Closed-form representation for equivalent electromagnetic parameters of irregular hexagonal honeycomb radar-absorbing materials

In this study, a new closed-form expression is developed to determine the equivalent electromagnetic parameters (permittivity and permeability) of biaxial anisotropic honeycomb radar-absorbing materials (RAMs). Based on the equivalent medium theory, the nonmagnetic substrate and absorbing coating of the honeycomb structure are equivalent to one kind of material, and then, the effective electromagnetic properties of irregular hexagonal (compressed or stretched) honeycombs are obtained by using the layered anisotropic model. In order to validate the effectiveness and correctness of this new closed-form expression, experimental tests and numerical simulation are adopted. The results show good agreement among the experimental tests, numerical simulation, and theoretical analysis within the specified frequency range (2–18 GHz), which confirms the validly of the proposed new method. Compared with the previous layered anisotropic model, the modified new model is more accurate for irregular hexagonal honeycomb RAMs. Furthermore, it can predict the effective permittivity (permeability) precisely without experimental measurements or numerical simulation, and it is of great significance for the design of honeycomb RAMs.