Agilent Technologies X Series Manual page 556

Sweep/Control
Initial S/W Revision
FFT
When Gate is set to On, an FFT is performed whenever the gate conditions as specified in the Gate menu
are satisfied by the signal at the Gate Source. This is an FFT measurement which begins when the gate
conditions are satisfied. Since the time period of an FFT is approximately 1.83/RBW, you get a
measurement that starts under predefined conditions and takes place over a predefined period. So, in
essence, this is a gated measurement. You have limited control over the gate length but it works in FFT
sweeps, which the other two methods do not.
Gated FFT cannot be done in zero span since the instrument is not sweeping. So in zero span the Gated
LO method is used. Data is still only taken while the gate conditions are satisfied, so the gate settings do
impact when data is acquired.
The Gate Length will be 1.83/RBW.
This is a convenient way to make a triggered FFT measurement under control of an external gating
signal.
Key Path
Dependencies
Readback
Initial S/W Revision
Gate Source
The menus under the Gate Source
exception that neither
Free Run
settings in the setup menus under each Gate Source selection key (for example:
affect the settings under the Trigger menu keys. Note that the selected Trigger Source does not have to
match the Gate Source.
Key Path
Remote Command
Dependencies
556
Prior to A.02.00
Sweep/Control, Gate
Key is unavailable when Gate is On and Swept Sweep Type manually
selected.
Key is unavailable when gate Control is set to Level.
When selected, Sweep Type is forced to FFT and the Swept key in Sweep
Type is grayed out
Forces Gate Length to 1.83/RBW
FFT
Prior to A.02.00
key follow the same pattern as those under the
nor are available as Gate Source selections. Any changes to the
Video
Sweep/Control, Gate
[:SENSe]:SWEep:EGATe:SOURce EXTernal1|EXTernal2
|LINE|FRAMe|RFBurst
[:SENSe]:SWEep:EGATe:SOURce?
In some models, there is no second External input. In these models, the
External 2 key is blanked and the EXTernal2 parameter will generate a
"Hardware missing; Not available for this model number" error.
Trigger key , with the
) also
Trigger Level