Subband Architecture for HFB-Based A/D Converters

The classic structure of hybrid filter bank (HFB) A/D converters is very sensitive to realization errors. The relation between input and output is time-variant in the original HFB because of decimation. It causes the blind techniques not to be applicable for compensating the realization errors. In this paper, a new structure is proposed for HFB-based A/D converters which is called subband HFB architecture. The analog input is assumed to be decomposed into M narrowband signals and decimated for an M-channel HFB structure. They are considered as the new virtual inputs of the subband HFB. Subband HFB-based A/D converters estimate these virtual inputs and provide M output signals. The distortion and inter-channel interference (ICI) functions are defined for this new architecture. The synthesis part of subband HFB structure is designed using a matrix of FIR filters. The realization errors of subband HFB may be compensated using the techniques such as blind deconvolution. The new architecture is simulated for an eight-channel structure considering simply realizable RC and RLC circuits as the analysis filter bank. A good performance is reported in terms of distortion and ICI in the case where some parts of the spectrum are allocated to guard bands. The new subband HFB structure exhibits a better performance in comparison with the original one