A design technique for recursive linear time-varying digital filters

A reexamination of the frozen time approximation (FTA) is presented. It has been demonstrated that the FTA is still a viable option for the synthesis of LTV (linear-time-varying) filters. Since most applications of LTV filters are slowly varying the FTA is natural. Since optimization procedures on moderate-length LTV filters have prohibitive computational requirements, the FTA is efficient in comparison. Improvements have been proposed to synthesize FTA-based filters which are more accurate than those synthesized by the available optimization techniques at a small fraction of the computational load. It is concluded that it is reasonable to consider that other techniques for LTV filter synthesis should be implemented only on those quickly varying filters for which all FTA-based techniques fail