Planar IT-088, Руководство по эксплуатации

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NOTE When operating with a channel plan, in case if the modulation set
for the frequency point is other than COFDM-QPSK, COFDM-QAM16,
COFDM-QAM64, signal parameters auto detection mode will be activated.
Signal quality parameters measurement
After DVB-T/H demodulator synchronization has been achieved, the Analyzer will
measure the signal quality. During the process of measurement you will see in the value
field the
Sampling message.
When measuring channels with hierarchical modulation, MER , preBER and postBER
parameters measuring is performed for low-priority stream.
To check the current channel parameters you can use the supplementary table. To
access this table, press «F3» . The view of the table is represented in figure 4.10. Press
«MENU/ENTER» or « F3 » key to return to the measurement mode.
4.3.9. DVB-T/H CONSTELLATION Measurement Mode
The icon in the main menu refers to this mode. Before measuring the
Demodulator tuning message will appear on the screen, and in several seconds the
DVB-T/H demodulator will be activated. In case any error has been detected during
startup, the screen will show
Tuning error message and the Analyzer will return to the
main menu (methods of error correction are given in section 6). After successful startup,
DVB-T/H signal quality measurements in the form of a table will appear on the screen.
The main menu of the mode displays the table of parameters featuring the input DVB-
T/H signal quality and constellation diagram. The view of the screen is shown in figure
4.12:
Figure 4.12
The top line displays the following setting parameters: channel number, channel name
within the channel plan (if a channel plan was selected), and the symbol of DVB-T/H signal
synchronization. Before synchronization is achieved, its progress is indicated in the status
bar. After synchronization is achieved,
«LOCK» message appears instead of the status
bar.
In the left part of the screen you can see the constellation diagram of the DVB-T/H
signal, which is the graphic representation of vector diagram. The diagram is divided into
four quadrants, each containing dots made by the peaks of the vectors of demodulated
signals quadratures. In the ideal case the diagram represents a number of dots (nods) on
the phase plane. For example for COFDM-QAM64 it will be 64 dots of data stream vectors
and 4 dots of pilot subcarriers vectors. The noise influence makes the dots to ‘spread’ into
spots. Analyzing the form of the spots and their distribution on the phase plane it is
possible to define the noise behavior.
In the right part of the screen the measured parameters are displayed. The first
parameter is the modification error ratio MER . The second parameter is the bit error rate in
the digital stream before Viterbi decoder ( perBER ). The third one represents bit error rate
in the digital stream after Viterbi decoder ( postBER ).
Frequency adjustment