Waveguide simulation approach for transmission analysis of reinforced concrete wall structures

The determination of electromagnetic wall transmittance of buildings is important for mobile communications and with reference to safety issues for (intentional) electromagnetic interference (EMI/IEMI) problems. Thus, the knowledge of the inhomogeneous wall structure is significant for the transmittance analysis. Here, a reinforced concrete wall with a double rebar steel grid is considered. In most numerical simulation software tools, the calculation of a perpendicular field incidence is much easier than for oblique angles of incidence. To model obliquely incident waves in a finite space, field propagation features of a rectangular waveguide are used with an inserted representative sample of the inhomogeneous wall. Operation of the waveguide with the TE10-eigenmode is decomposable into two obliquely propagating waves allowing to compute the transmission factor for an obliquely incident uniform plane wave at reduced computational time and costs. This method is extended to provide for higher frequencies in the MHz range by using suitable higher eigenmodes (TE20, TE30, …) and to overcome the problem of neglecting grid periodicities of the rebar steel grid. Some of the numerical results achieved with the waveguide model are compared with results based on a model of a free Gaussian beam.