In this paper, a comprehensive analysis of hardware complexity of different configurations for the realization of approximately linear phase filters is presented. Hardware complexity for the realization of the parallel all-pass structure (PA) is compared to the standard elliptic filters with the adequate group delay corrector (EC) in cascade. Both considered filters are designed to have the same cutoff frequency and magnitude approximation error, as well as the same maximal group delay error in all pass-bands. All analyzed infinite impulse response (IIR) filters will have an elliptic shape magnitude and approximately linear phase (i.e. constant group delay). In addition, the resulting group delay error of all the considered filters has an equiripple nature. The performed analysis revealed that consistently better results could be achieved with PA filters in terms of power consumption and hardware complexity. At the same time, the PA filters introduce significantly lower delay. The filter banks for efficient sub-band coding and signal transmission in communication systems could be successfully realized using the PA filters. The results presented here could be a valuable resource for designers of IIR filters to select the appropriate configuration for realization.

In this paper the design of selective digital filters that consists of a parallel connection of two all-pass sub-filters is presented. The phase of these filters has given an arbitrary shape ϕ(ω) in both pass-band and stop-band. The proposed method allows the calculation of selective filters with elliptic-like magnitude characteristic. Equations given in the paper are general and suitable for design of filters with arbitrary phase. The efficiency of the method is demonstrated on design of filters with piecewise linear and quadratic phases.