I would like to ask question bout the rrc filter that I applied as an matched filter for receiver side in communication. My aim after RRC filter is to draw the eye diagram, and so far the eye opening is small and I wonder if there are still ISI after applying rrc.

before RRC after RRC

This is my signal qpsk before / after applying RRC.

How do I know if the filter is applied well? How do I know if this signal still has ISI or not by looking at time domain signal? Obviously it seems so, because the eye opening is small.

Another question is, I have read some articles including how to design the filter, but it is still not clear for me how to set the tap(N). I would appreciate if you elaborate more about it.

Thank you in advance.

  • $\begingroup$ The best way to find if your system is working correctly is the eye diagram. If there's no noise in the system and the eye is not completely open, you're doing something wrong. I suggest starting with a 2-PAM signal. Once that works, you can move on to more complex constellations. $\endgroup$
    – MBaz
    May 17 '21 at 13:15
  • $\begingroup$ Hi and welcome to DSP.SE! Please ask separate questions as separate posts here as that will be cleaner for the Q&A format. Does this answer your second question? dsp.stackexchange.com/questions/51088/… If not please repost and be clear about what exactly your question is. For your first question, please include a plot of your actual eye-diagram since you refer to one, just in case what you call an eye diagram isn't actually that. $\endgroup$ May 18 '21 at 11:33

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