Optimization of two-layer electromagnetic wave absorbers composed of magnetic and dielectric materials in gigahertz frequency band

Both experimentally and theoretically, a two-layer electromagnetic (EM) wave absorber exhibits the possibility of meeting the demand for effective EM wave absorbers. The first layer, made up of magnetic micpowder (MMP), has a large permeability and magnetic loss, while the second layer, comprised of MMP and nanotitanium powder, has a frequency dispersion with the parameters of permittivity and permeability to match the incidence free space over a wide frequency range. The predicted results are based on the modulus of permittivity (permeability) which obeys a logarithmic law of mixtures, and the loss tangent is related through a linear law of mixtures. A linear regression analysis performed on the data points provides constants that can be used to predict the effective parameters at different frequencies. Finally, a program is presented that computes the optimum amount of MMP in the second layer and the required thickness for each layer. The predicted results agree quite well with the measured data.