Structure of first-order differentiator utilizing FIR and IIR sub-filters

In this paper, we propose a novel approach for constructing the first-order differentiator. It has been shown recently that an efficient FIR wideband differentiator can be synthesized when applying the multirate and frequency-response masking (FRM) techniques. The overall signal processing task is shared between a very low-order differentiator and an FIR half-band filter. The novelty of this paper is the usage of an approximately linear-phase IIR half-band filter based on the parallel connection of all-pass sub-filter and pure delay. The structure of resulting wideband differentiator consists of the approximately-linear phase all-pass sub-filter, two low-order FIR polyphase sub-filters, and the delay element. The proposed system exhibits a significantly smaller overall delay if compared with the corresponding solution based on FIR filters only.