Lattice wave digital filters with simultaneous conditions on amplitude and phase

A Systematic Algorithm for the Synthesis of Multiplierless Lattice Wave Digital Filters

“…The main drawback in this approach is that the phase response of the frequency-selective filter is usually very nonlinear and, therefore, a very high-order phase equalizer is needed in order to make the phase response of the overall filter approximately linear. It has turned out (Földvári-Orosz et al, 1991;Jaworski & Saramäki, 1994;Jones et al, 1991;Lawson & Wicks, 1992;Leeb, 1991;Surma-aho, 1997;Surma-aho & Saramäki, 1999) to be more beneficial to implement an approximately linear-phase recursive filter directly without using a separate phase equalizer. In the design techniques described in (Földvári-Orosz et al, 1991;Jaworski & Saramäki, 1994;Jones et al, 1991;Lawson & Wicks, 1992;Leeb, 1991;Surmaaho, 1997;Surma-aho & Saramäki, 1999), it has been observed that in order to simultaneously achieve a selective magnitude response and an approximately linear-phase performance in the passband, it is required that some zeros of the filter be located outside the unit circle.…”