Global Certification Corp.
Date of Issue: SEP.13,2007
Report No:F790506
Page9/16
The highest emissions were analyzed in details by operating the spectrum analyzer in
fixed tuned mode to determine the nature of the emissions and to provide information which
could be useful in reducing their amplitude.
Appendix B: Test Procedure for Radiated Emissions
Preliminary Measurements in the Anechoic Chamber
The radiated emissions are initially measured in the anechoic chamber at a measurement
distance of 3 meters. Desktop EUT are placed on a wooden stand 0.8 meter in height. The
measurement antenna is 3 meters from the EUT. The test setup in anechoic chamber is the
same as open site. The turntable rotated 360°. The antenna height is 1m. The primary
objective of the radiated measurements in the anechoic chamber is to identify the frequency
spectrum in the absence of the electromagnetic environment existing on the open test site. The
frequencies can then be pre-selected on the open test site to obtain the corresponding
amplitude. The initial scan is made with the spectrum analyzer in automatic sweep mode. The
spectrum peaks are then measured manually to determine the exact frequencies.
Measurements on the Open Site or Chamber
The radiated emissions test will then be repeated on the open site or chamber to measure
the amplitudes accurately and without the multiple reflections existing in the shielded room.
The EUT and support equipments are set up on the turntable. Desktop EUT are set up on a
wooden stand 0.8 meter above the ground.
For the initial measurements, the receiving antenna is varied from 1-4 meter height and is
changed in the vertical plane from vertical to horizontal polarization at each frequency. Both
reading are recorded with the quasi-peak detector with 120KHz bandwidth. For frequency
between 30 MHz and 1000MHz, the reading is recorded with peak detector or quasi-peak
detector.
At the highest amplitudes observed, the EUT is rotated in the horizontal plane while
changing the antenna polarization in the vertical plane to maximize the reading. The
interconnecting cables were arranged and moved to get the maximum measurement. Once
the maximum reading is obtained, the antenna elevation and polarization will be varied
between specified limits to maximize the readings.
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