Danish Interpretation Systems DCS 6000 User Manual

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Danish Interpretation Systems DCS 6000 User Manual Manual pdf 9 page image

DIS User ManualUser Manual DCS 6000 Digital IR System rev H.docx 9Aspects of IR distribution systems3.3A good infra-red distribution system ensuresthat all delegates in a conference venue receivethe distributed signals without disturbance. Thisis achieved by using enough radiators, placed atwell planned positions, so that the conferencevenue is covered with uniform Irradiation ofadequate strength.There are several aspects that influence theuniformity and quality of the infra-red signal,which must be considered when planning aninfra-red radiation distribution system. Theseare discussed in the next sections.Receiver directional sensitivity3.3.1The sensitivity of a receiver is at its best when itis aimed directly towards a radiator. The axis ofmaximum sensitivity is tilted upwards at anangle of 45 degrees (see Figure 3.2-C).Rotating the receiver will decrease thesensitivity. For rotations of less than +/- 45degrees this effect is not large, but for largerrotations the sensitivity will decrease rapidly.Footprint of the radiator3.3.2The coverage area of a radiator depends on thenumber of transmitted carriers and the outputpower of the radiator. The coverage area of theRA 6025 radiator is twice as large as thecoverage area of the RA 6013. The coverage areacan also be doubled by mounting two radiatorsside by side. The total radiation energy of aradiator is distributed over the transmittedcarriers. When more carriers are used, thecoverage area gets proportionally smaller.The receiver requires a strength of the IR signalof 4 mW/m2 per carrier to work without errors(resulting in a 80 dB S/N ratio for the audiochannels). The effect of the number of carrierson the coverage area can be seen in Figure 3.3-Aand Figure 3.3-B. The radiation pattern is thearea within which the radiation intensity is atleast the minimum required signal strength.Figure 3.3-A Total coverage area of RA 6013 & RA 6025 for 1to 8 carriersFigure 3.3-B Polar diagram of the radiation pattern for 1, 2, 4& 8 carriersThe cross section of the 3-dimensional radiationpattern with the floor of the conference venue isknown as the footprint (the white area in Figure3.3-C to Figure 3.3-E).This is the floor area in which the direct signal isstrong enough to ensure proper reception, whenthe receiver is directed towards the radiator. Asshown, the size and position of the footprint