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Abstract
Schelknuoff in his book Electromagnetic Waves presented the presently accepted "Shielding Effectiveness Equations". FIe illustrated the use of the equations with an example where the shield material (copper lube 0.2mm thick) was 1.0 centimeter from the source of the radiated wave. The frequency he used in his example was 1.0MHZ.
At Broaddus presented a paper at the 1992 IEEE International Symposium on EMC in Anaheim and George Kunkel presented a demonstration at the 1999 IEFF International Symposium on EMC in Seattle. Both the paper and demonstration illustrated test data over the frequency range of 1 0OkI IZ to 1 .OMFfZ. The test sample in both cases was an aluminized mylar space blanket having an impedance of about 2 ohms. In both cases the test sample was in the near Held of the radiating sources where both the E and H fields were measured for shielding effectiveness.
The arguments and results of Schelkunoff's example are compared with the test data obtained by Broaddus and Kunkel. A thorough evaluation of the "Shielding Effectiveness Equations" is presented.
(ProQuest: ... denotes formulae omitted.)
Introduction
The example used by Schelkunoff to illustrate the use of the "Shielding Effectiveness Equations" consisted of a pair of "closely spaced current filaments" centered inside a 2 centimeter copper lube 0.2 millimeters thick as shown in figure 1.
The impedance of the wave radiating from the "closely space current filaments" is consistent with the impedance of a wave 1 centimeter from a magnetic dipole antenna. The wave according to Schelkunoff is reflected at the incident side of the shield and again inside the barrier at the exit side. There is also an attenuation factor inside the barrier due to skin effect. A level of shielding efficiency was given where it is implied that the shielding level is to power.
The test performed and reported in the paper by Broaddus had the shield material (1.4 ohm space blanket) attached to the wall of a shielded enclosure with a 24 by 24 inch opening. The radiating sources were both an electric and a magnetic cupole antenna (see Figure 2 for typical setup.)
The shielding effectiveness to both the E and H Fields were measured and recorded for both of the sources of the wave....