A Dual-Band Microwave Imaging System Prototype for Quantitative 3-D Dielectric Reconstruction

We present a microwave imaging (MWI) system prototype to reconstruct 3-D complex dielectric relaxation images of various complicated phantom models. The imaging cavity of this system is filled with a newly compounded emulsion. To achieve multifrequency operation, the proposed system utilizes a new multifrequency tapered patch antenna array. A novel method based on the principal component analysis (PCA) is first proposed to select optimal frequencies and useful data channels in MWI applications, which is the major innovation of this article. For 3-D imaging, particularly, under the black-box condition with no a priori information of the unknown targets, the enhanced variational Born iterative method (VBIM) is applied as the inverse solver, enabling the dielectric relaxation reconstruction from the multifrequency measured data. Multiple experiments with various phantoms are conducted to evaluate the system’s performance and imaging capabilities. These include single, double, and multiple spherical targets filled with various water–isopropyl alcohol mixtures and submerged either directly in the background emulsion or within another water–alcohol mixture that is submerged in the emulsion. Imaging results, including the comparison between measured data and simulated data, multifrequency and single-frequency reconstructed dielectric images, inversions with different PCA contribution thresholds, and reconstruction under black-box and preconditioned setup, can quantitatively demonstrate a good performance of the MWI system prototype.