Predição de cobertura em enlaces radioelétricos sobre terrenos irregulares através de equações integrais

Abstract

In the present work two deterministic techniques, based on the electric- and magnetic- field integral equations (EFIE and MFIE, respectively) are applied in the propagation prediction of VHF and UHF vertically-polarized waves over irregular terrains. An electrically-smooth terrains profile and a near-grazing incidence are assumed, enabling the terrains to be treated as a perfect magnetic conductor (PMC). By means of the equivalent principle, the terrain is further removed and equivalent magnetic currents placed to impose the necessary boundary conditions. In the equivalent problem, both source and equivalent currents are assumed to radiate in an ideal free-space. To reduce the numerical burden, the terrains is further assumed perpendicular invariant (with respect to the plane of incidence). Also, a spherical distribution is assumed for the magnetic current enabling the reduction of the involved integrals into simple line integrals. The usual Moment-Method technique is applied to solve for theunknown currents. However, to render the problem numerically tractable in practical scenarios, backskattering is further neglected and a forward scheme implemented to recurrently obtains the currents. The scattered field is then obtained from the source and equivalent currents. Both techniques are then compared in two case studies: a PMC wedge and apractical terrains profile. Numerical predictions are conducted to establish the pathloss behavior as a function of both the distances from the transmitter and the height above ground. For the cases investigated, is demonstrated that the MFIE-based technique provides the same level of accuracy (as the EFIE-based one) but with less basis functions to describe the currents (specially where the line-of-sight is obstructed), thus speeding up the whole process