%File:c3_sna.com
k=50;      %sample per lobe
nsamp=50000;  %total frequency sample
snrdb=zeros(1,17);  %initialize memory
x=4:20;   %vector for plotting
for m=4:20  %iterate samples per symbol
signal=0;noise=0;%initialize sum values
f_fold=k*m/2;%folding frequency
for j=1:f_fold
    term=(sin(pi*j/k)/(pi*j/k)).^2;
    signal=signal+term;
end
for j=(f_fold+1):nsamp
    term=(sin(pi*j/k)/(pi*j/k)).^2;
    noise=noise+term;
end
snrdb(m-3)=10*log10(signal/noise);
end
plot(x,snrdb,'r')
xlabel('Samples per symbol')
ylabel('Signal-to-aliasing noise ratio')