Complex Permittivity Determination From Far-Field Scattering Patterns

An accurate knowledge of the complex permittivity value of materials is compulsory when performing experimental electromagnetic applications. Unfortunately, these values are not so obvious to determine in practice. In this letter, we propose a novel approach for determining the complex dielectric constant of materials. This method combines free-space far-field scattering pattern measurements with a Bayesian procedure, which fully exploits the measurement uncertainties. Therefore, the measured values weighted according to their experimental accuracy are incorporated in the permittivity determination algorithm. In this letter, the samples are all shaped as spheres in order to benefit from efficient Mie scattered field computations. The dielectric properties of typical plastic samples are first determined and compared to values found in the literature in order to assess the validity and the accuracy of the proposed methodology. A more “exotic” sample extracted from a microwave absorber, which is a polyurethane foam charged with carbon particles, is also analyzed.