---

d = 1.6; k1 = 2;
K = k1*k2*k3;
den = conv([T2 1],[T3^2 2*d*T3 1]);
Wjw = K ./ polyval(den, 1i*w);
idx = find(imag(Wjw(1:end-1)).*imag(Wjw(2:end)) < 0, 1);
P180 = real(Wjw(idx))
k1kr = k1/abs(P180)