J. Phys. IV France 07 (1997) C1-427-C1-428
Organic Materials Filled with Ferrite Powder for Electromagnetic CompatibilityJ.-L. Forveille, L. Olmedo and J. Raby
C.E.A. Le Ripault, DMAT/SCF, BP. 16, 37260 Monts, France
ElectroMagnetic Compatibility (E.M.C.) measuements, that today becomes more and more important, requires materials having high attenuation level, typically -20 dB from 30 MHz to 20 GHz. Because of their low frequency range absorption, ferrite are only efficient up to 1 GHz. The use of dispersion techniques for development of granular materials as microwave absorbers is a convenient way to make coatings with good attenuation characteristics in the 1 - 20 GHz range . Especially, elastomer mixing is a very good technique for dispersion and individualization of each grain of ferromagnetic powder (iron, cobalt, permalloy,...) or ferrimagnetic powder up to 60% (volume) while maintaining electrical insulation . Such materials are easy to process by classical processing polymer techniques and can be processed in various shapes. It has already been shown that combination of magnetic material properties and geometrical effect by molding under the form of conical or pyramidal shapes significantly broadens the absorber frequency range working . These absorbers with conical or pyramidal pattern, are very efficient above 1 GHz due to creation of a geometrical gradient. The realization of an architecture by combining a ferrite tile with a conical shaped ferrimagnetic granular material leads to very braodband absorbers suitable for E.M.C. applications. Their high level of performances (typically -20 dB from 30 MHz to 20 GHz for a thichness less than 100 mm) makes them a new generation of absorbers for anechoïc chambers compared to classical pyramidal dielectric foams.
© EDP Sciences 1997