Methods for substantiating the electrodynamic and design parameters of absorbing materials of waveguide type

The paper considers the issues related to the microwave diffraction on periodic structures of waveguide type. An approach used for assessing the reflective characteristics of absorbing material is proposed. This approach is based on the assumption that in accordance with the energy conservation law, the entire power of the incident microwave radiation on the absorbing material is distributed into two components. One of them characterizes electromagnetic radiation reflection from material surface and is determined through wave impedance at the interface “medium - absorbing material”, and the other, obeying the law of electromagnetic waves diffraction on non-perfectly conducting closed surfaces of waveguide type, propagates into the lattice, then it is partially absorbed in the bulk of the material and reflected from the object (metal substrate), after which it is summed with the first component at the output. A feature of the proposed technique is the design ratios, allowing to determine rational values of dielectric permeability of material, lattice elements conductivity as well as the period and thickness of the lattice which enable to achieve “a semi-infinite layer” at which the minimum value of material reflection coefficient is observed and its no longer depends on the presence or absence of an object (metal substrate).