EMI and Mechanical Design Considerations
154 Design Guide
11.2.6 EMI Test Capabilities
FCC regulations in the United States specify the maximum test frequency for products with clocks
in excess of 1 GHz is five times the highest clock frequency or 40 GHz, which ever is lower. OEMs
are advised to inquire into the capabilities of their preferred EMC test lab to ensure they are able to
scan up to the required frequency range.
Processor performance and frequency double approximately every two years. With this in mind, it
is advisable to be prepared for the frequencies that will need to be scanned in the next few years.
Since the FCC rules ultimately require testing to 40 GHz, commercial test equipment has been
developed that is capable of making measurements to that frequency. Although it will be some time
before processors require testing at this frequency, it may be cheaper to upgrade to 40 GHz now,
rather than making several intermediate steps.
It is also possible to upgrade various parts at different times. The spectrum analyzer may be
upgraded to 40 GHz today with only the necessary antennas to support the initial processor
frequencies. As processor speed increases, the necessary antennas and cables can be purchased that
support testing to the higher levels.
Figure 11-4. Conceptual Processor Ground Frame
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