Specifications

EMC-CS-2009.1
© Copyright Ford Motor Company – All Rights Reserved Page 91 of 121
February 11, 2010
Annex B (Normative): Modulation and Leveling Requirements for RI 112, RI 114 and
RI 115
B1 Peak Conservation
Peak Conservation, per Annex B of ISO 11452-1 (2005) shall be used for application of AM and Peak modulation during
radiated immunity testing (see section 11). Peak conservation is illustrated in Figure B-1. Peak conservation shall be
verified via physical measurement as part of the EMC laboratory's calibration process
.
Figure B-1: RF Immunity Peak Conservation Profile
CW AM PULSE
U
PEAK
U
CAL
U
CAL
= Stress Level (RMS) listed in Tables 11-1, 11-3, and 11-4
U
PEAK
= Peak Stress Level
B2 Stress Leveling Process
During testing per RI 112, RI 114 and RI 115, there are a minimum of three distinct stages that occur at each test frequency
as illustrated in Figure B-2.
Stage 1 consists of the leveling process to achieve the required stress level at each test frequency. Stage 1 is initiated by
setting the signal generator output to produce a stress level > 10 dB below the required stress level (i.e.
U
CAL
). Signal
generator values are derived based on the stress level calibration. The leveling process is critical to assure that the required
stress level is not exceeded by more than 1.0 dB. Two factors may affect this
1
Selection of the stress increment "A" (see Figure B2)
The lab may elect to use a small, fixed stress increment value during the leveling process however consideration
shall be given toward minimizing the leveling time while not exceeding the target stress level by more than 1 dB.
Alternatively, the selected stress increment may variable depending on difference between the measured stress level
and the target stress level. The total leveling time should not exceed 6 seconds.
2
RF signal source overshoot during step changes in its output to the RF amplifier.
Overshoot may not exceed 1 dB of the target stress level. A number of hardware and software parameters may be
employed to minimize overshoot. The test laboratory should avoid step changes in electromechanical attenuation
during the leveling process, which can be a significant source of overshoot. Although not required, use of signal
generators with electronic attenuation is recommended.
Stage 2 occurs when the required stress level has been achieved. The stress level shall remain constant for a minimum dwell
time of 2 seconds unless longer times are documented in the DUT's EMC test plan. During this time, CW, AM, or Pulse
modulation may be used. The laboratory may perform separate tests for each modulation type or cascade the modulation
types at each frequency (recommended). This later approach is illustrated in Figure B-3. If this approach is taken, the
laboratory shall take steps to differentiate DUT anomalies attributed to a specific modulation type.
When the dwell time is completed, the required stress level shall be reduced by > 10 dB (Stage 3). At this time, the next test
frequency is selected and the process described above is repeated. By default, the time duration of Stage 3 is affected only by