A simple hybrid method for ELF shielding by imperfect finite planar shields

A simple method is described for calculating the shielding performance of a two-dimensional (2-D) thin finite-width shield made of imperfect material in the presence of the magnetic field from line source conductors. First, solutions to two canonical problems with closed-form simple analytic formulas are presented; shielding by reflection from and absorption in thin planar shields of infinite extent and shielding by perfect conductor shields of finite width. Then the method for calculation of magnetic-field shielding by perfect conductor finite-width shields is extended using the simple interpolation method, to thick shields made of imperfect material. Finally, the hybrid solution is developed by adding the two results in quadrature. The result is a simple theory for shielding by finite-width shields made of any real shielding material of arbitrary thickness. Its accuracy has been validated by comparison to finite-element method solutions and existing measurements.