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Design >> High-Speed I/O Design >> impact of group delay on eye closser
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Message started by raja.cedt on Jan 31^st, 2013, 4:14pm

Title: impact of group delay on eye closser
Post by raja.cedt on Jan 31^st, 2013, 4:14pm

dear all,

To analyze digital data Quality we use eye diagram, i agree but i want to know what are the impacts of different parameters like BW,GD. At the end of the day a good sampler should sample with less BER. For example less BW will limit the signal swing in a given Tb, hence BER degradation which shows less horizontal opening on the eye diagram. Coming to group delay, assume i have receiver chain with enough BW but un- acceptable in band group delay ripple , so now signal will reach the level but the transition time between logic 1 and logic 0 depends on the bit pattern hence eye will be closed (i have no doubt on this), but if i have good CDR which tracks slight dithering then this won't be a problem. I would be glad if any expert can comment if any thing wrong in the above description.

If there is no mistake in the above argument, then i would like partition between two causes which closes eye, one effect closes eye which is a real problem and another also closes eye, but with good CDR can be track-able.

Thanks,
Raj.

Title: Re: impact of group delay on eye closser
Post by ywguo on Mar 1^st, 2013, 11:18pm

Hi Raj.

I think the finite bandwidth dominates in your case. Group delay is not so important because the energy concentrates on fixed frequency point.

Best Regards,
Yawei