Electromagnetic characterization of barium ferrite thick film samples in the KP band

A method for the broadband measurement of the complex permittivity of barium ferrite (BaF) thick film samples in a partially filled rectangular waveguide is presented. The material characterization is based on the measurement of the reflection and the transmission coefficients of the rectangular waveguide containing the demagnetized ferrite sample. We present the detailed numerical method for the calculation of the complex permittivity from the measured scattering matrix. First the propagation constant is deduced from the scattering parameters followed by the determination of the cutoff wavenumber for the partially filled section of the waveguide. Finally, the material parameters are calculated based on the analytical solution of the partially filled waveguide. The method is verified by 3-D electromagnetic simulation tools and by reference measurements on known samples.