An integral solution for the propagation of electromagnetic field in complex environments

The aim of this work is to show how a full integral technique (the method of moments) has been applied, by means of the use of acceleration procedures, to the calculation of the electromagnetic field radiated from radio phonic emitters working in amplitude modulation, on the bands 525-1605 khz (medium-wave), to produce an instrument of evaluation, useful for radio-protection applications. If dedicated to this purpose, measurements of electromagnetic field in the zone of near field are extremely difficult and often influenced by various sources of error. Alternatively, the application of simulation techniques must take into account the presence of all the obstacles: for the analysed bands the buildings and all the obstacles have dimensions comparable with the wavelength. In general, when the calculation of the radiated electromagnetic field concerns the zone of near field of an antenna, or the scattering objects are smaller than the wavelength, optical techniques do not represent a convenient resort, while it is necessary to use techniques based on the direct solution of the Maxwell equations in an integral or differential form. The recent development of algorithms of acceleration for the integral solution of the Maxwell equations has permitted the application of the method of moments to a great variety of problems finalized to the estimation of the propagation of the electromagnetic field. Different codes have been produced: some of them based on the Multilevel Fast Multipole Algorithm (MLFMA), that have permitted the calculation of the RCS of extremely complex objects, some other have permitted the 2D characterization of the propagation of field very far from the source, some more have permitted the calculation of scattering of electromagnetic field in generic structures. For the application discussed in this work, it has been chosen a completely integral formulation, applied to the 2D and 3D cases, accelerated by means of the MLFMA, which takes into account the effect of the finite conductivity of the ground and the propagation through the obstacles deployed in the region object of the study