Synthesis of recursive LTV digital filters using the frozen-time approximation

A reexamination is made of the frozen-time approximation (FTA) for the synthesis of recursive linear time-varying (LTV) digital filters. While the use of the FTA has been discouraged, analysis shows that this approach is still valuable. Improvements on the FTA are proposed that take advantage of the simplicity of the frozen-time approach, being based on the assumption that for any desired LTV filter there exists a related filter whose FTA produces a better realization of the desired filter than its own FTA. Methods of finding such a related filter are discussed. The resulting filters are superior in performance to those obtained by the currently available optimization techniques at a fraction of the computational load