I am studying MIMO control systems, and I have found that in the Nyquist stability criterion for MIMO system, one of the condition for stability is that:
and also that
$det(I+L(j\omega))$ has a number of encirclements of the origin equal to the number of poles in the RHP.
but what is $det(I+L(j\omega))$?
In SISO systems I know that we have to look at the encirclements of $L(j\omega)$ around $-1$.
But why in MIMO we have to look at $det(I+L(j\omega))$?
I put here the reference in which I found this: link