3 VMA Mode
3.9 SEM Measurement
This tab does not appear in EXM, VXT.
Noise Floor Extension
Allows you to turn on/configure the Noise Floor Extension (NFE) function. Some
Modes (such as Spectrum Analyzer Mode), support two states of NFE, Full and
Adaptive. The ON state (in Modes that do not support Adaptive NFE) matches the
FULL state (in Modes that do support Adaptive NFE).
In ON or FULL NFE, the expected noise power of the instrument (derived from a
factory calibration) is subtracted from the trace data. This usually reduces the
apparent noise level by about 10 dB in low band, and 8 dB in high band (>~3.6 GHz).
In Adaptive NFE, there is not the same dramatic visual impact on the noise floor as
there is in Full NFE. Adaptive NFE controls the amount of correction that is applied
based on other instrument settings like RBW, averaging and sweep time. Adaptive
NFE controls the degree of potential improvement in the noise floor to give more
improvement for those instrument settings that can make good use of the potential
improvement, such as settings that provide more averaging. The result is that when
not much averaging is being performed, the signal displays more like the NFE-off
case; and when lots of averaging is being performed, the signal displays more like
the full-NFE case.
Adaptive NFE (in Modes that support it) is recommended for general-purpose use.
For fully ATE (automatic test equipment) applications, where the distraction of a
person using the instrument is not a risk, Full NFE is recommended.
NFE works with any RBW, VBW, detector, any setting of Average Type, any amount
of trace averaging, and any signal type. It is ineffective when the trace is not
smoothed (smoothing processes include narrow VBWs, trace averaging, and long
sweep times with the detector set to Average or Peak). It works best with extreme
amounts of smoothing, and with the average detector, with Average Type set to
Power.
In those cases where the cancellation is ineffective, it nonetheless has no
undesirable side-effects. There is no significant speed impact to having Noise Floor
ExtensionON.
The best accuracy is achieved when substantial smoothing occurs in each point
before trace averaging. Thus, when using the average detector, results are better
with long sweep times and fewer trace averages. When using the sample detector,
the VBW filter should be set narrow with less trace averaging, instead of a wide VBW
filter with more trace averaging.
NOTE
Noise Floor Extension has no effect unless the RF Input is selected, therefore it
does nothing when External Mixing is selected.
1569 Vector Modulation Analyzer Mode User's &Programmer's Reference
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