Asynchronous implementation of transient suppression in tunable IIR filters

In many applications we may want to control digital filters on-line and change their characteristics, like the passband width or group delay. IIR filters often provide more efficient implementation but they may suffer from long transients caused by sudden coefficient changes. Techniques are known to suppress these transients by modifying the state (or delay) variables of the filter, but they suffer from high computational complexity, high processing speed, and may require intolerable processing delay before the coefficient change. We propose a practical asynchronous implementation to avoid high-frequency processing. Closed-form expressions for the asynchronous system are derived and their complexity is analyzed both analytically and with a design example.