Skin Effect

AbstractThe skin effect is the property that electromagnetic waves penetrate only a small distance into a conductor. The fields and induced currents decay exponentially with the distance from the surface. The distance over which the fields and induced currents decrease by a factor ofeis the skin depth. The ratio of the voltage drop along the surface of the conductor to the current flowing in the conductor and causing this voltage drop is the surface impedance. Expressions for the skin depth and the surface impedance are in the first instance derived for a plane conductor interface. The results for a plane conductor are also applicable for a curved conductor as long as the radius of curvature is large compared to the wavelength. For a conductor with a finite thickness an expression for the surface impedance is derived that takes into account the finite thickness of the conductor. The roughness of the conductor surface increases the surface resistance. This increase is quantified by an empirical law. The concept of the surface impedance allows an efficient inclusion of conductors with finite conductivity in numerical electromagnetic simulation techniques such as integral equation techniques, finite‐element techniques, and finite‐difference time‐domain techniques.