using DSP
function tfest(y,u)
    Cyu = xcorr(y,u)
    Cuu = xcorr(u,u)
    Syu = welch_pgram(Cyu)
    Suu = welch_pgram(Cuu)
    return H = TF(Syu.power./Suu.power,Syu.freq)

end


N = 200000;
u = randn(N);
y = filt(ones(30),30,u);

H = tfest(y,u);
loglog(H.f,abs(H.P))