Freedom R8100 SERIES, Руководство оператора

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Figure 2.2.7.3.1.3-7 Constellation Plot (Samples / Trajectories)
Distribution Plot (Display Zone selection)
This selection displays a graph showing the distribution of symbol deviations of the received signal
grouped into frequency bins of 10 Hz or less (i.e. the frequency offset versus the rate of occurrence of that
frequency). Each plot consists of at least a second of the most current data available. The protocol consists
of four symbol values (-3, -1, +1, +3) at proportional carrier deviations; see Table 2.2.7.3.1.2-1. The four
ideal symbol deviations are labeled at gridlines. Additional gridlines half way between labels divide the
plot into four equal regions and mark the thresholds where symbol decisions change from one to the other.
For example, in low power conditions noise may cause a symbol’s deviation to appear in the adjacent
region thus causing a bit error.
All distribution amounts are displayed by automatic adjustment of the vertical axis scaling to show the
full amount of symbols falling into each bin. Distribution amounts are the percentage of the number of
symbols whose deviation falls within that point’s frequency bin based on the number of symbols in the
analysis population. The better a signal is, the more symbols will actually land in the ideal bin to increase
its percentage. Deviations that are past the graph edge limits (e.g. for noise if there is no signal) are
collected and shown in the bin at the limit.