Linear phase design of lattice wave digital filters

This paper presents a novel design method and its implementation for Lattice Wave Digital Filters (LWDF) with very low group delay variations. These filters are a particular kind of Infinite Impulse Response (IIR) filters which exhibit excellent hardware implementation characteristics, since they are based on allpass filters with prescribed phase function. Allpass filters are particularly suited for hardware implementation, since the required multiplications are very low. The novel design method described in this paper aims at minimizing the inherent group delay variations of IIR filters using modern approximation techniques from applied linear algebra. The integration into a dedicated LWDF design toolbox allows a broader audience to make use of this design method. The results show the effectiveness of this design method compared to a reference Butterworth implementation. Through the integration into the filter design toolbox it is possible to analyze quantization effects as well as to directly retrieve the filter coefficients needed for hardware implementation.