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

Abstract

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 timevarying 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.

A Variational Approach for Designing Infinite Impulse Response Filters With Time-Varying Parameters

“…By means of LTV filters the characteristic function, the damping factor and the Q-parameter of second-order systems are modified, in a timely manner. The variation of filter parameters is normally adjusted by means of linear and exponential functions as well as curves derived from second order systems and Bézier curves [1], [25]. In addition, other reports establish nonzero initial conditions to further reduce the transient behavior [26].…”

“…the quantities t, w 0 and h(w 0 , t) represent time, characteristic frequency and the impulse response in case of first-and secondorder systems, respectively. The integrand given in ( 4) is related to the definition of T R in (1). The number I(ω 0 ), defined in (4), gives a measure of rise-time, since with lower I(ω 0 ) the rise-time assumes a smaller value.…”

“…The concept is first addressed to deal with processing time and correctness trade-off [1]. The dynamic parameters of systems are varied in time to reduce the transient behavior as much as possible.…”