Method based on energy spectrum imaging

Abstract

The invention provides a method based on energy spectrum imaging. The method comprises the steps that radar signal data are obtained through three-dimensional radar testing; acquiring a radar measurement signal file according to the radar signal data; executing digital band-pass filtering calculation according to the radar measurement signal file to obtain band-pass filtering data; executing HT conversion according to the band-pass filtering data to obtain an HT conversion result; energy spectrum imaging parameter extraction is executed according to the HT conversion result; and executing radar image interpretation according to the energy spectrum imaging parameters. On the basis of traditional radar waveform data, the technologies of band-pass filtering, HT analysis, medium intrinsic energy spectrum matching and the like are adopted, and on the basis of achieving accurate detection of holes, piping and other target bodies in a dam, the technologies of band-pass filtering, HT analysis, medium intrinsic energy spectrum matching and the like are adopted to achieve accurate detection of the holes, piping and other target bodies in the dam.

Description

Technical Field

[0001] The invention belongs to the field of geophysical exploration technology, and in particular relates to a method based on energy spectrum imaging. Background Art

[0002] The current three-dimensional radar detection imaging method mainly adopts reflection waveform imaging, and its main principle and method are: the transmission and reception are composed of a row of paired antenna units, and each pair of antenna units consists of a transmitting unit and a receiving unit (the front row is the transmitting unit, and the back row is the receiving unit). When the radar antenna moves forward, the units in the front row simultaneously transmit radar waves, and the corresponding units in the back row simultaneously receive radar reflection waves from the underground, forming a multi-channel radar reflection wave train diagram corresponding to the antenna position. After filtering, gain adjustment, and amplitude imaging of the reflection wave train diagram, a three-dimensional radar reflection image corresponding to the radar antenna trajectory is formed. This radar image mainly relies on the reflection amplitude and common phase characteristics of underground targets to identify, requiring a strong reflection wave signal. However, due to the strong absorption capacity of the surface rock and soil layer for radar waves, the reflection signal in the deep part of the dam is weak, and the reflection wave amplitude and phase characteristics cannot be identified, resulting in a shallower depth and poorer accuracy of three-dimensional radar detection. Energy spectrum analysis can effectively capture micro-signal characteristics, making the three-dimensional radar detection deeper and more accurate. Summary of the invention

[0003] The purpose of this embodiment is to provide a method based on energy spectrum imaging, which solves the problem of accurate detection of target objects such as cavities and piping in the dam.

[0004] A method based on energy spectrum imaging, comprising:

[0005] Three-dimensional radar test to obtain radar signal data;

[0006] Acquire a radar measurement signal file according to the radar signal data;

[0007] Perform digital bandpass filtering calculation according to the radar measurement signal file to obtain bandpass filtering data:

[0008] Performing HT transformation according to the bandpass filtering data to obtain an HT transformation result;

[0009] Execute energy spectrum imaging parameter extraction based on HT transformation results;

[0010] Radar image interpretation is performed according to the energy spectrum imaging parameters.

[0011] Furthermore, the bandpass filter formula is:

[0012]

[0013] Where: ω0 is the cutoff frequency, Q is the quality factor, and s is the signal function.

[0014] Furthermore, the center frequency f0 of the bandpass filter is consistent with the antenna frequency.

[0015] Furthermore, the HT transformation calculation formula is:

[0016]

[0017] Where P represents the integral operator of the Cauchy principal value, which is defined as:

[0018]

[0019] Furthermore, s(t) in the HT transformation calculation formula is:

[0020] s(t)=A(t)·e jφ(t) .

[0021] Furthermore, A(t) in the s(t) formula is the instantaneous amplitude.

[0022] Furthermore, s(t) is the instantaneous phase of Φ(t).

[0023] Furthermore, the calculation formula of the instantaneous frequency of the s(t) signal is:

[0024] Furthermore, energy spectrum imaging parameter extraction is performed according to the HT transformation result, including frequency point extraction and three-dimensional image generation.

[0025] Furthermore, energy spectrum imaging parameter extraction including frequency point extraction and three-dimensional image slice analysis is performed according to the HT transformation result.

[0026] The present invention provides a method based on energy spectrum imaging, which solves the problem of accurate detection of target objects such as cavities and piping in dams.

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 : A method step diagram of a method based on energy spectrum imaging provided by an embodiment of the present invention;

[0029] Figure 2 : A three-dimensional radar energy spectrum diagram of the method based on energy spectrum imaging provided by an embodiment of the present invention;

[0030] Figure 3 : A longitudinal slice of a three-dimensional radar energy spectrum diagram according to the energy spectrum imaging method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The technical solution in the embodiment of the present invention will be described below in conjunction with the accompanying drawings in the embodiment of the present invention. In this embodiment, the radar antenna is a wide-band three-dimensional radar antenna: a back-type fully shielded wide-band three-dimensional radar antenna: the center frequency is 200MHz, and the bandwidth is 40MHz.

[0032] It also includes a wide-band three-dimensional radar host: the passband range of the three-dimensional radar host is 50 to 900 MHz.

[0033] In order to solve the problems of three-dimensional radar detection accuracy and resolution.

[0034] The present invention provides a method based on energy spectrum imaging (see Figure 1 ),include:

[0035] S1: 3D radar test to obtain radar signal data: Use a vehicle-mounted radar system, connect the antenna, host, positioning and navigation equipment, set the frequency, detection depth, signal attenuation intensity related to the radar antenna frequency, recording time, sampling interval, gain, number of superpositions and other parameters, set the survey line trajectory, use automatic recording mode, the radar vehicle moves forward at a constant speed, completes the measurement of the entire survey belt, and proceeds to step S2.

[0036] S2: Obtain a radar measurement signal file according to the radar signal data: obtain a three-dimensional radar measurement data file of a measurement strip, including information data such as recording position (position coordinates of each antenna unit), waveform parameters (recording length, number of recording points or time interval, amplitude, gain), and proceed to step S3.

[0037] S3: Perform digital bandpass filtering calculation according to the radar measurement signal file to obtain bandpass filtering data: The bandpass filter is used to eliminate radar system and environmental interference signals. In this embodiment, the bandpass filter formula is:

[0038]

[0039] Where: ω0 is the cutoff frequency, Q is the quality factor, and s is the signal function.

[0040] The center frequency f0 of the bandpass filter is consistent with the antenna frequency, the bandwidth Δf (specific parameters), and the wide external suppression > Ed.

[0041] S4: Perform HT transformation according to the bandpass filtered data to obtain HT transformation results: Perform HT transformation on the radar waveform signal after bandpass filtering to obtain the instantaneous frequency and instantaneous amplitude of the signal. In this embodiment, the HT transformation uses a broadband radar signal of a nonlinear non-stationary signal to perform energy spectrum analysis according to the formula:

[0042]

[0043] Where P represents the integral operator of the Cauchy principal value, which is defined as:

[0044]

[0045] Where: s(t) = A(t)·e jφ(t) , A(t) is the instantaneous amplitude, Φ(t) is the instantaneous phase.

[0046] The instantaneous frequency of the s(t) signal is expressed as:

[0047]

[0048] HT has the following characteristics:

[0049] The purpose of analyzing nonlinear non-stationary signals by HT is the same as that of the present invention (spectral analysis of broadband non-stationary radar signals).

[0050] HT can adaptively generate bases. The bases of Fourier transform and wavelet transform are pre-selected trigonometric functions. Radar spectrum analysis imaging is suitable for analyzing the characteristics of data or signals.

[0051] HT is not restricted by the uncertainty principle and is suitable for the sudden change signals of radar.

[0052] The instantaneous frequency of HT is obtained by derivation and is timely; while Fourier transform and wavelet transform are generated by convolution with basis functions, and the instantaneous frequency obtained is limited and regional, and step S5 is performed.

[0053] S5: Execute energy spectrum imaging parameter extraction according to HT transformation result: In this embodiment, after HT processing is performed on the radar signal, a radar energy spectrum signal is obtained, and frequency point extraction is performed. According to the detection accuracy and resolution requirements, the dominant frequency value f0i at each moment (depth) and the coordinates of the point are searched and extracted according to △t (corresponding to a depth interval of 10cm to 50cm) for each radar energy spectrum signal, and the depth value is calculated according to zi=vti / 2 (z window center depth, v radar wave speed, ti window center time), and the radar energy spectrum data file (x, y, z, f0i) of each point is edited. The energy spectrum imaging parameter extraction includes the steps of:

[0054] S5.1: Select the corresponding energy spectrum window △t according to different resolution requirements.

[0055] S5.2: Energy spectrum imaging processing: Use three-dimensional image processing software to import the radar energy spectrum data file (x, y, z, f0i) to generate a three-dimensional image and proceed to step S6.

[0056] S6: Perform radar image interpretation according to the energy spectrum imaging parameters: Use the advantages of field tests or empirical data to calibrate the medium (cavity, soil, rock, water) to obtain radar energy spectrum values. Figure 2 , determine the surrounding rock medium and hidden dangers based on the dominant radar energy spectrum value of the medium, estimate the defect size and position based on the distribution range and position of the hidden danger energy spectrum in the image, and perform radar image interpretation, including:

[0057] Establish radar spectrum databases and images of various target anomalies for different regions and project types;

[0058] Perform slice analysis on 3D images, see Figure 3 .

[0059] The present invention provides a method based on energy spectrum imaging. Based on traditional radar waveform data, it adopts bandpass filtering, HT analysis, medium intrinsic energy spectrum matching and other technologies to achieve accurate detection of target objects such as cavities and pipe bursts in dams.

[0060] The above description is only an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method based on energy spectrum imaging, characterized in that: include: Three-dimensional radar test to obtain radar signal data; Acquire a radar measurement signal file according to the radar signal data; Perform digital bandpass filtering calculation according to the radar measurement signal file to obtain bandpass filtering data: Performing HT transformation according to the bandpass filtered data to obtain an HT transformation result; Execute energy spectrum imaging parameter extraction based on HT transformation results; Radar image interpretation is performed according to the energy spectrum imaging parameters.

2. The method based on energy spectrum imaging according to claim 1, characterized in that: The bandpass filter formula is: Where: ω0 is the cutoff frequency, Q is the quality factor, and s is the signal function.

3. The method based on energy spectrum imaging according to claim 1, characterized in that: The center frequency f0 of the bandpass filter is consistent with the antenna frequency.

4. The method based on energy spectrum imaging according to claim 1, characterized in that: The HT transformation calculation formula is: Where P represents the integral operator of the Cauchy principal value, which is defined as:

5. The method based on energy spectrum imaging according to claim 4, characterized in that: The s(t) in the HT transformation calculation formula is: s(t)=A(t)·e jφ(t) 。 6. The method based on energy spectrum imaging according to claim 5, characterized in that: In the s(t) formula, A(t) is the instantaneous amplitude.

7. The method based on energy spectrum imaging according to claim 5, characterized in that: In the s(t) formula, Φ(t) is the instantaneous phase.

8. The method based on energy spectrum imaging according to claim 5, characterized in that: The calculation formula of the instantaneous frequency of the s(t) signal is:

9. The method based on energy spectrum imaging according to claim 1, characterized in that: The energy spectrum imaging parameter extraction is performed according to the HT transformation result, including frequency point extraction and three-dimensional image generation.

10. The method based on energy spectrum imaging according to claim 1, characterized in that: The energy spectrum imaging parameter extraction according to the HT transformation result includes frequency point extraction and three-dimensional image slice analysis.

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