WILLTEK 4400 Mobile Phone Tester Series, Руководство пользователя

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Chapter 6 Tools
Audio measurements
4460 GSM System Option and 4468 EDGE System Option Version 12.20
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Audio measurements
The Audio Option provides an AF generator and an AF analyzer.
The audio analyzer may also be used to perform measurements on audio signals
transmitted over the air interface and converted back into analog signals by the
optional codecs.
The coder part of an audio codec (coder and decoder) translates the analog signal
or its binary representation into a compressed digital signal which can be trans-
mitted on a traffic channel. The decoder part takes the compressed data from a
TCH and transforms them to an analog signal or its binary representation. – An
audio codec is sometimes also referred to as a
vocoder (voice coder).
This section consists of the following parts:
– “Audio measurements – test basics” – This section gives an overview of the
options needed for audio measurements and the basic test functionality.
– “Audio frequency generator” – Here you will find all information regarding
the audio generator of the 4400 and the relevant parameters.
– “AF basic analyzer” – The so-called basic analyzer incorporates all
nongraphic measurements (like AC voltage, DC voltage, frequency, distortion
and SINAD).
– “AF spectrum analyzer” – This section will explain the built-in audio spec-
trum analyzer functionality of the 4400.
Audio measurements –
test basics
In its basic configuration, the 4400 does not support audio measurements. In
order to provide audio test functions, you need to install the Audio Option. This
option provides your 4400 with both an audio generator and an audio analyzer.
To convert the digital data exchanged between the mobile under test and the
4400 into audible sound, you also need to add at least the Basic Codec Option.
As you know, GSM currently uses three different codecs:
– Full Rate is what GSM started with and what is still the most common
codec type. To convert Full Rate into audible sound, the Basic Codec Option
is all you need.
– Half Rate is supported by most of the mobiles available. However, the
network operators are reluctant to use this feature as they are mainly afraid
of loosing speech quality.
– Enhanced Full Rate is a new Codec algorithm that will provide better
speech quality than Full Rate. To convert Enhanced Full Rate into audible
sound, you will need the Codec Extension Option in addition to the Basic
Codec Option.
Input and output ports for
audio measurements
The following connectors (interfaces) are used by the audio option:
– “AF in” , a BNC connector on the front panel of the 4400. This connector is
where the audio signal to be measured needs to be connected.
This input can be used either as a balanced or as an unbalanced input (soft-