Characterization of composite materials in waveguides

The effective properties of a composite material can be predicted using homogenization techniques. In order to verify these predictions, it is common to extract material data from a scattering experiment, where the primary data extracted are wave parameters such as wave number and wave impedance. Using Cramér-Rao lower bounds, we show that in a waveguide setting the wave impedance is ill-determined at resonance and the wave number is well-determined, but both permittivity and permeability are ill-determined. We also show that a priori knowledge is essential in order to extract anisotropic material data.