Modal transmission-line modelling of radio wave propagation through periodic inhomogeneous walls

For an accurate planning of microcellular mobile radio communication networks, new radio wave propagation models for the estimation of the losses on the radio path must be used. At UHF frequencies, transmission of radio waves through buildings can be the dominant propagation mechanism. In this paper transmission through walls is studied in more detail, using one special typical property: the periodicity. This property allows the use of a novel full-wave method, the so-called modal transmission-line (MTL) method, for an accurate and at the same time computationally efficient prediction of the transmitted field. The description of the MTL-method is based on matrix notations of Tamir and Zhang (1996). The theory is applied to the computation of the radio wave transmission through complex walls, like reinforced-concrete walls. In order to apply the MTL-method, these walls are modelled as multilayer periodic structures. The MTL-results are compared with the results obtained by another numerical technique.