Background condition effect and modified SOM with frequency hopping applied in inverse scattering

Subspace-based optimization methods (SOM) for locating scatterers have been reported recently. The positions and shapes of scatterers are reconstructed by checking the contour of permittivity. Background conditions, including the shape of domain of interest, aperture, and frequency of incident wave, have an influence on the process of permittivity reconstruction. We examine the domain shape effect through the comparison among different types of domains. We also study the effect of full and partial aperture on the performance of SOM. Single-side view (partial aperture) gives a poor result in the reconstructed permittivity at a relatively low frequency. The optimization process of SOM has been modified in order to improve the result under single-side view. General SOM takes the free space as the initial guess in the optimization process, while modified SOM uses frequency hopping, and it significantly improves the reconstruction results.