Papers by Keyword: Relative Complex Permeability

Abstract: A low-cost composite electromagnetic wave absorber made of sendust dispersed in resin was developed that does not contain any rare metals. In this study, spherical sendust particles with average particle sizes of approximately 5 and 20 μm were dispersed in polystyrene resin at volume ratios in the range 2040 vol% to broaden the absorption frequency bandwidth at frequencies above 10 GHz. The optimal volume ratios of sendust with average particle sizes of approximately 5 and 20 μm were found to be approximately 30 and 35 vol%, respectively. Electromagnetic wave absorbers can be flexibly designed by controlling the volume ratio of spherical sendust particles in resin.

Abstract: In order to design a ferrite absorber that can be used at frequencies of several GHz, the frequency dependences of the relative complex permeability μ_r^*, the relative complex permittivity ε_r^*, and return loss were investigated for a composite made of Ni-Zn ferrite and SiO₂. When ferrite particles were dispersed and isolated in an SiO₂ medium, the frequency dependence of μ_r^* was different from that for a composite made of SiO₂ particles dispersed and isolated in the ferrite medium. Moreover, when ferrite particles were isolated and a suitable mixture ratio of ferrite and SiO₂ was selected, the return loss was less than −20 dB at frequencies of several GHz. The dispersion states of ferrite and SiO₂ particles are thus important factors to design an absorber, and improvement in the absorption characteristics of the ferrite tile which is used as a practical absorber could be achieved using a composite made of Ni-Zn ferrite particles dispersed and isolated in an SiO₂ medium.

Abstract: To design an electromagnetic wave absorber with good absorption properties at frequencies above 1 GHz, the frequency dependences of the relative complex permeability μr*, the relative complex permittivity εr*, and return loss were investigated for the composite made of both sendust (an alloy of Al 5%, Si 10%, and Fe 85%) and aluminum particles dispersed in polystyrene resin. It was found that the frequency dependence of μr* for this composite can be changed by adjusting the particle size of aluminum and the volume mixture ratio of sendust and aluminum. Therefore, a flexible design of an absorber with good absorption characteristics was proposed based on the ability to control μr*. The composite made of both sendust and aluminum was found to exhibit a return loss of less than −20 dB in the frequency range of not only several GHz but also around 20 GHz if appropriate volume mixture ratio and particle size were selected.

Abstract: The effects of the particle size of sendust, which is an alloy of Al 5%, Si 10%, and Fe 85%, on the absorption characteristics of composite electromagnetic wave absorbers made of polystyrene resin and sendust were investigated in the frequency range from 1 to 40 GHz. The size of sendust particles was varied between approximately 5 and 20 m. A metal-backed single-layer absorber made of 20 m sendust particles absorbed more than 99% of electromagnetic wave power at frequencies above 20 GHz. Meanwhile, a composite made of 5 m particles exhibited a return loss of less than −20 dB in the frequency range of not only several GHz but also above 30 GHz. In addition, the relative complex permeability r* was shown to be controlled by adjusting the particle size of sendust, and an electromagnetic wave absorber with a flexible design was proposed.