On the design of door-less access passages to shielded enclosures

RF shielded enclosures have been common features in laboratories and manufacturing areas for over 70 years. They provide a quiet environment where RF measurements can be performed without interference from outdoor sources and are used to keep potentially classified frequencies and modulations from leaking out. In general, these shielded rooms have shielded doors to maintain the shielding integrity of the enclosure until they are opened. In some cases, to maintain the shielding integrity as personnel moves from the inside to the outside of the room and vice-versa, dual shielded doors with a small vestibule between them are used. However, the presence of multiple doors increases the time to access the enclosure. To solve this, some enclosures are designed featuring access passages to maintain the shielding integrity over a broad frequency without the use of doors. Although this type of access has been around for over 40 years, its design has never been discussed in the literature. In this paper, a door-less access is analyzed and some design rules are presented. The limitations of these accesses are also presented. While clearly they do not have the shielding performance of a shielded door, they are ideal for certain applications.