A method for locating targets in non-line-of-sight areas using frequency modulated continuous wave radar

Abstract

The present invention discloses a positioning method for locating targets in a non-line-of-sight area using a frequency modulated continuous wave radar. The method comprises the following steps: detecting the non-line-of-sight area by scanning a frequency modulated continuous wave radar beam to obtain radar data; performing discrete Fourier transform in a distance direction on the radar data to obtain distance-Fourier transform maps of different frames; performing environmental noise suppression processing on the distance-Fourier transform maps of different frames to obtain noise-reduced distance-Fourier transform maps of different frames; randomly selecting a frame and determining and sorting the distance information of all static targets in the noise-reduced distance-Fourier transform map; determining an estimated target coordinate position and a length of a combined reflection path from the distance information of the static target; determining the length of the combined reflection path based on the estimated target coordinate position and a main reflection path; and determining the estimated target coordinate position as the actual target coordinate position if the length of the reflection path matches the distance information of the static target.

Description

Technical Field

[0001] The invention belongs to the field of frequency modulated continuous wave radar signal processing, and in particular relates to a positioning method for locating a target in a non-line-of-sight area by using a frequency modulated continuous wave radar. Background Art

[0002] Using millimeter-wave radar to detect targets in non-line-of-sight areas is expected to play an important role in many tasks such as search and rescue, firefighting, autonomous driving, and counter-terrorism. In non-line-of-sight areas, the propagation of the detection electromagnetic waves emitted by the radar and the target echoes are subject to complex multipath effects. How to quickly and accurately achieve target positioning is a difficult problem.

[0003] For the detection and positioning of hidden targets in non-line-of-sight multipath environments, some solutions have been proposed for different radar systems at home and abroad.

[0004] Based on prior knowledge of scenes and geometric optics, M. Gustafsson and others from the Swedish Defense Research Institute proposed an algorithm that uses X-band radar multipath propagation to locate static objects behind corners.

[0005] R. Zetik et al. from the Technical University of Ilmenau in Germany described a method for one-dimensional localization of moving targets in shadowed areas using ultra-wideband radar. As a follow-up to this work, the team obtained the two-dimensional localization of the target on the ground from the path equations of the diffraction path and the combination of the main reflection path and the diffraction path.

[0006] Songlin Li from the University of Electronic Science and Technology of China proposed a matching-based ultra-wideband radar imaging algorithm for target detection in the non-line-of-sight area after an L-shaped corner with complex multipath ghost signals. The positions of multiple targets are obtained through the imaging algorithm.

[0007] The K.Thai research team of the French Aerospace Laboratory also proposed the use of corner radar for target detection, which can obtain diffraction and secondary reflection (or high-order) multipath information to achieve target positioning.

[0008] For millimeter-wave radar detection, Huagui Du et al. from the National University of Defense Technology proposed a detection and positioning algorithm based on the time of arrival (TOA) and angle of arrival (AOA) of multipath echoes;

[0009] F. Muhammad et al. from the Shenzhen Institutes of Advanced Technology of the Chinese Academy of Sciences proposed a target positioning algorithm based on phase comparison, which utilizes the multipath phase difference between multiple channels of millimeter-wave radar.

[0010] N. Scheiner et al. from Mercedes-Benz proposed a new method for joint non-line-of-sight detection and tracking of obscured targets using automotive Doppler radar.

[0011] However, the above methods require prior information about the structural geometric parameters of the non-line-of-sight detection scene, which limits the real-time application of non-line-of-sight multipath positioning detection in actual complex environments. Summary of the Invention

[0012] In view of this, the main object of the present invention is to provide a positioning method for locating targets in a non-line-of-sight area using a frequency modulated continuous wave radar.

[0013] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0014] An embodiment of the present invention provides a method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar. The method comprises:

[0015] The non-line-of-sight area is detected by frequency modulated continuous wave radar beam scanning to obtain radar data of different frames;

[0016] Perform discrete Fourier transform in the distance direction on radar data of different frames to obtain range-Fourier transform graphs of different frames;

[0017] Performing environmental noise suppression processing on the distance-Fourier transform images of the different frames to obtain noise-reduced distance-Fourier transform images of the different frames;

[0018] Randomly select a frame of denoised distance-Fourier transform image;

[0019] Determine the distance information r of all static targets in the noise-reduced distance-Fourier transform image i ′={r1′,r′2,r′3,...} and sort;

[0020] Determining an estimated target coordinate position and a length of a combined reflection path from the distance information of the static target;

[0021] Determine the length of the combined reflection path according to the estimated target coordinate position and the main reflection path;

[0022] If the length of the reflection path matches the distance information of the static target, the estimated target coordinate position is the actual target coordinate position.

[0023] In the above solution, the distance information r of all static targets in the noise-reduced distance-Fourier transform image is determined. i ′={r1′,r′2,r′3,...} and sort them, specifically: define the accumulator A corresponding to different distance directions i ={a1,a2,..,a M}, traverse the distance peaks corresponding to different Chirps, and add 1 to the accumulator corresponding to the distance peak, set a suitable threshold s, and filter out those that are greater than the threshold and are within the boundary distance range (r min ,r max ) in the accumulator f Ai , the accumulator f Ai Sort in descending order according to the value, obtain the distance information of all static targets within the search range and add the accumulator f Ai Sort in descending order according to the value, and obtain the distance information r of all static targets within the search range. i ′={r1′,r′2,r′3,...}.

[0024] In the above solution, the estimated target coordinate position and the length of the combined reflection path are determined in the distance information of the static target, specifically: in the distance information r of all static targets i The largest value r1′ among ′={r1′,r′2,r′3,...} is assumed to be the main reflection path, and the azimuth angle θ1 corresponds to A si The maximum angle peak and the distance relationship of the main reflection path are used to determine the estimated target coordinate position; then, the secondary reflection path r2 and the azimuth angle θ2 are determined by the estimated target coordinate position and the distance relationship of the main reflection path; finally, the length of the combined reflection path is determined according to the main reflection path r1 and the secondary reflection path r2.

[0025] In the above scheme, the azimuth angle θ1 corresponds to A si The maximum angular peak of is obtained by performing horizontal scanning by rotating the radar system in steps of 2° to obtain the amplitude values ​​at different angles, A si ={a s1 ,a s2 ,a s3 ,...,a sn}, find the azimuth angle θ1 corresponding to A si The maximum angle peak.

[0026] In the above scheme, the azimuth angle θ1 corresponds to A si The maximum angle peak value and the distance relationship of the main reflection path are used to determine the estimated target coordinate position, specifically: the estimated target coordinate position (x p ,y p ):

[0027] In the above solution, the secondary reflection path r2 and the azimuth angle θ2 are determined by the estimated target coordinate position and the distance relationship of the primary reflection path, specifically: Among them, L1 is the distance between the antenna and Wall-2, L3 is the distance between the millimeter wave radar antenna and the diffraction angle, (x p ,y p ) is the target coordinate position.

[0028] In the above solution, the length of the combined reflection path is determined according to the primary reflection path r1 and the secondary reflection path r2, specifically:

[0029] In the above solution, if the length of the reflection path can match the distance information of the static target, then the estimated target coordinate position is the actual target coordinate position, specifically: verify the distance information r of the static target i r′={r1′,r′2,r′3,...} i ′ whether r2 and r c , if they exist, r1 and the corresponding angle r1 are determined, and the target coordinate position is estimated successfully.

[0030] In the above solution, the method further includes continuing to determine the distance information r of the static target if the length of the reflection path does not match the distance information of the static target. i r′={r1′,r′2,r′3,...} i ' is empty, if not empty, from r i Delete r1′ from ′ and continue searching. Otherwise, reselect a frame of denoised distance-Fourier transform image.

[0031] Compared with the existing technology, the present invention uses frequency modulated continuous wave radar beam scanning to detect non-line-of-sight areas. Through radar beam scanning, echo information is recorded and analyzed to establish a "path dictionary". The NLOS multipath target search and position estimation algorithm (NLOS-mTSPE) is directly used to search the "path dictionary" to locate the target in the non-line-of-sight area. Without the need to obtain the geometric parameters of the scene in advance, the position information of the target object can be accurately obtained from the radar data measured on site. This greatly expands the application of non-line-of-sight multipath positioning detection in actual complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings described herein are used to further understand the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0033] Figure 1 A flowchart of a method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar is provided for an embodiment of the present invention.

[0034] Figure 2 An embodiment of the present invention provides a radar non-line-of-sight observation scene diagram in a positioning method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar.

[0035] Figure 3 An embodiment of the present invention provides a typical propagation path of electromagnetic waves in an L-shaped corner area in a positioning method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar.

[0036] Figure 4 An embodiment of the present invention provides an equivalent virtual detectable area of ​​a primary reflection and a secondary reflection in a positioning method for positioning a target in a non-line-of-sight area using a frequency modulated continuous wave radar.

[0037] Figure 5 The present invention provides an embodiment of a method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar and a processing flow of an NLOS-mTSPE algorithm.

[0038] In the figure: (100) distance FFT; (101) background subtraction; (102) randomly select data frame; (103) traverse the distance bin, corresponding to A i Add 1; (104)r min <Distance(f Ai >s) <r max ; (105) sort in descending order f Ai , calculate r i ′, assuming r1=r1′; (106) Rotate the radar to find θ1; (107) Calculate (x p ,y p ),r2,θ2,r c ;(108) judge r2,r c , whether the conditions are met; (109) judge r i ’ is empty; (110) remove r1’. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of the present invention, it should be understood that the terms "upper", "lower", "left", "right", "inner", "outer", etc. indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0041] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, article, or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, article, or device comprising the element.

[0042] The present invention uses a frequency-modulated continuous wave radar to perform beam scanning on the non-line-of-sight detection area, and records and analyzes the echo information to establish a "path dictionary". It does not need to obtain the geometric parameters of the scene in advance. The "path dictionary" can be searched from the radar data measured on site to accurately obtain the location information of the target object. This greatly expands the real-time application scenarios of non-line-of-sight multipath positioning detection in actual complex environments.

[0043] The present invention does not rely on any prior information about the geometry of the environment. The required information is the distance between the millimeter-wave radar antenna and the diffraction angle (L3), and the distances between the antenna and the walls that constitute the non-line-of-sight environment (L1 and L2); these distance information can be measured on site by rotating the radar antenna at the appropriate angle, so that the radar operator does not have to be exposed to any possible threats in the detection area.

[0044] Assuming that walls produce specular reflections of electromagnetic waves, targets will produce specular, retroreflection, and diffuse reflections. Since diffuse reflections are typically very weak, the target's retroreflection plays a key role in the received radar signal. Therefore, distance, angle, and Doppler velocity information can be obtained from the reflected signal of a hidden target, which is used to estimate the target's position. Under the illumination of electromagnetic waves emitted by the radar, diffraction occurs at the edges and specular reflection occurs on the wall. The target's echo is mainly retroreflection. Because electromagnetic waves diffracted from the edges and reflected after multiple (three or more) reflections are too weak to detect the target, only the electromagnetic waves reflected by the primary reflection, secondary reflection, and their combination are considered in radar detection analysis.

[0045] For target detection in non-line-of-sight (NLOS) areas, beam scanning is used to record and analyze echo information, creating a "path dictionary" containing all possible "target radar path" models. Therefore, the target can be located in non-line-of-sight areas by searching the "path dictionary."

[0046] The embodiment of the present invention provides a method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar. Figure 1 As shown, the method is implemented by the following steps:

[0047] Step 101: Scanning a non-line-of-sight area using a frequency modulated continuous wave radar beam to obtain radar data of different frames;

[0048] Step 102: performing discrete Fourier transform in the range direction on the radar data of different frames to obtain range-Fourier transform graphs of different frames;

[0049] Step 103: performing environmental noise suppression processing on the distance-Fourier transform images of the different frames to obtain noise-reduced distance-Fourier transform images of the different frames;

[0050] Step 104: Randomly select a frame of noise-reduced distance-Fourier transform image;

[0051] Step 105: Determine the distance information r of all static targets in the noise-reduced distance-Fourier transform image i ′={r1′,r′2,r′3,...} and sort;

[0052] Specifically, define the accumulator A corresponding to different distance directions i ={a1,a2,..,a M}, traverse the distance peaks corresponding to different Chirps, and add 1 to the accumulator corresponding to the distance peak, set a suitable threshold s, and filter out those that are greater than the threshold and are within the boundary distance range (r min ,r max ) in the accumulator fAi , the accumulator f Ai Sort in descending order according to the value, obtain the distance information of all static targets within the search range and add the accumulator f Ai Sort in descending order according to the value, and obtain the distance information r of all static targets within the search range. i ′={r1′,r′2,r′3,...}.

[0053] Step 106: Determine the estimated target coordinate position and the length of the combined reflection path from the distance information of the static target;

[0054] Specifically, the distance information r of all static targets i The largest value r1′ among ′={r1′,r′2,r′3,...} is assumed to be the main reflection path, and the azimuth angle θ1 corresponds to A si The maximum angle peak and the distance relationship of the main reflection path are used to determine the estimated target coordinate position; then, the secondary reflection path r2 and the azimuth angle θ2 are determined by the estimated target coordinate position and the distance relationship of the main reflection path; finally, the length of the combined reflection path is determined according to the main reflection path r1 and the secondary reflection path r2.

[0055] The azimuth angle θ1 corresponds to A si The maximum angular peak of is obtained by performing horizontal scanning by rotating the radar system in steps of 2° to obtain the amplitude values ​​at different angles, A si ={a s1 ,a s2 ,a s3 ,...,a sn}, find the azimuth angle θ1 corresponding to A si The maximum angle peak.

[0056] The estimated target coordinate position (x p ,y p ):

[0057] The secondary reflection path r2 and the azimuth angle θ2 are determined by the estimated target coordinate position and the distance relationship of the primary reflection path, specifically: Where L1 is the distance between the antenna and Wall-2, and L3 is the distance between the millimeter wave radar antenna and the diffraction angle, (x p ,y p ) is the target coordinate position.

[0058] The length of the combined reflection path is determined according to the main reflection path r1 and the secondary reflection path r2:

[0059] Step 107: determining the length of the combined reflection path according to the estimated target coordinate position and the main reflection path;

[0060] Step 108: If the length of the reflection path matches the distance information of the static target, the estimated target coordinate position is the actual target coordinate position.

[0061] Specifically, verify the distance information r of the static target i r′={r1′,r′2,r′3,...} i ′ whether r2 and r c , if they exist, r1 and the corresponding angle r1 are determined, and the target coordinate position is estimated successfully.

[0062] Furthermore, the method further includes continuing to determine the distance information r of the static target if the length of the reflection path cannot be matched in the distance information of the static target. i r′={r1′,r′2,r′3,...} i 'Is it empty? If not, please i Delete r1′ from ′ and continue searching. Otherwise, reselect a frame of denoised distance-Fourier transform image.

[0063] Example

[0064] Consider an L-shaped corner scenario, such as in a corridor, where a millimeter-wave radar is placed near an angular wall and detects a target in the NLOS area.

[0065] like Figure 2 As shown in the figure, a Cartesian coordinate system is defined, where the radar is located at the origin O and the target is at the coordinate P(x p ,y p ).

[0066] Different from the traditional non-line-of-sight position estimation method, the present invention first measures the geometric structure of the L-shaped angle by appropriately rotating the radar, then evaluates the search range according to the primary and secondary reflection distances, and finally estimates the position of the target in the NLOS area through three propagation paths.

[0067] Typically, radar antennas have a beamwidth in azimuth. The narrower the beamwidth, the more accurate the position estimate made by radar rotation detection. In practice, precision can also be ensured by using fine rotation angle steps (e.g., 2°).

[0068] The present invention does not rely on any prior information about the environment geometry. The only information required is the distance between the millimeter wave radar antenna and the diffraction angle (L3), and the distances between the antenna and Wall-2 and Wall-3 (L1 and L2); that is, Figure 2 In the L-shaped corner geometry, the characteristics are OC, OB and OA. These three distances can be measured in the field by rotating the antenna at the appropriate angle so that the radar operator does not have to expose the detection area to any possible threats.

[0069] First, place the millimeter-wave radar in a suitable corner. Second, when the azimuth angle is 0°, the radar measures the distance from the antenna to Wall-2 as L1. When the azimuth angle is 90°, the radar measures the distance from the antenna to Wall-3 as L2. Finally, select the appropriate azimuth angle and measure the distance from the antenna to the corner, L3.

[0070] Assume that the wall will produce specular reflection of electromagnetic waves, and the target will produce specular reflection, retroreflection and diffuse reflection, such as Figure 2 As shown in Figure 2. Since diffuse reflection is usually very weak, the back reflection of the target plays a key role in the received radar signal; therefore, the range, angle, and Doppler velocity information can be obtained from the reflected signal of the hidden target. This information is used to estimate the target's position.

[0071] When electromagnetic waves emitted by the radar are irradiated, diffraction occurs at the edges and specular reflection occurs on the wall, and the target's echo is mainly reverse reflection. Since the electromagnetic waves diffracted from the edges and the electromagnetic waves reflected after multiple reflections are too weak to detect the target, only the electromagnetic waves after the first and second reflections need to be considered in radar detection analysis.

[0072] Therefore, if Figure 3 As shown, three types of propagation paths with combined primary and secondary reflections will be included in the NLOS detection model, including:

[0073] #1 Main reflection path: has the path O→P21→P→P21→O. The electromagnetic wave is transmitted to P through the main reflection path and returns to the radar along the same main reflection path.

[0074] #2nd reflection path: The path is O→P22→P11→P→P11→P22→O. The electromagnetic wave is transmitted to P through the secondary reflection path and returns to the radar through the same secondary reflection path.

[0075] #3 Primary and secondary reflection combined path: with the path O→P21→P→P11→P22→O, or using the path O→P22→P11→P→P21→O. The signal detects the target P through a primary reflection path and a secondary reflection path.

[0076] Since there are only three types of electromagnetic wave paths, namely, paths #1, #2, and #3, as Figure 3For non-line-of-sight target detection, the present invention establishes a "path dictionary" that includes all possible "target radar path" models. Therefore, the location of the target in the non-line-of-sight area can be achieved by searching the "path dictionary".

[0077] The “path dictionary” is a collection of the actual distances of all static targets within the search distance range and the distances of virtual targets formed by reflection.

[0078] For non-line-of-sight detection after L-shaped corners, both the primary and secondary reflection paths have minimum-maximum boundaries in the "path dictionary". For the primary reflection path, such as Figure 4 As shown, the minimum length r 1min and the maximum length r 1max This can be calculated as follows:

[0079]

[0080]

[0081] obey:

[0082] x′ p <2L1-L3cosβ

[0083] x′ p tanβ-y′ p >0

[0084] x′ p tanβ+y′ p -2L1tanβ>0.

[0085] For the secondary reflection path, such as Figure 4 As shown, the minimum length r 2min and the maximum length r 2max This can be calculated as follows:

[0086]

[0087]

[0088] obey:

[0089] x″ p <L3cosβ

[0090] x″ p tanβ-y″ p +2(L1tanβ-L2)>0

[0091] x″ p tanβ+y″ p -2L2>0.

[0092] Therefore, the search path can be restricted to the following:

[0093] r min =min{r 1min ,r 2min} <r<max{r 1max ,r 2max}=r max

[0094] Once the radar beam path (i.e., Path #1, Path #2, or Path #3) and the path direction and length (i.e., azimuth and path length) are determined, the target position in the non-line-of-sight (NLOS) area can be determined. However, due to the complex static clutter present in the NLOS environment, it is difficult to directly obtain the path length from the measured value. This is where the "path dictionary" comes in. When scanning the radar beam for target detection in the NLOS area, the return signal will be enhanced if the target is scanned. Based on the value of the scanning azimuth and the path length from the radar to the target location, the target position can be determined by looking up the path dictionary.

[0095] For path finding, the present invention discloses a non-line-of-sight multipath target search and position estimation algorithm (NLOS-mTSPE). The core idea of ​​NLOS-mTSPE is to find two or more radar wave paths and obtain the coordinates of the target position in the non-line-of-sight area by solving the two path length equations. The solution is achieved by finding the path direction, such as Figure 5 As shown, the implementation is as follows:

[0096] Step 1 (100) performs discrete Fourier transform on radar data of different frames in the range direction to obtain range-Fourier transform images of different frames.

[0097] Step 2 (101), using a background subtraction algorithm based on exponential averaging to suppress environmental noise.

[0098] Step 3 (102), randomly select a frame of radar data for further analysis and processing.

[0099] Step 4 (103), define the accumulator A corresponding to different distance directions (also in fast time) i ={a1,a2,..,a M Traverse the distance peaks corresponding to different chirps and add 1 to the accumulator corresponding to the distance peak.

[0100] Step 5 (104), set a suitable threshold s, filter out the ones that are greater than the threshold and are within the boundary distance range (r min ,r max ) in the accumulator f Ai .

[0101] Step 6 (105), the accumulator f Ai Sort in descending order according to the value of the accumulator f to obtain the distance information of all static targets within the search range. Ai By sorting in descending order according to the value, the distance information r of all static targets within the search range can be obtained. i ′={r1′,r′2,r′3,...}. Since the reflection of the main path is relatively strong, it is assumed here that r1=r1′.

[0102] Step 7 (106), performing horizontal scanning by rotating the radar system in small angle steps (such as 2°) to obtain amplitude values ​​at different angles, A si ={a s1 ,a s2 ,a s3 ,...,a sn}, find the azimuth angle θ1 corresponding to A si The maximum angle peak.

[0103] Step 8 (107), estimate the target coordinate position (x p ,y p ):

[0104]

[0105] The secondary reflection path r2 and azimuth angle θ2 are derived based on the target coordinate position and the distance relationship of the primary reflection path:

[0106]

[0107] Calculate the length of the combined reflection path:

[0108]

[0109] Step 9 (108), verify r i ′ whether r2 and r c If they exist, r1 and the corresponding angle r1 are determined, and the target coordinate position is successfully estimated. If not, continue to step 10 (109).

[0110] Step 10 (109), determine r i 'Is it empty? If not, please i Delete r1′ from ′ and continue searching; otherwise, reselect a frame of data.

[0111] In summary, the method of the present invention does not require the prior acquisition of the geometric parameters of the scene, and can accurately obtain the position information of the target object in the non-line-of-sight area from the radar data measured on site, greatly expanding the application of non-line-of-sight multipath positioning detection in actual complex environments.

[0112] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention.

Claims

1. A method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar, characterized in that: The method is: The non-line-of-sight area is detected by frequency modulated continuous wave radar beam scanning to obtain radar data of different frames; Perform discrete Fourier transform in the distance direction on radar data of different frames to obtain range-Fourier transform graphs of different frames; Performing environmental noise suppression processing on the distance-Fourier transform images of the different frames to obtain noise-reduced distance-Fourier transform images of the different frames; Randomly select a frame of denoised distance-Fourier transform image; Determine the distance information r of all static targets in the noise-reduced distance-Fourier transform image i ′={r1′,r2′,r3′,...} and sort; Determining an estimated target coordinate position and a length of a combined reflection path from the distance information of the static target; Determine the length of the combined reflection path according to the estimated target coordinate position and the main reflection path; If the length of the reflection path matches the distance information of the static target, the estimated target coordinate position is the actual target coordinate position; The estimated target coordinate position and the length of the combined reflection path are determined in the distance information of the static target, specifically: the distance information r of all static targets i ′={r1′,r2′,r3′,...}The largest value r1′ is the value of the main reflection path r1, and the azimuth angle θ1 corresponds to A si The maximum angle peak and the distance relationship of the main reflection path are used to determine the estimated target coordinate position; then, the secondary reflection path r2 and the azimuth angle θ2 are determined by the estimated target coordinate position and the distance relationship of the main reflection path; finally, the length of the combined reflection path is determined according to the main reflection path r1 and the secondary reflection path r2.

2. The method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar according to claim 1, characterized in that: The distance information r of all static targets in the noise-reduced distance-Fourier transform image is determined. i ′={r1′, r2′, r3′, ...} and sort them, specifically: define the accumulator A corresponding to different distance directions i ={a1,a2,..,a M }, traverse the distance peaks corresponding to different Chirps, and add 1 to the accumulator corresponding to the distance peak, set the threshold s, and filter out those that are greater than the threshold and are within the boundary distance range (r min ,r max ) in the accumulator f Ai , the accumulator f Ai Sort in descending order according to the value, obtain the distance information of all static targets within the search range and add the accumulator f Ai Sort in descending order according to the value, and obtain the distance information r of all static targets within the search range. i ′={r1′,r2′,r3′,...}.

3. The method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar according to claim 2, characterized in that: The azimuth angle θ1 corresponds to A si The maximum angular peak of is obtained by performing horizontal scanning by rotating the radar system in steps of 2° to obtain the amplitude values ​​at different angles, A si ={a s1 ,a s2 ,a s3 ,...,a sn }, find the azimuth angle θ1 corresponding to A si The maximum angle peak.

4. The method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar according to claim 3, wherein: The azimuth angle θ1 corresponds to A si The maximum angle peak value and the distance relationship of the main reflection path are used to determine the estimated target coordinate position, specifically: the estimated target coordinate position (x p ,y p ):

5. The method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar according to claim 4, characterized in that: The secondary reflection path r2 and azimuth angle θ2 are determined by the estimated target coordinate position and the distance relationship of the primary reflection path, specifically: Among them, L1 is the distance between the antenna and Wall-2, L3 is the distance between the millimeter wave radar antenna and the corner of the wall, (x p ,y p ) is the target coordinate position.

6. The method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar according to claim 5, characterized in that: The length of the combined reflection path is determined according to the main reflection path r1 and the secondary reflection path r2, specifically:

7. The method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar according to claim 6, characterized in that: If the length of the reflection path matches the distance information of the static target, the estimated target coordinate position is the actual target coordinate position, specifically: verifying the distance information r of the static target i r ′={r1′,r2′,r3′,...} i ′ whether r2 and r c , if they exist, r1 and the corresponding angle are determined, and the target coordinate position is successfully estimated.

8. The method for locating a target in a non-line-of-sight area using a frequency modulated continuous wave radar according to claim 7, characterized in that: The method further includes continuing to determine the distance information r of the static target if the length of the reflection path cannot be matched in the distance information of the static target. i r ′={r1′,r2′,r3′,...} i ' is empty, if not empty, from r i Delete r1′ from ′ and continue searching. Otherwise, reselect a frame of denoised distance-Fourier transform image.

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