A comparison of two IIR filter structures for adaptive digital filtering

The interaction between IIR (infinite-impulse-response) filter structures and adaptive algorithms is examined with particular emphasis given to the IIR normal filter structure. The relationship between the direct form and normal IIR filter structures and the RLMS and SHARF algorithms is explored. The normal form is shown to improve the convergence behavior of the SHARF algorithm over implementations with the direct form. The error surfaces of the normal and direct form filters are examined and the desirable properties of the normal form surfaces are identified