The region of application in GTD/UTD

The performance of an antenna on a conducting structure can be computed using diffraction theory (GTD/UTD) at high frequencies and there are many examples of such computations. Diffraction theory has proved to be highly accurate when dealing with structures where the components have dimensions greater than 10 /spl lambda/. This paper deals the approximations made in generating diffraction coefficients in an attempt to define more closely the lowest limits to dimensions at which the theory can be used. The importance of this is in determining when a given structure model can be used for a specified frequency or in determining the lowest usable frequency for a particular structure.