and f are as identified as in Equation 8-8. The high impedance EM wave reflection loss is seen to
depend upon the separation distance, r, between the EM source and the shield, as does the low impedance case.
The reflection loss is seen to decrease as the frequency increases and to be better when the ratio
higher. Figure 8-9 is a universal curve for the high impedance reflection loss; the upper line is for the
and the lower line covers the range
Figure 8-10 shows a plot of the high impedance EM wave reflection loss as a function of frequency for iron,
copper, and aluminum for source-to-shield separation distances of one and ten inches. Separate curves for
copper and aluminum are not shown since the high impedance reflection loss for aluminum is only 2 dB below
that of copper.
The reflection losses for iron, copper, and aluminum shields at representative frequencies for magnetic,
electric, and plane waves are given in Table 8-4. The source-to-shield distance for the magnetic and electric
wave cases is one foot (30.5 cm).
Figure 8-9. Universal Reflection Loss Curve for High Impedance Fields (8-3)