Analysis and Improvement of Direct Sampling Method in the Monostatic Configuration

The recently introduced noniterative imaging method entitled “direct sampling method” (DSM) is known to be fast, robust, and effective for inverse scattering problems in the multistatic configuration but fails when applied to the monostatic one. To the best of our knowledge, no explanation of this failure has been provided yet. Thanks to the framework of the asymptotic and the far-field hypothesis in the 2-D scalar configuration, an analytical expression of the DSM indicator function in terms of the Bessel function of order zero and sizes, shapes, and permittivities of the inhomogeneities is obtained and the theoretical reason of the limitation identified. A modified version of DSM is then proposed in order to improve the imaging method. The theoretical results are supported by numerical results using synthetic data.