Common measurement settings
R&S
®
FSVA3000/ R&S
®
FSV3000
467
User Manual 1178.8520.02 ─ 08
Optimization
In FFT mode, FFT analysis is performed to determine a spectrum of frequencies. Sev-
eral analysis steps are required to cover the entire span. The subspan which is cov-
ered by one FFT analysis depends on the RBW. The subspan cannot be defined
directly, but it can be optimized according to measurement requirements.
Narrow subspans provide a higher dynamic range, and also allow you to perform mea-
surements near a carrier with a reduced reference level. With a wide subspan, the car-
rier and the useful signal are likely to be measured at the same time, in which case the
powers of both signals are summarized, so the reference level must be high enough to
consider this factor. With a narrow subspan, this is less likely to happen, so the refer-
ence level can be reduced.
For an optimal dynamic range
, the narrowest possible subspan (depending on the
RBW) is used. Furthermore, the autorange function for the internal IF gain calculation
is activated to obtain the best control range of the A/D converter.
On the other hand, the narrower the subspan, the more steps are required to cover the
entire span, thus increasing analysis and calculation time. To
optimize the sweep
rate
, the widest possible subspan (depending on the RBW) is used.
For an optimal sweep rate, it is recommended that you set the "Sweep Time" to "Auto",
as well.
For general purpose measurements, an "Auto" mode is available, which provides a
compromise between a large dynamic range and a fast sweep
. In this case, a
medium-sized subspan is used.
FFT mode and external mixers (R&S
FSV3-B21)
The subspan optimation modes "Dynamic" and "Auto" include automatic suppression
of unwanted mixing products. Thus, when using external mixers (R&S
FSV3-B21), use
the "Speed" mode to obtain similar results in FFT mode as in normal sweep mode.
FFT mode and EMI measurements (R&S
FSV3-K54)
For EMI measurements (using R&S
FSV3-K54), the subspan optimization mode
"Dynamic" is not supported. "Auto" mode always uses "Speed" optimization.
Optimization for zero span sweeps
For normal sweeps in the time domain (zero span), the optimization mode determines
the selection of the A/D converter prefilter, which depends on the RBW.
In
"Dynamic" mode
, the narrowest possible prefilter is used.
In
"Speed" mode
, the widest possible prefilter is used.
In
"Auto" mode
, a medium-sized prefilter is used.
Bandwidth, filter and sweep configuration
