Improvement of direct sampling method in transverse electric polarization

Recently, the mathematical structure of the direct sampling method (DSM) was investigated in transverse-electric (TE) polarization, and the reason why the exact locations of small inhomogeneities cannot be retrieved through traditional DSM has been revealed. In this paper, we present an improved DSM for identifying the exact locations of small inhomogeneities in TE polarization. Furthermore, we investigate a multi-frequency indicator function to obtain a better result. Corresponding mathematical analysis and simulations are performed to show the feasibilities of the proposed improvement techniques.