I don't yet completely understand eye diagrams. Why isn't the noise in the centre of this polar BPSK diagram and instead are 2 margins at -4 and 4.. surely that's not where the noise would be in relation to the carrier. Also, how do you work out the SNR looking at this, I'm assuming it's the proportion of the full height of the eye to the noise height?

enter image description here

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    $\begingroup$ You mention the carrier, but the eye diagram is created from a baseband signal (with no carrier). $\endgroup$
    – MBaz
    Sep 28, 2020 at 23:55
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    $\begingroup$ It is not a polar plot but the baseband waveform vs time synchronized with the symbol clock such as you could do with an oscilloscope triggered by the symbol clock with infinite persistence. Does this answer your question?: Eye pattern construction and interpretation $\endgroup$ Sep 29, 2020 at 1:56
  • $\begingroup$ @Mbaz oh I just thought this must be the carrier that we can see because it's a sinusoidal shape. Is it actually the baseband waveform using a cosine filter or something? $\endgroup$ Sep 29, 2020 at 3:46
  • $\begingroup$ Yeah you can see it on there. It's not noise but it's continuous with the symbol. It's clearly just plotting raised cosine symbols after demodulation with the carrier $\endgroup$ Sep 29, 2020 at 12:06
  • $\begingroup$ dspillustrations.com/pages/posts/misc/eye-diagram-examples.html $\endgroup$ Sep 29, 2020 at 12:14


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