Investigation of forward-looking synthetic circular array for subsurface imaging in tunnel boring machine application

Aubry

IEEE Trans. Geosci. Remote Sensing

2018

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Ground penetrating radar (GPR) imaging from the data acquired with arbitrarily oriented dipole-like antennas is considered. To take into account variations of antenna orientations resulting in spatial rotation of antenna radiation patterns and polarizations of transmitted fields, the full-wave method that accounts for the near-, intermediate-and far-field contributions to the radiation patterns is applied for image reconstruction, which is formulated as a linear inversion problem. Two approaches, namely an interpolation based method and a Nonuniform Fast Fourier transform (NUFFT) based method, are suggested to efficiently implement the full-wave method by computing exact Green's functions. The effectiveness and accuracy of the method proposed have been verified via both numerical simulations and experimental measurements and significant improvement of the reconstructed image quality compared to the traditional scalarwave based migration algorithms is demonstrated. The results can be directly utilized by forward-looking microwave imaging sensors such as installed at tunnel boring machine or can be used for the observation matrix computation in regularization-based inversion algorithms.

Section: Signal Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Efficient Implementation of GPR Data Inversion in Case of Spatially Varying Antenna Polarizations

Aubry

IEEE Trans. Geosci. Remote Sensing

2018

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“…It enables to significantly reduce the number of antennas needed in an antenna array system, thus saving the system cost as well as the space for its installation. So synthetic aperture technique provides a cost-efficient and compact array solution to imaging systems, which is extremely attractive for some excessively cost/space-limited circumstances, e.g., ground prediction system used for tunnel boring machine [7], [8].…”

Section: Introductionmentioning

confidence: 99%

A Novel Rotated Antenna Array Topology for Near-Field 3-D Fully Polarimetric Imaging

Aubry

IEEE Trans. Antennas Propagat.

2018

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In this communication, a novel approach to rotated antenna array topology design is proposed for fully polarimetric short-range imaging. The rotated antenna array proposed acquires two co-pol and one cross-pol signals in terms of the "local" polarization basis by means of three antenna pairs. Then, the fully polarimetric signals in a global polarization basis are retrieved via simple polarization basis transformation, which overcomes the spatially varied polarizations of the signals acquired at different positions and makes valid the assumption of traditional imaging algorithms that the polarization is constant within the aperture. The proposed rotated antenna array takes advantage of the synthetic aperture technique to synthesize a 2-D array for 3-D full-pol imaging. It utilizes a significantly smaller number of antennas in comparison to traditional fully polarimetric imaging arrays and also provides sufficiently accurate estimation to the full-pol electromagnetic signals scattered from targets. Both numerical simulations and experimental measurements have been performed and the results show the tolerance of the antenna array topology proposed to the quasi-monostatic measurements, its effectiveness, and accuracy for full-pol short-range microwave imaging.

“…1). This new SAR modality is very attractive for cost-tight and/or space-limited applications, such as the cardiac catheter used for intravascular imaging [5] and ground prediction radar (GPR) system for tunnel boring machine (TBM) [6]. The latter is actually our motivation of this study, where the GPR antennas mounted on the cutter-head of a TBM acquire signals with its rotation but the available space for GPR antennas is extremely limited due to mechanical constraints.…”

mentioning

confidence: 99%

Sampling Design of Synthetic Volume Arrays for Three-Dimensional Microwave Imaging

IEEE Trans. Comput. Imaging

2018

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In this paper, sampling design of three-dimensional (3-D) synthetic array (i.e., synthetic volume array) for microwave imaging is considered. Generally, the spatial sampling criteria for one-or two-dimensional arrays can be determined based on some narrowband/ultrawideband array theories. However, for 3-D arrays, where antennas are located in a volume instead of over a surface, these existing array theories are no longer straightforwardly applicable. To address the spatial sampling problem of 3-D arrays, we formulate it as a sensor/observation selection problem in this paper. Although some selection approaches exist and are conveniently applicable to small-scale problems, they are either less efficient or provide less optimal results for selection problems with data dimensions of hundreds or even thousands which is typical for microwave imaging. To get the (near-) optimal spatial sampling scheme for 3-D arrays, a greedy algorithm named clustered maximal projection on minimal eigenspace (CMPME) is proposed to select the most informative sampling positions based on some optimality criteria. This algorithm attempts to select the fewest sampling positions by considering an error threshold for the estimated images. Moreover, it has higher computational efficiency compared to the existing approaches. Finally, its effectiveness and selection performances are demonstrated through some imaging examples.