Control of complex permeability and permittivity by air cavity in ferrite-rubber composite sheets and their wide-band absorbing characteristics

Wide-band absorbing characteristics in the GHz-range are identified in the ferrite-rubber composite sheets with the periodic structure of an air cavity. Co/sub 2/Z and Ni-Zn ferrites, which have been prepared by ceramic processing, are used as the absorbent fillers. On the basis of a synthesized capacitance and inductance model, the equivalent permeability (/spl mu//sub eq/) and permittivity (/spl epsiv//sub eq/) are calculated as a function of the volume of air cavity (K). Reduction in the material parameters (especially, permittivity and magnetic loss) has been estimated with the increase of K. By plotting the /spl mu//sub eq/ and /spl epsiv//sub eq/ on the solution map of wave-impedance-matching, wide-band microwave absorbance has been estimated in both Co/sub 2/Z and Ni-Zn ferrite composites with an optimum value of K.