Localization of small perfectly conducting cracks from far-field pattern with unknown frequency
For researchers in inverse scattering, this work provides a theoretical explanation for a known empirical failure of subspace migration with unknown frequency, though the contribution is incremental.
The paper analyzes why subspace migration fails to accurately locate small perfectly conducting cracks when the applied frequency is unknown, establishing a theoretical relationship with Bessel functions. Numerical simulations confirm the analysis and suggest improvement directions.
In inverse scattering problem, it is well-known that subspace migration yields very accurate locations of small perfectly conducting cracks when applied frequency is known. In contrast, when applied frequency is unknown, inaccurate locations are identified via subspace migration with wrong frequency data. However, this fact has been examined through the experimental results so, the reason of such phenomenon has not been theoretically investigated. In this paper, we analyze mathematical structure of subspace migration with unknown frequency by establishing a relationship with Bessel function of order zero of the first kind. Identified structure of subspace migration and corresponding results of numerical simulation answer that why subspace migration with unknown frequency yields inaccurate location of cracks and gives an idea of improvement.