Efficient biorthogonal cosine-modulated filter banks

Biorthogonal modulated filter banks, when compared to paraunitary ones, provide the advantage that the overall system delay can be chosen independently of the filter length, thus allowing to design low delay filter banks. They have recently been studied by several authors. In this paper, we connect two different design methods, namely the quadratic constrained least-squares optimization and the principle of cascading sparse self-inverse matrices. Moreover, we show how factorizations into zero-delay and maximum-delay matrices can be utilized in order to achieve desirable features such as structure-inherent perfect reconstruction, no DC leakage of the filter bank, and a low implementation cost.