Comment on "Electromagnetic missile launched from a uniform current sheet of arbitrary shape"

For original paper, see Zhan and Wan (IEEE Trans. Electromagn. Compat. vol.33, no.1, p.61-3, Feb. 1991). Theoretical findings by Wu (1985) of some previously unexpected behaviors of the energy flux carried by a very-broad-band pulse makes it desirable to investigate the electromagnetic missile (EMM) launchers. Previously, current pulse distributions over a surface, or along a line, or a point source in certain reflecting or defracting systems, have been investigated. Some authors have begun to investigate an arbitrary current distribution for EMM launchers. The present authors think that this is possible directly. A circular current plate with a proper time characteristic has been found that can radiate an EMM. One may think of a current with a proper time characteristic of arbitrary shape, to be comprised of many circular current distributions whose radii are very small. Each circular current can generate an EMM on its center axis, thus a current of arbitrary shape is capable of launching an EMM over the area equal to that of the shape. Zhan and Wan tried to prove the idea in the time domain. The results show that it seems to be exact, but there is a problem in the process of the derivation. By discussing the problem, the present authors point out an additional conclusion that only a current with a proper time characteristic can generate an EMM.<>