Simulation of a Multi-Frequency Continuous-Wave Reconstruction Technique for Subsurface Conductivity and Dielectric-Constant Profiles

In this paper, an efficient inversion method to reconstruct conductivity and dielectric-constant profiles by launching a continuous sinusoidal wave from the surface of a layered medium is presented. The reconstruction code consists of two main partsthe forward model and the inversion algorithm. Two forward models are developed for applications in shallow subsurface sensing and nondestructive evaluation of disbonding in a layered dielectric medium. In the inversion process, the Jacobian Matrix method is used to modify the inverted profile iteratively toward the real formation profile. A constrained optimization method is applied in order to obtain maximum stability when noise is present. The choice of the discrete frequencies depends on the required spatial resolution, investigation depth, and the parameters to be inverted. At the present stage, only synthetic models with signal-to-noise ratio around 40 dB are used to test the inversion method. The conductivity and the dielectric constant profiles for different kinds of synthetic models are satisfactorily reconstructed by using this method.