Reducing the number of multipliers in the parallel realization of half-band elliptic IIR filters

It is shown in this correspondence that a halfband IIR filter with the poles on the imaginary axis can be derived by the bilinear transformation of an elliptic minimal Q-factors analog prototype. For an odd degree transfer function, the residues at the poles are real or imaginary. Consequently, in the parallel realization, the number of multipliers can be reduced by half.