ERRORS AND CORRECTION FACTORS FOR SCHELKUNOFFS SHIELDING EFFECTIVENESS FORMULA

This paper presents the error of the resistive film approximation and that of Schelkunoffs equation with respect to the rigorous solution. B oth of these approximate equations cause errors for the planar shield for which either an infinitesimal electric dipole or an infinitesimal magnetic dipole is the source. Hence, the four types of planar shield with different directions and types of dipole source are investigated. Next, the conditions for causing the error is studied. When Schelkuno ffs equation and the resistive film approximation are rewritten, they become functions of three dimensionless parameters. However, the numer ical analysis reveals that only two error-causing parameters are suffi cient if the choice is carefully made. With these two parameters, the correction factors are derived with which the rigorous value is obtain ed from Schelkunoffs equation or the resistive film approximation. The rigorous solution is a complicated equation including integral calcul ation. On the other hand, Schelkunoffs equation is relatively simple. If this correction value is used, a solution equivalent to the rigorou s solution can be obtained from Schelkunoffs equation or even simpler resistive film approximation.