Hybrid Electromagnetic Inversion of 3-D Irregular Scatterers Embedded in Layered Media by VBIM and MET

This communication presents an efficient hybrid nonlinear electromagnetic inversion method. The voxel-based variational Born iterative method (VBIM) is combined with the maximum entropy thresholding (MET) technique to reconstruct 3-D irregular scatterers embedded in the layered media. In each iteration, the VBIM first outputs the model parameters in discretized cells of the inversion domain, and the MET is then used to categorize them into "background" and "scatterer" types. Partial "background" cells will be removed in the next round iteration according to an adjustable threshold corresponding to the maximum entropy since they have no contribution to the measured scattered fields. Consequently, the inversion domain is gradually downsized in the successive iterations. The computation efficiency, memory cost, and the reconstruction accuracy are compared for VBIM with and without the MET. Their antinoise ability is also compared.