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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

Lewis Kelsey
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    You mention the carrier, but the eye diagram is created from a baseband signal (with no carrier). – MBaz Sep 28 '20 at 23:55
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    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 – Dan Boschen Sep 29 '20 at 01:56
  • @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? – Lewis Kelsey Sep 29 '20 at 03:46
  • 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 – Lewis Kelsey Sep 29 '20 at 12:06
  • https://dspillustrations.com/pages/posts/misc/eye-diagram-examples.html – Lewis Kelsey Sep 29 '20 at 12:14

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