Rohde & Schwarz R&S UPP, Руководство пользователя

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Instrument Functions
R&S
®
UPP
526 User Manual 1411.1055.32 ─ 10
"Noise Density, Noise Density dB"
Noise density measurement.
Offered only in the FFT subsystem.
If you perform an FFT analysis via a noise signal, the level of a bin
will change with respect to its width. The width of a bin, which is also
called analysis bandwidth, depends on the FFT size. Thus, the level
of a bin changes with respect to the FFT size.
To become independent of the actual analysis bandwidth, you calcu-
late the noise density. This is the noise power that would occur in an
analysis bandwidth of 1
Hz.
The noise density depends on the FFT window. When calculating the
noise density, the set window is taken into consideration to eliminate
the effect of the window.
Thus, the noise-density measurement is not an independent mea-
surement function but a referenced level display, based on the rela-
tive unit V/Vr.
Depending on the selection "Noise Density" or "Noise Density dB",
the FFT graphic displays the result in the unit
V/√Hz or dBV/√Hz .
"Hold" No further changes are made to the reference value or reference
trace. If a trace file having a reference value or reference trace is loa-
ded, the reference values from the file have no effect, and the refer-
ence value or reference trace last set is used.
If a floating reference value (Meas Ch1, Meas Ch2 or Gen Track) was
set before the switchover to "Hold", this reference trace is used.
If "Hold" is selected in the absence of any valid reference trace data,
a warning is issued and the last chosen valid reference is set again.
Remote command:
DISPlay:SWEep<n2>:A:REFerence
on page 795
DISPlay:SWEep<n2>:B:REFerence
on page 795
Reference Value
Reference value with unit for the reference parameter Value.
Regardless of the graphic system, the value range allows the value 0 V or negative
values to be entered. A reference value of 0
V or a negative reference value makes
good sense for display units, such as ∆V or ∆W, but causes problems in the case of
logarithmic units such as dBr and in the case of units that have the reference value in
the denominator, such as V/Vr.
To get round these problems, a reference value around 0.0 (or more exactly: between
-1.0E-12 and 1.0E-12) is always computed using the value 1.0E-12.
Curve, Spectrum and Bar Graph Display