Analysis of Low Pass IIR Digital Filter Design

Digital Differentiator is a vital signal processing tool. It is found in many applications, from low frequency biomedical equipment to high frequency radars. New developing fields such as touch screen tablets and online signature verification also has digital differentiators as basic building block. A approach is proposed to design approximately linear phase infinite-impulse-response (IIR) digital filters in the pass band region. Low-pass IIR differentiator has been introduced in the paper. To design a low pass differentiator, we will design a differentiator in cascade with a appropriate low pass filter. The range and high-frequency suppression of the proposed low-pass differentiators are comparable to those obtained by higher order FIR low-pass differentiators. In addition, the differentiators exhibit almost linear phases in the pass band regions.