Read JBL ON STAGEII (serv.man5) EMC - CB Certificate online
REPORT # 56050AF
1 0
Radiated Test Setup and Procedure - contd.
The EUT is put into the operational test mode as stated in Section 1.4, it is then started.
The spectrum analyzer is setup to store the peak emission over the frequency range of
the antenna. Peak EUT and ambient emissions are stored while the turntable is rotated
360
0
. The Peak spectrum analyzer trace is then plotted with the addition of antenna and
cable correction factors. The limit is plotted on the same graph. A receiver with CISPR
Quasi Peak detector is then used on the frequencies identified as the highest with
respect to the plotted limit. Ambients are noted on the graph along with EUT emissions.
The highest emissions are maximized.
To maximize emissions levels, the turntable is rotated and the antenna is raised and
lowered to determine the point of maximum emanations. The cables are then
manipulated at that point to maximize emissions. Measurements are made with the
antennas in each horizontal and vertical polarization. The data obtained from these tests
is corrected with the proper cable, preamplifier and antenna factors. The results are then
transcribed onto tables that show the maximum emission levels. The highest emissions
are listed in a Radiated Emissions Summary table.
If no emissions can be found, the lowest harmonics of the EUT clocks within the bands
of the standard are tuned into with the receiver. If no emissions are found, the noise floor
will be entered to the table and noted. A minimum of six frequencies will be logged.
Summary results will reflect only actual emissions from the EUT.
Quasi Peak detector is then used on the frequencies identified as the highest with
respect to the plotted limit. Ambients are noted on the graph along with EUT emissions.
The highest emissions are maximized.
To maximize emissions levels, the turntable is rotated and the antenna is raised and
lowered to determine the point of maximum emanations. The cables are then
manipulated at that point to maximize emissions. Measurements are made with the
antennas in each horizontal and vertical polarization. The data obtained from these tests
is corrected with the proper cable, preamplifier and antenna factors. The results are then
transcribed onto tables that show the maximum emission levels. The highest emissions
are listed in a Radiated Emissions Summary table.
If no emissions can be found, the lowest harmonics of the EUT clocks within the bands
of the standard are tuned into with the receiver. If no emissions are found, the noise floor
will be entered to the table and noted. A minimum of six frequencies will be logged.
Summary results will reflect only actual emissions from the EUT.
The field intensity measurements are made using standard techniques with a spectrum
analyzer or EMI receiver as the calibrated Field Intensity Meter (FIM). Preamplifiers and
filters are used when required.
analyzer or EMI receiver as the calibrated Field Intensity Meter (FIM). Preamplifiers and
filters are used when required.
When using the Hewlett Packard 8566B Spectrum Analyzer as the FIM, the Analyzer is
calibrated to read signal level in dBm. Where:
calibrated to read signal level in dBm. Where:
0 dBm (50 ohms) = 107 dBµV (50 ohms)
The signal level (dBµV) = indicated signal level (dBm) + 107 dB. To obtain the signal
level in dBuV/m it is necessary to add the antenna factor in dB.
level in dBuV/m it is necessary to add the antenna factor in dB.
Example of Typical Calculation
Measurement Distance = 3 Meter
Measurement Distance = 3 Meter
Rohde and Schwarz reading @ 60 MHz
49.0 dBµV
Antenna Factor
+7.5 dB
Cable Loss
+2.0 dB
Preamplifier
-25.5 dB
Total Factors
-16.0 dB/m
Field Strength dBµV/m at 3 Meter =
33.0 dBµV/m
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