Missile Circumferential Current Density for Plane Wave Electromagnetic Field Illumination,

The study of shadowing of plane wave electromagnetic fields by missiles is of importance because RF leakage into a missile through holes and slots in the wall and the RF pickup of cables furrowed into the skin leading to interior circuitry depends on the amplitude and the variation of current density along the circumference of the scattering obstacle. Clearly the azimuthal orientation of the missile with respect to the incident field has a bearing on the RF receiving characteristics of the slots and cables, if indeed electromagnetic field shadowing is significant. One topic discussed briefly in this memoradum is a theory for shadowing by tubular cylinders of arbitrary dimensions developed by Kao. As a practical matter, the coupled integral equations derived by him cannot readily be solved for very long cylinders because of the limited number of storage locations in a computer. To circumvent this, the author presents a theory for shadowing by a cylinder of infinite length. In the entire discussion of both finite and infinite tubes, it is assumed that the electric field is polarized parallel to the axis of the cylinder. This is the case of dominate interest in the field of RF hazards to ordnance. But this specific polarization is an unnecessary restriction. The angle the incident field makes with the axis of the cylinder may be arbitrary. In particular, the magnetic field may be polarized parallel to the conductor. Author