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perform measurements from 150 kHz
through 30 MHz. Many vendors of
spectrum analyzers include the ability
to perform quasi-peak measurements
and
incorporate
conformance
parameter limits in the display to
simplify EMC compliance testing.
Preliminary testing for radiated
emissions can be accomplished with a
spectrum analyzer and an appropriate
antenna. The spectrum analyzer
should have the capability to make
measurements from 30 MHz through
at least 900 MHz. The ability of the
spectrum analyzer to perform quasi-
peak measurements and display
conformance parameter limits in the
display will make the preliminary
testing tasks easier to perform. The
antenna used for preliminary radiated
emissions testing should have a
bandwidth similar to the spectrum
analyzer and the gain versus frequency
characteristics needing to be known.
It is preferable to be able to perform
the radiated emissions testing in an
electrically quiet room with at least
three meters (10 feet) between the
radiated emissions EMC antenna and
the EUT. An initial measurement in
the room with the EUT powered off
will provide information regarding the
ambient RF noise present during the
testing.
Most management teams appreciate
projects completed under budget and
ahead of schedule. Unfortunately,
EMC compliance issues can be a
common source of last minute budget
and schedule increases for projects.
Performing pre-compliance EMC
testing during the system assembly
phases of a project can help to
eliminate those last minute changes
to a design that impact budgets
and schedules. Pre-compliance EMC
testing also helps to ensure no issues
arise during final compliance testing.
Full service power supply vendors,
such as CUI, have the equipment and
experience to assist in power supply
design and selection, including pre-
compliance and final EMC testing.
Figure 2: Conducted emissions filter components
Figure 3: Conducted emissions test set-up
Figure 4: Radiated emissions test set-up
New-Tech Magazine Europe l 59