A method to convert near-perfect into perfect reconstruction FIR prototype filters for modulated filter banks

In this contribution we propose a simple method of obtaining a perfect reconstruction (PR) FIR prototype filter starting from a given near-perfect reconstruction (NPR) prototype filter for complex modulated filter banks. Our method consists of two steps. First, we calculate the product of a pair of polyphase components that fulfill the PR conditions, and second, we search for spectral factors that maximize the correlation coefficients between the impulse response of the new polyphase components and of the original ones. Our preliminary numerical results show that the price to be payed to satisfy the PR conditions is some loss in the spectral characteristics.