The generalized Halpern filter
J. Attikiouzel, Dang Tan Phuc · Proceedings of the IEEE · 1978
In this letter, a general method is introduced for the design of monotonic all-pole low-pas filters. It is shown that by using the shifted Jacobi polynomials the Halpern filter and the maximally flat magnitude beyond the origin filters can be obtained as special cases of this method. Many useful filter designs can be achieved by the variation of two parameters.