New solution for the ideal filter approximation problem

A new solution is proposed for the ideal filter approximation problem consisting of a cascade connection of a non-minimum-phase filter and a phase-correcting network which are synthesised simultaneously. As illustrated by numerical examples, the new solution is more economical than the conventional Cauer filter and phase corrector combination when comparison is made on the basis of the total number of elements used in practical realisation. It is also shown that filters with a monotonic passband response can be used to advantage over the filters with weighted Chebyshev approximation of the passband magnitude response.