A frequency domain ground penetrating radar signal synthesis method and system based on receiving end amplitude-phase weighting

Abstract

The present application relates to the technical field of radar signal processing, and particularly relates to a frequency domain ground penetrating radar signal synthesis method and system based on receiving end amplitude and phase weighting, setting a frequency sequence of a stepped frequency continuous wave ground penetrating radar; controlling a transmitting end to transmit equal amplitude and equal phase continuous wave signals according to the frequency sequence; obtaining echo signals of each frequency point received by a receiving end, and demodulating and processing the echo signals of each frequency point to obtain complex frequency domain responses corresponding to the echo signals of each frequency point; obtaining a target time domain waveform, performing frequency domain transformation on the target time domain waveform to obtain frequency spectrum amplitude information and frequency spectrum phase information corresponding to the target time domain waveform, and constructing complex weights according to the frequency spectrum amplitude information and the frequency spectrum phase information; performing amplitude and phase weighting on the complex frequency domain responses according to the complex weights to obtain weighted complex frequency domain responses; arranging the weighted complex frequency domain responses according to the frequency sequence, and performing inverse Fourier transformation on the weighted complex frequency domain responses to obtain an equivalent time domain wideband signal.

Description

Technical Field

[0001] This invention relates to the field of radar signal processing technology, specifically to a method and system for synthesizing frequency domain ground-penetrating radar signals based on receiver amplitude and phase weighting. Background Technology

[0002] Ground-penetrating radar (GPR) is a geophysical exploration technology that utilizes the propagation characteristics of electromagnetic waves to perform non-destructive testing of underground structures. It is widely used in road structure inspection, underground pipeline location, tunnel lining inspection, and detection of underground anomalies. Based on the different forms of transmitted signals, GPR mainly includes time-domain pulse-based GPR and frequency-domain continuous-wave GPR.

[0003] Time-domain pulse ground-penetrating radar typically uses broadband pulse signals as the transmitted signal and determines the target location by receiving the echo reflected from the underground medium. This system has high time resolution, but due to the short duration of the transmitted pulse, the average transmitted power is limited, and the echo signal-to-noise ratio is easily affected in complex underground media, environments with strong electromagnetic interference, and scenarios involving the detection of deep, weakly reflective targets.

[0004] Frequency-domain continuous wave ground-penetrating radar transmits continuous wave signals point-by-point according to a frequency sequence within a preset frequency range and acquires the corresponding echo response at each frequency point. Through frequency-domain data processing, an equivalent time-domain broadband signal is obtained. This system can synthesize broadband signals using information from multiple discrete frequency points, and has application value in improving detection sensitivity and anti-interference capabilities.

[0005] In existing frequency-domain continuous wave ground-penetrating radar signal synthesis methods, to ensure the synthesized time-domain signal possesses the target waveform characteristics, it is typically necessary to set amplitude and phase parameters for the continuous wave signal at each frequency point of the transmitting end based on the spectral amplitude and phase information corresponding to the target time-domain waveform. This allows the transmitted signal at each frequency point to carry the spectral characteristics corresponding to the target waveform. This approach requires independent amplitude and phase control at the transmitting end for different frequency points, increasing the complexity of transmitting link parameter configuration. Furthermore, due to differences in the frequency response of radio frequency devices and phase drift, calibration is required for multiple frequency points, affecting the consistency of system implementation.

[0006] Meanwhile, when the detection mission requires different target time-domain waveforms, existing methods usually need to readjust the amplitude and phase parameters corresponding to each frequency point of the transmitter to make the transmitter signal rematch the target waveform spectrum characteristics. This results in the target waveform switching process relying on the reconfiguration of transmitter parameters, which reduces the flexibility of frequency domain continuous wave ground-penetrating radar signal synthesis. Summary of the Invention

[0007] This invention aims to solve the above-mentioned technical problems by providing a frequency domain ground-penetrating radar signal synthesis method and system based on receiver amplitude and phase weighting, which can achieve frequency domain amplitude and phase adjustment through receiver digital signal processing while maintaining the stability of the transmitter signal form.

[0008] The objective of this invention can be achieved through the following technical solutions: A frequency-domain ground-penetrating radar signal synthesis method based on receiver amplitude and phase weighting includes: S1. Set the frequency sequence of the step-frequency continuous wave ground-penetrating radar; control the transmitter to transmit continuous wave signals of equal amplitude and equal phase at frequency points according to the frequency sequence; S2. Acquire the echo signals at each frequency point received by the receiver, and demodulate the echo signals at each frequency point to obtain the complex frequency domain response corresponding to the echo signals at each frequency point. S3. Obtain the target time-domain waveform, perform frequency domain transformation on the target time-domain waveform to obtain the spectral amplitude information and spectral phase information corresponding to the target time-domain waveform, and construct complex weights based on the spectral amplitude information and spectral phase information. S4. Apply amplitude and phase weights to the complex frequency domain response according to the complex weights to obtain the weighted complex frequency domain response; S5. Arrange the weighted complex frequency domain response according to the frequency sequence, and perform inverse Fourier transform on the weighted complex frequency domain response to obtain the equivalent time-domain broadband signal.

[0009] Furthermore, step S1 includes: Determine the starting frequency Frequency step value and the number of frequency points ; Based on the starting frequency and frequency step value The frequency sequence is generated by the number of frequency points, and the frequency sequence includes multiple discrete frequency points arranged in ascending order of frequency. Each frequency point is represented as: Frequency stepping The total time window is used to determine the equivalent time-domain synthesized signal, and the synthesis bandwidth is used to determine the distance resolution; the frequency sequence transmits equal-amplitude, equal-phase continuous wave signals point by point, and the continuous wave signals transmitted at each frequency point are represented as follows: in, To standardize the launch amplitude, To unify the initial phase.

[0010] Furthermore, step S2 includes: Synchronous demodulation of the echo signals at each frequency point yields the in-phase components corresponding to each frequency point's echo signal. and orthogonal components ; The in-phase component is used as the real part of the complex frequency domain response; the quadrature component is used as the imaginary part of the complex frequency domain response; the complex frequency domain response is constructed based on the in-phase and quadrature components: Synchronous demodulation methods include simulation Any one of demodulation, digital downconversion, or frequency and phase extraction of steady-state echo.

[0011] Furthermore, step S3 includes: Obtain the preset target time-domain waveform ; Perform a Fourier transform on the target time-domain waveform to obtain the corresponding spectral information. ; Based on the discrete frequency points in the frequency sequence, extract the spectral amplitude information of the corresponding frequency points from the spectral information. and spectral phase information ; Furthermore, step S3 includes: Determine the amplitude weights corresponding to each frequency point based on the spectral amplitude information corresponding to the target time-domain waveform; The phase weights corresponding to each frequency point are determined based on the spectral phase information corresponding to the target time-domain waveform. The complex weights corresponding to each frequency point are generated based on the amplitude weights and phase weights: Furthermore, step S4 includes: The complex frequency domain response corresponding to each frequency point Complex weights at corresponding frequency points Perform complex multiplication to obtain the weighted complex frequency domain response: The in-phase and quadrature components are updated based on amplitude and phase weights to obtain the weighted in-phase components. and weighted orthogonal components : Furthermore, step S4 also includes: Obtain the frequency response calibration parameters corresponding to the ground penetrating radar system. ; Generate the total complex weights based on the frequency response calibration parameters and complex weights: Among them, the total complex weight is used to simultaneously represent the target waveform spectral weight and the system frequency response calibration relationship; The amplitude and phase weights of the complex frequency domain response are assigned using total complex weights.

[0012] Furthermore, step S5 includes: According to the arrangement order of each frequency point in the frequency sequence, the weighted complex frequency domain responses corresponding to each frequency point are combined into a discrete complex frequency domain sequence. The equivalent time-domain broadband signal is obtained by performing an inverse Fourier transform on the discrete complex frequency domain sequence. The total time window corresponding to the equivalent time-domain broadband signal satisfies: in, This represents the frequency step value between adjacent frequency points in the frequency sequence; Furthermore, it also includes: Acquire echo signals corresponding to multiple scan positions; Frequency sequence transmission, complex frequency domain response acquisition, complex weighted amplitude and phase weighting, and inverse Fourier transform processing are performed on the echo signals corresponding to each scanning position to obtain the equivalent time-domain broadband echo corresponding to each scanning position. According to the sequence of the survey line positions corresponding to multiple scanning positions, the equivalent time-domain broadband echoes are arranged to form ground-penetrating radar B-scan profile data. When it is necessary to adjust the target time domain waveform, the frequency sequence and the equal amplitude and equal phase continuous wave signal remain unchanged. The complex frequency domain response is weighted by replacing the complex weight sequence corresponding to the complex weight.

[0013] A frequency-domain ground-penetrating radar signal synthesis system based on receiver amplitude and phase weighting includes: The frequency sequence setting module is used to set the frequency sequence of the step-frequency continuous wave ground-penetrating radar. The transmission control module is used to control the transmitter to transmit equal-amplitude, equal-phase continuous wave signals one frequency point at a time according to the frequency sequence; The receiving and processing module is used to acquire the echo signals at each frequency point received by the receiving end, and to demodulate the echo signals at each frequency point to obtain the complex frequency domain response corresponding to each echo signal. The complex weight construction module is used to obtain the spectral amplitude and spectral phase information corresponding to the target time-domain waveform, and construct complex weights based on the spectral amplitude and spectral phase information. The amplitude and phase weighting module is used to perform amplitude and phase weighting on the complex frequency domain response according to the complex weights to obtain the weighted complex frequency domain response; The signal synthesis module is used to perform inverse Fourier transform on the weighted complex frequency domain response to obtain an equivalent time-domain broadband signal.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention controls the transmitter to transmit equal-amplitude and equal-phase continuous wave signals at frequency points according to the frequency sequence, transferring the configuration process of amplitude and phase information corresponding to the target waveform from the transmitter to the digital processing process at the receiver. This reduces the need for the transmitter to configure amplitude and phase parameters for different frequency points and lowers the control complexity of the frequency domain ground-penetrating radar transmission link.

[0015] 2. This invention performs amplitude and phase weighting processing based on complex frequency domain response, and jointly processes the amplitude and phase information in the echo signal. Compared with the method of adjusting only the single amplitude information, it can preserve the phase characteristics in the frequency domain signal and improve the waveform consistency in the process of frequency domain to time domain signal conversion.

[0016] 3. This invention constructs corresponding complex weights based on the spectral amplitude and spectral phase information corresponding to different target time-domain waveforms. While keeping the signal form at the transmitting end unchanged, it only needs to adjust the complex weight parameters used at the receiving end to adapt to the signal synthesis requirements corresponding to different target time-domain waveforms, thereby improving the flexibility of the frequency domain ground-penetrating radar signal processing process.

[0017] 4. This invention converts the discrete frequency domain response into a time domain signal by performing an inverse Fourier transform on the amplitude-phase weighted complex frequency domain response, forming a frequency domain ground-penetrating radar signal synthesis process based on receiver digital processing, thus providing a new signal synthesis method for broadband signal processing of frequency domain continuous wave ground-penetrating radar. Attached Figure Description

[0018] Figure 1 This is a flowchart of a frequency domain ground-penetrating radar signal synthesis method based on receiver amplitude and phase weighting provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the forward model of road structure used in an embodiment of the present invention. Figure 3 A schematic diagram of the target waveform (taking the Ricker wavelet with a center frequency of 600MHz as an example) and its spectral amplitude and phase characteristics. Figure 4 The amplitude and phase sampling results of the complex weights of the target waveform Figure 5 Comparison chart of amplitude and phase weighted synthesis results at the receiver and direct forward modeling results of the target waveform. Figure 6 Comparison of amplitude and phase weighted synthesis results at the receiver for different target waveforms Figure 7Comparison of receiver amplitude and phase weighted synthesized B-scan with reference B-scan under noise conditions. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0020] like Figures 1 to 7 The method for synthesizing frequency-domain ground-penetrating radar signals based on receiver amplitude and phase weighting, as shown, includes: S1. Set the frequency sequence of the step-frequency continuous wave ground-penetrating radar; by determining multiple discrete frequency points corresponding to the frequency domain sampling of the ground-penetrating radar, a frequency index basis is provided for subsequent continuous wave signal transmission, echo frequency domain response acquisition, and frequency domain signal reconstruction, enabling the ground-penetrating radar to acquire the frequency domain response information corresponding to underground targets based on multiple discrete frequency points. Control the transmitter to transmit continuous wave signals of equal amplitude and equal phase point by point according to the frequency sequence; ensure that the transmitter outputs continuous wave signals with uniform amplitude and uniform phase only according to the preset frequency sequence, avoiding the need to adjust the transmission amplitude and phase separately for different frequency points according to the target waveform spectrum characteristics, and transferring the target waveform control process from the radio frequency transmission stage to the subsequent digital signal processing stage.

[0021] S2. Acquire the echo signals at each frequency point received by the receiver, and demodulate the echo signals at each frequency point to obtain the complex frequency domain response corresponding to each frequency point echo signal; extract the frequency domain information of the underground target reflected echoes corresponding to different frequency points, and convert the received echo signals into complex frequency domain responses containing amplitude and phase information, so as to provide a data basis for subsequent amplitude and phase joint adjustment at the receiver.

[0022] S3. Obtain the target time-domain waveform, perform frequency domain transformation on the target time-domain waveform to obtain the spectral amplitude and spectral phase information corresponding to the target time-domain waveform, and construct complex weights based on the spectral amplitude and spectral phase information; convert the spectral features corresponding to the target time-domain waveform into digital complex weight parameters, so that the amplitude and phase features in the target waveform can be loaded into the signal processing process at the receiving end in complex form, providing a weight basis for subsequent adjustment of the complex frequency domain response.

[0023] S4. Apply amplitude and phase weights to the complex frequency domain response according to the complex weights to obtain the weighted complex frequency domain response. During the digital processing at the receiving end, apply the amplitude and phase weights corresponding to the target waveform to the complex frequency domain response. By adjusting the amplitude and phase of the complex frequency domain response at each frequency point through complex domain amplitude and phase adjustment, the frequency domain data at the receiving end carries the spectral characteristics corresponding to the target waveform.

[0024] S5. Arrange the weighted complex frequency domain response according to the frequency sequence, and perform inverse Fourier transform on the weighted complex frequency domain response to obtain the equivalent time-domain broadband signal, thus completing the frequency domain ground-penetrating radar signal synthesis process based on receiver digital processing.

[0025] Specifically, step S1 includes: Determine the starting frequency Frequency step value and the number of frequency points The starting frequency is used to determine the starting position of the frequency sequence, the frequency step value is used to determine the frequency interval between adjacent discrete frequency points, and the number of frequency points is used to determine the number of discrete frequency points contained in the frequency sequence.

[0026] Based on the starting frequency and frequency step value The frequency sequence is generated by the number of frequency points, and the frequency sequence includes multiple discrete frequency points arranged in ascending order of frequency. Each frequency point is represented as: By generating multiple discrete frequency points in ascending order of frequency, the ground-penetrating radar can collect underground target reflection information point by point according to a preset frequency sequence, forming discrete frequency domain sampling data within a continuous frequency band.

[0027] The synthetic bandwidth is used to determine the range resolution. The effective synthetic bandwidth is determined by the coverage range of the frequency sequence, establishing a correspondence between the frequency domain sampling range and the time-domain signal resolution capability of the ground-penetrating radar. This provides a frequency domain basis for the spatial resolution capability of the subsequent equivalent time-domain broadband signal. The frequency sequence transmits equal-amplitude, equal-phase continuous wave signals point by point. The continuous wave signal transmitted at each frequency point is represented as follows: in, To standardize the launch amplitude, To unify the initial phase, the control transmitter outputs a continuous wave signal with consistent amplitude and phase according to the frequency sequence, ensuring that there are no amplitude and phase differences introduced by the target waveform between different frequency points, and removing the spectral amplitude and spectral phase information corresponding to the target waveform from the transmitter.

[0028] Specifically, step S2 includes: Synchronous demodulation of the echo signals at each frequency point yields the in-phase components corresponding to each frequency point's echo signal. and orthogonal components By synchronously demodulating the echo signals at each frequency point, the time-domain echo signals acquired by the receiver are converted into orthogonal baseband signals at the corresponding frequency points, and the amplitude and phase information contained in the echo signals at each frequency point are extracted. Among them, the in-phase component is used to characterize the projection information of the echo signal in the reference phase direction, and the orthogonal component is used to characterize the projection information of the echo signal in the orthogonal phase direction.

[0029] The in-phase component is used as the real part of the complex frequency domain response; the quadrature component is used as the imaginary part of the complex frequency domain response; the complex frequency domain response is constructed based on the in-phase and quadrature components: Establish the correspondence between the amplitude and phase information of the echo signal and its complex domain representation, and convert the echo signal at each frequency point from two orthogonal components into a unified complex form.

[0030] Synchronous demodulation methods include simulation Any one of demodulation, digital down-conversion, or frequency point amplitude and phase extraction from steady-state echoes. By using different forms of frequency domain information extraction methods, the in-phase and quadrature components corresponding to the echo signals at each frequency point are obtained, enabling the receiver to select the appropriate signal demodulation method according to the actual ground-penetrating radar hardware structure, thereby improving the applicability of the complex frequency domain response acquisition process.

[0031] Specifically, step S3 includes: Obtain the preset target time-domain waveform The target time-domain waveform serves as a waveform reference during the amplitude and phase weighting process at the receiver, and is used to determine the amplitude and phase adjustment parameters corresponding to each frequency point.

[0032] Perform a Fourier transform on the target time-domain waveform to obtain the corresponding spectral information. The target time-domain waveform is transformed to the frequency domain, and the time-domain waveform features are decomposed into spectral information corresponding to different frequency components, so that the amplitude and phase features of the target waveform at each discrete frequency point can be extracted and used to construct complex weights.

[0033] Based on the discrete frequency points in the frequency sequence, extract the spectral amplitude information of the corresponding frequency points from the spectral information. and spectral phase information ; Based on the determined frequency sequence, the continuous spectrum information corresponding to the target time-domain waveform is mapped to the discrete frequency points actually sampled by the ground penetrating radar, thereby obtaining the target amplitude weight and target phase weight corresponding to the echo signal at each frequency point, and establishing a correspondence between the target waveform spectrum characteristics and the frequency sampling frequency points of the ground penetrating radar in the frequency domain.

[0034] Furthermore, step S3 also includes: Extract the energy distribution characteristics of the target time-domain waveform at each discrete frequency point, and convert the spectral amplitude information of the target waveform into amplitude adjustment parameters for the corresponding frequency points.

[0035] Extract the phase distribution characteristics of the target time-domain waveform at each discrete frequency point, and convert the spectral phase information of the target waveform into phase adjustment parameters for the corresponding frequency points.

[0036] The complex weights corresponding to each frequency point are generated based on the amplitude weights and phase weights: The amplitude and phase information corresponding to the target time-domain waveform are uniformly converted into complex weights in complex form, so that each discrete frequency point has a corresponding amplitude and phase adjustment parameter, which can directly affect the complex frequency domain response obtained by the receiver and realize the loading of the target waveform spectral characteristics in the digital domain.

[0037] Specifically, step S4 includes: The complex frequency domain response corresponding to each frequency point Complex weights at corresponding frequency points Perform complex multiplication to obtain the weighted complex frequency domain response: By performing complex domain multiplication on the complex frequency domain response corresponding to each frequency point at the receiving end, the amplitude weight and phase weight in the complex weight are simultaneously applied to the complex frequency domain response, so that the amplitude and phase characteristics of the echo signal at each frequency point are adjusted according to the spectral characteristics corresponding to the target time domain waveform.

[0038] The complex multiplication process does not simply scale the signal amplitude, but simultaneously performs amplitude adjustment and phase rotation in the complex domain, so that the receiver's complex frequency domain response carries the spectral information corresponding to the target time domain waveform.

[0039] The in-phase and quadrature components are updated based on amplitude and phase weights to obtain the weighted in-phase components. and weighted orthogonal components : By performing a joint transformation on the in-phase and quadrature components in the complex frequency domain response, the amplitude and phase weights corresponding to the complex weights are mapped to the real and imaginary parts of the complex frequency domain response, respectively, thereby achieving synchronous adjustment of the amplitude and phase information of the echo signal.

[0040] Furthermore, step S4 also includes: Obtain the frequency response calibration parameters corresponding to the ground penetrating radar system. The goal is to acquire the frequency response characteristics of a ground-penetrating radar system at different frequencies, which will be used to describe the amplitude attenuation and phase shift relationships of the transmit link, receive link, and radio frequency devices to signals of different frequencies. Generate the total complex weights based on the frequency response calibration parameters and complex weights: The total complex weight is used to simultaneously represent the target waveform spectral weight and the system frequency response calibration relationship. The complex weight corresponding to the target time-domain waveform is fused with the frequency response calibration parameters of the ground penetrating radar system to form a total complex weight that simultaneously includes the target waveform spectral characteristics and the system frequency response characteristics, so that the amplitude and phase weighting process at the receiver can comprehensively consider the target waveform requirements and the frequency response characteristics of the radar system itself.

[0041] The total complex weight is applied to the complex frequency domain response to perform comprehensive amplitude and phase adjustment on the echo signals at each frequency point, so that the complex frequency domain response simultaneously meets the spectral requirements corresponding to the target time domain waveform and the frequency response compensation requirements of the ground penetrating radar system.

[0042] Specifically, step S5 includes: Based on the frequency sequence, the complex frequency domain responses of each frequency point after amplitude and phase weighting are arranged according to their corresponding frequency positions to restore the frequency order relationship of the discrete frequency domain data, forming a complete discrete complex frequency domain sequence for time domain reconstruction.

[0043] The frequency domain data after amplitude and phase weighting at the receiving end is converted to the time domain, and the spectral characteristics corresponding to the target time domain waveform are mapped from the frequency domain to the time domain to obtain the corresponding equivalent time domain broadband signal.

[0044] The inverse Fourier transform utilizes discrete frequency domain sampling data to recover the time domain response, converting the frequency domain information after amplitude and phase adjustment in the complex frequency domain into a time domain echo signal that can be analyzed by ground penetrating radar.

[0045] The total time window corresponding to the equivalent time-domain broadband signal satisfies: in, The frequency step value is the frequency step value between adjacent frequency points in the frequency sequence; the time domain observation range corresponding to the inverse Fourier transform is determined according to the frequency step value, so that the discrete frequency sampling range corresponds to the preset maximum unambiguous time range, ensuring that the time domain broadband signal can cover the effective time area in the propagation process of the ground penetrating radar echo.

[0046] Specifically, it also includes: Echo signals corresponding to multiple scanning positions are acquired; echo signals corresponding to different spatial positions are collected during the movement of the ground penetrating radar along the survey line, so that frequency domain signal processing can be performed separately for different scanning positions to obtain spatially continuously distributed underground target response information.

[0047] Frequency sequence transmission, complex frequency domain response acquisition, complex weighted amplitude and phase weighting, and inverse Fourier transform processing are performed on the echo signals corresponding to each scanning position to obtain the equivalent time-domain broadband echo corresponding to each scanning position. For the echo signals corresponding to different scanning positions, the frequency domain signal acquisition and receiver amplitude and phase weighting processing procedures are repeated to ensure that each scanning position obtains the corresponding equivalent time-domain broadband echo.

[0048] According to the sequence of the survey lines corresponding to multiple scanning positions, the equivalent time-domain broadband echoes are arranged to form ground-penetrating radar B-scan profile data; based on the spatial position information during the ground-penetrating radar's moving scan process, the equivalent time-domain broadband echoes corresponding to different scanning positions are arranged according to the survey line direction to establish the correspondence between spatial position and time-domain echoes, forming two-dimensional profile data for underground structure analysis.

[0049] Specifically, when adjusting the target time-domain waveform, the frequency sequence and the equal-amplitude, equal-phase continuous wave signal remain unchanged. The amplitude and phase weights of the complex frequency domain response are assigned by replacing the complex weight sequence corresponding to the complex weights. Under the condition that the frequency sequence and transmitted signal form at the transmitting end remain unchanged, the amplitude and phase relationship of the complex frequency domain response are adjusted by changing the complex weight sequence used at the receiving end, so that the same set of frequency domain acquired data can adapt to the signal synthesis requirements corresponding to different target time-domain waveforms.

[0050] See Figures 2 to 7 This embodiment uses numerical forward modeling to verify the amplitude and phase weighting process of the receiver of the present invention. The numerical forward model and impulse response convolution are used to obtain the echo signals at each frequency point, simulating the echo signals acquired by the receiver during actual detection. The receiver extracts the in-phase and quadrature components corresponding to the echo signals at each frequency point, and constructs a complex frequency domain response based on the in-phase and quadrature components; then, it constructs complex weights based on the spectral amplitude and spectral phase information corresponding to the target time-domain waveform, and performs amplitude and phase weighting on the complex frequency domain response; finally, it obtains the equivalent time-domain broadband signal by performing inverse Fourier transform on the weighted complex frequency domain response.

[0051] like Figure 2As shown, in this embodiment, a forward model closely resembling an actual road engineering scenario is constructed as the verification object. The model size is 3m × 2.5m, and it contains five media layers from top to bottom: air, asphalt, concrete, gravel, and clay. Random perturbations of ±0.006m are introduced at each layer interface to simulate the roughness of the actual interface. The gravel and clay layers are composed of a random mixture of various materials. Specifically, the gravel layer contains 75% gravel, 20% fine stone particles, and 5% air pores; the clay layer contains 85% subgrade soil and 15% wet soil. Two circular anomalies are set in the model, both located within the soil layer, with a radius of 0.1m. The left circular anomaly is a metal pipe, and the right circular anomaly is an air anomaly, used to simulate underground cavities. The transmitter and receiver are both located on the surface of the asphalt layer, with a distance of 0.2m between the transmitting and receiving antennas and a movement step of 0.02m. A total of 130 data channels are collected.

[0052] Using a unit impulse signal as the emission source, the above model was subjected to a forward modeling operation using the open-source ground-penetrating radar forward modeling software gprMax, yielding the impulse response sequence at each observation point. The impulse response sequence characterizes the linear time-invariant response information of the forward model to a broadband excitation signal.

[0053] During the actual detection process, the transmitting end transmits equal-amplitude, equal-phase continuous wave signals point by point according to the frequency sequence. The receiving end acquires the echo signal corresponding to each frequency point. In the digital simulation verification process, the constant-amplitude, constant-phase continuous wave signal is convolved with the impulse response sequence to obtain the echo signal corresponding to each frequency point. .

[0054] Demodulate the echo signals at each frequency point to obtain the in-phase components corresponding to each frequency point echo signal. and orthogonal components And based on the in-phase components and orthogonal components Constructing the complex frequency domain response .

[0055] like Figure 3 As shown, a Ricker wavelet with a center frequency of 600MHz is selected as the target time-domain waveform. A Fourier transform is performed on the target time-domain waveform to obtain its spectral amplitude and phase information. Based on the spectral amplitude information, the effective frequency band of the target time-domain waveform is determined to be 0–2GHz. Discrete sampling is performed within the effective frequency band at 20MHz frequency steps to obtain the amplitude and phase weights corresponding to 101 frequency points.

[0056] Construct complex weights based on amplitude and phase weights; The complex frequency domain response is weighted by a complex weight to obtain the weighted complex frequency domain response.

[0057] The complex frequency domain responses corresponding to the 101 weighted frequency points are arranged according to the frequency sequence and then subjected to inverse Fourier transform to obtain the equivalent time-domain broadband signal.

[0058] Figure 5 The paper presents a comparison between the equivalent broadband time-domain signal synthesized by amplitude and phase weighting at the receiver in this embodiment and the time-domain signal obtained by forward modeling using a Ricker wavelet with a center frequency of 600MHz as the transmitter source. The two signals are essentially identical in terms of waveform morphology, arrival time of the main reflected wave, peak and trough amplitudes, and polarity characteristics.

[0059] Furthermore, by extracting the spectral amplitude and spectral phase information corresponding to the Gaussian waveform and the first-order Gaussian derivative waveform, corresponding complex weights are constructed respectively. The complex weights are then used to perform amplitude and phase weighting on the complex frequency domain response obtained under the same set of equal-amplitude and equal-phase continuous wave signal transmission conditions to obtain the equivalent time-domain broadband signal of the corresponding target time-domain waveform. Figure 6 These are the synthesized results corresponding to the Gaussian waveform and the synthesized results corresponding to the first-order Gaussian derivative waveform.

[0060] The above results show that when the target time-domain waveform changes, the amplitude and phase weights of the complex frequency domain response can be assigned by replacing the complex weight sequence corresponding to the complex weights, while keeping the frequency sequence and the equal amplitude and equal phase continuous wave signals unchanged.

[0061] To evaluate the processing stability of the present invention under noise disturbance conditions, this embodiment adds zero-mean Gaussian white noise to the above forward model, and sets the noise standard deviation to 20% of the signal amplitude range.

[0062] like Figure 7 As shown, for the reference time-domain response, Gaussian white noise is superimposed on each time-domain reflection signal obtained by Ricker wavelet forward modeling to form a ground-penetrating radar B-scan profile image.

[0063] In the method of the present invention, the same noise is superimposed on the echo signals at each frequency point obtained under the condition of equal amplitude and equal phase continuous wave signal transmission. Then, demodulation processing, complex frequency domain response construction, complex weighted amplitude and phase weighting, and inverse Fourier transform processing are performed in sequence to obtain 130 equivalent time domain broadband signals, which are arranged according to the measurement line positions corresponding to the scanning positions to form ground penetrating radar B-scan profile images.

[0064] The results show that, under the set noise conditions, the ground-penetrating radar B-scan profile image formed after amplitude and phase weighting processing at the receiver can still maintain the main stratigraphic reflection and anomalous body diffraction characteristics. The hyperbolic diffraction characteristics corresponding to the metal pipe and air anomalous body are clearly distinguishable, and the stratigraphic interface reflection phase axis is continuous and complete.

[0065] In addition to the above-described embodiments, the present invention can be adjusted according to the actual system structure. For example, the complex frequency domain response can be obtained through analog IQ demodulation, digital down-conversion, phase-locked loop extraction, and frequency domain amplitude and phase estimation; the target time domain waveform can be selected according to different broadband pulse waveforms based on the detection task; the frequency sequence can be set according to the system bandwidth, the maximum unambiguous time window, and the detection resolution requirements; the complex weights can also be fused with the system frequency response calibration factor to form a total complex weight. All of the above adjustments do not deviate from the technical concept of the present invention for frequency domain ground-penetrating radar signal synthesis based on equal-amplitude, equal-phase continuous wave signal transmission and amplitude and phase weighting at the receiving end.

[0066] A frequency-domain ground-penetrating radar signal synthesis system based on receiver amplitude and phase weighting includes: The frequency sequence setting module is used to set the frequency sequence of the step-frequency continuous wave ground-penetrating radar. The transmission control module is used to control the transmitter to transmit equal-amplitude, equal-phase continuous wave signals one frequency point at a time according to the frequency sequence; The receiving and processing module is used to acquire the echo signals at each frequency point received by the receiving end, and to demodulate the echo signals at each frequency point to obtain the complex frequency domain response corresponding to each echo signal. The complex weight construction module is used to obtain the spectral amplitude and spectral phase information corresponding to the target time-domain waveform, and construct complex weights based on the spectral amplitude and spectral phase information. The amplitude and phase weighting module is used to perform amplitude and phase weighting on the complex frequency domain response according to the complex weights to obtain the weighted complex frequency domain response; The signal synthesis module is used to perform inverse Fourier transform on the weighted complex frequency domain response to obtain an equivalent time-domain broadband signal.

[0067] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0068] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0069] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the nature and scope of the present invention. Various modifications made to the above embodiments by those skilled in the art after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for synthesizing frequency-domain ground-penetrating radar signals based on receiver amplitude and phase weighting, characterized in that, include: S1. Set the frequency sequence of the step-frequency continuous wave ground-penetrating radar; control the transmitter to transmit continuous wave signals of equal amplitude and equal phase at frequency points according to the frequency sequence; S2. Acquire the echo signals at each frequency point received by the receiving end, and demodulate the echo signals at each frequency point to obtain the complex frequency domain response corresponding to the echo signals at each frequency point. S3. Obtain the target time-domain waveform, perform frequency domain transformation on the target time-domain waveform to obtain the spectral amplitude information and spectral phase information corresponding to the target time-domain waveform, and construct complex weights based on the spectral amplitude information and the spectral phase information; S4. Apply amplitude and phase weights to the complex frequency domain response according to the complex weights to obtain the weighted complex frequency domain response; S5. Arrange the weighted complex frequency domain response according to the frequency sequence, and perform inverse Fourier transform on the weighted complex frequency domain response to obtain an equivalent time-domain broadband signal.

2. The frequency domain ground-penetrating radar signal synthesis method based on receiver amplitude and phase weighting according to claim 1, characterized in that, Step S1 includes: Determine the starting frequency Frequency step value and the number of frequency points ; Based on the starting frequency and the frequency step value The frequency sequence is generated by the number of frequency points, and the frequency sequence includes multiple discrete frequency points arranged in ascending order of frequency. Each frequency point is represented as: The frequency step The total time window is used to determine the equivalent time-domain synthesized signal, and the synthesis bandwidth is used to determine the distance resolution; the frequency sequence transmits equal-amplitude, equal-phase continuous wave signals point by point, and the continuous wave signal transmitted at each frequency point is represented as follows: in, To standardize the launch amplitude, To unify the initial phase.

3. The frequency domain ground-penetrating radar signal synthesis method based on receiver amplitude and phase weighting according to claim 1, characterized in that, Step S2 includes: Synchronously demodulate the echo signals at each frequency point to obtain the in-phase components corresponding to the echo signals at each frequency point. and orthogonal components ; The in-phase component is used as the real part of the complex frequency domain response; the quadrature component is used as the imaginary part of the complex frequency domain response; the complex frequency domain response is constructed based on the in-phase component and the quadrature component: The synchronous demodulation method includes simulation. Any one of demodulation, digital downconversion, or frequency and phase extraction of steady-state echo.

4. The frequency domain ground-penetrating radar signal synthesis method based on receiver amplitude and phase weighting according to claim 1, characterized in that, Step S3 includes: Obtain the preset target time-domain waveform ; Perform a Fourier transform on the target time-domain waveform to obtain the spectral information corresponding to the target time-domain waveform. ; Based on the discrete frequency points in the frequency sequence, the spectral amplitude information corresponding to the frequency points is extracted from the spectral information. and the spectral phase information ; 。 5. The frequency domain ground-penetrating radar signal synthesis method based on receiver amplitude and phase weighting according to claim 4, characterized in that, Step S3 includes: The phase weights corresponding to each frequency point are determined based on the spectral phase information corresponding to the target time-domain waveform. The complex weights corresponding to each frequency point are generated based on the amplitude weights and the phase weights: 。 6. The frequency domain ground-penetrating radar signal synthesis method based on receiver amplitude and phase weighting according to claim 1, characterized in that, Step S4 includes: The complex frequency domain response corresponding to each frequency point The complex weights corresponding to the frequency points Perform complex multiplication to obtain the weighted complex frequency domain response: The in-phase component and the quadrature component are updated according to the amplitude weight and the phase weight to obtain the weighted in-phase component. and weighted orthogonal components : 。 7. The frequency domain ground-penetrating radar signal synthesis method based on receiver amplitude and phase weighting according to claim 6, characterized in that, Step S4 further includes: Obtain the frequency response calibration parameters corresponding to the ground penetrating radar system. ; Generate the total complex weight based on the frequency response calibration parameters and the complex weight: The total complex weight is used to simultaneously represent the target waveform spectral weight and the system frequency response calibration relationship; The total complex weight is used to assign amplitude and phase weights to the complex frequency domain response.

8. The frequency domain ground-penetrating radar signal synthesis method based on receiver amplitude and phase weighting according to claim 1, characterized in that, Step S5 includes: According to the arrangement order of each frequency point in the frequency sequence, the weighted complex frequency domain response corresponding to each frequency point is used to form a discrete complex frequency domain sequence; The equivalent time-domain broadband signal is obtained by performing an inverse Fourier transform on the discrete complex frequency domain sequence. The total time window corresponding to the equivalent time-domain broadband signal satisfies: in, It is the frequency step value between adjacent frequency points in the frequency sequence.

9. A method for synthesizing frequency-domain ground-penetrating radar signals based on receiver amplitude and phase weighting according to claim 8, characterized in that, Also includes: Acquire echo signals corresponding to multiple scan positions; Frequency sequence transmission, complex frequency domain response acquisition, complex weighted amplitude and phase weighting, and inverse Fourier transform processing are performed on the echo signals corresponding to each of the scanning positions to obtain the equivalent time-domain broadband echoes corresponding to each of the scanning positions. Arrange the equivalent time-domain broadband echoes according to the sequence of the survey line positions corresponding to the multiple scanning positions to form ground-penetrating radar B-scan profile data; Specifically, when it is necessary to adjust the target time-domain waveform, the frequency sequence and the equal-amplitude, equal-phase continuous wave signal are kept unchanged, and the complex frequency domain response is weighted by replacing the complex weight sequence corresponding to the complex weight.

10. A frequency-domain ground-penetrating radar signal synthesis system based on receiver amplitude and phase weighting, characterized in that, include: The frequency sequence setting module is used to set the frequency sequence of the step-frequency continuous wave ground-penetrating radar. The transmission control module is used to control the transmitting end to transmit equal-amplitude, equal-phase continuous wave signals point by point according to the frequency sequence; The receiving and processing module is used to acquire the echo signals at each frequency point received by the receiving end, and to demodulate the echo signals at each frequency point to obtain the complex frequency domain response corresponding to the echo signals at each frequency point. The complex weight construction module is used to obtain the spectral amplitude information and spectral phase information corresponding to the target time-domain waveform, and construct complex weights based on the spectral amplitude information and the spectral phase information. The amplitude and phase weighting module is used to perform amplitude and phase weighting on the complex frequency domain response according to the complex weights to obtain the weighted complex frequency domain response. The signal synthesis module is used to perform inverse Fourier transform on the weighted complex frequency domain response to obtain an equivalent time-domain broadband signal.

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