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Copper Screen Rooms
Screen rooms are the next most popular shielded enclosure after modular shielded rooms. The addition of the copper screen allows the room to be partially see-through and makes it easier to communicate through the panels without drastically affecting the shielding integrity.
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Typical Performance
Magnetic Field: 18dB @ 1kHz, 50dB @ 15kHz
Electric Field: 100dB from 15kHz to 10MHz
Plane Wave Field: 100dB from 10MHz to 1GHz
Microwave Field: 60dB @ 10GHz
Construction
Panels and Framing
Copper screen rooms are constructed in a similar fashion to Modular Shielded Rooms: pre-fabricated panels and framing elements. However, in a screen room, the upper half of the walls and the entire ceiling are made with wooden frames faced with two layers of copper screen. The floor and lower half of the walls consist of two layers of 26 or 28 gauge galvanized sheet metal laminated to both sides of a 3/4" particle board core. The panels are then connected with extruded steel framing elements that clamp on the panel and screen edges and lock everything together. Framing elements are zinc plated like the panels to resist corrosion.
The framing elements consist of 3 pairs of components typically named "hats and flats" (in reference to the shape of their cross section), "coves" for the elements that make the 90 degree connections between the walls and the ceiling and floor, and the trihedral corners. The pairs of framing elements are positioned inside and outside the room and joined together using cadmium plated fasteners spaced 4" apart. These fasteners provide a uniform pressure along the framing elements thereby insuring a consistent RF seal with the panels.
To maintain electrical isolation from the parent structure, the screen room is constructed on top of a 6-mil dielectric vapor barrier and two 1/8" dielectric hard-board underlayments. In addition, all penetrations into and out of the room must be made using specially designed accessories described below.
Shielded Door
Access into the screen room is provided by a shielded door. The door provides an RF-tight seal by bringing a brass knife edge on the door into contact with beryllium-copper fingerstock in the door frame. When the door leaf is nearly closed, a cam actuated latch draws the knife edge of the door into the fingerstock, completing the seal. The door is attached to the screen room by two self-adjusting, thrust and radial bearing hinges. These hinges also allow the door to be adjusted within the door frame to within a tolerance of 0.005" in both the vertical and horizontal directions in order to insure a tight electrical seal between the knife edge and the fingerstock.
Shielded door sizes are normally 3' x 7' and 4' x 7'. However, we can provide double doors and custom sizes at your request.
Click here to read more about our "QuietDoor."
Power and Signal Line Filters
With the exception of RF cables, all conductors penetrating the screen room must be filtered. We offer a complete line of filters for most power and signal line requirements. For the latest digital signals (like 100mb Ethernet) that cannot be electrically filtered without destroying the signal integrity, we can provide specially designed optical isolation filters.
Click here to read more about our EMI/RFI Filters.
Waveguides
Waveguides are used to allow water, gas or air to penetrate the shielded enclosure without compromising the shielding effectiveness. The diameter of the waveguide determines the cutoff frequency while the length of the waveguide affects the shielding effectiveness. Our waveguides come in a variety of shapes and sizes depending on the application. For air vents, we use a honeycomb waveguide construction which looks like a see-through metal screen and can interface with HVAC ducts. Feedthrough waveguides resemble pipes and come in sizes ranging from ¼" to 4" diameters. They are commonly used to allow fiber optic cables into the shielded room and for fire suppression sprinklers. In all cases, a dielectric must be included in the construction of the waveguide in order to maintain electrical isolation between the shielded enclosure and the outside environment.
Additional Accessories
DJM Shielding can provide additional cosmetic enhancements at your request. These can range from computer flooring to wood paneling or white-board interiors. Please feel free to contact us to discuss your preferences.
Sizes
Although copper screen panels come in a standard sizes of 4' x 8', it is common to cut the panels to sizes that suit our customer's needs. Please contact us with your requirement.
For small requirements (less than 3' x 3' x 3') we recommend our table top shielded enclosures.
Specialty Rooms
In addition, standard modular shielded rooms can be modified for particular applications:
MRI Rooms and Magnetic Shielding
Modular shielded rooms can be modified to include additional shielding material (eg steel or mu-metal) that is more effective against low frequency magnetic waves and the critical operating frequency.
Shielded Workstations
A modular shielded room with accessories designed to satisfy the requirements of wireless engineers. These include wheels on the room to make it mobile, rack mounting for instruments preinstalled, and wall-mounted working surfaces.
High Voltage Shielding
High Voltage Shielding is typically used for controlling discharge from corona testing and to provide isolation from ambient RF noise or signals. The shielded enclosure provides a uniform and consistent ground plane on all surfaces of the room. Any undesired high voltage discharge is safely directed to ground.
Tempest Rooms
A standard shielded room that is modified to comply with NSTISSAM TEMPEST/1-92 and/or NSA NO. 94-106
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