THE NEAR FIELD TO FAR FIELD TRANSFORMATION

If a scattering problem is solved by finite element, finite volume or finite difference methods, it is necessary to predict the far field pattern (or radar cross‐section) by using a near field to far field transformation. Usually this is done using the Stratton‐Chu integral relations, which give the far field pattern in terms of a near field surface integral. When volume‐based methods are used this is unnatural, and it may be necessary to employ interpolation procedures to provide the necessary surface data. In this paper an alternative method based on volume integrals is proposed. The main advantage of the new procedure is that it allows the use of discrete quantities that are naturally available from the numerical scheme. However, it is now necessary to perform volume integrals. The error in the new procedure is examined, and a simple numerical example provided.