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6) The system is now ready to be tested with a swept analog or stepped frequency input signal. All
IFI component blocks shown in Figure 8.0 are capable of operating continuously from 10 kHz to
220 MHz. Extended frequency coverage, over the full range of the unit, can be provided by
substituting an EFS-5 for the EFS-1 and adding a second log periodic or ridged horn antenna.
Set a sweep rate that enables good level control with the field gradients encountered in the test
room. This may be anywhere from 15 seconds to 2 minutes depending on the field conditions
and the bandwidth of continuous sweep. Dwell time, a user determined specification, will also
determine the proper sweep or step rate.
7) Electric Null Fields, or E Null Fields, are a phenomena that may be observed when performing a
sweep test. In a typical EMI/EMC Set Up where an amplifier and a frequency generator are used
to generate an E Field, an E Null Field can be noted when the generated E Field is swept through
a frequency range and at certain frequencies the field level will drop. These nulls are due to
antenna pattern nulls and/or out of phase reflections from screen room walls or other obstacles
that cancel or nullify the generated E Fields at the precise location of the E Field Sensor. This
phenomenon is a natural occurrence and can be corrected by temporarily relocating the E Field
Sensor with the test sample for those specific noted frequencies where these phenomena
occurred.
FIGURE 8.0
E-FIELD LEVELING SET-UP
