Recent Advances in FIR Approximation by IIR Digital Filters

This paper provides a tutorial review on several recent design methods for approximating FIR by IIR digital filters with reduced order. These methods can generally be classified as time-domain method, frequency-domain method, and mixed-domain method. The numerator and denominator of IIR digital filters are obtained in different steps under some criteria. The final result of each design method cannot be ensured to be optimal or even suboptimal for such approximation problem. Also, some methods do not incorporate a stability constraint hence stability is not really ensured. In this paper the design steps of each of these methods are outlined. Through three examples, we analyze their performances and identify the strengths and weaknesses of each design method