Low-complexity design framework of all-pass filters with application in quadrature mirror filter banks design

Digital all-pass filters design problem can be simplified by solving a set of linear equations associated with a Toeplitz-plus-Hankel matrix in the least-squares sense. Consequently, the Cholesky decomposition or split Levinson technique can be appropriately used to obtain the optimal solution. In this study, the determination of the set of linear equations to calculate the all-pass-based quadrature mirror filter banks is achieved by exploiting some trigonometric identities and the frequency sampling method. The proposed simplification allows for expressing a sum of sinusoids by a single expression. The simulation results indicate that the presented new and simpler closed-form expressions of the Toeplitz-plus-Hankel associated matrices can achieve accurate performance with a considerable reduction in computational complexity.