Wall-penetrating radar imaging method based on maximum echo energy selection back-projection

Abstract

The application discloses a through-wall radar imaging method based on maximum echo energy selection and back projection, comprising the following steps: acquiring multi-channel original echo signals through a through-wall radar; performing pulse compression processing on the acquired original echo signals; performing clutter suppression processing on the echo signals obtained after processing; performing compensation processing on the additional time delay through a refraction angle approximate wall time delay compensation algorithm; dividing an imaging area, establishing a mapping relationship between distance direction pixels and azimuth direction pixels by using the echo signals obtained after processing and the compensation processing result; obtaining a final imaging result through coherent superposition processing based on the established mapping relationship, and completing imaging processing; the method selects echo signals with relatively large energy as target scattering echoes, establishes a mapping relationship between the distance direction and the azimuth direction, and performs coherent imaging; the method has reduced redundant calculation, accelerated imaging speed and improved imaging precision.

Description

Technical Field

[0001] This invention belongs to the field of image processing technology, specifically relating to a through-wall radar imaging method based on selecting back projection according to maximum echo energy. Background Technology

[0002] Multiple Input Multiple Output (MIMO) ultra-wideband through-wall radar has attracted much attention due to its many advantages, including strong penetration, active detection, high resolution, and all-weather and all-time operation. It has a huge advantage in target detection under non-metallic media penetration conditions and is widely used in disaster relief, health monitoring, and counter-terrorism and stability maintenance. However, in the above application scenarios, real-time detection is a prerequisite.

[0003] In target detection and reconstruction, imaging technology is the most intuitive and effective method. Compared to other imaging algorithms, including compressed sensing, inverse scattering tomography, boundary estimation, and time-reversal mirroring, back projection (BP) imaging has become one of the most commonly used imaging algorithms in through-wall radar due to its simple principle, ease of engineering implementation, lack of antenna array limitations, and ability to accurately compensate for the influence of walls on the signal. BP imaging divides the imaging scene into a uniform pixel grid, calculates the time delay between the radar antenna and the pixels, and projects the echo data onto each pixel in the imaging area, ultimately achieving high-resolution imaging through coherent accumulation. However, because the BP imaging algorithm requires traversing the entire detection scene during imaging, it involves a large amount of redundant computation, resulting in high computational complexity and long imaging time. Furthermore, since multiple pixels in the imaging area correspond to the echo signal of the same range gate, the main lobe of the image is broadened, reducing the imaging resolution.

[0004] To address the high computational complexity of back-projection (BP) imaging algorithms, scholars both domestically and internationally have proposed several improved BP imaging algorithms. For example, the paper "Lei Wentai, Huang Chunlin and Su Yi, 'A real-time backprojection imaging algorithm for impulse surface penetrating radar,' Proceedings. 2005 IEEE International Geoscience and Remote Sensing Symposium, 2005. IGARSS '05., Seoul, Korea (South), 2005" proposes a real-time recursive back-projection imaging algorithm by adaptively expanding the imaging area to match the scanning area. However, it does not fully utilize sub-apertures for coherent superposition of the entire imaging area, resulting in a reduction in imaging resolution. Another example is "L. Zhou, C. Huang and Y. Su, 'AFast Back-Projection Algorithm Based on Cross Correlation for GPR Imaging,' in IEEE Geoscience and Remote Sensing Letters, vol. 9, no. 2, pp. 228-232, March." "2012." Using a pre-established imaging region-time delay table to reduce redundancy in the classic BP imaging algorithm, but this will cause a large storage burden and scene adaptability issues.

[0005] The paper "C. Han, W. Tian and H. Mei, "MIMO Radar Fast Imaging Algorithm Based on Sub-image Combination," 2019 6th Asia-Pacific Conference on Synthetic Aperture Radar (APSAR), Xiamen, China, 2019" proposes a MIMO radar imaging algorithm based on coherent sub-image combination, which can achieve fast processing of MIMO radar data. However, this algorithm uses multiple approximations to simplify calculations, which sacrifices imaging resolution. The patent "Li Jiaqiang, Chen Yanbo, Liu Ran et al. A Fast Gaussian Gridded Non-Uniform FFT Through-Wall Imaging Radar BP Method [P]. Jiangsu Province: CN112147608A, 2020-12-29" proposes a BP imaging method based on Gaussian gridded non-uniform FFT, which can avoid repeated calculations and storage of pixel amplitude expressions in the BP imaging algorithm, reducing the number of calculations and memory requirements, but the imaging accuracy is lower than that of BP imaging.

[0006] In summary, although most of the aforementioned BP imaging algorithms have reduced computational complexity, they have sacrificed imaging accuracy and have relatively low imaging speed. Summary of the Invention

[0007] The purpose of this invention is to provide a through-wall radar imaging method based on selecting back projection with maximum echo energy, which reduces redundant calculations, speeds up imaging, and improves imaging accuracy.

[0008] The through-wall radar imaging method based on selecting back projection according to maximum echo energy provided by this invention includes the following steps:

[0009] S1. Acquire multi-channel raw echo signals using through-wall radar;

[0010] S2. Perform pulse compression processing on the raw echo signal obtained in step S1;

[0011] S3. Perform clutter suppression processing on the echo signal obtained after step S2;

[0012] S4. Compensation for additional time delay is achieved by using an approximate wall delay compensation algorithm based on the refraction angle;

[0013] S5. Using the echo signal obtained after processing in step S3 and the compensation processing result in step S4, the imaging area is divided, and the mapping relationship between range-oriented pixels and azimuth-oriented pixels is established.

[0014] S6. Based on the mapping relationship established in step S5, the final imaging result is obtained through coherent superposition processing, thus completing the imaging process;

[0015] Step S1, which involves acquiring multi-channel raw echo signals using through-wall radar, specifically includes:

[0016] The following formula is used to express time. Below, having Raw echo signals from a MIMO stepped-frequency continuous-wave radar system with multiple channels:

[0017] in, Indicates the first The original echo signals of each channel; Indicates the first Each channel's clutter signal; Indicates the first The target signal of each channel; Indicates noise echo;

[0018] Calculate using the following formula :

[0019] in, Indicates the first Clutter amplitude factor for each channel; Indicates the number of sub-pulses; Represents a rectangular function; Indicates the sub-pulse number; Indicates the duration of the sub-pulse; Indicates clutter in the first Two-way delay in each channel; Represents the imaginary unit; Indicates the starting frequency; Indicates the frequency step size;

[0020] Calculate using the following formula :

[0021] in, Indicates the first Target amplitude factor for each channel; Indicates the target is in the first place. Two-way delay in each channel;

[0022] Step S2, which involves pulse compression processing of the raw echo signal obtained in step S1, specifically includes:

[0023] For the raw echo signal of each channel acquired in step S1, through Pulse compression is performed using point-fast discrete inverse Fourier transform;

[0024] The following formula represents the pulse compression process after the first pulse. The first channel Echo data from each distance gate:

[0025] in, Indicates the number of pulses after compression processing The first channel Echo data from a distance gate;

[0026] Step S3, which involves performing clutter suppression processing on the echo signal obtained after step S2, specifically includes:

[0027] The singular value decomposition algorithm is used to suppress clutter in the echo signal obtained after step S2.

[0028] Regarding the first Each channel obtained Frame radar data Singular value decomposition (SVD) is performed, and the SVD process is represented by the following formula:

[0029] in, ; Indicates the pulse compression of the 1st The first channel Echo data of frames; express An orthogonal matrix of order 1; This represents the order of singular values ​​in descending order. A diagonal matrix of order 1; express An orthogonal matrix of order 1; Indicates the first The left eigenvalue vector corresponding to each singular value; express rank; Indicates the first One singular value; Indicates the first The right eigenvalue vector corresponding to each singular value;

[0030] The target signals corresponding to the first two singular values ​​are selected as "clutter", and the external noise is evenly distributed in the echo data;

[0031] The echo data is further represented by the following formula. :

[0032] in, Represents the clutter matrix; Represent the target matrix;

[0033] Step S5, which involves using the echo signal obtained after processing in step S3 and the compensation processing result from step S4 to divide the imaging region and establish a mapping relationship between range pixels and azimuth pixels, specifically includes:

[0034] Set in the radar target echo of the first The target at the distance of the gate To the transmitting antenna and receiving antenna The sum of the distances is , Representing a path The length is calculated using the following formula. :

[0035] in, Indicates the azimuth position of the transmitting antenna; Indicates the azimuth position of the receiving antenna; Indicates the direction or location; Indicates location in the direction of distance; The additional compensation distance is represented by the following formula:

[0036] in, Indicates uniform wall thickness; Represents the relative permittivity;

[0037] The following formula expresses the value obtained from radar target echoes. :

[0038] in, Represents the speed of light; This indicates the number of points in the Fast Discrete Inverse Fourier Transform;

[0039] Based on the above calculation results, the positional relationship between the radar target echo range gate index and the pixels in the imaging area is obtained as follows:

[0040] After determining the distance gate index of the target, select As an independent variable, As the dependent variable, a mapping relationship between range position and azimuth position is established using numerical analysis methods. As shown below:

[0041] in, Indicates location in the direction of distance; Indicates the direction or location;

[0042] Step S6, based on the mapping relationship established in step S5, uses coherent superposition processing to obtain the final imaging result, thus completing the imaging process. Specifically, this includes:

[0043] Select the front of the target echo The data of the maximum energy value is used as the target's scattering data for coherent imaging processing;

[0044] The following formula represents the multi-channel coherent stacking imaging result within the final imaging region. :

[0045] in, Indicates the first One channel; Indicates the total number of channels; This represents the index in the target echo after sorting by energy level; Indicates the number of azimuth pixels within the imaging area; Indicates the direction upwards. 1 pixel; Indicates the first The channel located in the first The target of the distance gate is determined by the orientation pixel. Mapped distance to location; Indicates the first The energy in the target echo of the first channel The range gate index corresponding to a large echo; Indicates the center frequency.

[0046] This invention provides a through-wall radar imaging method based on maximum echo energy selection and back projection. It obtains high-resolution echo signals by pulse compression of the received multi-channel echo signals; it suppresses strong clutter interference in the echo signals using a clutter suppression algorithm to improve the echo signal-to-noise ratio; it compensates for additional time delay using a refraction angle approximation wall delay compensation algorithm to eliminate the influence of wall refraction, correct the target position, and achieve precise image focusing; it selects the echo signal with higher energy as the target's scattered echo, constructs a range-azimuth mapping relationship, and performs coherent imaging. This invention reduces redundant calculations, accelerates imaging speed, and improves imaging accuracy. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the method flow of the present invention.

[0048] Figure 2 This is a schematic diagram of the through-wall radar signal propagation path of the method of the present invention.

[0049] Figure 3 This is a schematic diagram illustrating the experimental results analysis of the method of the present invention: Figure 3 (a) is a schematic diagram of the pulse compression time of the echo signal of channel 1; Figure 3 (b) is a schematic diagram of the fast and slow times of the 1-channel echo signal after singular value decomposition and clutter suppression.

[0050] Figure 4 This is a schematic diagram comparing the imaging results of the method of the present invention: Figure 4 (a) is a schematic diagram of traditional BP imaging results; Figure 4 (b) is a schematic diagram of the imaging results of the present invention.

[0051] Figure 5 This is a schematic diagram showing the resolution comparison of the method of the present invention: Figure 5 (a) is a schematic diagram comparing range resolution; Figure 5 (b) is a schematic diagram of the azimuth resolution comparison.

[0052] Figure 6 This is a schematic diagram comparing the imaging time of the method of the present invention: Figure 6 (a) is a schematic diagram of the imaging time curve of the traditional BP algorithm as the number of pixels changes; Figure 6 (b) is a schematic diagram of the imaging time curve of the method of the present invention as the number of pixels changes. Detailed Implementation

[0053] like Figure 1 The diagram shown is a flowchart of the method of the present invention: The through-wall radar imaging method based on selecting back projection according to maximum echo energy provided by the present invention includes the following steps:

[0054] S1. Acquire multi-channel raw echo signals using through-wall radar; specifically including:

[0055] The following formula is used to express time. Below, having Raw echo signals from a MIMO stepped-frequency continuous-wave radar system with multiple channels:

[0056] in, Indicates the first The original echo signals of each channel; Indicates the first Each channel's clutter signal; Indicates the first The target signal of each channel; Indicates noise echo;

[0057] Calculate using the following formula :

[0058] in, Indicates the first Clutter amplitude factor for each channel; Indicates the number of sub-pulses; Represents a rectangular function; Indicates the sub-pulse number; Indicates the duration of the sub-pulse; Indicates clutter in the first Two-way delay in each channel; Represents the imaginary unit; Indicates the starting frequency; Indicates the frequency step size;

[0059] Calculate using the following formula :

[0060] in, Indicates the first Target amplitude factor for each channel; Indicates the target is in the first place. Two-way delay in each channel;

[0061] S2. Perform pulse compression processing on the raw echo signal obtained in step S1; specifically including:

[0062] For the raw echo signal of each channel acquired in step S1, through Pulse compression is performed using point-fast discrete inverse Fourier transform;

[0063] The following formula represents the pulse compression process after the first pulse. The first channel Echo data from each distance gate:

[0064] in, Indicates the number of pulses after compression processing The first channel Echo data from a distance gate;

[0065] S3. Perform clutter suppression processing on the echo signal obtained after step S2; specifically including:

[0066] The singular value decomposition algorithm is used to suppress clutter in the echo signal obtained after step S2.

[0067] Regarding the first Each channel obtained Frame radar data Singular value decomposition (SVD) is performed, and the SVD process is represented by the following formula:

[0068] in, ; Indicates the pulse compression of the 1st The first channel Echo data of frames; express An orthogonal matrix of order 1; This represents the order of singular values ​​in descending order. A diagonal matrix of order 1; express An orthogonal matrix of order 1; Indicates the first The left eigenvalue vector corresponding to each singular value; express rank; Indicates the first One singular value; Indicates the first The right eigenvalue vector corresponding to each singular value;

[0069] The target signals corresponding to the first two singular values ​​are selected as "clutter", and the external noise is evenly distributed in the echo data;

[0070] The echo data is further represented by the following formula. :

[0071] in, Represents the clutter matrix; Represent the target matrix;

[0072] S4. Compensation for additional time delay is achieved using a wall delay compensation algorithm approximating the refraction angle; specifically including:

[0073] In through-wall radar imaging, the wall causes the target image to defocus and the target position to shift. By compensating for the additional time delay caused by the wall refraction, the target image is focused and the target position is corrected.

[0074] Instructions for selecting a single-transmitter, single-receiver antenna for compensation processing:

[0075] like Figure 2 The diagram shows the through-wall radar signal propagation path of the method of the present invention: transmitting antenna. and receiving antenna Place it close to the wall; target Located in the The first directional pixel and the first 1.5 distance-oriented pixels; among which... Indicates the azimuth position of the transmitting antenna; Indicates the azimuth position of the transmitting antenna; Indicates direction; Indicates distance direction;

[0076] Electromagnetic waves are transmitted by the transmitting antenna. To the target The refraction point inside the wall is Electromagnetic waves originate from the target to receiving antenna The refraction point inside the wall is ;

[0077] Ignoring the effects of wall refraction, the following formula is used to express the effect from the transmitting antenna. To the target Then to the receiving antenna free space propagation delay :

[0078] in, Represents the speed of light;

[0079] Based on the refraction angle approximation wall time delay compensation algorithm, the precise time delay is expressed by the following formula. :

[0080] in, Indicates uniform wall thickness; Represents the relative permittivity;

[0081] S5. Using the echo signal obtained after processing in step S3 and the compensation processing result in step S4, the imaging region is divided, and a mapping relationship between range pixels and azimuth pixels is established; specifically including:

[0082] Set in the radar target echo of the first The target at the distance of the gate To the transmitting antenna and receiving antenna The sum of the distances is , Representing a path The length is calculated using the following formula. :

[0083] in, Indicates the azimuth position of the transmitting antenna; Indicates the azimuth position of the receiving antenna; Indicates the direction or location; Indicates location in the direction of distance; The additional compensation distance is represented by the following formula:

[0084] in, Indicates uniform wall thickness; Represents the relative permittivity;

[0085] The following formula expresses the value obtained from radar target echoes. :

[0086] in, Represents the speed of light; This indicates the number of points in the Fast Discrete Inverse Fourier Transform;

[0087] Based on the above calculation results, the positional relationship between the radar target echo range gate index and the pixels in the imaging area is obtained as follows:

[0088] After determining the distance gate index of the target, select As an independent variable, As the dependent variable, a mapping relationship between range position and azimuth position is established using numerical analysis methods. As shown below:

[0089] in, Indicates location in the direction of distance; Indicates the direction or location;

[0090] S6. Based on the mapping relationship established in step S5, the final imaging result is obtained through coherent superposition processing, thus completing the imaging process; specifically including:

[0091] Select the front of the target echo The data of the maximum energy value is used as the target's scattering data for coherent imaging processing;

[0092] The following formula represents the multi-channel coherent stacking imaging result within the final imaging region. :

[0093] middle, Indicates the first One channel; Indicates the total number of channels; This represents the index in the target echo after sorting by energy level; Indicates the number of azimuth pixels within the imaging area; Indicates the direction upwards. 1 pixel; Indicates the first The channel located in the first The target of the distance gate is determined by the orientation pixel. Mapped distance to location; Indicates the first The energy in the target echo of the first channel The range gate index corresponding to a large echo; Indicates the center frequency;

[0094] The method of this invention is illustrated in the following example for further explanation:

[0095] The hardware platform for this invention is an Intel(R) Core(TM) i5-10400 CPU and Intel(R) UHD Graphics 630; the software platform is MATLAB 2019b; radar data is acquired using a MIMO ultra-wideband through-wall radar prototype developed by the research group; the radar adopts a frequency-stepping system, with a 2-transmit and 2-receive antenna array, a total of 4 transmit and receive channels, a frequency range of 800MHz to 1.6GHz, and a sub-pulse number of... The value is 256; the radar is placed close to a concrete wall, the thickness of which is... For a distance of 30 cm, the corresponding relative permittivity is... The value is 6; with the radar as the origin, the human target is located behind the wall. Location;

[0096] like Figure 3 The diagram shown illustrates the experimental results analysis of the method of this invention: where, Figure 3 (a) is a schematic diagram of the pulse compression time of the echo signal of channel 1; Figure 3 (b) is a schematic diagram showing the time difference of the echo signal from channel 1 after singular value decomposition and clutter suppression; through Figure 3 (a) It can be seen that the target is completely submerged in direct-coupled waves and wall clutter, through Figure 3 (b) The target signal can be clearly seen;

[0097] Set the imaging area size to The imaging region is divided along the azimuth and range directions into... Pixels; Maximum Energy Select the number of Imaging processing is performed using the method of this invention and the traditional BP imaging method, respectively, such as... Figure 4 The diagram shown is a comparison of the imaging results of the method of the present invention: where, Figure 4 (a) is a schematic diagram of traditional BP imaging results; Figure 4 (b) is a schematic diagram of the imaging results of the present invention. The imaging time of the traditional BP method is 0.6948s, and the imaging time of the method of the present invention is 0.0101s.

[0098] The pixel width at the point where the maximum amplitude of the image drop is -3dB is selected as the metric for comparing image resolution; for example... Figure 5 The diagram shown is a resolution comparison illustration of the method of the present invention: where, Figure 5 (a) is a schematic diagram comparing range resolution; Figure 5 (b) is a schematic diagram of azimuth resolution comparison; in Figure 5 In (a), the range resolution of the BP imaging algorithm is 7 range pixel widths, 0.1709m; the range resolution of the imaging method of this invention is 5.5 pixel widths, 0.1343m; Figure 5 In (b), the azimuth resolution of the BP imaging algorithm is approximately 17 azimuth pixel widths, or 1.0376m, while the azimuth resolution of the imaging method of the present invention is 14 pixel widths, or 0.8545m. Through actual measurement, it is proven that the imaging accuracy of the method of the present invention is better than that of the traditional BP imaging algorithm.

[0099] To further demonstrate the superior imaging speed of this invention, calculations were performed for different numbers of pixels and different maximum energy selections. The imaging time of the traditional BP algorithm and the method of this invention are as follows; Figure 6 The diagram shown is a comparison of imaging time using the method of the present invention: where, Figure 6 (a) is a schematic diagram of the imaging time curve of the traditional BP algorithm as the number of pixels changes; Figure 6 (b) is a schematic diagram of the imaging time curve of the method of the present invention as the number of pixels changes; through Figure 6 This demonstrates that the imaging time of the method of the present invention is significantly reduced, especially in large imaging scenarios, where the imaging speed advantage of the present invention is even more obvious.

Claims

1. A method for through-wall radar imaging based on selecting back projection according to maximum echo energy, comprising the following steps: S1. Acquire multi-channel raw echo signals using through-wall radar; S2. Perform pulse compression processing on the raw echo signal obtained in step S1; S3. Perform clutter suppression processing on the echo signal obtained after step S2; S4. Compensation for additional time delay is achieved by using an approximate wall delay compensation algorithm based on the refraction angle; S5. Using the echo signal obtained after processing in step S3 and the compensation processing result in step S4, the imaging area is divided, and the mapping relationship between range-oriented pixels and azimuth-oriented pixels is established. S6. Based on the mapping relationship established in step S5, the final imaging result is obtained through coherent superposition processing, thus completing the imaging process; In practice, select the front of the target echo. The data of the highest energy value is used as the target's scattering data for coherent imaging processing.

2. The through-wall radar imaging method based on maximum echo energy selection of back projection according to claim 1, characterized in that... Step S1, which involves acquiring multi-channel raw echo signals using through-wall radar, specifically includes: The following formula is used to express time. Below, having Raw echo signals from a MIMO stepped-frequency continuous-wave radar system with multiple channels: in, Indicates the first The original echo signals of each channel; Indicates the first Each channel's clutter signal; Indicates the first The target signal of each channel; Indicates noise echo; Calculate using the following formula : in, Indicates the first Clutter amplitude factor for each channel; Indicates the number of sub-pulses; Represents a rectangular function; Indicates the sub-pulse number; Indicates the duration of the sub-pulse; Indicates clutter in the first Two-way delay in each channel; Represents the imaginary unit; Indicates the starting frequency; Indicates the frequency step size; Calculate using the following formula : in, Indicates the first Target amplitude factor for each channel; Indicates the target is in the first place. Two-way delay in each channel.

3. The through-wall radar imaging method based on maximum echo energy selection of back projection according to claim 2, characterized in that... Step S2, which involves pulse compression processing of the raw echo signal obtained in step S1, specifically includes: For the raw echo signal of each channel acquired in step S1, through Pulse compression is performed using point-fast discrete inverse Fourier transform; The following formula represents the pulse compression process after the first pulse. The first channel Echo data from each distance gate: in, Indicates the number of pulses after compression processing The first channel Echo data from a distance gate.

4. The through-wall radar imaging method based on maximum echo energy selection of back projection according to claim 3, characterized in that... Step S3, which involves performing clutter suppression processing on the echo signal obtained after step S2, specifically includes: The singular value decomposition algorithm is used to suppress clutter in the echo signal obtained after step S2. Regarding the first Each channel obtained Frame radar data Singular value decomposition (SVD) is performed, and the SVD process is represented by the following formula: in, ; Indicates the pulse compression of the 1st The first channel Echo data of frames; express An orthogonal matrix of order 1; This represents the order of singular values ​​in descending order. A diagonal matrix of order 1; express An orthogonal matrix of order 1; Indicates the first The left eigenvalue vector corresponding to each singular value; express rank; Indicates the first One singular value; Indicates the first The right eigenvalue vector corresponding to each singular value; The target signal corresponding to the first two singular values ​​is selected as "clutter", and the external noise is uniformly distributed in the echo data; The echo data is further represented by the following formula. : in, Represents the clutter matrix; Represents the target matrix.

5. The through-wall radar imaging method based on maximum echo energy selection of back projection according to claim 4, characterized in that... Step S5, which involves using the echo signal obtained after processing in step S3 and the compensation processing result from step S4 to divide the imaging region and establish a mapping relationship between range pixels and azimuth pixels, specifically includes: Set in the radar target echo of the first The target at the distance of the gate To the transmitting antenna and receiving antenna The sum of the distances is , Representing a path The length is calculated using the following formula. : in, Indicates the azimuth position of the transmitting antenna; Indicates the azimuth position of the receiving antenna; Indicates the direction or location; Indicates location in the direction of distance; The additional compensation distance is represented by the following formula: in, Indicates uniform wall thickness; Represents the relative permittivity; The following formula expresses the value obtained from radar target echoes. : in, Represents the speed of light; This indicates the number of points in the Fast Discrete Inverse Fourier Transform; Based on the above calculation results, the positional relationship between the radar target echo range gate index and the pixels in the imaging area is obtained as follows: After determining the distance gate index of the target, select As an independent variable, As the dependent variable, a mapping relationship between range position and azimuth position is established using numerical analysis methods. As shown below: in, Indicates location in the direction of distance; Indicates the direction or location.

6. The through-wall radar imaging method based on maximum echo energy selection of back projection according to claim 5, characterized in that... Step S6, based on the mapping relationship established in step S5, uses coherent superposition processing to obtain the final imaging result, thus completing the imaging process. Specifically, this includes: The following formula represents the multi-channel coherent stacking imaging result within the final imaging region. : in, Indicates the first One channel; Indicates the total number of channels; This represents the index in the target echo after sorting by energy level; Indicates the number of azimuth pixels within the imaging area; Indicates the direction upwards. 1 pixel; Indicates the first The channel located in the first The target of the distance gate is determined by the orientation pixel. Mapped distance to location; Indicates the first The energy in the target echo of the first channel The range gate index corresponding to a large echo; Indicates the center frequency.

Images