Aladdin Digital Infrared Language Distribution
Installation and User Manual
Televic Conference Systems
2011-09-01
12
1.2.3.
Signal Processing
Aladdin uses high frequency carrier signals (typically
2-6 MHz) to prevent interference by contemporary
light sources. Fully digital audio processing
guarantees a constant high audio quality.
The signal processing in the transmitter consists of
the following main steps (see figure 1.3):
1.
Code – each analogue audio channel is
converted to a digital signal; the digital signals
are compressed to increase the amount of
information that can be distributed on each
carrier (compression ratio is related to required
audio quality); groups of up to 4 digital signals
are combined into a digital information steam.
Extra redundancy information is added. This
information is used by the receivers for error
detection and correction.
2.
Modulation – a high frequency carrier signal is
phase-modulated with the digital information
stream by DQPSK digital modulation technique.
3.
Filter.
4.
Magnify.
5.
Radiation – up to 2 modulated carrier signals
are combined and sent to the IR radiators,
which convert the carrier signals to modulated
infrared light.
In the IR receivers, a reverse processing is used to
convert the modulated infrared light to separate
digital audio channels.
(a) Digital infrared transmitter schematic
(b) Digital infrared radiator schematic
(c) Digital infrared receiver schematic
Figure 1.3: Overview of the signal processing
