OPTION 008 RF PROFILES AND COMPLEX SWEEP
Annex-C-17
COMPLEX SWEEPS
RF profiles, offset and sequence sweep
The sequence sweep can be combined with the RF profile and RF offset facility to
provide a swept signal source where the signal generator displays the RF level at the output of an
external frequency dependent amplifier or attenuator.
To set up a sweep of this type use the required sequence sweep, and RF profile and RF
offset can be set up as previously described. If the required RF offset and RF profile are then
enabled and the sequence sweep selected a complex sweep incorporating all these facilities can
be generated.
Suppressing attenuator changes
In addition to being used with RF profiles and RF offsets, sequence sweeps can also be
used in conjunction with Extended Hysteresis. Sweeps generated with the Extended Hysteresis
mode enabled, will use the modified electronic control facility to apply the RF profiles and to
vary the RF output level. Provided the required level does not exceed the Extended Hysteresis
electronic control range the mechanically actuated attenuator will not be operated.
Note...
When the -HYST flag is displayed the RF level of the generator is not as accurate as
normal modes of operation.
Tutorial example for immunity testing
Example: Immunity testing in a GTEM cell
Problem:
A device is to be tested to check its immunity to electro-magnetic fields using a GTEM
cell. The test requires that the device is tested for field strengths of 10 V/m at frequencies from
1 MHz to 100 MHz and 3 V/m from 100 MHz to 400 MHz. The tests call for checks to be made
at 10 kHz intervals from 1 MHz to 30 MHz, 12.5 kHz from 30 MHz to 100 MHz and 100 kHz
intervals from 100 MHz to 400 MHz. The GTEM system requires a nominal signal of -10 dBm
to drive an amplifier that provides a 10 V/m field strength in the cell.
Solution:
The test requires a combination of the sequence sweep, RF offset and RF profile
facilities. In this case the "RF Levels" required at the remote point are field strengths of 10 V/m
and 3 V/m. The RF offset facility can be used to convert a nominal signal of -10 dBm to a
displayed 10 V PD by using an offset of +43 dB (10 V PD is approximately +33 dBm).
Use a field probe to check the field strength in the GTEM cell. With the generator set to
10 V PD use the RF profile facility to obtain a 10 V/m reading on the field probe for frequencies
between 1 MHz and 400 MHz. While creating the RF profile remember that the signal generator
software interpolates between profile points so points need to be entered only when the profile
slope changes. Store the RF profile produced and check that the field strength is substantially
constant as the frequency is changed.
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