Complex permittivity and permeability of iron-based composite absorbers measured by cavity perturbation method in X-band frequency range

A cavity perturbation resonance technique is used to determine the complex permittivity and permeability of iron-based composite absorbers prepared by mixing various weight percentages of carbonyl iron powder with epoxy as the matrix. The complex permittivity (ε′-jε″) and permeability (μ′-jμ″) are measured around X-band (7–12.5 GHz for permittivity and 7.5–14 GHz for permeability) by the cavity perturbation resonance technique and the results are compared with those obtained by the transmission/reflection method. Experimental results show that the average differences of real parts of permittivity (ε′) and real and imaginary parts of permeability (μ′ and μ″) measured by these two techniques are less than 10%. The differences in ε″, however, is apparently higher than the others. As a general trend, the difference increases with increasing weight percentage of carbonyl iron.