A graphical user interface for designing time-varying IIR filters with equalized group delay

The paper presents a graphical user interface for designing time-varying IIR filters with equalised group delay characteristic. The problem of non-constant group delay characteristic of the IIR filters is well known. The allpass based equalisers are used as a solution with fine results. Unfortunately, the equalisation introduces distortions to the time-domain characteristics of the original IIR filter. The concept of the time-varying coefficients proved to deal with that fact. Due to complex calculations and needed optimisation a tool in the form of a graphical system is greatly required to improve the robustness of simulations and studies of the equalised time-varying IIR filters.