Choosing the Relevant Frequency Range

Regardless of which model we invert (magnitude or phase), we must acknowledge that there are limitations on the frequency ranges in which either model is valid. These ranges are functions of the accuracy desired and of the true value of $\alpha$. We already have noted in previous sections that as $\alpha$ becomes very small, the current model is not valid. Thus, none of the constraints on $\alpha$ for backsolving should cause alarm in this context. We present more detail below.