R&S ESU Series Operating Manual page 150

R&S ESU
MAIN PLL The MAIN PLL BANDWIDTH softkey defines the bandwidth of the main PLL of the
BANDWIDTH analyzer synthesizer and thus influences the phase noise of the analyzer. Three
bandwidth settings are possible (High / Medium / Low); if AUTO is selected, the
bandwidth is set automatically (default).
Remote command:
FFT FILTER The softkey FFT FILTER MODE allows to specify between the following three
MODE options for FFT filters:
WIDE:
AUTO:
NARROW: The FFT filters with the smaller partial span are used, this allows mea-
Remote command:
VBW MODE The VBW MODE LIN/LOG softkey determines the position of the video filter in the
signal path for resolution bandwidths ≤ 100 kHz:
LIN | LOG
•
•
The essential difference between the two operating modes relates to the settling in
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.
This is important for EMI measurements above 1 GHz. Below 1 GHz, CISPR 16-1-1
defines the linear average detector only. Above 1 GHz both, the linear and the loga-
rithmic average detector may be specified in product standards. Some standards
(e.g. ANSI C63.4:2000) require the linear average detector, whereas microwave
oven measurements may be made with the log average detector. CISPR 11 speci-
fies weighted measurements with a VBW of 10 Hz.
Fig. 4.2
pulse-modulated signals.
Operating Manual 1302.6163.12 - 03
The FFT filters with the greater partial span (this is the span which is
covered with one FFT analysis) are used always.
The firmware decides whether to use wide or narrow filters to achieve
the best performance of the measurement.
surements near a carrier with reduced reference level, because of a
more narrow analog prefilter.
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.
shows the response of the linear and the logarithmic average detector for
BAND:PLL AUTO
SENS:BWID:FFT WIDE | AUTO | NARR
Instrument Functions
Analyzer Mode
4.119