The eye diagram is a convenient visual
method of diagnosing problems with data systems.
An eye diagram is generated conventionally using an oscilloscope connected to the
demodulated, filtered symbol stream, prior to conversion of
the symbols to binary digits. The oscilloscope is re-triggered at every symbol period or
fixed multiple of symbol periods using a symbol timing signal
derived from the received waveform. By relying on the persistence of a typical
oscilloscope display, the result is an overlaying of consecutive received symbol samples
which form an eye pattern on the screen. (This
effect is re-created using modern digital storage scopes or computer displays in test
equipment.)
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