Appendix D: Test Procedure For Radiated Emissions - AOpen CD-952E/TKU Manual

4.4 Appendix D: 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 10 meters. Desktop EUTs are placed on a wooden stand 0.8 meter in height. The
measurement antenna is 10 meters from the EUT. The test setup in anechoic chamber is the same as
open site. The turntable rotated 360°C. The antenna height is varied from 1-2.5m. 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 preselected 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.
The anechoic chamber preliminary test may be waived if it is known that the EUT has a low
radiated emissions characteristic.
Measurements on the Open Site
The radiated emissions test will then be repeated on the open site to measure the amplitudes
accurately and without the multiple reflections existing in the shielded room. The EUT and support
equipment are set up on the turntable of one of the 3 or 10 meter open field sites. Desktop EUTs are
set up on a wooden stand 0.8 meter above the turntable.
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 and with the 120 kHz bandwidth.
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 according to ANSI C63.4-1992, and/or
EN55022:1994/A1:1995/A2:1997 / CISPR 22:1993/A1:1995/A2:1997. Once the maximum
reading is obtained, the antenna elevation and polarization will be varied between specified limits to
maximize the readings.
During the open site measurements, the peaks are selected, the scan width is reduced to 0, the
audible modulation is monitored with a loudspeaker and the quasi-peak reading is recorded at the
indicated frequency and at the specified bandwidth.
International Standards Laboratory
(NVLAP Lab. Code: 200234-0)
Declaration of Conformity
-12-
Report Number: ISL-99135FB