The delay paradox when combining the outputs of non-quadrature filter networks and its importance to subband coding schemes

It is theorized that an apparent paradox can occur when combining the outputs of non-quadrature-filter networks. Under certain conditions, it can be shown that the group delay of the final output signal can be substantially less than the group delay of the constituent signals prior to the combination node. It is noted that this phenomenon is useful in delay-critical applications. It is suggested that it is particularly relevant to subband coding schemes, where it can lead to significant delay savings compared with other realizations. Background theory and practical examples are given to illustrate the effect