Feedback-based orthogonal digital filters

A synthesis procedure for generating orthogonal structures to implement arbitrary transfer functions is described. As compared to earlier techniques associated with orthogonal filter synthesis, which used a cascade of sections or a parallel combination of sections, this method uses feedback to simplify the design process, and results in filter structures that have the low-passband-sensitivity properties associated with orthogonal structures. Additionally, the structure is inherently L2-scaled; thus, the design process is simplified because an additional scaling step is not necessary. One of the other advantages of the new structure is that its stability monitoring is very easy; thus, it is extremely well suited for adaptive applications. The method is motivated by some recently reported resonator-based digital-filter structures