ETS-Lindgren 5411 GTEM! Test Cell - Manual (Page 86)

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Radiated Emissions Test Performance of GTEM!
Table 11 on page 86 shows Pearson’s correlation coefficient and the regression
coefficients for the first three sets of dipole measurements and the first two sets
of personal computer measurements. The correlation is good enough, though
while these results came from measurements in which certain parts of the
process were different, they can be combined with the rest of the data for further
analysis.
A similar summary for the personal computer data is shown in the following table.
Table 10: Summary of Personal Computer Measurements
Data Set
Average Difference
(dB) Standard Deviation
(dB)
PC 1 at 3 Meters 3.18 3.85
PC 1 at 10 Meters 2.18 4.57
PC 2 at 3 Meters 0.19 2.09
The personal computer data is again on reasonably good agreement between
the GTEM! and the OATS measurements. There is a difference between the first
two data sets and the third that is in part attributable to the improvement in test
procedures as the learning curve flattened. The last data set is felt to be
representative of the measurement capability of the GTEM! much more than the
first two.
As can be seen by comparing the data between Table 9 and Table 10, there is a
larger deviation in personal computer data and dipole data. This is thought to be
related to the difference in the type of EUT from dipoles to a personal computer
system. Dipoles are strongly polarized in that the two planes that are orthogonal
to the plane of polarization show radiated emission levels that are low with
respect to the primary plane. The personal computer system shows much
smaller differences in the three orthogonal measurements. It is suspected that
this difference as related to the characteristic of the personal computer array to
radiate more equally in three orthogonal directions.
R
ESULTS OF
S
TATISTICAL
A
NALYSIS
The general results of the statistical analysis are shown in the following tables.
Table 11: Correlation of Data from the First Three Dipole Measurements
and the First Two Personal Computer Measurements
Coefficient
Dipole I
(Tables 1, 2, 3) PC 1
(Tables 4 & 5)
R 0.941 0.988
a -2.36 +3.30
b +1.00 0.95