Harmonic radar weak target signal detection method and system

Abstract

The present application relates to the technical field of radar detection, and proposes a harmonic radar weak target signal detection method and system, which comprises: performing digital processing on echo signals to obtain baseband complex signals; performing phase disturbance analysis on the baseband complex signals to obtain persistent phase components, constructing time domain slices according to the distribution interval of the persistent phase components; extracting the second harmonic frequency components of the time domain slices and recording the phase initial values of the second harmonic frequency components; performing phase rotation alignment processing on the baseband complex signals, coherently accumulating the energy of homologous harmonic signals to obtain enhanced signals; constructing a dynamic clutter background field according to echo data, eliminating the dynamic clutter background field to obtain a cancellation residual signal; determining sampling points exceeding a preset dynamic threshold as weak target echoes, and determining the spatial coordinates of the target signals according to distance data and azimuth information in combination with real-time positioning data; and the present application can improve the efficiency of harmonic radar weak target signal detection.

Description

Technical Field

[0001] This invention relates to the field of radar detection technology, and more specifically, to a method and system for detecting weak target signals using harmonic radar. Background Technology

[0002] In the field of weak target signal detection by harmonic radar, existing detection technologies are limited by the limitations of signal processing methods. They are insufficient in mining the phase characteristics of echo signals, cannot effectively extract the continuous phase components in harmonic signals, and are difficult to accurately screen the characteristic frequency components of targets. This results in the energy dispersion of harmonic signals from the same source, making it impossible to complete coherent accumulation, resulting in poor signal enhancement and difficulty in identifying weak target harmonic signals from complex echoes.

[0003] Meanwhile, existing technologies construct clutter background fields that are mostly static models, which cannot accurately reflect the clutter changes during the scanning process of harmonic radar in real time. This results in poor removal of dynamic clutter, and the residual signal after clutter cancellation still contains a large amount of background interference. Furthermore, the target localization process lacks precise coordinate system transformation and fusion logic, making it easy for threshold determination to result in misjudgments or missed detections. Ultimately, this leads to low detection accuracy and efficiency for weak targets, failing to meet the practical application requirements for rapid and accurate detection of weak target signals by harmonic radar. Therefore, how to overcome the shortcomings of misjudging weak target signals by harmonic radar has become an urgent technical problem to be solved in the industry. Summary of the Invention

[0004] To address the aforementioned problems in the existing technology, embodiments of the present invention provide a method and system for detecting weak target signals using harmonic radar.

[0005] To achieve the above objectives, the present invention provides a method for detecting weak target signals using harmonic radar, comprising: A. The echo signal of the harmonic radar is digitally processed to obtain the baseband complex signal of the harmonic radar; B. Perform phase perturbation analysis on the baseband complex signal to obtain the persistent phase component of the baseband complex signal, and construct the time domain slice of the harmonic radar based on the distribution range of the persistent phase component. C. Extract the second harmonic frequency components in the time-domain slice that correspond to the nonlinear junction characteristics in the target signal, and record the initial phase values ​​of the second harmonic frequency components; D. Based on the initial phase value, the baseband complex signal is subjected to phase rotation and alignment processing, and the energy of the homogeneous harmonic signals dispersed in the baseband complex signal is coherently accumulated to obtain the enhanced signal of the harmonic radar; E. Based on the echo data of the harmonic radar, construct the dynamic clutter background field of the harmonic radar, and remove the dynamic clutter background field from the enhanced signal to obtain the cancellation residual signal of the harmonic radar. F. The sampling points where the cancellation residual signal exceeds the preset dynamic threshold are determined to be weak target echoes, and the distance data and azimuth information corresponding to the sampling points are extracted; G. Based on the distance data and azimuth information, and combined with the real-time positioning data of the harmonic radar, determine the spatial coordinates of the target signal.

[0006] Preferably, the step of performing phase perturbation analysis on the baseband complex signal to obtain the persistent phase component of the baseband complex signal, and constructing a time-domain slice of the harmonic radar based on the distribution range of the persistent phase component, includes: The baseband complex signal of the harmonic radar is subjected to sliding windowing processing to obtain the window data segment of the baseband complex signal; The instantaneous phase values ​​in the window data segment are analyzed for change trends to obtain the monotonic change trend components of the window data segment, and the monotonic change trend components are recorded as the local phase perturbation baseline of the window data segment. The local phase perturbation baseline is smoothed and connected to obtain the continuous phase component of the baseband complex signal; Based on the phase value of the persistent phase component on the time axis, the value range of the persistent phase component is divided into a continuous phase dwell interval. Based on the start and end points of the phase dwell interval, the baseband complex signal is extracted to obtain a time-domain slice of the harmonic radar.

[0007] Preferably, the step of extracting the second harmonic frequency component in the time-domain slice that corresponds to the nonlinear junction characteristics in the target signal, and recording the initial phase value of the second harmonic frequency component, includes: The time-domain slice is subjected to spectral decomposition to obtain the amplitude spectrum and phase spectrum data of the time-domain slice; Based on the transmission frequency of the harmonic radar, locate the second harmonic frequency point in the amplitude spectrum that is twice the frequency of the transmission frequency, and read the complex spectral line value corresponding to the second harmonic frequency point. The complex spectral line value is compared and analyzed with the nonlinear junction response amplitude threshold in the target signal. If the complex spectral line value is greater than the nonlinear junction response amplitude threshold, the complex spectral line value is determined to be a second harmonic frequency component that conforms to the characteristics of a nonlinear junction. The phase value corresponding to the second harmonic frequency point is extracted from the phase spectrum data, and the phase value is recorded as the initial phase value of the second harmonic frequency component.

[0008] Preferably, the step of performing phase rotation and alignment processing on the baseband complex signal based on the initial phase value, and coherently accumulating the energy of the homogeneous harmonic signals dispersed in the baseband complex signal to obtain the enhanced signal of the harmonic radar, includes: Based on the pulse repetition period of the harmonic radar, the baseband complex signal is divided into a continuous pulse echo sequence. Complex value sampling points corresponding to the preset target range gate are extracted from the pulse echo sequence to obtain the homogeneous signal of the harmonic radar; Based on the initial phase value, determine the phase value corresponding to the sampling point in the same source signal; The same source signal is enhanced to obtain the enhanced signal of the harmonic radar.

[0009] Preferably, the formula for calculating the enhanced signal is: ; in, This refers to the enhanced signal. This indicates the total number of pulse echo sequences. Indicates the first One complex value sampling point, No. The instantaneous phase value of each complex-valued sampling point This indicates the preset reference phase value. Represents the imaginary unit. Represents the natural constant.

[0010] Preferably, constructing the dynamic clutter background field of the harmonic radar based on the echo data of the harmonic radar includes: Historical echo data of the harmonic radar are collected during continuous scanning cycles to obtain the historical echo dataset of the harmonic radar; Range-direction matched filtering is performed on the echo data in the historical echo dataset to obtain the range image data of the harmonic radar. Align the range image data according to the range cells to obtain the range-slow time two-dimensional data matrix of the harmonic radar; Based on the distance-slow time two-dimensional data matrix, the amplitude value of the distance unit in the historical scanning cycle is extracted along the slow time dimension to obtain the amplitude time series of the distance unit; Outlier removal is performed on the amplitude time series to obtain the background amplitude sample of the distance unit; The statistical center value of the background amplitude sample is used as the estimated background amplitude value of the distance unit; Arrange the background amplitude estimates according to the order of the range cells to construct the dynamic clutter background field of the harmonic radar.

[0011] Preferably, the step of removing the dynamic clutter background field from the enhanced signal to obtain the cancellation residual signal of the harmonic radar includes: The enhanced signal is divided according to a range gate to obtain an enhanced amplitude sequence corresponding to the range cell in the dynamic clutter background field; The amplitude values ​​in the enhanced amplitude sequence are coupled with the background amplitude estimates of the corresponding range cells in the dynamic clutter background field on a range cell-by-range cell basis to obtain the initial cancellation residual of the range cell. The initial cancellation residual is smoothed and filtered to obtain the cancellation residual of the distance unit; The sampling points whose amplitude values ​​in the cancellation residual are lower than the preset background fluctuation threshold are set to zero, while the sampling points whose amplitude values ​​are higher than the preset background fluctuation threshold are retained, thus obtaining the cancellation residual signal of the harmonic radar.

[0012] Preferably, determining the spatial coordinates of the target signal based on the distance data and azimuth information, combined with the real-time positioning data of the harmonic radar, includes: The real-time positioning data of the current moment is read from the positioning system of the harmonic radar. The real-time positioning data includes the longitude coordinates, latitude coordinates and altitude coordinates of the radar station. Based on the distance data and the azimuth angle in the orientation information, the planar projection distance and vertical height difference of the target signal relative to the radar station are analyzed in the local horizontal coordinate system where the radar station is located. The eastward and northward offsets of the target signal are obtained by vector synthesis of the plane projection distance and the azimuth angle. The eastward offset, the northward offset, and the vertical height difference are combined with the longitude, latitude, and altitude coordinates of the radar station to perform coordinate system transformation and fusion to obtain the three-dimensional spatial coordinates of the target signal. The three-dimensional spatial coordinates are converted into the longitude, latitude, and altitude of the target signal in the geographic coordinate system, which serve as the final spatial coordinates of the target signal.

[0013] Preferably, the step of transforming and fusing the eastward offset, the northward offset, and the vertical height difference with the longitude, latitude, and altitude coordinates of the radar station to obtain the three-dimensional spatial coordinates of the target signal includes: The longitude coordinates, latitude coordinates, and altitude coordinates of the radar station are converted into three-dimensional rectangular coordinates of the radar station in the geocentric coordinate system according to the parameters of the Earth ellipsoid model. The offset vector in the local horizontal coordinate system, which is composed of the eastward offset, the northward offset, and the vertical height difference, is used to construct a rotation matrix from the local horizontal coordinate system to the geocentric coordinate system based on the longitude and latitude of the radar station's location. The three-dimensional Cartesian coordinate components of the target signal are determined based on the offset vector and the rotation matrix. The three-dimensional spatial rectangular coordinate components and the three-dimensional spatial rectangular coordinates in the geocentric coordinate system of the radar station are vector-added together to obtain the three-dimensional spatial coordinates of the target signal.

[0014] Furthermore, the present invention also provides a weak target signal detection system for harmonic radar, comprising: The signal processing module is used to digitize the echo signal of the harmonic radar to obtain the baseband complex signal of the harmonic radar. The signal slicing module is used to perform phase perturbation analysis on the baseband complex signal to obtain the persistent phase component of the baseband complex signal, and to construct the time domain slice of the harmonic radar based on the distribution range of the persistent phase component. The phase extraction module is used to extract the second harmonic frequency component in the time-domain slice that corresponds to the nonlinear junction characteristics in the target signal, and to record the initial phase value of the second harmonic frequency component. The signal enhancement module is used to perform phase rotation alignment processing on the baseband complex signal based on the initial phase value, and to coherently accumulate the energy of the homogeneous harmonic signals dispersed in the baseband complex signal to obtain the enhanced signal of the harmonic radar. The signal cancellation module is used to construct the dynamic clutter background field of the harmonic radar based on the echo data of the harmonic radar, and remove the dynamic clutter background field from the enhanced signal to obtain the cancellation residual signal of the harmonic radar. The signal determination module is used to determine the sampling points where the cancellation residual signal exceeds a preset dynamic threshold as weak target echoes, and to extract the distance data and azimuth information corresponding to the sampling points. The target positioning module is used to determine the spatial coordinates of the target signal based on the distance data and azimuth information, combined with the real-time positioning data of the harmonic radar.

[0015] The beneficial effects of this invention are as follows: 1. This invention constructs time-domain slices by analyzing the phase perturbation of echo signals, accurately extracts the second harmonic frequency components corresponding to the nonlinear junction characteristics, and then completes phase rotation alignment and coherent accumulation of the energy of the same source harmonic signals based on the initial phase value. This effectively enhances the energy of weak target signals, significantly improves the ability of harmonic radar to identify and extract weak target signals, and makes the originally scattered and weak target signals clearly stand out, significantly improving the accuracy and effectiveness of signal detection.

[0016] 2. This invention effectively eliminates clutter interference to target signals by constructing a dynamic clutter background field and performing precise clutter removal. Combined with multi-dimensional coordinate transformation and fusion, it achieves accurate spatial positioning of target signals. The entire process from signal processing to target positioning is optimized, significantly improving the overall efficiency of weak target signal detection by harmonic radar. It also ensures the accuracy of information acquisition such as range, azimuth, and spatial coordinates during the detection process, thus comprehensively enhancing the application performance of harmonic radar in weak target detection scenarios. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a method for detecting weak target signals using harmonic radar according to the present invention; Figure 2 This is a schematic diagram illustrating the functional modules of a harmonic radar weak target signal detection system according to the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This application provides a method for detecting weak target signals using harmonic radar. The execution entity of this method includes, but is not limited to, at least one of the following electronic devices that can be configured to execute the method provided in this application: a server, a terminal, etc. In other words, the method for detecting weak target signals using harmonic radar can be executed by software or hardware installed on a terminal device or a server device. The server includes, but is not limited to, a single server, a server cluster, a cloud server, or a cloud server cluster. The server can be an independent server or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, content delivery networks (CDNs), and big data and artificial intelligence platforms.

[0020] Reference Figure 1 The diagram shown is a flowchart illustrating a method for detecting weak target signals using harmonic radar according to an embodiment of the present invention. In this embodiment, the method for detecting weak target signals using harmonic radar includes: In this embodiment of the invention, A. the echo signal of the harmonic radar is digitally processed to obtain the baseband complex signal of the harmonic radar; The radar transceiver unit receives the echo signal reflected during the harmonic radar detection process and transmits the echo signal to the matching signal processing hardware. This hardware has a physical link for signal reception and preliminary processing, which can realize the stable transmission and reception of the echo analog signal.

[0021] The received echo analog signal is processed by analog-to-digital conversion. A fixed sampling rate is set according to the operating frequency characteristics of the harmonic radar. The continuous echo analog signal is sampled at equal intervals, and the continuous amplitude of the analog signal is converted into discrete digital quantities, thus completing the basic conversion from analog signal to digital signal.

[0022] The digital signal after analog-to-digital conversion is down-converted by a mixer to reduce the carrier frequency of the digital signal to near zero frequency, thereby eliminating the influence of the carrier frequency on signal feature analysis and preserving the original phase and amplitude information of the signal.

[0023] The down-converted signal is low-pass filtered to remove high-frequency spurious components generated by the down-conversion, retaining only the effective signal components near zero frequency to ensure signal purity.

[0024] The signal after low-pass filtering is subjected to orthogonal decomposition to obtain the in-phase component and the quadrature component. The in-phase component is taken as the real part and the quadrature component is taken as the imaginary part, and they are integrated to form the baseband complex signal of the harmonic radar that has both amplitude and phase information.

[0025] The beneficial effects are that this step, through phased hardware processing and signal conversion operations, achieves a complete conversion of the echo signal from analog to digital baseband complex signal, preserving the core characteristic information of the echo signal such as phase and amplitude throughout the process, without loss or distortion of signal characteristics. This provides an accurate and complete signal foundation for subsequent operations such as phase perturbation analysis and frequency component extraction of the baseband complex signal. At the same time, the standardized digital processing allows various subsequent signal analysis operations to be carried out based on a unified digital signal format, improving the continuity and operability of subsequent signal processing links.

[0026] Phase perturbation analysis is performed on the baseband complex signal to obtain the persistent phase component of the baseband complex signal, and a time-domain slice of the harmonic radar is constructed based on the distribution range of the persistent phase component. In this embodiment of the invention, the step of performing phase perturbation analysis on the baseband complex signal to obtain the persistent phase component of the baseband complex signal, and constructing a time-domain slice of the harmonic radar based on the distribution range of the persistent phase component, includes: The baseband complex signal of the harmonic radar is subjected to sliding windowing processing to obtain the window data segment of the baseband complex signal; The instantaneous phase values ​​in the window data segment are analyzed for change trends to obtain the monotonic change trend components of the window data segment, and the monotonic change trend components are recorded as the local phase perturbation baseline of the window data segment. The local phase perturbation baseline is smoothed and connected to obtain the continuous phase component of the baseband complex signal; Based on the phase value of the persistent phase component on the time axis, the value range of the persistent phase component is divided into a continuous phase dwell interval. Based on the start and end points of the phase dwell interval, the baseband complex signal is extracted to obtain a time-domain slice of the harmonic radar.

[0027] A fixed-length sliding window is determined based on the time series length of the baseband complex signal. The sliding window is continuously translated along the time axis of the baseband complex signal, with a fixed step size each time. During the translation process, all baseband complex signal data within the coverage area of ​​the sliding window are captured to form a window data segment of the baseband complex signal that is continuous and has some data overlap.

[0028] Extract the instantaneous phase values ​​corresponding to all sampling points in each window data segment, arrange the instantaneous phase values ​​in chronological order to form a phase sequence, judge the changing trend of the phase sequence point by point, identify the parts of the phase sequence that show a single increase or a single decrease, integrate the phase data of the single changing part and the corresponding changing pattern into the monotonic changing trend component of the window data segment, and directly use the monotonic changing trend component as the local phase perturbation baseline of the window data segment and complete the recording.

[0029] The local phase disturbance baselines of all window data segments are sorted out in chronological order along the time axis. Linear interpolation is performed at the connection points of adjacent local phase disturbance baselines to supplement the phase data at the connection points, so that all local phase disturbance baselines form a continuous phase curve without any breaks. This continuous phase curve is the persistent phase component of the baseband complex signal.

[0030] Iterate through the phase values ​​of the persistent phase components at each moment on the time axis, count the distribution range of all phase values, and divide the distribution range into multiple non-overlapping and continuously connected intervals according to the continuous change characteristics of the phase values. The phase values ​​in each interval remain relatively stable and without jumps. These intervals are the phase dwell intervals of the persistent phase components.

[0031] Record the start and end times of each phase dwell interval on the time axis. Using this time range as the basis for extraction, accurately extract all baseband complex signal data within the corresponding time interval from the original baseband complex signal time series. The baseband complex signal data segment extracted from each time interval is the time domain slice of the harmonic radar.

[0032] The beneficial effects are that this process achieves regional phase analysis of baseband complex signals through sliding windowing, accurately extracts the local phase disturbance baselines of each region and completes smooth connection, and the obtained persistent phase components can truly reflect the overall phase change law of the baseband complex signal. Based on the time domain slices extracted from the phase dwell interval, baseband complex signal data with similar phase characteristics can be integrated, and interference caused by phase jumps can be eliminated. This defines a precise signal analysis range for subsequent extraction of second harmonic frequency components, improving the pertinence and accuracy of subsequent frequency component extraction.

[0033] C. Extract the second harmonic frequency components in the time-domain slice that correspond to the nonlinear junction characteristics in the target signal, and record the initial phase values ​​of the second harmonic frequency components; In this embodiment of the invention, the step of extracting the second harmonic frequency component in the time-domain slice that corresponds to the nonlinear junction characteristics in the target signal, and recording the initial phase value of the second harmonic frequency component, includes: The time-domain slice is subjected to spectral decomposition to obtain the amplitude spectrum and phase spectrum data of the time-domain slice; Based on the transmission frequency of the harmonic radar, locate the second harmonic frequency point in the amplitude spectrum that is twice the frequency of the transmission frequency, and read the complex spectral line value corresponding to the second harmonic frequency point. The complex spectral line value is compared and analyzed with the nonlinear junction response amplitude threshold in the target signal. If the complex spectral line value is greater than the nonlinear junction response amplitude threshold, the complex spectral line value is determined to be a second harmonic frequency component that conforms to the characteristics of a nonlinear junction. The phase value corresponding to the second harmonic frequency point is extracted from the phase spectrum data, and the phase value is recorded as the initial phase value of the second harmonic frequency component.

[0034] The time-domain slice contains all data and is subjected to spectral decomposition to transform the time-domain signal into a frequency-domain signal. Simultaneously, the amplitude spectrum and phase spectrum data corresponding to the frequency-domain signal are generated. The amplitude spectrum data reflects the signal amplitude characteristics at each frequency point, and the phase spectrum data reflects the signal phase characteristics at each frequency point.

[0035] The fixed transmission frequency of the harmonic radar signal is retrieved, and the second harmonic value of the transmission frequency is calculated. Using the second harmonic value as a reference, the corresponding frequency point is located in the amplitude spectrum. This frequency point is the second harmonic frequency point. Then, the complex spectral line value corresponding to the second harmonic frequency point in the amplitude spectrum is directly read.

[0036] The complex spectral value corresponding to the read second harmonic frequency point is compared with the preset target signal nonlinear junction response amplitude threshold. Only when the complex spectral value is greater than the amplitude threshold is the second harmonic frequency point signal corresponding to the complex spectral value determined as a second harmonic frequency component that conforms to the nonlinear junction characteristics in the target signal.

[0037] After determining the second harmonic frequency component, the phase spectrum data is precisely matched based on the position of the second harmonic frequency point. The unique phase value corresponding to the position of the frequency point is extracted, and the extracted phase value is directly used as the initial phase value of the second harmonic frequency component for recording and storage.

[0038] The beneficial effects are that this process realizes the transformation of time-domain sliced ​​signals from the time domain to the frequency domain through spectral decomposition, accurately locates the second harmonic frequency point, and completes the screening of effective frequency components by combining the nonlinear junction response amplitude threshold. This ensures that the extracted second harmonic frequency components conform to the nonlinear junction characteristics of the target signal. At the same time, the corresponding initial phase value is directly extracted and recorded, providing an accurate phase reference for the subsequent phase rotation and alignment processing of the baseband complex signal. This effectively avoids the interference of invalid frequency components on subsequent signal processing and improves the accuracy of target signal feature extraction.

[0039] D. Based on the initial phase value, the baseband complex signal is subjected to phase rotation and alignment processing, and the energy of the homogeneous harmonic signals dispersed in the baseband complex signal is coherently accumulated to obtain the enhanced signal of the harmonic radar; In this embodiment of the invention, the step of performing phase rotation and alignment processing on the baseband complex signal based on the initial phase value, and coherently accumulating the energy of the homogeneous harmonic signals dispersed in the baseband complex signal to obtain the enhanced signal of the harmonic radar, includes: Based on the pulse repetition period of the harmonic radar, the baseband complex signal is divided into a continuous pulse echo sequence. Complex value sampling points corresponding to the preset target range gate are extracted from the pulse echo sequence to obtain the homogeneous signal of the harmonic radar; Based on the initial phase value, determine the phase value corresponding to the sampling point in the same source signal; The same source signal is enhanced to obtain the enhanced signal of the harmonic radar.

[0040] The formula for calculating the enhanced signal is as follows: ; in, This refers to the enhanced signal. This indicates the total number of pulse echo sequences. Indicates the first One complex value sampling point, No. The instantaneous phase value of each complex-valued sampling point This indicates the preset reference phase value. Represents the imaginary unit. Represents the natural constant.

[0041] The preset pulse repetition period of the harmonic radar is retrieved. Using this period as the basis for time division, the baseband complex signal is divided into equal intervals along the time axis. The entire baseband complex signal is split into multiple pulse echo sequences with the same time length and arranged in chronological order. Each pulse echo sequence corresponds to the echo signal data of a single pulse transmission of the harmonic radar.

[0042] Based on the detection range of the harmonic radar, a target range gate is preset. In each pulse echo sequence, the signal position corresponding to the target range gate is accurately located, and all complex value sampling points at that position are extracted. The complex value sampling points of this type extracted from all pulse echo sequences are integrated to form the homogeneous signal of the harmonic radar. This homogeneous signal is the harmonic signal data corresponding to the same target that is dispersed in different pulse echo sequences.

[0043] The initial phase value of the recorded second harmonic frequency component is retrieved and used as the reference phase. Combined with the phase characteristics of each complex numerical sampling point in the same source signal, the specific phase value corresponding to each complex numerical sampling point in the same source signal is determined one by one through phase mapping, thus completing the phase value calibration of all sampling points.

[0044] Based on the determined phase values ​​of each sampling point, phase rotation and alignment processing is performed on the signals from the same source. The phases of all complex-valued sampling points in the signals from the same source are uniformly calibrated to the reference phase, so that the dispersed harmonic signals from the same source are kept in phase. Then, energy coherent accumulation is performed on all complex-valued sampling points after phase alignment. The accumulated signal data is integrated to form the enhanced signal of the harmonic radar.

[0045] The pulse echo sequence is obtained by dividing the baseband complex signal of the harmonic radar according to the pulse repetition period. The complex numerical sampling point is the value corresponding to the preset target range gate extracted from the pulse echo sequence. The instantaneous phase value is the phase characteristic value carried by the complex numerical sampling point itself. The reference phase value is the initial phase value corresponding to the second harmonic frequency component that conforms to the nonlinear junction characteristics in the target signal. The total number of pulse echo sequences is the number of continuous pulse echo sequences obtained after segmentation.

[0046] Each complex numerical sampling point is multiplied by a complex exponent, which is the product of the natural constant, the imaginary unit, and the difference between the instantaneous phase value and the reference phase value. The results of all the multiplication operations are then accumulated sequentially. The accumulated result is the enhanced signal. This operation process realizes the phase rotation and alignment processing of the baseband complex signal, which can coherently accumulate the energy of the same source harmonic signals dispersed in the baseband complex signal, and allow the energy of the same source harmonic signals to converge and superimpose.

[0047] As the number of pulse echo sequences increases, the number of complex numerical sampling points after multiplication in the accumulation operation continues to increase, the energy accumulation effect of the same source harmonic signals will be continuously strengthened, the energy of the target signal carried by the enhanced signal will continue to increase, and the characteristic performance of the target signal will become more prominent.

[0048] The beneficial effects are that the process achieves accurate segmentation of the baseband complex signal based on the pulse repetition period, extracts the same source signal through the target range gate to achieve the screening and convergence of the same target harmonic signal, and the phase rotation alignment completed by the initial phase value keeps the phase of the dispersed same source harmonic signal consistent. The subsequent coherent accumulation can effectively converge the energy of the same source harmonic signal, greatly improve the amplitude intensity of the target signal, and suppress the interference of non-same source signals. This provides a signal basis with more concentrated energy and more obvious characteristics for subsequent clutter cancellation and target determination.

[0049] E. Based on the echo data of the harmonic radar, construct the dynamic clutter background field of the harmonic radar, and remove the dynamic clutter background field from the enhanced signal to obtain the cancellation residual signal of the harmonic radar. In this embodiment of the invention, constructing the dynamic clutter background field of the harmonic radar based on the echo data of the harmonic radar includes: Historical echo data of the harmonic radar are collected during continuous scanning cycles to obtain the historical echo dataset of the harmonic radar; Range-direction matched filtering is performed on the echo data in the historical echo dataset to obtain the range image data of the harmonic radar. Align the range image data according to the range cells to obtain the range-slow time two-dimensional data matrix of the harmonic radar; Based on the distance-slow time two-dimensional data matrix, the amplitude value of the distance unit in the historical scanning cycle is extracted along the slow time dimension to obtain the amplitude time series of the distance unit; Outlier removal is performed on the amplitude time series to obtain the background amplitude sample of the distance unit; The statistical center value of the background amplitude sample is used as the estimated background amplitude value of the distance unit; Arrange the background amplitude estimates according to the order of the range cells to construct the dynamic clutter background field of the harmonic radar.

[0050] The step of removing the dynamic clutter background field from the enhanced signal to obtain the cancellation residual signal of the harmonic radar includes: The enhanced signal is divided according to a range gate to obtain an enhanced amplitude sequence corresponding to the range cell in the dynamic clutter background field; The amplitude values ​​in the enhanced amplitude sequence are coupled with the background amplitude estimates of the corresponding range cells in the dynamic clutter background field on a range cell-by-range cell basis to obtain the initial cancellation residual of the range cell. The initial cancellation residual is smoothed and filtered to obtain the cancellation residual of the distance unit; The sampling points whose amplitude values ​​in the cancellation residual are lower than the preset background fluctuation threshold are set to zero, while the sampling points whose amplitude values ​​are higher than the preset background fluctuation threshold are retained, thus obtaining the cancellation residual signal of the harmonic radar.

[0051] The system continuously collects all echo data generated by the harmonic radar in multiple consecutive scanning cycles, and organizes and integrates all the collected echo data in chronological order of the scanning cycles to form a complete historical echo dataset of the harmonic radar.

[0052] Range-direction matched filtering is performed on each set of echo data in the historical echo dataset. The range dimension pulse width of the echo data is compressed by the filtering process to improve the range resolution. The signal data with range resolution characteristics obtained after processing is the range image data of the harmonic radar.

[0053] All processed range image data are aligned according to preset range units, so that each range unit corresponds to the echo signal data of all scanning cycles. All data are arranged in the form of range units as rows and scanning cycles as columns to form a two-dimensional range-slow time data matrix of harmonic radar.

[0054] Based on the distance-slow time two-dimensional data matrix, along the direction of the slow time dimension, the signal amplitude value corresponding to each distance unit in all historical scan cycles is extracted. The extracted amplitude values ​​are arranged in the order of scan cycles to obtain the amplitude time series corresponding to each distance unit.

[0055] Outlier removal is performed on the amplitude time series of each distance unit. By judging the degree of deviation of the amplitude value from the overall characteristics of the sequence, outlier data is screened out and directly removed. The amplitude value data retained after removal is the background amplitude sample of that distance unit.

[0056] Calculate the statistical center value of the background amplitude sample for each distance unit, and use the statistical center value directly as the background amplitude estimate for the corresponding distance unit to complete the calculation of the background amplitude estimate for all distance units.

[0057] According to the order of the range cells detected by the harmonic radar, the background amplitude estimates corresponding to all range cells are arranged in sequence. The arranged numerical sequence is then matched one-to-one with the range cells to construct the dynamic clutter background field of the harmonic radar.

[0058] The enhanced signal of the harmonic radar is divided into equal intervals according to the range gates of the dynamic clutter background field. The signal amplitude values ​​within each range gate are arranged in sequence to form an enhanced amplitude sequence that corresponds one-to-one with the range cells in the dynamic clutter background field.

[0059] According to the correspondence of the range cells, amplitude cancellation is performed on the amplitude values ​​in the enhanced amplitude sequence and the background amplitude estimate of the same range cell in the dynamic clutter background field one by one. The difference obtained by subtracting the background amplitude estimate of the corresponding range cell from the amplitude value in the enhanced amplitude sequence is the initial cancellation residual of the range cell.

[0060] The initial cancellation residuals obtained for each range cell are smoothed by filtering to remove irregular small-amplitude interference caused by clutter fluctuations. The resulting stable difference data is the cancellation residual for that range cell.

[0061] The preset background fluctuation threshold is retrieved, and the cancellation residual of all range units is judged point by point. The sampling point values ​​with amplitude values ​​lower than the background fluctuation threshold are directly set to zero, while the original values ​​of the sampling points with amplitude values ​​higher than the background fluctuation threshold are retained. The signal data formed by integrating all retained and zeroed values ​​is the cancellation residual signal of the harmonic radar.

[0062] The beneficial effects are that the dynamic clutter background field constructed by collecting multi-cycle historical echo data and processing it through a series of steps can accurately match the real-time change characteristics of clutter during harmonic radar detection, achieving dynamic and accurate estimation of the clutter background. Subsequently, dynamic clutter in the enhanced signal is removed by unit-by-unit amplitude cancellation, smoothing filtering, and threshold judgment, effectively filtering out the interference of clutter background and significantly reducing the impact of background noise on the target signal. This makes the signal characteristics of weak targets in the cancellation residual signal more prominent, laying a solid signal foundation for the subsequent accurate determination of weak target echoes. At the same time, the dynamic clutter removal method effectively reduces the possibility of misjudgment and missed judgment, improving the overall detection accuracy.

[0063] In this embodiment of the invention, F. determines the sampling points of the cancellation residual signal that exceed the preset dynamic threshold as weak target echoes, and extracts the distance data and azimuth information corresponding to the sampling points; A preset dynamic threshold is retrieved and used as the criterion for judging weak target echoes. The amplitude data of all sampling points in the residual signal are compared with the dynamic threshold one by one. Sampling points whose amplitude data exceeds the dynamic threshold are directly judged as valid sampling points carrying weak target echo information.

[0064] After determining the effective sampling points, the signal acquisition calibration parameters of the harmonic radar are retrieved. Based on the position of the effective sampling point in the time series of the canceled residual signal, combined with the radar's sampling interval and electromagnetic wave propagation characteristics, the target distance data corresponding to the effective sampling point is calculated. This data accurately reflects the actual distance between the target and the radar detection station.

[0065] Simultaneously extract the harmonic radar detection azimuth data corresponding to the effective sampling point, and combine it with the radar's antenna scanning angle, beam pointing and other calibration information to calibrate the detection azimuth data to obtain the accurate azimuth information corresponding to the effective sampling point. This information fully reflects the azimuth angle characteristics of the target relative to the radar detection station.

[0066] The beneficial effects are that the process uses a preset dynamic threshold as the judgment standard to accurately screen weak target echo sampling points, effectively distinguishing target signals from background interference. Combined with the range data and azimuth information extraction completed by radar calibration parameters, the accuracy and completeness of the data and information are guaranteed. This provides accurate and effective basic data support for determining the target's spatial coordinates in conjunction with real-time radar positioning data. At the same time, the standardized judgment and extraction process improves the efficiency of target signal recognition and reduces the interference of invalid data on subsequent positioning processes.

[0067] G. Based on the distance data and azimuth information, and combined with the real-time positioning data of the harmonic radar, determine the spatial coordinates of the target signal.

[0068] In this embodiment of the invention, determining the spatial coordinates of the target signal based on the distance data and azimuth information, combined with the real-time positioning data of the harmonic radar, includes: The real-time positioning data of the current moment is read from the positioning system of the harmonic radar. The real-time positioning data includes the longitude coordinates, latitude coordinates and altitude coordinates of the radar station. Based on the distance data and the azimuth angle in the orientation information, the planar projection distance and vertical height difference of the target signal relative to the radar station are analyzed in the local horizontal coordinate system where the radar station is located. The eastward and northward offsets of the target signal are obtained by vector synthesis of the plane projection distance and the azimuth angle. The eastward offset, the northward offset, and the vertical height difference are combined with the longitude, latitude, and altitude coordinates of the radar station to perform coordinate system transformation and fusion to obtain the three-dimensional spatial coordinates of the target signal. The three-dimensional spatial coordinates are converted into the longitude, latitude, and altitude of the target signal in the geographic coordinate system, which serve as the final spatial coordinates of the target signal.

[0069] The step of transforming and fusing the eastward offset, the northward offset, and the vertical height difference with the longitude, latitude, and altitude coordinates of the radar station to obtain the three-dimensional spatial coordinates of the target signal includes: The longitude coordinates, latitude coordinates, and altitude coordinates of the radar station are converted into three-dimensional rectangular coordinates of the radar station in the geocentric coordinate system according to the parameters of the Earth ellipsoid model. The offset vector in the local horizontal coordinate system, which is composed of the eastward offset, the northward offset, and the vertical height difference, is used to construct a rotation matrix from the local horizontal coordinate system to the geocentric coordinate system based on the longitude and latitude of the radar station's location. Determine the three-dimensional Cartesian coordinate components of the target signal according to the offset vector and the rotation matrix; Vectorially add the three-dimensional Cartesian coordinate components and the three-dimensional Cartesian coordinates of the radar site in the Earth-centered Earth-fixed coordinate system to obtain the three-dimensional coordinates of the target signal.

[0070] Retrieve the real-time positioning data of the radar site at the current moment from the positioning system supporting the harmonic radar, and directly extract the longitude coordinate, latitude coordinate, and altitude coordinate of the radar site included in the data to complete the acquisition and collation of the positioning basic data.

[0071] Based on the extracted target distance data and combined with the azimuth angle specified in the azimuth information, establish a local horizontal coordinate system with the radar site as the origin. Through spatial geometric analysis within this coordinate system, calculate the planar projection distance of the target signal relative to the radar site, and simultaneously analyze and obtain the vertical height difference between the target signal and the radar site.

[0072] Taking the radar site as the vector starting point, using the planar projection distance as the vector modulus length, and combining the azimuth angle to determine the vector direction, perform vector decomposition calculations in the local horizontal coordinate system to respectively obtain the eastward offset and northward offset of the target signal relative to the radar site.

[0073] First, retrieve the parameters of the Earth ellipsoid model, and according to the conversion rules set by the parameters, perform coordinate conversion on the longitude coordinate, latitude coordinate, and altitude coordinate of the radar site to obtain the three-dimensional Cartesian coordinates of the radar site in the Earth-centered Earth-fixed coordinate system.

[0074] Construct an offset vector in the local horizontal coordinate system with the eastward offset, northward offset, and vertical height difference. Calculate the rotation parameters required for coordinate conversion according to the longitude and latitude of the radar site, and accordingly build a rotation matrix from the local horizontal coordinate system to the Earth-centered Earth-fixed coordinate system.

[0075] Perform matrix multiplication on the constructed offset vector and the rotation matrix, and determine the three-dimensional Cartesian coordinate components of the target signal relative to the radar site in the Earth-centered Earth-fixed coordinate system through the operation result.

[0076] Perform vector addition on the calculated three-dimensional Cartesian coordinate components of the target signal and the three-dimensional Cartesian coordinates of the radar site in the Earth-centered Earth-fixed coordinate system, and obtain the three-dimensional coordinates of the target signal in the Earth-centered Earth-fixed coordinate system through the operation.

[0077] According to the conversion rules of the geographic coordinate system, perform inverse transformation on the three-dimensional coordinates of the target signal in the Earth-centered Earth-fixed coordinate system, and convert the Cartesian coordinate form to the longitude, latitude, and altitude forms in the geographic coordinate system. The coordinate data in this geographic coordinate system is the final spatial coordinate of the target signal.

[0078] The beneficial effects are that this process, through precise transformation and fusion of multiple coordinate systems and combined with the Earth ellipsoid model, achieves a complete derivation from the relative coordinates of the radar station to the absolute geographic coordinates. Each coordinate calculation relies on clear spatial geometric rules and transformation logic, ensuring the accuracy of the target signal's spatial coordinate calculation. At the same time, the entire process from relative offset extraction to final geographic coordinate transformation is closely connected, effectively avoiding data errors in the coordinate transformation process. This allows the final spatial coordinates of the determined target signal to accurately reflect the target's actual spatial location, providing reliable coordinate data support for the accurate positioning of weak targets by harmonic radar, and significantly improving the spatial positioning accuracy of weak targets by harmonic radar.

[0079] like Figure 2 The diagram shown is a functional block diagram of a harmonic radar weak target signal detection system provided in an embodiment of the present invention.

[0080] The harmonic radar weak target signal detection system described in this invention can be installed in an electronic device. Depending on the functions implemented, the harmonic radar weak target signal detection system may include a signal processing module, a signal slicing module, a phase extraction module, a signal enhancement module, a signal cancellation module, a signal determination module, and a target localization module. The modules described in this invention can also be referred to as units, which are a series of computer program segments that can be executed by the processor of an electronic device and perform a fixed function, stored in the memory of the electronic device.

[0081] In this embodiment, the functions of each module / unit are as follows: The signal processing module is used to digitize the echo signal of the harmonic radar to obtain the baseband complex signal of the harmonic radar. The signal slicing module is used to perform phase perturbation analysis on the baseband complex signal to obtain the persistent phase component of the baseband complex signal, and to construct the time domain slice of the harmonic radar based on the distribution range of the persistent phase component. The phase extraction module is used to extract the second harmonic frequency component in the time-domain slice that corresponds to the nonlinear junction characteristics in the target signal, and to record the initial phase value of the second harmonic frequency component. The signal enhancement module is used to perform phase rotation alignment processing on the baseband complex signal based on the initial phase value, and to coherently accumulate the energy of the same source harmonic signals dispersed in the baseband complex signal to obtain the enhanced signal of the harmonic radar. The signal cancellation module is used to construct the dynamic clutter background field of the harmonic radar based on the echo data of the harmonic radar, and remove the dynamic clutter background field from the enhanced signal to obtain the cancellation residual signal of the harmonic radar. The signal determination module is used to determine the cancellation residual signal at sampling points that exceed a preset dynamic threshold as weak target echoes, and to extract the distance data and azimuth information corresponding to the sampling points. The target positioning module is used to determine the spatial coordinates of the target signal based on the distance data and azimuth information, combined with the real-time positioning data of the harmonic radar.

[0082] In the several embodiments provided by this invention, it should be understood that the disclosed methods and systems can be implemented in other ways. For example, the system embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and other division methods may be used in actual implementation.

[0083] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0084] Furthermore, the functional modules in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware plus software functional modules.

[0085] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0086] This application embodiment can acquire and process relevant data based on artificial intelligence technology. Artificial intelligence is the theory, method, technology, and application system that uses digital computers or machines controlled by digital computers to simulate, extend, and expand human intelligence, perceive the environment, acquire knowledge, and use that knowledge to obtain optimal results.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for detecting weak target signals using harmonic radar, characterized in that, The method includes: A. The echo signal of the harmonic radar is digitally processed to obtain the baseband complex signal of the harmonic radar; B. Perform phase perturbation analysis on the baseband complex signal to obtain the persistent phase component of the baseband complex signal, and construct the time domain slice of the harmonic radar based on the distribution range of the persistent phase component. C. Extract the second harmonic frequency components in the time-domain slice that correspond to the nonlinear junction characteristics in the target signal, and record the initial phase values ​​of the second harmonic frequency components; D. Based on the initial phase value, the baseband complex signal is subjected to phase rotation and alignment processing, and the energy of the homogeneous harmonic signals dispersed in the baseband complex signal is coherently accumulated to obtain the enhanced signal of the harmonic radar; E. Based on the echo data of the harmonic radar, construct the dynamic clutter background field of the harmonic radar, and remove the dynamic clutter background field from the enhanced signal to obtain the cancellation residual signal of the harmonic radar. F. The sampling points where the cancellation residual signal exceeds the preset dynamic threshold are determined to be weak target echoes, and the distance data and azimuth information corresponding to the sampling points are extracted; G. Based on the distance data and azimuth information, and combined with the real-time positioning data of the harmonic radar, determine the spatial coordinates of the target signal.

2. The method for detecting weak target signals using harmonic radar as described in claim 1, characterized in that, The step involves performing phase perturbation analysis on the baseband complex signal to obtain the persistent phase component of the baseband complex signal, and constructing a time-domain slice of the harmonic radar based on the distribution range of the persistent phase component, including: The baseband complex signal of the harmonic radar is subjected to sliding windowing processing to obtain the window data segment of the baseband complex signal; The instantaneous phase values ​​in the window data segment are analyzed for change trends to obtain the monotonic change trend components of the window data segment, and the monotonic change trend components are recorded as the local phase perturbation baseline of the window data segment. The local phase perturbation baseline is smoothed and connected to obtain the continuous phase component of the baseband complex signal; Based on the phase value of the persistent phase component on the time axis, the value range of the persistent phase component is divided into a continuous phase dwell interval. Based on the start and end points of the phase dwell interval, the baseband complex signal is extracted to obtain a time-domain slice of the harmonic radar.

3. The method for detecting weak target signals using harmonic radar as described in claim 1, characterized in that, The step of extracting the second harmonic frequency components in the time-domain slice that correspond to the nonlinear junction characteristics in the target signal, and recording the initial phase values ​​of the second harmonic frequency components, includes: The time-domain slice is subjected to spectral decomposition to obtain the amplitude spectrum and phase spectrum data of the time-domain slice; Based on the transmission frequency of the harmonic radar, locate the second harmonic frequency point in the amplitude spectrum that is twice the frequency of the transmission frequency, and read the complex spectral line value corresponding to the second harmonic frequency point. The complex spectral line value is compared and analyzed with the nonlinear junction response amplitude threshold in the target signal. If the complex spectral line value is greater than the nonlinear junction response amplitude threshold, the complex spectral line value is determined to be a second harmonic frequency component that conforms to the characteristics of a nonlinear junction. The phase value corresponding to the second harmonic frequency point is extracted from the phase spectrum data, and the phase value is recorded as the initial phase value of the second harmonic frequency component.

4. The method for detecting weak target signals using harmonic radar as described in claim 1, characterized in that, The step of performing phase rotation and alignment processing on the baseband complex signal based on the initial phase value, and coherently accumulating the energy of the homogeneous harmonic signals dispersed in the baseband complex signal to obtain the enhanced signal of the harmonic radar, includes: Based on the pulse repetition period of the harmonic radar, the baseband complex signal is divided into a continuous pulse echo sequence. Complex value sampling points corresponding to the preset target range gate are extracted from the pulse echo sequence to obtain the homogeneous signal of the harmonic radar; Based on the initial phase value, determine the phase value corresponding to the sampling point in the same source signal; The same source signal is enhanced to obtain the enhanced signal of the harmonic radar.

5. The method for detecting weak target signals using harmonic radar as described in claim 4, characterized in that, The formula for calculating the enhanced signal is as follows: ； in, This refers to the enhanced signal. This indicates the total number of pulse echo sequences. Indicates the first One complex value sampling point, No. The instantaneous phase value of each complex-valued sampling point This indicates the preset reference phase value. Represents the imaginary unit. Represents the natural constant.

6. The method for detecting weak target signals using harmonic radar as described in claim 1, characterized in that, The step of constructing the dynamic clutter background field of the harmonic radar based on the echo data of the harmonic radar includes: Historical echo data of the harmonic radar are collected during continuous scanning cycles to obtain the historical echo dataset of the harmonic radar; Range-direction matched filtering is performed on the echo data in the historical echo dataset to obtain the range image data of the harmonic radar. Align the range image data according to the range cells to obtain the range-slow time two-dimensional data matrix of the harmonic radar; Based on the distance-slow time two-dimensional data matrix, the amplitude value of the distance unit in the historical scanning cycle is extracted along the slow time dimension to obtain the amplitude time series of the distance unit; Outlier removal is performed on the amplitude time series to obtain the background amplitude sample of the distance unit; The statistical center value of the background amplitude sample is used as the estimated background amplitude value of the distance unit; Arrange the background amplitude estimates according to the order of the range cells to construct the dynamic clutter background field of the harmonic radar.

7. The method for detecting weak target signals using harmonic radar as described in claim 1, characterized in that, The step of removing the dynamic clutter background field from the enhanced signal to obtain the cancellation residual signal of the harmonic radar includes: The enhanced signal is divided according to a range gate to obtain an enhanced amplitude sequence corresponding to the range cell in the dynamic clutter background field; The amplitude values ​​in the enhanced amplitude sequence are coupled with the background amplitude estimates of the corresponding range cells in the dynamic clutter background field on a range cell-by-range cell basis to obtain the initial cancellation residual of the range cell. The initial cancellation residual is smoothed and filtered to obtain the cancellation residual of the distance unit; The sampling points whose amplitude values ​​in the cancellation residual are lower than the preset background fluctuation threshold are set to zero, while the sampling points whose amplitude values ​​are higher than the preset background fluctuation threshold are retained, thus obtaining the cancellation residual signal of the harmonic radar.

8. The method for detecting weak target signals using harmonic radar as described in claim 1, characterized in that, The step of determining the spatial coordinates of the target signal based on the distance data and azimuth information, combined with the real-time positioning data of the harmonic radar, includes: The real-time positioning data of the current moment is read from the positioning system of the harmonic radar. The real-time positioning data includes the longitude coordinates, latitude coordinates and altitude coordinates of the radar station. Based on the distance data and the azimuth angle in the orientation information, the planar projection distance and vertical height difference of the target signal relative to the radar station are analyzed in the local horizontal coordinate system where the radar station is located. The eastward and northward offsets of the target signal are obtained by vector synthesis of the plane projection distance and the azimuth angle. The eastward offset, the northward offset, and the vertical height difference are combined with the longitude, latitude, and altitude coordinates of the radar station to perform coordinate system transformation and fusion to obtain the three-dimensional spatial coordinates of the target signal. The three-dimensional spatial coordinates are converted into the longitude, latitude, and altitude of the target signal in the geographic coordinate system, which serve as the final spatial coordinates of the target signal.

9. The method for detecting weak target signals using harmonic radar as described in claim 8, characterized in that, The step of transforming and fusing the eastward offset, the northward offset, and the vertical height difference with the longitude, latitude, and altitude coordinates of the radar station to obtain the three-dimensional spatial coordinates of the target signal includes: The longitude coordinates, latitude coordinates, and altitude coordinates of the radar station are converted into three-dimensional rectangular coordinates of the radar station in the geocentric coordinate system according to the parameters of the Earth ellipsoid model. The offset vector in the local horizontal coordinate system, which is composed of the eastward offset, the northward offset, and the vertical height difference, is used to construct a rotation matrix from the local horizontal coordinate system to the geocentric coordinate system based on the longitude and latitude of the radar station's location. The three-dimensional Cartesian coordinate components of the target signal are determined based on the offset vector and the rotation matrix. The three-dimensional spatial rectangular coordinate components and the three-dimensional spatial rectangular coordinates in the geocentric coordinate system of the radar station are vector-added together to obtain the three-dimensional spatial coordinates of the target signal.

10. A harmonic radar weak target signal detection system, characterized in that, For implementing the method for detecting weak target signals using harmonic radar as described in claim 1, the system comprises: The signal processing module is used to digitize the echo signal of the harmonic radar to obtain the baseband complex signal of the harmonic radar. The signal slicing module is used to perform phase perturbation analysis on the baseband complex signal to obtain the persistent phase component of the baseband complex signal, and to construct the time domain slice of the harmonic radar based on the distribution range of the persistent phase component. The phase extraction module is used to extract the second harmonic frequency component in the time-domain slice that corresponds to the nonlinear junction characteristics in the target signal, and to record the initial phase value of the second harmonic frequency component. The signal enhancement module is used to perform phase rotation alignment processing on the baseband complex signal based on the initial phase value, and to coherently accumulate the energy of the homogeneous harmonic signals dispersed in the baseband complex signal to obtain the enhanced signal of the harmonic radar. The signal cancellation module is used to construct the dynamic clutter background field of the harmonic radar based on the echo data of the harmonic radar, and remove the dynamic clutter background field from the enhanced signal to obtain the cancellation residual signal of the harmonic radar. The signal determination module is used to determine the sampling points where the cancellation residual signal exceeds a preset dynamic threshold as weak target echoes, and to extract the distance data and azimuth information corresponding to the sampling points. The target positioning module is used to determine the spatial coordinates of the target signal based on the distance data and azimuth information, combined with the real-time positioning data of the harmonic radar.

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