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Sweep/Control
gate closed.
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.
Gate Source
The menus under the
Gate Source key are the same as those under the Trigger key, with the exception
that neither
Free Run nor Video are available as Gate Source selections. However, a different SCPI
command is used to select the Gate Source (see table below) because you may independently set the
Gate Source and the Trigger Source.
Any changes to the settings in the setup menus under each
Gate Source selection key (for example:
Trigger Level, Trigger Delay, etc) also affect the corrssponding settings under the Trigger menu keys.
Key Path: Sweep/Control, Gate, Method
Dependencies: Key is unavailable when Gate is On and FFT Sweep Type manually selected.
When selected, Sweep Type is forced to Swept and the FFT key in Sweep
Type is grayed out
Readback: Video
Initial S/W Revision: Prior to A.02.00
Key Path:
Sweep/Control, Gate
Dependencies: Key is unavailable when Gate is On and Swept Sweep Type is 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
Readback: FFT
Initial S/W Revision: Prior to A.02.00