Predição de cobertura radioelétrica em terrenos irregulares usando método de funções de base características

Abstract

This work deals with the propagation of electromagnetic waves in the VHF (Very High Frequencies) and UHF (Ultra High Frequencies) bands over irregular terrain. This study is concerned in development an computationally algorithm capable of providing an accurate solution in predicting the behavior of electromagnetic wave. The formulation proposed is based on the Electric Field Integral Equation (EFIE) and Magnetic Field Integral Equation (MFIE) in frequency domain. These equations are discretized by The Method of Moments (MoM) and the solutions are obtained numerically applying the Characteristic Basis Function Method (CBFM). The CBFM utilizes special functions defined on macro-domains (blocks). These functions are constructed from the use of conventional basis functions defined on sub-domains (segments). One of the advantages of the method is the possibility of taking into account the effects of back-scattering in problems where the terrain is considered electrically large. In the formulation, some approaches have been adopted to allow the implementation of the solution. The terrain is considered irregular, homogeneous and the transverse variation is disregarded. The ground losses are estimated by the Leontovich boundary condition. For the treatment of purely two-dimensional problem the transmitting source is considered as the infinite electrical line source for horizontal polarization (H-Pol) and magnetic for vertical polarization (V-Pol). To test the accuracy and efficiency of the method, three cases are analyzed using theoretical terrain profiles and three other cases using real terrain profiles (two located in Denmark and one in Turkey). In each case, simulations are performed for both H-Pol and V-Pol, varying the main parameters allowed by the method CBFM in order to find the best solution. The results obtained are presented and compared with measurements or previously published reference solution in the scientific literature. It has been observed that CBFM provides good results and can be used in the investigation of problems of electromagnetic wave propagation over rough terrain.