Optimization of an inhomogeneous radio-absorbing dielectric layer

Dependences of permittivity on the depth of an inhomogeneous dielectric layer are obtained which assure low (or null) reflection at a fixed wavelength. These dependences can be used, in combination with transition smoothness, to obtain a maximally broadband absorber with a permittivity dispersion allowed by the Kramers-Kronig relationships. A direct-optimization method is proposed which makes it possible to determine the permittivities of the individual layers of a multilayer structure, for which the reflection coefficient, averaged with respect to a given set of wavelengths, is minimal.