MOMENT METHOD ANALYSIS OF THE ELECTRIC SHIELDING FACTOR OF A CONDUCTING TM SHIELD AT ELF

This paper presents an integral equation and method of moments (MM) so lution to the problem of TM transmission by a metallic conducting shie ld at extremely low frequencies (ELF), To obtain an accurate and effic ient solution, the equivalent volume polarization currents representin g the shield are expanded in terms of physical basis functions, corres ponding to two planewaves propagating normal to the surface of the shi eld, ELF approximations are used to obtain closed form expressions for certain crucial elements in the MM matrix equation where extreme accu racy between the relative magnitudes of self and mutual impedance term s are required, Numerical data will illustrate that despite the fact t hat the equivalent polarization currents are being computed very accur ately, the method is not capable of computing the extreme near zone el ectric fields of these currents with sufficient accuracy to compute th e electric shielding factor, An alternate method, based upon the use o f the volume equivalence theorem to directly compute the total electri c field in the shield is devised, and is found to accurately compute t he electric shielding factor.