DCT-based general structure for linear phase paraunitary filter banks

The factorization of linear-phase paraunitary filter banks (LPPUFB) has been well studied. In this paper, we show that it can be further simplified by fixing the last stage without losing its completeness. The structure can be viewed as the dual of the GenLOT when the last stage is chosen to be the DCT. However, the new structure is more flexible since it can generate basis functions of arbitrary length. The implementation for finite-length signals is discussed. A DCT-oriented initialization method for filter bank optimization is developed to improve its convergence. The proposed method leads to an effective way of handling the sign parameters when modeling orthogonal matrices via Givens rotations. As a result, better optimization results can be obtained.