Multi-Layered Circular Dielectric Structures’ Synthetic Aperture Radar Imaging Based on Green’s Function Using Non-Uniform Measurements

Abstract

The electromagnetic imaging of multi-layered circular structures can be accomplished by means of different approaches. Among these approaches, the use of synthetic aperture radar (SAR) techniques with the compensation of the Green’s function for multi-layered circular cylinders provides a trade-off between accuracy and computational complexity. Nevertheless, this approach relies on measurement points acquired uniformly. Thus, this prevents the adoption of more flexible sampling schemes, limiting the use of inaccurate positioners or manual scanners. To overcome this limitation, this paper proposes a method to handle non-uniform cylindrically acquired data, enabling multi-layered circular imaging based on non-uniformly acquired measurements. For this purpose, the presented method starts by projecting the non-uniformly measured points onto different circles with equally-spaced points. After that, the Green’s function-based circular-SAR imaging method is applied to each projection circle. Lastly, the final SAR image is obtained by the superposition of the images from the previous step. Numerical simulations and experimental results demonstrated the effectiveness and robustness of the proposed method for practical nondestructive testing (NDT) applications.

Multilayered Circular Dielectric Structure SAR Imaging Using Time-Reversal Compressed Sensing Algorithms Based on Nonuniform Measurement

“…In Fig. 1(a), similar to [12], the schematic of the non-uniform measurement case for three-layered circular dielectric structures is depicted. The first layer corresponds to the background medium, which is typically air.…”

“…If the number of the measurement points were very large, the computation time would also be very long. In order to improve the computational efficiency, the acquisition points can be projected into a regular grid of virtual points located on projection circles [12] so that these virtual points are equally spaced along the angular and radial directions (see Fig. 2).…”

“…Approaches based on GF are able to take into account the effect of multiple reflections at the expense of a complex formulation [11]. Moreover, GF approaches must be modified to use non-uniform data as proposed in [12].…”