Microwire composite electromagnetic parameters extraction by waveguide measurements at X-band

Composite materials consisting of amorphous magnetic microwires added to a matrix of paint have been proven to be very useful for electromagnetic absorption of microwave frequencies. The main goal of this article is to calculate the values of the electrical permittivity and the magnetic permeability of several such composites depending on the microwire mass fraction added. In order to analyze this dependency of electromagnetic parameters on microwire mass fraction, three composites with mass fractions 2, 3, and 4%, respectively, have been prepared. The values of the electromagnetic parameters have been extracted by S-parameter measurements using a rectangular waveguide at band X. Three different methods have been applied in the extraction of the electromagnetic parameter values: Nicolson-Ross-Wier, Impedances, and Optimization. It has been found that the real part of the electrical permittivity linearly increases with the mass fraction of microwires, while the imaginary component does not follow the same linear trend. Regarding the electrical permeability, the values calculated for both the real and imaginary componentsof composites with different concentrations are too similar to extract any relevant dependency.