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The average polarizabilities of a helix are computed using the far-field forward and backward scattering amplitudes, and subsequently used for deriving the constitutive parameters of helix-loaded composites via a Maxwell Garnett treatment. Computational results are first compared with some results obtained earlier with other effective-medium theories. Then, Maxwell Garnett estimates for the effective properties of several helix-loaded materials (chiral and transversely bianisotropic uniaxial composites) are compared with experimental data measured by the means of a free space bench in the 6-18 GHz range. Numerical and experimental determinations of the rotation angle, ellipticity, chirality parameter, permittivity, and permeability are presented and discussed in detail. Results for the reflection and transmission coefficients of helix-loaded slabs and the reflection coefficients of metal-backed slabs are also presented.

A boundary element code is used to study the electromagnetic field scattered by a helix at microwave frequencies. The far-field forward and backward scattering amplitudes are computed for an incident linearly polarized wave with various polarization directions, and a number of orientations of the helix. These computations allow us to study the magnitude of the field scattered in the forward and backward directions as a function of frequency and orientation. They are also the starting point for computing the effective wavenumbers of left and right circularly polarized waves in a chiral composite made of a dispersion of helices in a host medium. Several methods to compute the effective impedance of chiral composites in order to obtain all three constitutive parameters of such media are proposed. Numerical results are given and compared with existing experimental and theoretical data.