A Note on Filter Synthesis

An equal-ripple type of approximation to constant attenuation in both stop and pass bands is often desirable in electric filter design. Elliptic functions have been extensively employed in solutions of problems of this sort. Double-entry tables are required and the mathematics is, in general, involved. This paper describes a design method that avoids the use of elliptic functions. A closed-form solution is obtained for networks of low complexity. Even for high complexity it appears that a rapidly con- vergent iterative process will solve the resulting equation.