Realization of 2-D variable IIR digital filter structures with a small amount of calculations for coefficient update

This paper proposes a 2-D variable IIR digital filter structure with a small amount of calculations for coefficient update. In the proposed realization method, the parallel allpass 2-D variable filter structure is modularized in order to reduce the number of first-order complex allpass sections. Then, one of the first-order complex allpass section pair in the modularized variable structure is replaced by the complex conjugate converter. By means of the proposed method, the variable structure with minimal hardware elements can be realized. Comparison of the amount of calculation between variable structures shows that the proposed variable structure requires less calculations for coefficient update than the conventional variable structure.