Analysis of shielded tents and other electrically thin shielded rooms

An analysis of a large shielded tent or enclosure with electrically thin walls showed that three frequency ranges were important. At low frequencies, the shielding effectiveness for a single shield increases at the rate of 20 dB/decade and depends on the surface resistivity and enclosure size. At mid frequencies, the shielding effectiveness is frequency independent and depends on the surface resistivity. At high frequencies, the standing waves inside the enclosure become apparent and the shielding effectiveness depends on the absorption in the enclosure and the apertures in the walls. With metallized fabric presently available, the effectiveness of a single shield on a large facility can be in the range of 60 to 85 dB for frequencies above a few hundred kHz. A shielded floor is essential if significant shielding was required.