Tree-structured IIR/FIR octave-band filter banks with very low-complexity analysis filters

A class of tree-structured octave-band digital filter banks is introduced. The filter banks make use of half-band IIR filters in the analysis bank and FIR filters in the synthesis bank which results in very low-complexity analysis filters. Further, the overall complexity is lower than, or comparable to, that of conventional filter banks. The overall filter banks approximate perfect reconstruction in the following sense. The distortion function is a linear-phase function approximating one in magnitude whereas the aliasing terms approximate zero. The filter banks are designed using linear and nonlinear programming. Design examples are included demonstrating the properties of the new filter banks