V. Valimaki et Ti. Laakso, Suppression of transients in variable recursive digital filters with a novel and efficient cancellation method, IEEE SIGNAL, 46(12), 1998, pp. 3408-3414
A new method for suppressing transients in recursive infinite impulse respo
nse (IIR) digital filters is proposed. The technique is based on modifying
the state (delay) variables of the filter when coefficients are changed so
that the filter enters a new state smoothly without transient attacks, as o
riginally proposed by Zetterberg and Zhang. In this correspondence, we modi
fy the Zetterberg-Zhang algorithm to render it feasible for efficient imple
mentation. We define a mean square error (MSE) measure for transients and d
etermine the optimal transient suppresser to cancel the transients down to
a desired level at the minimum complexity of implementation. The applicatio
n of the method to all-pole and direct-form II (DF II) IIR filter sections
is studied in detail. Time-varying recursive filtering with transient elimi
nation is illustrated for tunable fractional delay filters and variable-ban
dwidth lowpass filters.