Composite electromagnetic wave absorber made of soft magnetic material and polystyrene resin and control of permeability and permittivity

The frequency dependences of the relative complex permeability μr*, the relative complex permittivity εr* and the absorption characteristics for composite electromagnetic wave absorbers made of polystyrene resin and sendust particles or permalloy particles were investigated in the frequency range from 1 to 40 GHz. The size of sendust particles was varied between approximately 5 and 20 μm and the particle size dependence of μr* was observed. The value of μr* was shown to be controlled by adjusting the particle size of sendust, and an electromagnetic wave absorber with a flexible design was proposed. A metal-backed single-layer absorber made of sendust particles or permalloy particles absorbed more than 99% of electromagnetic wave power at frequencies above 20 GHz. In addition, a composite made of 5 μm particles exhibited a return loss of less than −20 dB in the frequency range of not only several GHz but also above 30 GHz.