A new definiton and relevant measurement techniques for evaluating shielding effectiveness of equipment enclosures

The most common technique for evaluating the shielding effectiveness (SE) of a large screened enclosure is the twin-antenna method. The SE of the enclosure is usually determined by the ratio of two electric fields taken during the measurement procedure. However, the dimension of a typical equipment enclosure is generally much smaller; the equipment enclosure, which contains equipment inside, also has a number of apertures for different applications. Because of these characteristics, the traditional definition of SE and the relevant measurement techniques for large screened enclosures are not suitable for equipment enclosures. To evaluate the shielding performance of an equipment enclosure, a new definition based on the ratio of two power values was proposed in this paper. Two measurement environments: the anechoic chamber and the reverberation chamber were considered and compared. To avoid the huge measurement work in an anechoic chamber, the reverberation chamber is proposed as an ideal test environment to determine the shielding ability of equipment enclosures.