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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 5.0 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, a 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 phenomena 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 this phenomena occurred.
FIGURE 5.0
E-FIELD LEVELING SET-UP
