for j=0:99, b(j+1) = (cos(2*1200*pi*(1:80)/8000)*cos(2*(1200+j)*pi*(1:80)/8000)')^2+(cos(2*1200*pi*(1:80)/8000)*sin(2*(1200+j)*pi*(1:80)/8000)')^2, end;
plot(0:99,10*log10(b))
pause
plot(0:19,10*log10(b(1:20)))