An Approximate Solution of Scattering From Reinforced Concrete Walls

Scattering from reinforced concrete walls, such as vertical rebar and crossed rebar walls, is analyzed by using an approximate analytical approach. The solution is obtained for a plane-wave incidence with an arbitrary angle of incidence and polarization under the thin-wire approximation. The formulation is based on derivation of the Green´s function of a 1-D periodic sources inside a dielectric slab. Since the metal thickness is assumed to be small compared to the wavelength, the induced currents are predominantly axial and the transverse components of the induced currents are ignored. This drastically simplifies the solution for this problem which is obtained using a straightforward point-matching technique. The solution for two-dimensional periodic crossed rebar concrete walls is also cast in terms of the periodic Green´s function obtained for the 1-D periodic structure of the vertical rebar walls. Using the finite-difference time-domain (FDTD) simulation results, it is shown that the induced currents on thin crossed re- bars (diameter <lambda₀/5) have primarily a progressive phase equal to that of the incident field in both directions. This observation also points to a simple approximate solution where the problem of scattering from a 2-D periodic crossed rebar concrete wall is decomposed into two coupled 1-D periodic structures of vertical and horizontal rebar walls. The Bragg mode scattered fields of the reinforced walls are computed for different wall parameters and incidence angles for an operation frequency range of 0.5-2.0 GHz and validated by FDTD simulation results.