Philips 14AA3322/40B Installationsanleitung PDF herunterladen (Seite 104)

Generation of a transport stream for DVB and realisation of a HF-modulated DVB-signal

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segment (188 bytes) of the digital Transport Stream. The lower it is, the better the signal is.

ErrorSEC: it represents the Errored Seconds. An Errored Second is a second that has, at least, one error on

the transport stream.

Question4

What can we see on the “Modulation Scheme” tab? Explain the different parameters that we can see:

Constellation: the constellation is the way that the symbols are related to the bits combinations. In our

case (VRT’s TV service) it’s 64QAM, which means that every symbol carries 6 bits per symbol.

Code Rate: is the proportion of the useful data (redundant). In our case it’s ½. This means that for every

bit of information, the coder has generated 2 bits of data (one of them is not redundant).

Guard Interval: the guard interval is the space of time between two consecutive transmitted symbols.

The higher it is, the less amount of data can be transmitted.

Transmission: is the number of carriers that are being broadcasted. It can be 8K (6817 carriers) or 2K

(1705 carriers).

Hierarchy: it shows if the transmission has a hierarchical mode or not. The hierarchical transmission is

used when two different MPEG TS (Transport Streams) are broadcasted at the same time.

Mirroring: it’s an effect induced by the imbalance of the IQ.

Now go to the “Modulation Detail” tab. Here you can find two graphs; one is the Constellation Diagram,

and the other one is the Eye Diagram.

Figure 1.3: Constellation and Eye Diagram

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Philips 14AA3322/40B Installationsanleitung Seite 104