Shielding effectiveness measurements in resonant enclosure based on loaded reverberation chamber in a GTEM cell

Abstract

A novel approach is introduced for measuring the shielding effectiveness in resonant conductive enclosures having apertures in a removable side wall. The measurement setup was based on GTEM cell as a compact field-generating environment, capable of accommodating small enclosures as DUTs. The signal was fed into the GTEM cell, thus creating a controlled incident field impinging on the enclosure. The field level inside the exposed enclosure was collected as the output signal. Shielding effectiveness was calculated as the ratio of the S <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</inf> parameter measured without the side wall attached to the enclosure, to the S <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</inf> parameter measured with the side wall attached, both averaged over the full rotation of the stirrer. Highly expressed resonances were attenuated by introducing the mechanical stirring into the enclosure, thus turning the inside of the enclosure into a reverberation chamber. Additionally, the resonant behavior of the enclosure was reduced by introducing the water containers within the enclosure volume as dissipative load, consequently lowering the enclosure Q factor. The results were in excellent agreement with the ones previously obtained using mode stirred technique.