Testing of microwave shielding gaskets and cover panels-recent work at Rome Laboratories

Abstract

This paper discusses the experimental characterization at microwave frequencies of leakage sources such as gasketed seams and attenuating cover panels by methods that employ a reverberation chamber (REVCH) to measure the total power radiated into the REVCH by the leakage source. The preferred characterization of a leakage source is in terms of the effective transmission area (ETA) defined as the total radiated leakage power (watts) divided by the microwave flux (watts per square meter) incident on the leakage source from outside the REVCH. Several sources of error that can occur in measuring ETA are identified, non-uniformities in material and cross-sectional dimensions of the test panel or gasket being a significant source of error. The non-uniformities can result in "hot spots" which have unknown size and position along the length of a gasket or over the area of a panel, and therefore, can have uncertain power coupling into the REVCH. The results presented in this paper indicate clearly the need to further modify MIL-STD-285 to include a requirement for some form of mode stirring. Furthermore, "ETA" should be adopted as a preferred characterization for the microwave shielding performance of gaskets and cover panels.