Last Week's Question
At 100 MHz, the plane-wave shielding effectiveness of aluminum foil,
- is close to 0 dB
- is approximately 20 dB
- is more than 100 dB
- could be less than 0 dB
Answer
The correct answer is "c". Unlike the shielding effectiveness of enclosures or gaskets, plane wave shielding effectiveness can be calculated and measured in a consistent and repeatable manner. Aluminum foil with any reasonable thickness will have a plane wave shielding effectiveness higher than 100 dB. The shielding effectiveness calculator on the Clemson Vehicular Electronics Laboratory website can be used to show that even standard aluminum foil that is only 0.016 mm thick has a shielding effectiveness of over 102 dB.
Note: The shielding effectiveness of an enclosure made from aluminum foil could be less than 0 dB. Resonances set up inside an enclosure can create strong internal fields. When some of the energy in those fields leaks out through seams and apertures in the enclosure, the resulting radiation can be higher than the radiation from the same sources without the enclosure.
Have a comment or question regarding this solution? We'd like to hear from you. Email us at