RADIATION AND SURFACE CURRENTS FROM A SLOT ON AN INFINITE CONDUCTING CYLINDER

Abstract

The far field produced by an aperture in the surface of an infinite cylindrical antenna, whose interior is being electromagnetically excited in some way, has been calculated by Papas and others using a "saddle-point" method of approximation to the infinite integrals which express the external field. This method will not, however, serve to approximate to the far field near the antenna surface. Also, there seems to have been no attempt so far to estimate the order of magnitude of the error involved in using formulae derived by such methods. The object of the present paper is to remedy these deficiencies and to provide a basis for the calculation of the far field in wider regions than has so far been possible. In particular, the surface current distribution at large distances from the aperture has been worked out. Finally, a justification is given for the Papas procedure of integrating his approximation to the Poynting energy flux vector over the whole of the portion of the large sphere surrounding the aperture which is outside the cylinder itself.