In RF Shielded, Testing

How to Assure an RF/EMI Shielding Enclosure Will Perform for Your Application

It is critical that RF/EMI shielding enclosures actually function per your own specific requirements, whether you are protecting sensitive data from foreign and commercial espionage, or assuring the chain of evidence for data on seized mobile devices, or testing for EMI in time-critical major product launches.

So how can buyers of these enclosures assure they will perform? Product literature supplied by vendors often provides test data, but that must be carefully scrutinized to assure that the specific test used will predict the functionality of the enclosure in actual operation.

Different tests offer different insight as to effectiveness. Tests of the enclosure’s material may give a clue as to shielding effectiveness, but this is insufficient to predict functionality in use. The fully assembled enclosure needs standardized testing to ascertain shielding effectiveness. As leakage may come from seams, vents, filters, IO plates, or doors, shielding effectiveness should be measured through the wall at multiple locations. Shielding effectiveness can also vary greatly by frequency.

Select Fabricators tests their RF shielding tents with a third party independent IEEE-299 standardized test of the entire assembled enclosure. This standardized test measures dB shielding effectiveness at different frequencies. It also measures attenuation through the tent wall at a variety of locations, by the door, by the vents, etc.

The minimum shielding effectiveness that is recorded anywhere throughout the enclosure is the critical measure for security applications. Select Fabricators’ IEEE-299 test of their high attenuation tent plotted on the chart below shows shielding effectiveness of at least 85.7 dB from 400 MHz to 18 GHz throughout this portable chamber. Peak shielding performance of 98.7 dB was recorded at 1 GHz on the side with the door.

Shielding Effectiveness, Double Layer Tent with Internal Vestibu

Your specific application may have unique shielding effectiveness requirements. dB measurements are logarithmic, a 60 dB rating is ten times higher than a 50 dB rating. Shielding effectiveness needs vary greatly with the signal intensity encountered, which drops exponentially with the distance to the source. Critical security applications to prevent electronic eavesdropping in hotels and office buildings may need to shield computer and cellular equipment’s RF emissions from reaching the next room or floors above and below.

Proactively managing your RF shielding enclosure’s procurement process is critical to assure the buyer gets the results they need for their specific application. Specifying shielding requirements in the request for quotation is important. For highly critical applications, you may need to assure that the specific enclosure you purchase, as manufactured and delivered, will actually work for you on the site where and how it will be ultimately used. In these sensitive situations, the request for quotation may possibly include a receiving verification process to assure that the specific enclosure as configured and delivered performs in the field as used. This may require third party testing of the enclosure on the site where it will be used, perhaps requiring the supplier to make field modifications to adjust for any shielding issues. Select Fabricators will work with customers with highly sensitive requirements to facilitate this verification process.

To assure your RF / EMI Shielding Enclosure will work for your application, be sure to include a written request for a quotation including your minimum shielding requirements for the frequencies important to your needs. If your application is highly critical, consider specifying onsite 3rd party testing to assure the enclosure you receive meets your specifications. Most importantly, be sure to choose a supplier who will stand by their product. Select Fabricators is committed to delivering a product that meets your specifications.

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