Improved design of oversampled allpass transformed DFT filter-banks with near-perfect reconstruction

In this paper, the design of oversampled allpass transformed analysis-synthesis filter-banks is treated, which can be employed for non-uniform subband processing. Near-perfect reconstruction can be achieved by a synthesis filter-bank design which uses phase equalizers to compensate the phase modifications due to the allpass transformation of the analysis filter-bank. It is shown that an FIR phase equalizer, which is obtained by a least-squares approximation of the desired non-causal IIR phase equalizer, leads to almost perfect signal reconstruction and causes only a comparatively low signal delay. The devised synthesis filter-bank design can be described by a closed-form expression and allows to control the trade-off between reconstruction errors on the one hand and signal delay and computational complexity on the other hand.