Abstract
This investigation aims to present a structural design of a radio-wave absorber incorporating NiCuZn ferrite granules in a contiguous polyepoxide matrix. Electromagnetic properties of the composites in radio-wave frequency were characterized by a combined transmission/reflection method in a coaxial airline fixture. The response of the composites to radio-wave field was attributed to macroscopic magnetic loss and dielectric loss relating to domain wall resonance, spin relaxation, and dipole polarization. Return losses were evaluated using equations representing a structure with a single-layer absorber terminated by a layer of perfect conductor. The maximum return loss was -48 dB occurring at 4.6 GHz for 8 mm thick samples with a ferrite/polyepoxide (F/P) volume ratio = 0.55. The variations of return losses with absorber thickness and absorption bandwidth were also investigated. The macroscopic effective permeability of the composites was computed by a numerical finite elemental analysis (FEA) using a periodic elliptical structure. The FEA calculations are more accurate than values predicted by empirical mixture rules assuming uniform distribution, especially at higher ferrite fractions (F/P ≥ 0.73). © 2010 Elsevier B.V. All rights reserved.