Far field analysis of radiation sources

Summary form only given. Finding where the far field power originates from a scatterer or antenna is of interest not only from the viewpoint of antenna design or controlling radar scattering, but is also a problem of fundamental physics. One approach to this problem might be provided by the Lienard-Wiechert potentials. These show explicitly that radiation is due to accelerated charge. Although it is obvious where some of the charge acceleration occurs on a simple object such as a wire antenna or flat plate, apparently no analytical connection has been established between equivalent source distributions computed from numerical solutions and charge acceleration. Indeed, a connection between equivalent sources on the surface of a perfect electric conductor (PEC) and the behavior of physical charge within an actual conductor is not completely clear. Hence, the specific question of how much power is contributed per unit area from a PEC to far field radiation may not have an obvious answer, a situation that fortunately has not hindered analysis and design. The approach described here, called far field analysis of radiation sources (FARS), also uses bistatic far fields at a single frequency. Instead of imaging, we seek to determine the contribution made to the total power flow at a given far field observation point by each incremental source on the PEC boundary. Some results from this approach have been developed for simple prescribed current distributions and some straight-wire radiators and scatterers. Because it provides a good reference, the sinusoidal current filament was examined in detail.