A realization of oversampled cosine modulated filter banks with perfect reconstruction

In the design of filter banks, the cosine-modulated filter bank (CMFB) has drawn attention due to reduced computational overhead and case of design. In the conventional design method for a linear-phase CMFB, delay elements are added to the transfer function in order to realize the paraunitary property. Therefore, the polyphase structure carries out the rate transformation in two steps and the computation of the prototype filter is executed in a form where the rate is not completely reduced. Hence, the scheme is not optimum in terms of the computational overhead per unit time. Also, the splitting shape of the linear-phase split filter is a special one and is not equally split. In consideration of the above, a new method of realization is considered in this paper for an oversampled linear-phase CMFB. In its realization, reduction of the overall computation overhead is considered. At the same time, a transfer function with an equally split shape is presented. From the proposed transfer function, a polyphase structure is derived in which the computation is possible with a completely reduced rate for an arbitrary integer sampling. In realization of the perfect reconstruction, a method is proposed in which the paraunitary property is removed and the synthesis side can be constructed with a small amount of computation.