Khanh Nam NGUYEN
Hiroshi SHIRAI
In recent years, the growing demand for wireless communication services in urban areas with a large number of buildings has led to a need for an effective indoor-outdoor wave propagation model to accurately predict transmitted signals. Since the high frequency signals experience strong decay as they pass through building walls, an appropriate propagation path may be through the building windows. Since a thick slit can be a canonical structure of the window aperture, the study of electromagnetic wave diffraction from a thick conducting slit becomes important.
For practical applications of indoor-outdoor mobile radio wave propagation through windows, one has to pay attention that the window dimension is large with respect to the wavelength. Then the numerical methods and eigen-function methods are not efficient for this scenario, and high frequency asymptotic methods, such as the Kirchhoff approximation (KA) and the geometrical theory of diffraction (GTD) seem to be more appropriate. In this study, we utilize the KA method to analyze plane wave scattering by conducting thick slits. The primary scattering fields can be considered as field radiations from equivalent magnetic current sources postulated on the closing aperture of the slit. In order to obtain the diffracted field from the lower aperture of the thick slit, ray-mode conversion is used to obtain the internal waveguide fields inside the slit, and the magnetic current is postulated again at the lower aperture. The numerically obtained results are compared with those of other methods to evaluate the accuracy of the proposed formulation in different conditions of slit dimensions.
The KA method has great advantages for general scattering analysis, since the formulation is simpler than that of the GTD, and easy to adapt to complicated problems. By our analysis, it has been shown that the KA method can be applied confidently for large aperture cases especially for estimating the main diffraction beam behavior. Also, the simple formulation leads to a short calculation time. Accordingly, the method could be successfully applied to investigate the plane wave scattering by more complicated and realistic objects such as thick loaded slits which can be considered as a model of window aperture with glass layers. One confidently steps further to study more practical diffraction analysis by three-dimensional rectangular holes in a thick conducting screen.
Because of the above advantages and potential of the proposed method in scattering analysis, this paper can be highly evaluated as a paper suitable for the Best Paper Award of the Institute of Electronics, Information and Communication Engineers.
