R&S FSMR, Руководство по эксплуатации, Страница: 226 / 955

Analyzer - Bandwidths and Sweep Time R&S FSMR
1166.3363.12 4.8-10 E-1
MAIN PLL
BANDWIDTH
The MAIN PLL BANDWIDTH softkey defines the bandwidth of the main PLL of
the analyzer synthesizer and thus influences the phase noise of the analyzer.
Three bandwidth settings are possible (WIDE / NORMAL / NARROW); if
AUTO is selected, the bandwidth is set automatically (default).
IEC/IEEE-bus command:
SENS:BAND:PLL AUTO
FFT FILTER
MODE
The softkey FFT FILTER MODE allows to specify between the following three
options for FFT filters:
WIDE: The FFT filters with the greater partial span (this is the span
which is covered with one FFT analysis) are used always.
AUTO: The firmware decides whether to use wide or narrow filters to
achieve the best performance of the measurement.
NARROW: The FFT filters with the smaller partial span are used, this
allows measurements near a carrier with reduced reference
level, because of a more narrow analog prefilter.
IEC/IEEE-bus command:
SENS:BWID:FFT:MODE WIDE | AUTO | NARR
VBW MODE
LIN LOG
The VBW MODE LIN/LOG softkey determines the position of the video filter in
the signal path for resolution bandwidths 100 kHz:
•
If LINear is selected, the video filter will be in front of the logarithmic
amplifier (default).
•
If LOGarithmic is selected, the video filter will be behind the logarithmic
amplifier.
The essential difference between the two operating modes relates to the
settling in the case of falling signal edges:
With LINear, the falling signal edge will be "flatter" than with LOGarithmic.
This is due to the conversion from linear power to logarithmic level units: a
reduction of the linear power by 50% reduces the logarithmic signal level by
only 3 dB.
IEC/IEEE-bus-command:
SENS:BAND:VID:TYPE LIN