Linear Technology LINEARCOM3000 Operation Manual page 5

System composition
The system consists of a number (N) of audio sources, either analogue or digital, which are
connected to a transmitter. The transmitter processes the audio signals into an electrical
output to feed the infrared radiator. The infrared signal is received by the infrared receiver
that processes the signal and outputs an audio signal and/or associated data.
System radiation signal
IRR25 uses high frequency carrier signals (typically 2~8 MHz) to prevent interference by
modern light sources. Fully digital audio processing guarantees a constant high audio quality.
The signal processing in the main unit consists of the following main steps :
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 fault algorithm information is added. This
information is used by the receivers for fault detection and correction.
2. Modulation : A high frequency carrier signal is phase-modulated with the digital information
stream by digital wireless base station digital modulation technique.
3. Filter
4. Magnify
5. Radiation : Up to 8 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.
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