Wave Digital Filter Structures for High-Speed Narrow-Band and Wide-Band Filtering

Wave digital filter (WDF) structures for high-speed narrow-band and wide-band filtering are introduced. The narrow-band filter is composed of a periodic model filter and one or several, possibly periodic, masking filters in cascade. Lattice and bireciprocal lattice WDF filters are used for the model and masking filters, respectively. The wide-band filter consists of a narrow-band filter in parallel with an all-pass filter. The overall filters can be designed by separately designing the model and masking filters. The filters obtained in this approach also serve as good initial filters for further optimization. Both nonlinear and approximately linear phase filters are considered. One major advantage of the new filters over the corresponding conventional filters is that they have a substantially higher maximal sample frequency. In the case of approximately linear phase, the computational complexity can also be reduced. Further, the use of bireciprocal lattice wave digital (WD) masking filters also makes it possible to reduce the complexity, compared with the case in which FIR masking filters are used. Several design examples and a discussion of finite wordlength effects are included for demonstrating the properties of the new filters.