Noncausal forward/backward two-pass IIR digital filters in real time

A novel method for implementing noncausal forward/backward 2-pass recursive digital filters in real time is presented. It is based on a segment-wise block processing scheme without overlapping. Factors that degrade the linearity of the overall system’s transfer function are discussed. An analytical condition that corrects the system’s linearity is elaborated upon using the state variable approach. A recursive algorithm is developed to compute an implementable condition for real-time filtering. A single first in, first out queue memory is introduced to ensure an organized and continuous data stream into the proposed system. This technique allows real-time, sample-by-sample filtering, and it yields reduced delay and data storage memory compared to previous works. Better performances in total harmonic distortion were also obtained. Experimental results are illustrated.