An adaptive IIR digital filter based on estimation of allpass and minimum-phase system

In this paper, a new infinite impulse response (IIR) adaptive digital filter (ADF) which is composed of a cascade block of allpass system and a block of minimum-phase system connected in series is proposed. The allpass section is implemented using a series connection of second order allpass systems, while the minimum phase system has all its poles at the origin. The coefficients are updated using a simplified version of the LMS algorithm. By considering the unknown system to be having the same structure as that of the adaptive digital filter, it is proven that the poles of the ADF converges to the poles of the unknown system when the input is a stationary white signal. Computer simulation confirms our analysis.