an indoor multipath detection and positioning method for external radiation sources based on 5G signals provided in an embodiment of the present invention;

[0044] Figure 2This is a scene diagram of an indoor environment with abstracted obstacles, provided by an embodiment of the present invention.

[0045] Figure 3 This is a schematic diagram of coordinate axis establishment and multipath propagation path provided by an embodiment of the present invention;

[0046] Figure 4 This is a multipath allocation diagram provided in an embodiment of the present invention;

[0047] Figure 5 This is a distance-Doppler spectrum provided in an embodiment of the present invention;

[0048] Figure 6 This is a tracking result diagram of the target using Kalman filtering provided in an embodiment of the present invention. Detailed Implementation

[0049] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following describes in detail, with reference to the accompanying drawings and specific embodiments, a method for indoor multipath detection and positioning of external radiation sources based on 5G signals proposed in accordance with the present invention.

[0050] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0051] Example 1

[0052] Please see Figure 1 , Figure 1 This is a schematic diagram of an indoor multipath detection and localization method for external radiation sources based on 5G signals provided by an embodiment of the present invention. As shown in the figure, the indoor multipath detection and localization method for external radiation sources based on 5G signals in this embodiment includes:

[0053] Step 1: Acquire 5G signals in the indoor environment and use them as the source and reference signals for radar radiation;

[0054] Specifically, 5G signals in an indoor environment can be physical downlink signals transmitted using indoor 5G micro base stations.

[0055] In this embodiment, the downlink channel of the 5G base station is constructed according to the specifications and performance requirements in the 3GPP 5G white paper, as well as the physical layer construction of the 5G downlink channel, including modulation scheme, frame structure, PDSCH, PDCCH, DM-RS, SSB, etc. This downlink channel is used as the signal source and reference signal for the external radiation source radar. The expression of the constructed 5G signal is as follows:

[0056]

[0057] In the formula, N represents the number of subcarriers, s k (k = 0, 1, 2, ..., N-1) represents the communication information allocated to each subcarrier after modulation, T is the duration of an OFDM symbol, and f k Let denot be the carrier frequency of the k-th subcarrier, and rect(t) = 1, |t| ≤ T be a rectangular window function.

[0058] Step 2: Abstract the geometric configuration of the obstacles in the indoor environment, construct a coordinate system based on the positions of the base station and the receiver, divide the indoor environment into the line-of-sight range and non-line-of-sight range of the receiver, and obtain the length range of the multipath required for target localization in the line-of-sight range and non-line-of-sight range respectively.

[0059] Please refer to the above. Figure 2 and Figure 3 , Figure 2 This is an abstract scene diagram of an indoor environment provided by an embodiment of the present invention. The diagram includes two obstacles: obstacle A is an object where the base station's transmitted signal is diffracted, and obstacle B is an object where the base station's transmitted signal and the echo signal reflected from the target are reflected. In the diagram, points T and R represent the base station position and the receiver position, respectively, point t represents the target position, point C represents the diffraction point where the base station's transmitted signal is diffracted on obstacle A, point E represents the farthest reflection point where the base station's transmitted signal is reflected on obstacle B, L1 represents the distance between obstacle A and obstacle B, and L2 represents the distance between obstacle B and the receiver.

[0060] Furthermore, in this embodiment, the indoor environment is divided into the receiver's line-of-sight range and non-line-of-sight range by combining the geometric information of the indoor environment. Specifically, as shown... Figure 2 As shown, the area to the upper left of the extension of the RC line is the receiver's line-of-sight range, and the area to the lower right is the receiver's non-line-of-sight range. The triangular area formed by points C and D is the reflection area, and the triangular area formed by the intersection of point EC, the extension of the RC line, and obstacle B is the diffraction area.

[0061] Furthermore, in conjunction with see Figure 3 , Figure 3This is a schematic diagram of coordinate axis establishment and multipath propagation path provided by an embodiment of the present invention. Figure 3 Figure (a) in the diagram shows the line-of-sight situation of the receiver. Figure 3 Figure (b) illustrates the non-line-of-sight (LOS) case of the receiver. As shown in the figure, in this embodiment, the location of the base station is taken as the origin, and the straight line between the base station and the receiver is taken as the x-axis of the coordinate system. For the LOS case of the receiver, the first diffraction path is T→C→t→R, and the first reflection path is T→G→t→R; for the LOS case of the receiver, the first diffraction path is T→C→t→F→R, and the first reflection path is T→G→t→F→R.

[0062] For targets located in indoor environments, such as Figure 3 In the coordinate system shown, a quantitative analysis was conducted on the range of multipath (including reflection and diffraction paths) lengths required for target localization in both line-of-sight and non-line-of-sight scenarios. The following relationship was found to exist regardless of whether the target is within the receiver's line-of-sight or non-line-of-sight range:

[0063] r d ≤r r (2);

[0064] r min ≥|TC|+|RC| (3);

[0065] In the formula, r d r represents the first diffraction path length of the target. r The length of the target's reflection path in one pass, r min The shortest multipath length carrying target information (that is, the shortest path length among the paths carrying target information, which can be a diffraction path or a reflection path) is represented by point T, point C is represented by point C, which is the diffraction point where the base station's transmitted signal is diffracted on the obstacle (obstacle A), |TC| is represented by the distance between the base station and the diffraction point, point R is represented by the receiver location, and |RC| is represented by the distance between the receiver and the diffraction point.

[0066] When the target is within the receiver's line-of-sight range,

[0067] r max ≤|TC|+2|CE|+|RD| (4);

[0068] When the target is within the receiver's non-line-of-sight range

[0069] r max ≤2(|tF|+|FR|) (5);

[0070] In the formula, r maxThe longest multipath length carrying target information (i.e., the longest path length among the paths carrying target information, which can be either a diffraction path or a reflection path) is represented by: point E represents the farthest reflection point of the base station's transmitted signal on the obstacle (obstacle B); |CE| represents the distance between the diffraction point and the farthest reflection point; point D represents the intersection of the base station's transmitted signal after reflection at the farthest reflection point E and the obstacle (obstacle A); |RD| represents the distance between the receiver and the intersection point; point t represents the target position; point F represents the reflection point of the echo signal reflected by the target on the obstacle (obstacle B); |tF| represents the distance between the target and the reflection point; and |FR| represents the distance between the reflection point and the receiver.

[0071] It should be noted that in actual application, the target position represented by point t is unknown. When the target t moves to the critical point of the intersection of the diffraction area and the reflection area, the reflection path reaches its maximum value. This critical point can be obtained according to geometric relationships. Therefore, in this embodiment, the value of |tF| in formula (5) is the distance between the target and the reflection point F when the target moves to the critical point of the intersection of the diffraction area and the reflection area. At this time, the above unknown quantities can be obtained by actual measurement of the field environment or by calculation of coordinates.

[0072] The above analysis yields the multipath length range of the first diffraction and first reflection required for carrying target information and positioning. Based on this range, near-field static clutter and other secondary or multiple reflection paths carrying target information can be further eliminated in simulation and practical applications.

[0073] Step 3: Acquire the target echo signal and perform static clutter suppression, coherent accumulation and constant false alarm rate detection on the target echo signal in sequence to obtain several multipath information.

[0074] Specifically, step 3 includes:

[0075] Step 3.1: Acquire the target echo signal, perform static clutter suppression processing on the target echo signal to filter out static clutter reflected from obstacles, and obtain the clutter suppression signal;

[0076] Since the receiver receives not only the target echo signal but also clutter signals reflected by obstacles A and B, and because the primary diffraction and primary reflection signals suffer significant energy loss after being diffracted or reflected by obstacles, the energy of the clutter signals is often much higher than that of the diffracted and reflected signals containing target information. Therefore, these strong clutter signals need to be suppressed before detecting the target. In this embodiment, an open-loop ECA clutter suppression algorithm is used to filter out static clutter reflected by obstacles. The specific process is as follows:

[0077] (1) The subspace constructed using the reference signal and its time delay through a sliding method is represented by the following equation:

[0078]

[0079] In the formula, S ref (n) represents the reference signal, where n = 1, 2, ..., N, N represents the length of the reference signal, and L represents the set time delay.

[0080] (2) The main purpose of the ECA clutter suppression algorithm is to find the projection coefficients of the echo signal in the subspace constructed by the reference signal. The projection coefficients can be solved by the following optimization problem:

[0081]

[0082] In the formula, S echo Let V represent the echo signal received by the receiver, containing clutter, and let W represent the constructed reference signal delay subspace. This is a convex optimization problem, and the projection coefficients W = (V... H V) -1 V H S echo .

[0083] (3) After obtaining the projection coefficients, the echo signal and the reference signal subspace are weighted and subtracted to obtain the clutter-suppressed echo signal, i.e.:

[0084] S rem =S echo -VW=S echo -V(V H V) -1 V H S echo (8);

[0085] In the formula, S rem This represents the clutter suppression signal after filtering out static clutter.

[0086] Step 3.2: Perform coherent accumulation processing on the clutter-suppressed signal and the reference signal to obtain the range-Doppler matrix;

[0087] After ECA clutter suppression processing, although the clutter in the echo signal is basically eliminated, the energy of the first diffraction and first reflection signals in the remaining echo signal (clutter-suppressed signal) is still very weak, lower than that of the noise signal. This will cause the target to be unable to appear on the noise platform. Therefore, it is necessary to perform two-dimensional coherent accumulation between the clutter-suppressed signal and the reference signal to enhance the energy of the first diffraction and reflection signals and improve the signal-to-noise ratio.

[0088] In this embodiment, the expression for range-Doppler coherent accumulation is:

[0089]

[0090] In the formula, ΔT represents the coherent accumulation time, and A i τ represents the complex envelope of the multipath signal in the signal after clutter suppression. i Let f represent the time delay of the i-th multipath. di Let τ represent the Doppler frequency shift of the i-th multipath, i = 0, 1, ..., M, where M represents the number of multipaths, B represents the complex envelope of the reference signal, and τ represents the frequency shift of the i-th multipath. d This indicates the delay at the receiving station.

[0091] The specific implementation process of range-Doppler coherence is as follows: First, the reference signal is conjugate, and then multiplied by the clutter suppression signal vector. To reduce computational complexity, the result of the multiplication is decimated by a factor of K before the FFT (Fast Fourier Transform), and anti-aliasing filtering is performed to prevent spectral aliasing caused by decimation. After decimation, the number of points in the FFT becomes 1 / K times the original, significantly reducing the computational complexity of the FFT. After FFT processing, a range-Doppler vector of one range cell is obtained. Then, the reference signal is delayed by one range cell, and the above operation is repeated. This yields the range-Doppler matrix of the clutter suppression signal and the reference signal, in which the range and Doppler information of each multipath are contained.

[0092] Step 3.3: Use constant false alarm rate (CFAR) detection to filter out false targets in the range-Doppler matrix and obtain several multipath information.

[0093] After clutter suppression and range-Doppler processing, the echo signal yields a range-Doppler matrix containing information from various multipath paths. Extracting the information of the true target from this matrix and filtering out false targets requires constant false alarm rate (CFAR) detection. The core idea of ​​CFAR is to set threshold values, classifying points greater than the threshold as targets and those less than the threshold as noise or false targets.

[0094] In this embodiment, a fast threshold detection method is used, that is, the threshold value is related to each unit to be detected and changes with the changes of the detection units, which is highly adaptable.

[0095] Step 4: Based on several multipath information and the length range of the multipath required for target localization in both line-of-sight and non-line-of-sight situations, allocate the multipaths and extract the length of the first diffraction path and the length of the first reflection path containing the target information.

[0096] Specifically, step 4 includes:

[0097] Step 4.1: Based on several multipath information, obtain the range-Doppler spectrum. The first peak in the range-Doppler spectrum represents a diffraction path containing target information, and the peak with the highest amplitude after the first diffraction path represents a reflection path containing target information.

[0098] Step 4.2: Obtain the first diffraction path length and the first reflection path length based on the peak information of the distance-Doppler spectrum.

[0099] In this embodiment, after steps 1-3, information on each multipath is obtained. Based on the multipath length range obtained in step 2, the approximate range unit where the multipath exists is determined. Since static clutter is filtered out after step 3, and the first diffraction path is the shortest among the remaining multipaths, it can be determined that the first peak in the range-Doppler spectrum represents the first diffraction path. Because each reflection after passing an obstacle causes signal energy loss, the peak with the highest amplitude after the diffraction path is the first reflection path, while other multipaths containing target information are secondary or multiple reflection echoes. This determines the multipath allocation, such as... Figure 4 As shown, Figure 4 This is a multipath allocation map provided in an embodiment of the present invention. Figure 4 Figure (a) in the diagram shows the line-of-sight situation of the receiver. Figure 4 Figure (b) shows the non-line-of-sight case of the receiver. After allocating the first diffraction path and the first reflection path, the length of the first diffraction path and the length of the first reflection path can be obtained from the peak information of the range-Doppler spectrum.

[0100] Step 5: Based on the constructed coordinate system and the lengths of the first diffraction path and the first reflection path, calculate the target's position information to achieve target tracking and positioning.

[0101] Specifically, step 5 includes:

[0102] Based on the first diffraction path length and the first reflection path length, the target's position information is calculated by solving the intersection equation of the ellipse. Kalman filtering is then used to correct the target's position information to obtain the final observation result, thereby achieving target tracking and localization.

[0103] When the target is within the line-of-sight range of the receiver, the equation of the intersection point of the ellipse is as follows:

[0104]

[0105]

[0106] When the target is located outside the line-of-sight range of the receiver, the equation of the intersection point of the ellipse is as follows:

[0107]

[0108]

[0109] In the formula, x C y C Let x and y represent the x and y coordinates of the diffraction point in the coordinate system, respectively. t y t These represent the x and y coordinates of the target in the coordinate system, respectively. R L1 represents the horizontal coordinate of the receiver in the coordinate system, and L2 represents the distance between the receiver and the obstacle (obstacle B) where the base station's transmitted signal is reflected.

[0110] It should be noted that the calculated coordinates may be negative. Based on the scenario, negative coordinates indicate the target is at line-of-sight of the 5G base station, thus allowing us to exclude unreasonable coordinates. Even after excluding line-of-sight coordinates, the coordinates calculated from the multipath length still contain errors. The main cause of these errors is the range resolution issue in range-Doppler processing. Therefore, the classic Kalman filter algorithm is used to correct the target's position information to obtain the final observation result, enabling target tracking and localization.

[0111] The indoor multipath detection and localization method for external radiation source radar based on 5G signals in this embodiment is a multipath detection method under the external radiation source system. That is, it does not require the design of an integrated 5G signal transmission and reception radar, but uses indoor 5G micro base stations as radiation source detection and localization targets, which simplifies the design scheme and saves costs.

[0112] The indoor multipath detection and positioning method for external radiation sources based on 5G signals in this embodiment expands the multipath detection scenarios for external radiation sources. Based on the characteristics of separate transmission and reception, it considers line-of-sight and non-line-of-sight scenarios based on the receiver, enriching the multipath detection system. Moreover, it has low scenario dependence, and the positioning conditions can be measured on-site or calculated based on the environment. It has strong scenario adaptability and does not need to be converted due to changes in the scenario.

[0113] Example 2

[0114] This embodiment illustrates the effectiveness of the method in Embodiment 1 through simulation experiments.

[0115] 1) Experimental conditions

[0116] Specific experimental scenarios are as follows: Figure 2As shown, the signal processing platform in this embodiment is MATLAB. The multipath detection method is verified using a simulated 5G downlink channel. The signal frequency band is FR1, the bandwidth is 100MHz, the subcarrier spacing is 30kHz, and the coherence accumulation time is 10ms. In the scenario, the base station coordinates are set to (0,0), the receiving station coordinates to (-2,0), target 1 coordinates to (4,3) with a velocity of 1, and target 2 coordinates to (9,4) with a velocity of 0.5. Target 1 is placed within the line-of-sight range of the receiver, and target 2 is placed outside the line-of-sight range of the receiver.

[0117] 2) Experiment Content

[0118] The experiment can be divided into the following three parts:

[0119] ① Based on scene analysis, target 1 is located at the receiver's line-of-sight position. The received target echo signal is sequentially processed through clutter suppression, and coherent accumulation processing is used to enhance the signal-to-noise ratio of each multipath. After CFAR detection, the results are plotted on a three-dimensional coordinate system consisting of range (X-axis), velocity (Y-axis), and normalized amplitude (Z-axis), while identifying the more prominent peaks (i.e., information from each detected multipath). Subsequently, multipaths are assigned according to range cells in the result graph, and then... Figure 3 Using the coordinate system in Figure (a), calculate the coordinates (location information) of target 1.

[0120] ② Based on scene analysis, target 2 is located outside the receiver's line-of-sight position. The received target echo signal is sequentially processed with clutter suppression, and coherent accumulation processing is used to enhance the signal-to-noise ratio of each multipath. After CFAR detection, the results are plotted in a three-dimensional coordinate system consisting of range (X-axis), velocity (Y-axis), and normalized amplitude (Z-axis), while identifying the more prominent peaks (i.e., information from each detected multipath). Subsequently, multipaths are assigned according to range cells in the result graph, and then... Figure 3 Using the coordinate system in Figure (b), calculate the coordinates (location information) of target 2.

[0121] ③ The calculated coordinates sometimes turn negative. Based on the given scenario, negative coordinates indicate the target is at line-of-sight with the 5G base station, thus eliminating unreasonable coordinates. Even after eliminating line-of-sight coordinates, the coordinates calculated from the multipath length still contain errors. The main cause of these errors is the range resolution issue in range-Doppler processing. Therefore, the classic Kalman filter algorithm can be used to correct the calculated target position information and track the target trajectory.

[0122] 3) Analysis of experimental results

[0123] Please refer to the above. Figure 4 and Figure 5 , Figure 4 This is a multipath allocation map provided in an embodiment of the present invention. Figure 5 This is a distance-Doppler spectrum provided in an embodiment of the present invention.

[0124] like Figure 4 Figure (a) in the figure shows the multipath assignment of target 1. Figure 5 Figure (a) shows the first diffraction path length and the first reflection path length of target 1. It can be seen that the multipath length range obtained in step 2 can eliminate unfiltered static clutter and multiple reflection paths. Based on the characteristics of diffraction and reflection paths, the first peak represents the diffraction path, and the subsequent maximum peak represents the reflection path. After obtaining the first diffraction path length and the first reflection path length, the coordinates of target 1 are calculated to be (3.3, 2.9).

[0125] like Figure 4 Figure (b) shows the multipath allocation for target 2. Figure 5 Figure (b) shows the first diffraction path length and the first reflection path length of target 2. Similarly, the coordinates of target 2 can be obtained as (8.7, 4.5).

[0126] The simulation results above show that the calculated coordinates have an error of approximately 0.5m. The main reason for this error is the distance resolution. Kalman filtering is used to correct the coordinates. Please refer to [link / reference]. Figure 6 , Figure 6 This is a tracking result diagram of a target using Kalman filtering provided in an embodiment of the present invention. As can be seen from the diagram, the result after Kalman filtering is closer to the actual target trajectory.

[0127] Traditional integrated radars suffer from diffraction and reflection signals returning along the transmission path during multipath detection. This embodiment proposes a multipath detection scenario utilizing an external radiation source system based on 5G signals. It explores the multipath propagation process when the transmit and receive are separated, identifying a primary diffraction path and a primary reflection path in the results, and calculating the target's position using their lengths. Furthermore, this method requires minimal prior information, and the positioning conditions can be measured on-site or calculated from coordinates, thus demonstrating strong adaptability.

[0128] It should be noted that, in this document, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device comprising said element. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0129] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for indoor multipath detection and localization of external radiation sources based on 5G signals using radar, characterized in that, include: Step 1: Acquire 5G signals in the indoor environment and use them as the source and reference signals for radar radiation; Step 2: Abstract the geometric configuration of the obstacles in the indoor environment, construct a coordinate system based on the positions of the base station and the receiver, divide the indoor environment into the line-of-sight range and non-line-of-sight range of the receiver, and obtain the length range of the multipath required for target localization in the line-of-sight range and non-line-of-sight range respectively. Step 3: Obtain the target echo signal of the target, and perform static clutter suppression processing, coherent accumulation processing and constant false alarm rate detection on the target echo signal in sequence to obtain several multipath information; Step 4: Based on the multipath information and the length range of the multipath required for target localization in both line-of-sight and non-line-of-sight situations, allocate the multipaths and extract the length of the first diffraction path and the length of the first reflection path containing the target information. Step 5: Calculate the target's position information based on the constructed coordinate system, the length of the first diffraction path, and the length of the first reflection path, so as to achieve target tracking and positioning; In step 2, With the location of the base station as the origin, the straight line between the base station and the receiver is taken as the x-axis of the coordinate system; For targets located in the indoor environment ； ； In the formula, This represents the length of the target's first diffraction path. This indicates the length of the target's reflection path in one pass. Indicates the shortest multipath length carrying target information. T The dot represents the location of the base station. C The dot represents the diffraction point where the base station's transmitted signal is diffracted on the obstacle. This indicates the distance between the base station and the diffraction point. R The dot indicates the receiver position. This indicates the distance between the receiver and the diffraction point; When the target is within the line-of-sight range of the receiver, ； When the target is within the non-line-of-sight range of the receiver. ； In the formula, Indicates the longest multipath length carrying target information. The dot represents the farthest point where the base station's transmitted signal is reflected from an obstacle. This represents the distance between the diffraction point and the farthest reflection point. D The dot represents the farthest reflection point of the signal transmitted by the base station. E The point where the reflection intersects with the obstacle. This indicates the distance between the receiver and the intersection point. t The dot represents the target location. The dot represents the point on the obstacle where the echo signal reflected from the target is reflected. This indicates the distance between the target and the reflection point. This indicates the distance between the reflection point and the receiver.

2. The indoor multipath detection and localization method for external radiation sources based on 5G signals according to claim 1, characterized in that, Step 3 includes: Step 3.1: Obtain the target echo signal of the target, perform static clutter suppression processing on the target echo signal to filter out the static clutter reflected by the obstacle, and obtain the clutter suppression signal; Step 3.2: Perform coherent accumulation processing on the clutter suppression signal and the reference signal to obtain the range-Doppler matrix; Step 3.3: Use constant false alarm rate (CFAR) detection to filter out false targets in the range-Doppler matrix to obtain several multipath information.

3. The indoor multipath detection and localization method for external radiation sources based on 5G signals according to claim 1, characterized in that, Step 4 includes: Step 4.1: Based on several multipath information, obtain a range-Doppler spectrum, wherein the first peak in the range-Doppler spectrum represents a first diffraction path containing target information, and the peak with the highest amplitude after the first diffraction path represents a first reflection path containing target information. Step 4.2: Obtain the first diffraction path length and the first reflection path length based on the peak information of the distance-Doppler spectrum.

4. The indoor multipath detection and localization method for external radiation sources based on 5G signals according to claim 1, characterized in that, Step 5 includes: Based on the first diffraction path length and the first reflection path length, the target's position information is calculated by solving the intersection equation of the ellipse. Kalman filtering is then used to correct the target's position information to obtain the final observation result, thereby achieving target tracking and localization. When the target is within the line-of-sight range of the receiver, the equation of the intersection point of the ellipse is as follows: ； ； When the target is located outside the line-of-sight range of the receiver, the equation of the intersection point of the ellipse is as follows: ； ； In the formula, , These represent the x and y coordinates of the diffraction point in the coordinate system. , These represent the x and y coordinates of the target in the coordinate system, respectively. This represents the receiver's x-coordinate in the coordinate system. This indicates the distance between the obstacle from which the base station's transmitted signal is reflected and the receiver.

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