s = [ 0.5*cisd(-120) 0.08*cisd(-26); 0.08*cisd(-26) 0.99*cisd(172) ]
z0 = 50;
y0 = z0^-1


y11 = y0*((1-s(1,1))*(1+s(2,2)) + s(1,2)*s(2,1)) / ((1+s(1,1))*(1+s(2,2))-s(1,2)*s(2,1))
%to_pd(y11)
y12 = y0*(-2*s(1,2))/((1+s(1,1))*(1+s(2,2))-s(1,2)*s(2,1))

y22 = y0*((1+s(1,1))*(1-s(2,2)) + s(1,2)*s(2,1)) / ((1+s(1,1))*(1+s(2,2))-s(1,2)*s(2,1))

r1 = to_pd(inv(y11 + y12))
r2 = to_pd(inv(-y12))
r3 = to_pd(inv(y22 + y12))