Through-wall radar multi-path ringing suppression imaging method and system based on deconvolution processing

Abstract

The application discloses a through-wall radar multi-path ringing suppression imaging method and system based on deconvolution processing and relates to the technical field of imaging, which comprises the following steps: acquiring a single frame echo of a through-wall radar, acquiring wall multiple reflection echo amplitude and reflection time delay, and estimating basic parameters of the wall; filtering out directly coupled waves in the single frame echo, performing distance direction fast Fourier transform on the processed single frame echo, and obtaining distance frequency domain data; calculating a frequency domain expression of a kernel function of multi-path ringing suppression processing according to the estimated basic parameters of the wall; performing deconvolution operation on the frequency domain expression of the kernel function and the distance frequency domain data, and obtaining distance frequency domain data after multi-path ringing clutter suppression; performing inverse Fourier transform on the distance frequency domain data, and obtaining single frame echoes after multi-path ringing clutter suppression; and imaging a plurality of single frame echoes after multi-path ringing clutter suppression, and obtaining a through-wall radar target image. The application can improve the overall detection performance of the through-wall radar.

Description

Technical Field

[0001] This invention belongs to the field of imaging technology, specifically relating to a method and system for suppressing multipath ringing in through-wall radar based on deconvolution processing. Background Technology

[0002] Through-wall radar transmits and receives low-frequency, ultra-wideband signals, enabling it to penetrate various walls such as wood, brick, and concrete, achieving non-contact detection, localization, and feature identification of targets after penetrating obstacles. Leveraging its unique medium-penetrating detection and imaging advantages, through-wall radar has played a significant role in numerous fields.

[0003] Improving target detection resolution through various hardware and algorithm optimizations has always been a major direction in the development of through-wall radar. However, with the increase in resolution, the multipath problem of through-wall radar during operation has gradually become prominent, seriously affecting and restricting the further improvement of detection and imaging quality.

[0004] Therefore, there is an urgent need to provide a through-wall radar imaging method and system to improve the quality of detection imaging. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a method and system for multipath ringing suppression imaging of through-wall radar based on deconvolution processing. In a first aspect, the present invention provides a method for multipath ringing suppression imaging of through-wall radar based on deconvolution processing, comprising: Acquire a single frame echo from the through-wall radar; Based on the single-frame echo, the amplitude and reflection delay of multiple reflections from the wall are obtained, and the basic parameters of the wall are estimated. The direct coupling wave in the single-frame echo is filtered out to obtain the processed single-frame echo; The processed single-frame echo is subjected to a range-to-fast Fourier transform to obtain range-frequency domain data. Based on the estimated basic parameters of the wall, the frequency domain expression of the kernel function for multipath ringing suppression is calculated; the frequency domain expression of the kernel function is deconvolved with the range frequency domain data to obtain the range frequency domain data after suppressing multipath ringing clutter. The distance-frequency domain data after suppressing multipath ringing clutter is subjected to inverse Fourier transform to obtain the single-frame echo after suppressing multipath ringing clutter. By employing single-frame echo imaging after suppressing multipath ringing clutter, a through-wall radar target image is obtained.

[0006] In a second aspect, the present invention also provides a multipath ringing suppression imaging system for through-wall radar based on deconvolution processing, which is applied to the above-mentioned multipath ringing suppression imaging method for through-wall radar based on deconvolution processing, and includes: a transmitting unit and a receiving unit; The transmitting unit includes a transmitting antenna for transmitting signals; The receiving unit includes a receiving antenna for receiving single-frame echoes from through-wall radar; it also includes a calculation module for obtaining the amplitude and reflection delay of multiple wall reflections based on the single-frame echo, and estimating the basic parameters of the wall; the receiving unit further includes a direct-coupled wave filtering module for filtering out direct-coupled waves from the single-frame echo to obtain a processed single-frame echo; the receiving unit also includes a preprocessing module for performing a range-to-fast Fourier transform on the processed single-frame echo to obtain range-frequency domain data; and the receiving unit further includes a multipath ringing clutter suppression module. Based on the estimated basic parameters of the wall, the frequency domain expression of the kernel function for multipath ringing suppression is calculated. The frequency domain expression of the kernel function is deconvolved with the range frequency domain data to obtain the range frequency domain data after multipath ringing suppression. The receiving unit also includes a preprocessing module two, which performs an inverse Fourier transform on the range frequency domain data after multipath ringing suppression to obtain a single-frame echo after multipath ringing suppression. The receiving unit also includes an imaging module, which uses several single-frame echoes after multipath ringing suppression to image the target image of the through-wall radar.

[0007] The beneficial effects of this invention are: This invention provides a multipath ringing suppression imaging method and system for through-wall radar based on deconvolution processing. By acquiring the amplitude and reflection delay of multiple reflected echoes from a wall, the basic parameters of the wall are estimated. Based on these parameters, the frequency domain expression of the kernel function for multipath ringing suppression is calculated. This kernel function's frequency domain expression is used to process the frequency domain echoes to suppress the influence of multipath ringing clutter. The frequency domain echoes are then converted to the time domain to obtain the echoes with suppressed multipath ringing clutter, leading to the acquisition of the final image. This effectively suppresses the multipath ringing clutter interference problem encountered by existing through-wall radars during actual operation, significantly improves detection and imaging resolution, reduces the minimum detection distance, avoids near-field detection by wall ringing clutter, and significantly reduces false alarms and missed detections, thereby improving the overall detection performance of through-wall radar.

[0008] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of multipath ringing of through-wall radar signals provided in an embodiment of the present invention; Figure 2This is a schematic diagram of a single-frame echo provided in an embodiment of the present invention; Figure 3 This is a flowchart of a through-wall radar multipath ringing suppression imaging method based on deconvolution processing provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a simulation experiment test scenario provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of a single-target data domain processing result provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the imaging results of a multi-target test scene provided in an embodiment of the present invention. Detailed Implementation

[0010] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0011] Multipath propagation problems in through-wall radar are mainly caused by two factors: signal penetration through walls and the confined space of indoor environments. Based on their formation process, multipath propagation problems in through-wall radar can be categorized into four types: 1. The through-wall radar signal reflects multiple times between the four walls of the room, eventually encountering the target and reflecting back to the through-wall radar receiver; 2. The through-wall radar signal reflects multiple times between the ceiling and the floor, eventually encountering the target and reflecting back to the through-wall radar receiver; 3. The through-wall radar signal reflects multiple times between multiple targets, eventually reflecting back to the through-wall radar receiver; 4. Due to discontinuous transmission paths during wall penetration, the through-wall radar signal exhibits ringing and trailing problems. The above four types of multipath problems in through-wall radar can all occur during the operation of through-wall radar. Multipath transmission of through-wall radar signals will cause multiple secondary echoes to appear after the main echo of the target. The secondary echoes generally become multipath clutter, which manifests as target ghosting or ghosting problems in the imaging results. The impact of the above four types of multipath on the imaging results is also different. The first three types of multipath problems are caused by the interaction between the target and the surrounding walls and floors. Due to the influence of the geometric relationship between the target and the object, not all targets will produce multipath clutter. Only when specific geometric relationships are met will multiple reflected echoes affect the imaging results. The last type of multipath problem is caused by the multiple reflections of the through-wall radar signal on the inner and outer walls during the wall-penetration process. This causes the electromagnetic signal radiated into the detection scene to change from the initial ideal narrow pulse signal to a signal with multiple ringing tails. As a result, the reflected echoes of all objects and targets in the detection scene carry multipath ringing clutter. Since this multipath is manifested as a signal with ringing tails, it is also called multipath ringing.

[0012] In existing technologies, multipath suppression methods for through-wall radar mainly focus on the first three types of multipath problems, including: 1. Performing corresponding filtering processing in the echo data domain based on the difference between target features and multipath clutter features to eliminate or suppress multipath clutter; 2. Eliminating multipath clutter after the target's main peak based on improved constant false alarm rate (CFAR) detection and fusion binarization processing; 3. Gradually eliminating target ghosting in the image domain through iterative optimization. For the last type of multipath ringing problem, there are few effective methods in existing research. Although the first three types of multipath suppression methods can provide a reference for the last type of multipath ringing suppression, these methods are limited by their basic working principles. The suppression effect is closely related to the target echo features. When the echo signal-to-clutter ratio and signal-to-noise ratio are low, or the target features are inaccurate or unknown, the filtering and suppression effects of the above methods are poor. In addition, the image iterative optimization requires a long time, making it unsuitable for application scenarios with high real-time requirements. Existing research, including patent (CN201710753420.0), discloses a method for suppressing multipath oscillations in front and behind walls after multi-receiver through-wall radar imaging. This method, after obtaining initial radar data, extracts the center values ​​of all targets through binarization processing, and then judges the initial radar data based on the propagation distance, thereby eliminating multipath false targets in the initial radar data and achieving multipath suppression. However, when judging the initial radar data and eliminating multipath false targets, the judgment criteria are quite sensitive and lack robustness. A high judgment threshold easily leads to incomplete filtering of false targets, while a low threshold easily filters out the echoes of real targets. Furthermore, this method is severely affected by environmental clutter, echo signal-to-noise ratio, and signal-to-clutter ratio. Additionally, when the target is close to the wall, the ghosting of the wall overlaps with the target, and the multipath ringing clutter amplitude of the wall is much higher than that of the target, ultimately leading to the inability to detect close-range targets, causing the multipath ringing suppression method to fail.

[0013] In view of this, the present invention provides a multipath ringing suppression imaging method and system for through-wall radar based on deconvolution processing. Starting from the ringing tail generation mechanism of through-wall radar signals during wall penetration, this method models the multipath ringing of the signal and performs unified processing on the echo data to suppress multipath ringing clutter in the data domain. This method is entirely based on the principle of multipath ringing generation, does not require consideration of target characteristics, and is unaffected by other clutter in the environment. It has strong applicability and can effectively suppress multipath ringing signals in the echo, improving the detection resolution and imaging quality of through-wall radar.

[0014] Please see Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of multipath ringing of through-wall radar signals provided in an embodiment of the present invention. Figure 2This is a schematic diagram of a single-frame echo provided in an embodiment of the present invention; the phenomenon of multipath ringing in through-wall radar signals is that during the process of the signal penetrating the wall, due to the large difference in electromagnetic parameters between the wall and the air, the signal undergoes multiple reflections and transmissions between the inner and outer wall surfaces. These multiple reflections and transmissions ultimately manifest as multiple time delays and superpositions of the signal in the formation of the radiation wave.

[0015] like Figure 1 As shown, the ideal narrow pulse signal emitted by a through-wall radar When the signal is transmitted to the exterior wall, due to the interface between the wall and the air, part of the signal is reflected back to the through-wall radar, while the other part is transmitted into the wall and continues to transmit forward. The signal transmitted into the wall... Represented as: ; in, This represents the transmission coefficient of a signal from the air to the wall interface.

[0016] For simplicity in modeling and analysis, signal attenuation within the wall is ignored, and the signal transmitted into the wall is considered. When transmitted to the inner wall, due to the significant difference in electromagnetic parameters between the wall and the air, the signal undergoes both reflection and transmission. Part of the signal is reflected within the wall, while the other part penetrates the wall and enters the indoor detection space. The signal that penetrates the wall and enters the indoor detection space is represented as follows: ; in, This represents the transmission coefficient of the signal from the wall to the air interface. This indicates the one-way transmission delay of the signal within the wall. Indicates time.

[0017] The signal reflected inside the wall is transmitted towards the through-wall radar. It is reflected and transmitted again on the outer wall surface. The reflected signal is transmitted towards the indoor detection space. It is reflected and transmitted again on the inner wall surface. The signal that enters the indoor detection space after the second transmission is represented as follows: ; in, This represents the reflection coefficient of the signal transmitted from the wall to the air interface.

[0018] Similarly, the signal undergoes multiple reflections and transmissions between the inner and outer walls and on the surface, ultimately radiating into the indoor detection space and being used to detect the target. Represented as: ; in, Represents an ideal narrow pulse signal. This indicates the noise signal introduced by multipath ringing. Indicates the first Secondary wall multipath ringing reflection echo.

[0019] Because the signal radiated into the indoor detection space is no longer an ideal narrow pulse signal, but rather an ideal narrow pulse signal plus a series of multipath ringing clutter signals, the echoes from all objects in the indoor detection space become a single main peak followed by a series of regular clutter, such as... Figure 2 As shown, these clutters cause false alarms during target detection by through-wall radar, manifesting as ghosting or shadows behind the target in the final imaging result. Simultaneously, because the wall also exhibits ghosting and the energy of multiple wall-reflected waves is relatively strong, the near-range blind zone of the through-wall radar becomes larger, and the reflected echoes from targets close to the wall are completely submerged in the multiple ringing clutter from the wall.

[0020] Please see Figure 3 , Figure 3 This is a flowchart of a multipath ringing suppression imaging method for through-wall radar based on deconvolution processing provided in an embodiment of the present invention. The method includes: S101. Obtain a single frame echo from the through-wall radar.

[0021] Specifically, in this embodiment, the transmitting antenna of the through-wall radar transmits signals, and the receiving antenna receives multiple frames of echoes after being reflected by the target. The echoes include multipath ringing signals, i.e. clutter signals.

[0022] S102. Based on the single-frame echo, obtain the amplitude and reflection delay of the wall's multiple reflection echoes, and estimate the basic parameters of the wall.

[0023] Specifically, in this embodiment, based on the above analysis of the causes of multipath ringing and the multipath ringing signal model, it can be seen that the key parameters involved are the wall emission coefficient, transmission coefficient, and signal one-way transmission delay in the wall. These key parameters are related to the relative permittivity of the wall and the wall thickness. Therefore, it is necessary to estimate these two parameters first.

[0024] In this embodiment, the ratio of the amplitudes of different reflected wave signals from the wall can be determined based on the single-frame echo. and and the time delay between two adjacent reflections of the wall The basic parameters of the wall were further estimated; the estimated basic parameters of the wall include the relative permittivity of the wall. and wall thickness .

[0025] In this embodiment, the relative permittivity of the wall The expression is: ; in, and These represent the ratios of the amplitudes of different reflected wave signals from the wall. wall thickness The expression is: ; in, This indicates the speed at which a signal travels in a vacuum. This indicates the time delay between two adjacent reflections of the wall.

[0026] In this embodiment, the estimated basic parameters of the wall also include the transmission coefficient of the signal from the wall to the air interface. The reflection coefficient of the signal transmitted from the wall to the air interface The transmittance coefficient of the signal transmitted from the air to the wall interface. And the one-way transmission delay of signals within the wall .

[0027] In this embodiment, based on Fresnel's formula in electromagnetic field theory, the transmission coefficient and reflection coefficient of the signal transmitted from the wall to the air interface can be obtained; wherein, The transmittance coefficient of the signal from the wall to the air interface The expression is: ; The reflection coefficient of the signal transmitted from the wall to the air interface The expression is: ; in, This represents the estimated relative permittivity of the wall, which is assumed to be non-frequency-dependent. This indicates the signal incident angle. Since the through-wall radar is some distance from the wall, and the detection azimuth angle of the through-wall radar is relatively small, it is assumed that... .

[0028] It should be noted that the calculated transmission and reflection coefficients do not include the electrical conductivity of the wall, because the wall's conductivity is negligible compared to its dielectric constant. The processing based on the model constructed in this invention effectively suppresses multipath ringing noise in the echo, and experimental results demonstrate the rationality and feasibility of the approximate simplifications introduced in the above calculation process.

[0029] Based on the estimated basic parameters of the wall, namely the relative permittivity of the wall... and wall thickness The transmission coefficient of the signal from the air to the wall interface and the one-way transmission delay of the signal within the wall were calculated; among them, The transmittance of the signal from the air to the wall interface The expression is: ; Signal one-way transmission delay within the wall The expression is: ; in, This indicates the speed at which a signal travels in a vacuum.

[0030] S103. Filter out the direct coupling wave in the single-frame echo to obtain the processed single-frame echo.

[0031] Specifically, in this embodiment, the direct coupling wave in the single-frame echo refers to the signal transmitted by the through-wall radar transmitting antenna and directly received by the through-wall radar receiving antenna; since the direct coupling wave between the transmitter and receiver has not undergone through-wall multipath ringing modulation, it needs to be filtered out.

[0032] S104. Perform a range-to-fast Fourier transform on the processed single-frame echo to obtain range-frequency domain data.

[0033] S105. Based on the estimated basic parameters of the wall, calculate the frequency domain expression of the kernel function for multipath ringing suppression; perform deconvolution operation between the frequency domain expression of the kernel function and the distance frequency domain data to obtain the distance frequency domain data after suppressing multipath ringing clutter.

[0034] Specifically, in this embodiment, based on the constructed signal model of radiation entering the indoor detection space, it is considered that the clutter signal introduced by multipath ringing is the result of time-delay superposition and convolution of the ideal signal by the wall, which can be expressed as: ; in, Represents an ideal narrow pulse signal. The convolution kernel represents the superposition modulation of signal time delay by the wall. Knowing the reflection coefficient, transmission coefficient and signal transmission time delay of the wall, the convolution kernel can be obtained. Based on this characteristic, the convolution kernel can be used to suppress multipath ringing clutter.

[0035] The expression for the convolution kernel of the wall for signal delay superposition modulation is: ; in, Indicates the first Multipath ringing reflection echo of secondary wall This indicates the total number of superimposed multipath ringing reflection echoes. Represents the impulse function. Indicates time, This represents the transmission coefficient of the signal from the wall to the air interface. This represents the reflection coefficient of the signal transmitted from the wall to the air interface. This represents the transmission coefficient of a signal from the air to the wall interface. This indicates the one-way transmission delay of the signal within the wall. The convolution kernel modulated by the signal delay of the wall Transforming to the frequency domain, we obtain the frequency domain expression of the kernel function for multipath ringing suppression, which is expressed as: ; in, The frequency domain representation of the multipath ringing suppression kernel function. represents an imaginary number, Indicates frequency, Represents an exponential function. Indicates the first Multipath ringing reflection echo of secondary wall This indicates the total number of superimposed echoes from multipath ringing reflections.

[0036] In the echo frequency domain, multiply the distance data by Equivalent to time-domain deconvolution processing, it eliminates the multipath ringing problem of the signal during the wall penetration process. While reducing ringing clutter, it significantly improves the imaging quality, which is beneficial for multi-target identification in confined indoor detection spaces.

[0037] S106. Perform an inverse Fourier transform on the range-frequency domain data after suppressing multipath ringing clutter to obtain a single-frame echo after suppressing multipath ringing clutter.

[0038] S107. Single-frame echo imaging after suppressing multipath ringing clutter is used to obtain a through-wall radar target image.

[0039] Specifically, in this embodiment, after suppressing multipath ringing clutter in the echo, conventional through-wall radar imaging processing is performed to obtain the final imaging result.

[0040] In summary, the multipath ringing suppression imaging method for through-wall radar based on deconvolution processing provided by this invention has the following beneficial effects, specifically: First, it improves the performance of through-wall radar; it can effectively suppress the multipath ringing clutter interference problem that occurs in the actual operation of existing through-wall radar, effectively improve the detection and imaging resolution, reduce the minimum detection distance, avoid being submerged in wall ringing clutter at close range behind the wall, significantly reduce the radar's false alarms and missed detections, and improve the overall detection performance of through-wall radar.

[0041] Second, it has strong environmental adaptability; the method proposed in this invention starts from the mechanism of multipath ringing through walls to model and analyze radiation signals. After accurately estimating the wall parameters, subsequent processing can be carried out. It is independent of the detection environment and target characteristics, and the application of the method has few limitations and prerequisites.

[0042] Third, it has strong real-time performance; the method proposed in this invention does not require complex iterative optimization processing, and the suppression speed is relatively fast, which can meet the requirements of real-time detection by through-wall radar.

[0043] Fourth, universality and portability; since the post-disaster life search and rescue radars equipped by fire and rescue teams also penetrate various media to detect targets, and the signal also has multipath ringing problems during transmission, which is similar to the application scenario of through-wall radar, the method proposed in this invention can also be used in post-disaster life search and rescue radars.

[0044] Based on the same inventive concept, the present invention also provides a multipath ringing suppression imaging system for through-wall radar based on deconvolution processing, which is applied to the multipath ringing suppression imaging method for through-wall radar based on deconvolution processing provided in the above embodiments of the present invention. The imaging method is described above and will not be repeated here. The imaging system includes: a transmitting unit and a receiving unit. The transmitting unit includes a transmitting antenna for transmitting signals; The receiving unit includes a receiving antenna for receiving single-frame echoes from through-wall radar; it also includes a calculation module for obtaining the amplitude and reflection delay of multiple wall reflections based on the single-frame echo, and estimating the basic parameters of the wall; the receiving unit further includes a direct-coupled wave filtering module for filtering out direct-coupled waves from the single-frame echo to obtain a processed single-frame echo; the receiving unit also includes a preprocessing module for performing a range-to-fast Fourier transform on the processed single-frame echo to obtain range-frequency domain data; and the receiving unit further includes a multipath ringing clutter suppression module. Based on the estimated basic parameters of the wall, the frequency domain expression of the kernel function for multipath ringing suppression is calculated. The frequency domain expression of the kernel function is deconvolved with the range frequency domain data to obtain the range frequency domain data after multipath ringing suppression. The receiving unit also includes a preprocessing module two, which performs an inverse Fourier transform on the range frequency domain data after multipath ringing suppression to obtain a single-frame echo after multipath ringing suppression. The receiving unit also includes an imaging module, which uses several single-frame echoes after multipath ringing suppression to image the target image of the through-wall radar.

[0045] In an optional embodiment of the present invention, the effectiveness of the through-wall radar multipath ringing suppression imaging method based on deconvolution processing provided in the above embodiment is verified by simulation experiments, specifically as follows: I. Simulation Conditions To demonstrate the effectiveness of this invention, single-target and multi-target detection experiments were conducted, with test scenarios as follows: Figure 4 As shown, Figure 4 This is a schematic diagram of a simulation experiment test scenario provided in an embodiment of the present invention, wherein the wall thickness is 0.3 meters and the through-wall radar is 2 meters away from the outer surface of the wall. Figure 4 In the diagram (a), a single-target experimental test scenario is shown, with the coordinates of the single target being (3, 7). Figure 4 In the middle (b), a multi-target experimental test scenario is shown. There are a total of 7 targets in the multi-target test scenario. There are 3 targets in the near-range area A, with coordinates (2.5, 3.5), (3.5, 3.5) and (3, 3) respectively, and 4 targets in the far-range area B, with coordinates (2, 8), (4, 8), (2, 6) and (4, 6) respectively. The single-target test scenario shows the single-channel echo data domain processing result. Since there is overlap between the targets in the data domain, only the final detection and imaging result is shown.

[0046] II. Simulation Content and Result Analysis Please see Figure 5 , Figure 5 This is a schematic diagram of the single-target data domain processing result provided in an embodiment of the present invention. Two relatively strong echoes are located approximately 2 meters away, representing the reflected wave from the outer surface of the wall and the primary reflected echo from the inner surface, respectively. Figure 5 As can be seen in (a1), multiple echoes caused by multipath ringing occur after the reflected wave from the wall. Since the target echo has a smaller amplitude relative to the wall echo, it is not clearly displayed. Figure 5 The result of (a1) is obtained by local magnification. Figure 5 In (a2), it can be seen that there are also ringing clutters after the main echo of the target. These clutters will cause false alarms in the detection of through-wall radar. Figure 5 Image (b1) shows the result after processing with the present invention. It can be seen that the ringing noise after the wall echo has been effectively suppressed. Figure 5 In the magnified view (b2), the ringing clutter following the main echo of the target was also suppressed. It should be noted that... Figure 5 The method mentioned refers to the method proposed in this invention.

[0047] Please see Figure 6 , Figure 6 This is a schematic diagram of the imaging results of a multi-target test scene provided in an embodiment of the present invention, wherein, Figure 6 (a1) and (b1) show the results of the normal, unprocessed result and the result after processing using this method, respectively. In both results, the echo reflected from the outer surface of the wall is located 2 meters away on the left, and the first echo reflected from the inner surface of the wall is located on the right. It can be seen that due to the multipath ringing of the wall, Figure 6In the middle (a1), after the echo on the inner surface, there are still two straight-line echoes, which are the ghost images of the wall caused by the multi-path ringing of the wall. Figure 6 In section (b2), the ghosting effect of the wall is no longer present in the result after processing by the method proposed in this invention. It should be noted that... Figure 6 The method mentioned refers to the method proposed in this invention.

[0048] Because the echo signal from the wall is much stronger than the echo signal from the target, the imaging results are magnified in a localized area to obtain clearer images. Figure 6 (a2) and (b2). Comparing the two magnified views, we can see that: 1. At a distance of 2.8 meters to 3.8 meters (i.e., Figure 4 In the schematic diagram (b), the three targets in area A are obscured by the wall ghosting and cannot be detected normally. However, after processing with the method proposed in this invention, the three targets at close range are not affected by the wall ghosting and can be clearly displayed. That is, the method proposed in this invention can effectively solve the problem of close-range target obscuration and loss during through-wall radar detection and reduce the detection blind zone; 2. At a distance of 5 meters to 9 meters (i.e. Figure 4 (The four targets in area B of the schematic diagram in (b)) Figure 6 As can be seen from the right side of (a2), due to the presence of signal multipath ringing clutter, strong ghosting appears behind all four targets. These ghostings can cause false alarms in the actual detection process. However, the ghosting problem behind the four targets is effectively suppressed after processing with the method proposed in this invention.

[0049] The above simulation results of single-target and multi-target tests fully demonstrate the effectiveness of the method proposed in this invention. It suppresses multipath ringing clutter in the signal, eliminates wall ghosting caused by multiple wall reflections, and solves the problem of not being able to detect close-range targets. At the same time, the ghosting phenomenon behind all targets is suppressed, avoiding false alarms and missed detections in subsequent detection processes.

[0050] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, 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. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. 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 used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0051] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0052] 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 multipath ringing suppression imaging method for through-wall radar based on deconvolution processing, characterized in that, include: Acquire a single frame echo from the through-wall radar; Based on the single-frame echo, the amplitude and reflection delay of multiple reflections from the wall are obtained, and the basic parameters of the wall are estimated. The direct coupling wave in the single-frame echo is filtered out to obtain the processed single-frame echo. The processed single-frame echo is subjected to a range-to-fast Fourier transform to obtain range-frequency domain data. Based on the estimated basic parameters of the wall, the frequency domain expression of the kernel function for multipath ringing suppression is calculated; the frequency domain expression of the kernel function is deconvolved with the distance frequency domain data to obtain the distance frequency domain data after suppressing multipath ringing clutter. Perform an inverse Fourier transform on the range-frequency domain data after suppressing multipath ringing clutter to obtain a single-frame echo after suppressing multipath ringing clutter. By employing single-frame echo imaging after suppressing multipath ringing clutter as described above, a through-wall radar target image is obtained; The frequency domain expression of the kernel function for the multipath ringing suppression process is: ； in, The frequency domain representation of the multipath ringing suppression kernel function. represents an imaginary number, Indicates frequency, This represents the transmission coefficient of the signal from the wall to the air interface. This represents the reflection coefficient of the signal transmitted from the wall to the air interface. This represents the transmission coefficient of a signal from the air to the wall interface. This indicates the one-way transmission delay of the signal within the wall. Represents an exponential function. Indicates the first Multipath ringing reflection echo of secondary wall This indicates the total number of superimposed echoes from multipath ringing reflections.

2. The through-wall radar multipath ringing suppression imaging method based on deconvolution processing according to claim 1, characterized in that, The estimated basic parameters of the wall include the relative permittivity of the wall. and wall thickness .

3. The through-wall radar multipath ringing suppression imaging method based on deconvolution processing according to claim 2, characterized in that, The relative permittivity of the wall The expression is: ； in, and These represent the ratios of the amplitudes of different reflected wave signals from the wall. The thickness of the wall The expression is: ； in, This indicates the speed at which a signal travels in a vacuum. This indicates the time delay between two adjacent reflections of the wall.

4. The through-wall radar multipath ringing suppression imaging method based on deconvolution processing according to claim 2, characterized in that, The estimated basic parameters of the wall also include the transmission coefficient of the signal from the wall to the air interface. The reflection coefficient of the signal transmitted from the wall to the air interface The transmittance coefficient of the signal transmitted from the air to the wall interface. And the one-way transmission delay of signals within the wall .

5. The through-wall radar multipath ringing suppression imaging method based on deconvolution processing according to claim 4, characterized in that, The signal is transmitted from the wall to the air interface via the transmission coefficient. The expression is: ； in, Indicates the angle of incidence of the signal; The signal is transmitted from the wall to the reflection coefficient at the air interface. The expression is: ； The signal is transmitted from the air to the wall interface via the transmission coefficient. The expression is: ； The signal's one-way transmission delay within the wall The expression is: ； in, This indicates the speed at which a signal travels in a vacuum.

6. The through-wall radar multipath ringing suppression imaging method based on deconvolution processing according to claim 1, characterized in that, The frequency domain expression of the kernel function for multipath ringing suppression, calculated based on the estimated basic parameters of the wall, includes: Based on the transmission coefficient of the signal from the wall to the air interface The reflection coefficient of the signal transmitted from the wall to the air interface The transmittance coefficient of the signal transmitted from the air to the wall interface. And the one-way transmission delay of signals within the wall Calculate the convolution kernel of the wall for signal delay superposition modulation. Its expression is: ； in, Represents the impulse function. Indicates time; The convolution kernel modulated by the signal delay superposition of the wall body By converting to the frequency domain, the frequency domain expression of the kernel function for the multipath ringing suppression process is obtained.

7. A multipath ringing suppression imaging system for through-wall radar based on deconvolution processing, applied to the multipath ringing suppression imaging method for through-wall radar based on deconvolution processing as described in any one of claims 1 to 6, characterized in that, include: Transmitting unit and receiving unit; The transmitting unit includes a transmitting antenna for transmitting signals; The receiving unit includes a receiving antenna for receiving single-frame echoes from a through-wall radar. The receiving unit also includes a calculation module for obtaining the amplitude and reflection delay of multiple wall reflections based on the single-frame echo, and estimating the basic parameters of the wall. The receiving unit further includes a direct-coupled wave filtering module for filtering out direct-coupled waves from the single-frame echo to obtain a processed single-frame echo. The receiving unit also includes a preprocessing module for performing a range-to-fast Fourier transform on the processed single-frame echo to obtain range-frequency domain data. The receiving unit also includes a multipath ringing clutter suppression module. The receiving unit includes a preprocessing module, which calculates the frequency domain expression of the kernel function for multipath ringing suppression based on the estimated basic parameters of the wall; performs a deconvolution operation on the frequency domain expression of the kernel function and the range frequency domain data to obtain range frequency domain data after multipath ringing suppression; the receiving unit also includes an imaging module, which uses several single-frame echoes after multipath ringing suppression to image the target image of the through-wall radar; The frequency domain expression of the kernel function for the multipath ringing suppression process is: ； in, The frequency domain representation of the multipath ringing suppression kernel function. represents an imaginary number, Indicates frequency, This represents the transmission coefficient of the signal from the wall to the air interface. This represents the reflection coefficient of the signal transmitted from the wall to the air interface. This represents the transmission coefficient of a signal from the air to the wall interface. This indicates the one-way transmission delay of the signal within the wall. Represents an exponential function. Indicates the first Multipath ringing reflection echo of secondary wall This indicates the total number of superimposed echoes from multipath ringing reflections.

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