function imp = h_impulse(t,alpha)
if( t == 0)
    imp = 1;
elseif (abs(1 - 4*(alpha*t)^2) < 10^-6)
    imp = (pi/4)*sin(pi/2*alpha)/(pi/2*alpha);
else
    imp = sinc(t)*cos(alpha*pi*t)/(1 - 4*(alpha*t)^2);
    %imp = sin(pi*t)/(pi*t)*cos(alpha*pi*t)/(1 - 4*(alpha*t)^2);
end
end
