Constraints

When inverting the phase characteristic, we need not rely on the half height criteria. As a result, we may choose $b<1$ if we wish to obtain greater accuracy, rather than tolerate decreases in $c$ to ensure that $b=1$ as above.¹⁰ To find the $b$ value necessary to ensure the desired accuracy, we solve equation 63.

The only problem with finding $b$ this way is that some estimate of $\alpha$ is required to choose $b$. This estimate may be obtained by using the half height model in the subsection above.