An efficient interleaved tree-structured almost-perfect reconstruction filterbank

In the conventional DFT filterbanks, the required transition bandwidth of the constituent prototype filter becomes narrower with increasing the number of subbands. This happens at the expense of making the prototype filter length longer, rendering the corresponding hardware implementation impractical beyond a certain number of subbands. This paper presents an alternative approach to the design of almost-perfect reconstruction (almost-PR) filterbanks which circumvents the problem associated with a large number of subchannels. The resulting filterbank has a multi-stage tree-structured configuration, and can be efficiently implemented by using interleaving techniques (to eliminate all identical short-length digital filters). Unlike the conventional DFT filterbanks, the resulting filterbank requires much smaller number of non-zero multiplier coefficients, and when the number of subchannels changes, the design of this tree-structured filterbank needs to be modified only slightly.