Distortion of radiation patterns for leakage power transmitted through attenuating cover panels and shielding gaskets-need for reverberation chamber measurement of total leakage power

Measurements are presented on the free-space radiation patterns from large apertures (>λ) covered with an attenuating plastic cover panel that employs fibers or metal mesh to produce absorption. It is shown that the patterns can be significantly and unpredictably distorted due to non-uniform transmission through the panel caused by variations in material composition throughout the volume of the panel. The results also show that leakage around the edges of the panel can have a significant effect. Due to the complexity and unpredictability of these patterns, it is concluded that the total leakage power cannot be measured readily in an anechoic chamber, but can be measured most readily if the panel radiates into a reverberation chamber