Far-field Characterization of Material Permittivity Based on Nonlinear Inversions

Noncontact measurement of complex permittivity at microwave frequencies is significantly important in various areas of scientific research and engineering applications. In this work, we experimentally investigate a noncontact solution based on nonlinear inversion algorithms which is used in through wall imaging (TWI). Experiments are performed using a setup with the object surrounded by a closed wall. The inversion is based on a twofold subspace-based optimization method, and the results show that the complex permittivity of the object can be successfully retrieved from the measured data. This TWI solution can be modified to achieve a noncontact measurement method.