Analytical aspects of plane wave illuminated thin wires and slits

The paper deals with simple elementary approximations for the current and charge response on different straight wire structures, dipoles and short slits in the receiving case. After proof that transmission line equations are also valid for single wires without discontinuities, these equations are formulated including the incoming wave. They turn out have simple particular solutions that could be expected for the case, when the electric field is parallel to the wire, but holds true for the general case too. Satisfying the boundary condition at discontinuities (wire ends, lumped elements) gives rise to additional waves appearing as solutions of the homogeneous wave equation. The formulation of currents along and voltages across a slit, including an illuminating magnetic field at one side of the screen, leads again to transmission-line type equations and, consequently, to the inhomogeneous wave equation. As slits in screens are usually small in terms of wavelength, an approximative solution for the short slit will do. For this case, even closed-form expressions are possible for the magnetic near field.