(eyediagram) Why I cannot get the eyediagram?

clear;

M=2000

N=200;

temp= rand(1,M);

for i=1:M

if temp(i)>0.5

D(i)=1;

else

D(i)=-1;

end;

end;

Ns=10; % Ns=5 or Ns=10

for i=1:M

for j=1:Ns

D_ext((i-1)*Ns+j)=D(i);

end;

end;

h = firrcos(200,0.5,0.35,10, 'rolloff');%modify the parameter in different steps

out=conv(h,D_ext);

out_leng=length(out);

out_stable=(N+1:out_leng-N);

eyediagram(out_stable,20)

This is what I got.

This is the expected result.

[Cris LaPierre]

Consider pasting your code in rather than taking a screenshot. It's much easier to work with that way.

[Kwan Ho NG]

clear;
M=2000
N=200;
temp= rand(1,M);
for i=1:M
    if temp(i)>0.5
        D(i)=1;
    else
        D(i)=-1;
    end;
end;

Ns=10; % Ns=5 or Ns=10
for i=1:M
    for j=1:Ns
        D_ext((i-1)*Ns+j)=D(i);
    end;
end;

h = firrcos(200,0.5,0.35,10, 'rolloff');%modify the parameter in different steps
out=conv(h,D_ext);
out_leng=length(out);
out_stable=(N+1:out_leng-N);
eyediagram(out_stable,20)

Answer 1

[Cris LaPierre]

The issue appears to be with how you create out_stable. The result of this is a straight line. If you create an eyediagram using out instead, you see you are mostly there. You likley meant to trim the tails of out to clean up the eye diagram.

load vars.mat
h = firrcos(200,0.5,0.35,10, 'rolloff');%modify the parameter in different steps
out=conv(h,D_ext);
figure
plot(out)

figure
eyediagram(out,20)

out_leng=length(out);
out_stable=(N+1:out_leng-N);
figure
plot(out_stable)

eyediagram(out_stable,20)

That is likely due to the fact that out_stable is the index values of what you meant to keep from out. You forgot to tell the code to index these values from out. Try this instead.

figure
out_stable=out(N+1:out_leng-N);
%          ^^^ Need to use your values as indices to out
eyediagram(out_stable,20)

[Kwan Ho NG]

Thank you. It works.