Cédric Le Bastard

Time Delay and Permittivity Estimation by Ground-Penetrating Radar With Support Vector Regression

In the field of civil engineering, sounding the pavement layers is classically performed using standard ground-penetrating radar, whose vertical resolution is bandwidth dependent. The layer thicknesses are deduced from both the time delays of backscattered echoes and the permittivity of layers. In contrast with conventional spectral analysis approaches, this letter focuses on one of the machine learning algorithms, namely, the support vector machine, to perform time delay estimation and dielectric constant estimation of the medium from backscattered radar signals. This letter shows the super time resolution capability of such technique to resolve overlapping and fully correlated echoes within the context of thin pavement layer testing.

Modified ESPRIT (M-ESPRIT) algorithm for time delay estimation in both any noise and any radar pulse context by a GPR radar

This paper presents M-ESPRIT, a modified version of the ESPRIT algorithm, for the purpose of time delay estimation of backscattered radar signals. The proposed algorithm takes both the transmitted pulse shape and any noise into account. It can process raw data from experimental device without the preprocessing which would be required with the conventional ESPRIT algorithm.

Asymptotic Modeling of Coherent Scattering from Random Rough Layers: Application to Road Survey by GPR at Nadir

This paper studies the coherent scattering from random rough layers made up of two uncorrelated random rough surfaces, by considering 2D problems. The results from a rigorous electromagnetic method called PILE (propagation-inside-layer expansion) are used as a reference. Also, two asymptotic analytical approaches are presented and compared to the numerical model for comparison. The cases of surfaces with both Gaussian and exponential correlations are studied. This approach is applied to road survey by GPR at nadir.

Support Vector Regression method applied to thin pavement thickness estimation by GPR

In the field of civil engineering, sounding the layers is classically performed using standard ground-penetrating radar (GPR), whose vertical resolution is bandwidth dependent. The layer thicknesses are deduced from both the time delays of backscattered echoes and the dielectric constants of the layers. In contrast with the conventional spectral analysis approaches, we propose in this paper to use one of the most powerful machine learning algorithm, namely the Support Vector Machine(SVM), to perform Time Delay Estimation (TDE) of backscattered radar signals. In particular, this paper demonstrates the super time resolution capability of such technique in the context of overlapping and totally correlated echoes when thin pavement layers survey is under scope.

Generalization of PILE Method to the EM Scattering From Stratified Subsurface With Rough Interlayers: Application to the Detection of Debondings Within Pavement Structure

This paper presents the numerical method, generalized propagation-inside-layer expansion (GPILE), to calculate the scattered electromagnetic field by any stratified 1-D medium composed of three random rough interfaces separating homogeneous media. GPILE is a generalization of the propagation-inside-layer expansion method, which considers only two interfaces. Both methods rely on the rigorous implementation of the Maxwell equations, with a simple matrix formulation and which have a straightforward physical interpretation. In particular, this method allows us to distinguish the primary echo of the upper surface and also the multiple echoes arising from the intermediate and lower interfaces. This method is applied in this paper to simulate the ground-penetrating radar (GPR) signal at nadir. The simulated signals are analyzed to study the sensitivity of the GPR signal to any material debonding within the pavement layered structure.

Simplified High-Order DOA and Range Estimation With Linear Antenna Array

In this letter, we propose a new efficient method to estimate the direction-of-arrival (DOA) and range of near-field sources in a decoupled way. First, a non-Hermitian cumulant matrix is constructed, whose eigenvectors associated with zero eigenvalues are used to directly estimate the DOA by using the MUSIC algorithm. Then, the ranges are estimated with the estimated DOA by orthogonalizing the remained eigenvectors. Compared with other modified 2-D MUSIC, the proposed algorithm can greatly reduce the computational complexity by avoiding a 2-D search with only one matrix and one eigenvalue decomposition. Simulation results show the effectiveness of the proposed method.

Enhanced GPR Signal for Layered Media Time-Delay Estimation in Low-SNR Scenario

In this letter, a new method is proposed to enhance the ground-penetrating radar (GPR) signal for time-delay estimation in a low signal-to-noise ratio. It is based on a subspace method and a clustering technique. The proposed method makes it possible to improve the estimation accuracy in a noisy context. It is used with a compressive sensing method to estimate the time delay of layered media backscattered echoes coming from the GPR signal. Several simulations and an experiment are presented to show the effectiveness of signal enhancement.

Time-Delay Estimation Using ESPRIT With Extended Improved Spatial Smoothing Techniques for Radar Signals

In the electromagnetic field, radar is widely used to measure or estimate the media parameters or to detect targets through obstructions. For horizontally stratified media, the layer thickness can be deduced from the time delays of backscattered echoes and the dielectric constants. The high-resolution method estimation of signal parameters via rotation invariance techniques (ESPRIT) has been proposed for time-delay estimation. In practice with a radar, backscattered echoes are correlated. In order to apply the ESPRIT method, in this letter, we propose to use two adaptive improved spatial smoothing techniques with the propagator method for fighting against the correlation between the echoes. The proposed solution does not use any approximation. Numerical examples are provided to show the performance of the algorithm.

Time delay and interface roughness estimations by GPR for pavement survey

In civil engineering, ground-penetrating radar is widely used for road pavement surveys. In contrast to the existing literature, this paper takes account of the influence of interface roughness (surface and interlayer roughness) within the scope of data processing of radar signals. The rigorous electromagnetic method PILE (Propagation Inside Layer Expansion) provides simulated data that show the influence of the interface roughness on the backscattered primary echoes of stratified media; the interface roughness provides a continuous frequency decay of the magnitude of the echoes. The observed frequency variations of the radar magnitude introduce some shape distortion on the radar waveform. The latter variations can be modelled by an exponential function, which provides satisfactory results for a narrow bandwidth (2 GHz). An adaptation of the root-MUSIC algorithm is proposed. As a result, it is possible to jointly estimate the time delay and the interface roughness. The algorithm is tested on data simulated by the PILE method and numerical examples are provided to assess the performance of this algorithm. The associated results show that the proposed algorithm can estimate both the time delay and roughness parameters with a small relative error.

Time delay and surface roughness estimation by subspace algorithms for pavement survey by radar

In civil engineering, ground penetrating radar is widely used for road pavement surveys. In contrast to the existing literature, the influence of interface roughness (surface and interlayer roughness of stratified media) is accounted for within the scope of the data processing of radar signals. The rigorous electromagnetic method PILE (propagation inside layer expansion) provides the simulated data. The observed frequency variations of the radar magnitude introduce some shape distortion on the radar wavelet. An adaptation of the root-MUSIC algorithm is proposed on the basis of the work. As a result, it is allowed to jointly estimate the time delay and the interface roughness.