Digital Signal Processing Reference
In-Depth Information
21.3 Constellation Analysis of DVBT Signals
The great difference between the constellation analysis of DVB-T signals
and DVB-C is that in DVB-T, many thousands of COFDM subcarriers are
analyzed. The carrier range must be selectable. Often, displaying all the
constellation diagrams (carriers No. 0 to 6817 or 0 to 1705, resp.) as con-
stellation diagrams written on top of each other is of interest. The carrier
ranges can be selected in 2 ways:
•
start/stop carrier no.,
•
center/span carrier no.
Apart from the pure payload carriers, the pilot carriers and the TPS car-
riers can also be considered but no mathematical constellation analysis will
be performed on these carriers. In the following paragraphs, the individual
influences and measurement parameters will be discussed.
The following measurement values can be detected by using constella-
tion analysis:
•
Signal/noise ratio S/N
•
Phase jitter
•
I/Q amplitude imbalance
•
I/Q phase error
•
Modulation error ratio MER
Fig. 21.6.
Influence of noise
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