The effects of intrinsic test fixture isolation on material shielding effectiveness measurements using nested mode-stirred chambers

The paper evaluates the effects of test fixture isolation when using nested mode-stir chambers for conducting electromagnetic shielding measurements. The nested chamber technique is used by both government and industry to evaluate the electromagnetic attenuating properties of materials as varied as infrared sensor windows to the composites used in the hulls of new ships. Two cases are considered: (1) the test aperture provides little inherent isolation between the two chambers, and (2) the aperture provides reasonably good isolation. It is shown that in the former case, data taken in this fashion can exhibit significant deviation from the latter. A correction factor for the former case is developed