Linear Technology LINEARCOM3000 LC3.IRTX Operation Manual page 7

The direction and sensitivity of receiver unit
The sensitivity of a receiver is at its best when it is aimed directly towards a radiator. To
minimize the disadvantage of this aspect, IRRC08 receiver adopts an ingenious structural
design with peculiar 270° ultra wide angle to get perfect IR capture and sound quality at any
disposition.
The coverage area of radiator
The number of transmitted carriers and the output power of the radiator determine the
coverage area of a radiator. The total radiation energy of a radiator is distributed over
transmitted carriers. The coverage area becomes proportionally smaller if more carriers are
used. The receiver requires a strength of the IR signal of 4 mW / m2 per carrier to work well
(resulting in an 80 dB S/N ratio for uninterrupted audio channels)
The cross section of the 3 dimensional radiation with the reception level of participants is
the footprint (the dark grey area in figure 2.9 to figure 2.10) In this area, the direct signal is
strong enough to ensure proper reception when the receiver is directed towards the radiator.
The size and position of the footprint depends on the mounting height and the angle of the
radiator.
Area contrast of different installation height
Positioning the radiators
Because infrared radiation can reach a receiver directly and / or via diffused reflections, it's
important to take this into consideration when installing the radiators. For best reception
quality, receivers should pick up direct infrared radiation. In addition reflections will improve
the signal reception. In big conference halls, infrared signal will be blocked by the people in
front of the receiver. For that reason the radiator should be installed at an appropriate height,
usually not below 2.5 meters.
For concentrically arranged conference venues, radiators located high up and faced to the
center from every angle can cover the area very efficiently. If the direction of the receiver
changes, e.g. changing seat direction, the radiators can be installed in the corners of the
room.
In the case the seating is always directed towards the IR emitting source, there are no
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radiators needed at the back.
Area contrast between 15º and 45º to the ceiling