Specifications

EMC-CS-2009.1
© Copyright Ford Motor Company – All Rights Reserved Page 97 of 121
February 11, 2010
C2 Calibration and DUT Loading Check
The following procedure shall be performed prior to each test of the DUT. The DUT and any necessary supporting equipment
must be installed into the chamber. If the chamber was initially tested under maximum loading conditions, the loading check
prior to each test is optional.
a)
Place the receive antenna within the working volume (see C1.1.1 j)) at least 0.25 m from the DUT and supporting
equipment.
b)
At the lowest test frequency (fs = 400 MHz), inject an appropriate amount of RF power, into the transmit antenna.
Harmonics of the RF input to the chamber must be at least 15 dB below the carrier frequency.
c)
Operate the chamber and the tuner for the desired number of steps as indicated in Table C1 (alternatively, mode
stirring is allowed with a maximum stir speed of 16.5 seconds per tuner revolution). RF power shall be applied for an
appropriate amount of dwell time to ensure that the amplitude measuring device has time to respond properly.
d)
Calculate the maximum received power, average received power (P
MaxRec
, P
AveRec
), and the average input power (P
Input
)
over one tuner rotation. All calculated values shall be in linear units (i.e. W, not dBm; V/m, not dBV/m). Ensure that
the power measurement instruments have an equipment noise floor at least 20 dB below the maximum received power
(P
MaxRec
) for proper average data collection.
e)
Repeat step d) for each frequency defined in 3.4.
f)
The Chamber Calibration Factor (CCF) for each frequency is as follows:
n
Input
cReAve
P
P
CCF =
Where:
CCF = Normalized average received power over one tuner rotation with the DUT and support equipment in the chamber
P
AveRec
= Average received power over one tuner rotation from step g).
P
Input
= Forward power averaged over one tuner rotation from step g).
n = Number of antenna locations the CCF is evaluated over. Only one is required, however multiple antenna positions
may be used and the CCF averaged over the number of locations.
g)
Determine the Chamber Loading Factor (CLF) for each frequency as follows:
AC
F
CCF
CLF =
Where:
CCF = Ratio of the average received power to the input power obtained from step f).
ACF = Ratio of the average received power to input power obtained in the antenna calibration of C1.1.2. Use linear
interpolation to obtain the ACF.
If the reciprocal value of the magnitude of the chamber loading factor is larger than that measured in C1.1.4 for more than
10% of the frequencies, the chamber is loaded and the field uniformity is affected. If this happens, the field uniformity
measurements of C1.1.1 must be repeated with the DUT in the test chamber.
If the P
AveRec
measured in C2 d) is within (i.e., not greater than or less than) the values recorded for all eight locations in
C1.1.1 g), the CLF calculation is not necessary and the value of CLF is one (1).
C3 Q and Time Constant Calibration.
These measurements are conducted to ensure that the chamber can support the pulse waveforms outlined in 3.4.3.
a)
Calculate the Quality factor, Q, of the chamber using the CCF of C2 f) for each frequency:
() CCF
ληη
Vπ16
Q
3
RxTx
2
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