Nomographs and classical filter sensitivity optimization

In determining the filter order of a classical filter meeting a set of passband and stopband requirements, the engineer often finds several degrees of freedom to optimize the response in some sense without increasing filter order. We seek here to determine the set of requirements that is optimal in the sense of improving the implementation sensitivity of the magnitude response. It is shown that the proposed approach can yield good compromise in response while providing sensitivity margins for the given order. An elliptic filter design example is submitted and discussed. The technique is applicable to any filter having one or more degrees of freedom aside from filter order for requirements optimization.