Agilent Technologies ESA-E E4401B, Справочник пользователя/программиста

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Chapter 2 119
Front-Panel Key Reference
Peak Search
Fr
ont-P
ane
l K
e
y
Ref
e
re
nce
be distinguished from the LO feedthrough, which is excluded by intent
from the search algorithm.
NOTE
This function is intended to maintain the marker on signals with a
frequency that is changing, and an amplitude that is not changing.
Key Access:
Search
,
More
N dB Points
On Off
Activates the N dB function. Pressing
N dB Points (On)
turns on the
N dB feature and activates two arrows that are N dB down from the
marker. The frequency difference between the two arrows will be
displayed in the upper right-hand corner of the display. If the feature is
unable to find data N dB below the marker, the value of –100 Hz will be
displayed in the upper right-hand corner of the display.
For example, N dB Points can be used to measure the 3 dB bandwidth
of a filter in a transmission test with the tracking generator. The
default value is –3 dB. Possible values range from
−
1.00 dB to
−
80.00 dB. You can enter values to a resolution of 0.01 dB using the
numeric key pad, 0.1 dB using the knob, or 10 dB using the step keys.
The N dB function follows the active marker. If you turn on a marker
after N dB Points has been activated, the arrows will follow that
marker. If the marker associated with N dB Points moves, the arrows
will move with the marker unless there is no data N dB below the
marker.
Key Access:
Search
,
More
Search Criteria
Accesses the following menu keys:
Key access:
Search
,
More
Peak Excursion
Sets the minimum amplitude variation of signals that
the marker can identify as a peak. If a value of 10 dB is
selected, the marker moves only to peaks that rise and
fall more than 10 dB above the peak threshold value.
Pressing
Preset
(when
Preset Type
is set to
Factory
) or
turning on power resets the excursion to 6 dB and the
threshold to 90 dB below the reference level.
NOTE
Two signal peaks, which are so close together that the amplitude drop
between them is less than the peak-excursion value, are not recognized
as two peaks. A signal peak is recognized only if it has a peak excursion
drop above the noise floor, on both sides of the signal.
When the peak excursion value is 6 dB or higher, the
marker-peaking functions do not recognize signals less
than the peak excursion value above the noise floor. To
correct this, when measuring signals near the noise
floor, the excursion value can be reduced even further.