Inversion of inhomogeneous continuously varying dielectric profiles using open-ended waveguides

The problem of reconstructing one-dimensional inhomogeneous, continuously varying dielectric profiles using open-ended waveguides is studied. The measured or available data-which are actually simulated here-consist of the self-admittance of the open-ended waveguide ending in a flange, put in contact with the dielectric medium to be inverted. The self-admittance of the waveguide radiating into the medium is then formulated. Choosing the Levenberg-Marquardt optimization algorithm, a search for a multilayered model with a sufficient number of layers-using successive refinements-is carried out until the admittance of the trial medium agrees closely, within a certain tolerance, with the admittance of the actual medium.>