Reduction of Skin Effect Losses by the Use of Laminated Conductors

It has long been recognized that an electromagnetic wave propagating in the vicinity of an electrical conductor can penetrate only a limited distance into the interior of the material. This phenomenon is known as "skin effect" and is usually measured by a so-called "skin depth" 8. If y is measured from the surface of a conductor into its depth, the amplitude of the electromagnetic wave and the accompanying current density decreases as e~"' provided the conductor is several times 5 in thickness, so that for y = 5 the amplitude has fallen to 1/e = 0.367 times its value at the surface. The skin depth 8 is given by (1-1) where a is the conductivity of the material, n is its permeability and c0 is 2ir times the frequency/ under consideration. Throughout this paper rationalized M K S units are used. From one point of view, skin effect serves a most useful purpose; for instance, in shielding electrical equipment or reducing crosstalk between communication circuits. On the other hand, the effect severely limits the high frequency performance of many types of electrical apparatus, including in particular the various kinds of transmission lines. Surprisingly enough, it has been discovered that it is possible, within limits, to increase the distance to which an electromagnetic wave penetrates 491