Thanks everybody for the valuable explanations.
Actually, this video confuses me the most -
A 100MHz 1GSa/s DSO is not able to display the eye pattern.
![Shocked :o](https://www.eevblog.com/forum/Smileys/default/xshocked.gif.pagespeed.ic.CrwtrNUjLO.png)
Maybe because it's a cheap DSO.
I had bought an OWON VDS1022(25MHz 100MSa/s) but the eye pattern was not smooth -
Luckily I was able to return it.
![Phew :phew:](https://www.eevblog.com/forum/Smileys/default/phew.gif.pagespeed.ce.n2uLOVFYMP.gif)
In this video -
,
the RIGOL DS1054Z (50MHz 1GSa/s) is displaying an eye diagram perfectly. But it is quite expensive.
The Siglent SDS1052DL is within my budget. But don't know whether it is good or not. Because once I buy it, I will not be able to return or exchange it.