Axium Composites designs, engineers, and fabricates non metallic all fiberglass reinforced plastic building enclosures for Open Area Test Sites. Enclosures are designed to meet the requirements for RFI/EMC testing. Dome structures for turntables as well as building enclosures for an entire site are available.
In order to accept EMI measurements inside of the OATS, the site had to be validated in a process called Normalized Site Attenuation (NSA) testing. As described in ANSI C63.4-2003, this process is intended to ensure that the reflective/absorptive losses at the site are comparable to the standardís theoretical values. Essentially, it was our task to ensure that the OATS we had spent so much time developing, from design to construction, met the standard requirements in order to actually be utilized.
Some of the issues that gave us a challenge at the outside labs came into play in our design and build. Ambient signals are abundant near an airport within a city near a larger metropolitan area. Broadcast TV, AM and FM radio, wireless towers, family radio, air traffic control, emergency dispatchers and now, broadband high definition TV (HDTV), are consuming larger portions of the RF spectrum and can readily be detected by antenna at our location.
Due to ambient emissions, a careful site survey was conducted prior to site selection, wherein we measured the direction and amplitude of the ambient signal spectrum. After reviewing the data, we positioned the building such that, during testing, the receive antenna would be facing away from the highest ambient sources, attenuating those signals as much as possible. Ambient emission noise levels have increased tremendously in the past years, making the domes very impractable for today's EMC testing requirements.
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