I am writing a dissertation and for one part I want to validate an estimator I derived given different systems. In particular, the most basic system is a VAR(1) model: $$ X_t = AX_{t-1} + \epsilon_t $$
Where $\epsilon$ denotes white noise.
My question is, I want to test if my estimator works under non-linear transformations of this model. In particular I want to test a stable and an unstable coupling. I came up with the following: $$ X_t = Af(X_{t-1}) + \epsilon_t $$
Where in the stable case, $$ f(x) = \frac{1}{1+|x|} $$
and in the non-stable case, $$ f(x) = \frac{1}{x} $$
My question is thus, is this the normal way to transform a VAR model. Also, how can I verify whether the configuration of $A$ changes the stability / stationarity of the system?