Chapter 6
Tools
Audio measurements
242
4460 GSM System Option and 4468 EDGE System Option
Version 12.20
Ranging (AUX in) —
Selection field. Used to set the expected level of the AC
component of the audio signal connected to the
“AUX 4 (AUX in)”
socket. The
expected level is the peak-to-peak voltage of the AC component.
The settings possible are:
Auto
(default),
1 V
and
100 mV
.
Coupling (AF in) —
This selection field allows to switch the
“AF in”
connector
from
AC coupled
(default) to
DC coupled
or to
DC coupled / LP
.
– If the input signal is a DC voltage only, select
DC coupled
to measure the
DC voltage level.
– For a mixture of DC and AC signals, select
DC coupled / LP
to measure
the DC voltage level and to suppress the AC components of the signal.
– For measurements of the AC component of the signal only, select
AC
coupled
to achieve slightly higher accuracy.
Balancing —
This selection field toggles the
“AF in”
connector between
unbal-
anced
(default) and
balanced
.
–
unbalanced
means there is one ‘hot’ signal line and one ground line. This
is sometimes also referred to as ‘asymmetric’ or ‘single ended’.
–
balanced
means that there are two ‘hot’ signal lines and no ground line
(there may be a shield). This is sometimes also referred to as ‘symmetric’,
‘differential’, ‘bridged’ or ‘floating’.
FFT-Window —
Selection field. Allows to select the window for the
F
ast
F
ourier
T
ransformation of the audio signals.
The selections possible are:
Hanning
,
Hamming
,
Bartlett
,
Blackman/
Harris
,
Blackman
,
Rectangular
and
Flat Top
.
Statistical data evaluation
The AF basic analyzer also provides a menu for statistic data evaluation.
NOTE
For a quick availability of the first measurement result, avoid the
AUTO
set-
ting as this involves a time-consuming adaptation process.
NOTE
The settling time for the low-pass filter is approx. 300 ms. Therefore, the first
measurements taken with the low-pass filter in place might be erroneous.
NOTE
Be sure to switch the low-pass filter off when calibrating the audio path.
