Complex permeability and permittivity and microwave absorption property of barium ferrite/EPDM rubber radar absorbing materials in 2-18GHz

In this paper, the effective complex permeability and permittivity spectra in rubber radar absorbing materials (RAM) with various barium ferrite volume fractions are measured in 2-18GHz using transmission/reflection method with HP8722ET vector network analyzer. The effects of the ferrite volume fraction and the thickness of the RAM on the microwave absorption properties in the frequency range of 2-18GHz are studied. The real part ε\´ and imaginary part ε" of the complex permittivity for barium ferrite/EPDM rubber absorbing materials are nearly independent of the frequency. The ε\´ spectra of the radar absorbing materials increase as the ferrite volume fraction increases. There is a cross point in the frequency spectra of the real part μ\´ of the complex permeability. The μ" spectra increase as the ferrite volume fraction increases. The reflectivity of the radar absorbing materials is proportional to the thickness and barium ferrite volume fraction when the volume fraction and the thickness are 10% and 1.0mm respectively. But the reflectivity is not proportional to the thickness and barium ferrite volume fraction when the volume fraction and the thickness are 4.0% and 3.0mm respectively.