Rohde & Schwarz R&S FSP Series, Operating Manual

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R&S FSP Instrument Functions
Analyzer Mode
4.26 Operating Manual 1164.4556.12 - 06
*) This filter is avaible with modification index > 2 of the IF filter module (see softkey SETUP - SYSTEM INFO - HARDWARE INFO ).
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
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 shows the response of the linear and the logarithmic average detector for
pulse-modulated signals.
1.0 MHz
1.2288 MHz
1.5 MHz
2.0 MHz *)
3.0 MHz *)
3.84 MHz, a=0.22 *)
4.096 MHz, a=0.22 *)
5.0 MHz *)
5.6 MHz
6 MHz
6.4 MHz
CFILter
CFILter
CFILter
CFILter
CFILter
RRC
RRC
CFILter
CFILter
CFILter
CFILter
CDMAone
CDMAone
DAB
W-CDMA 3GPP
W-CDMA NTT DOCoMo
DVB-T (Japan)
J.83 (8VSB DVB, USA)
DVB-T
Filter Bandwidth Filter Type Application