Generalised boundary conditions for a material sheet with both sides coated by a dielectric layer

Many structures which play important roles in practical applications involve planar sheets coated with dielectric layers. In order to avoid the mathematical difficulties arising from this type of multilayered structures in antennas and propagation problems one tries to replace the coated sheet by an equivalent hypothetical plane having appropriate boundary conditions. A new and general method capable of obtaining these generalised boundary conditions is presented and applied to three important particular cases where the structure consists of a resistive or conductive or impedance plane with both faces coated with dielectric layers.