Microwave Imaging Based on a Subspace-based Two-step Iterative Shrinkage/Thresholding Method.

Area of Science:

• Electromagnetics
• Computational Physics
• Inverse Problems

Background:

• The Distorted Born iterative method (DBIM) is a common approach for inverse scattering problems.
• The original TwIST algorithm offers a framework for iterative inverse scattering solutions.
• Improving the accuracy and stability of inverse algorithms is crucial for analyzing complex structures.

Purpose of the Study:

• To introduce and evaluate the subspace-based two-step iterative shrinkage/thresholding (S-TwIST) method.
• To enhance the performance of the original TwIST inverse algorithm for electromagnetic inverse scattering.
• To improve the accuracy and robustness of current retrieval from scattered field data.

Main Methods:

• Developed a subspace-based extension of the TwIST algorithm (S-TwIST).
• Integrated the Distorted Born iterative method (DBIM) with the S-TwIST framework.
• Retrieved the deterministic component of induced currents using an inhomogeneous Green's function operator.
• Validated the method using synthetic geometries with fine structures at 2GHz.

Main Results:

• S-TwIST demonstrated superior accuracy in reconstructing multiple object profiles, with an error (εerr) of 0.1454%.
• Achieved a resolution of 1/16λ at 2GHz, outperforming the original TwIST.
• The S-TwIST method showed increased robustness against the initial guess, reducing instability during inversion.
• More accurate total field calculations were obtained at each iteration step compared to the original TwIST.

Conclusions:

• The S-TwIST method significantly improves upon the original TwIST algorithm for electromagnetic inverse problems.
• S-TwIST provides a more accurate and stable approach for reconstructing complex subsurface structures.
• The enhanced accuracy and robustness make S-TwIST a valuable tool for high-resolution inverse scattering analysis.