Permittivity and permeability of epoxy–magnetite powder composites at microwave frequencies

Abstract

Radio, millimeter, and sub-millimeter astronomy experiments as well as remote sensing applications often require castable absorbers with well known electromagnetic properties to design and realize calibration targets. In this context, we fabricated and characterized two samples using different ratios of two easily commercially available materials: epoxy (Stycast 2850FT) and magnetite (Fe3O4) powder. We performed transmission and reflection measurements from 7 GHz up to 170 GHz with a vector network analyzer equipped with a series of standard horn antennas. Using an empirical model, we analyzed the data to extract complex permittivity and permeability from transmission data; then, we used reflection data to validate the results. In this paper, we present the sample fabrication procedure, analysis method, parameter extraction pipeline, and results for two samples with different epoxy-powder mass ratios.