Agilent Technologies ESA-E Series User And Programming Manual page 58

Making Modulation Analysis Measurements
Interpreting Measurement Results
4. Figure 4-24
characteristic "V" shape is caused by the demodulator aligning the
expected symbol clock rate with the clock rate of the signal, for best
fit at the midpoint of the trace. The differences in the two clocks
show increasing "slip," or deviation further from the trace center. At
one arbitrary reference sample, the signal is sampled correctly. But
since the symbol rate is skewed, any other sample in the positive or
negative direction is slightly off in time. This causes an error which
increases linearly in time.
Figure 4-24 Zoomed EVM Versus Symbol Display Showing Symbol Rate
Error
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shows the EVM versus time graph in zoom mode. The
Chapter 4