Implementation of recursive filters having delay free loops

Certain types of recursive filters have been considered as non-realizable because they contain delayless recursive loops. Usually the problem is rather technical than theoretical. A method of implementing such filters is introduced. The general procedure is to split a delay free recursive filter to a non-delay free and a pure delay free structure. As a combination of these, the filter can be implemented directly and efficiently. In addition, following from the same formulation, a generic procedure to convert any such filter to an equivalent directly realizable structure is also given. As an example, a set of frequency warped all-pole filters is considered. The new warped all-pole lattice introduced in this paper completes the family of warped filters