A Delayless Alias-Free Subband Adaptive Filter Structure

AbstmctA d a p t i v e Subband techniques h a v e been developed t o solve complex i ty a n d s low convergence problems of t h e tradit i o n a l fu l lband h igh-order adapt ive f i l t ers . H o w e v e r , t h e ef fect of al iasing associated w i t h t h e m u l t i r a t e s t r u c t u r e . w h i c h i s a source of e r r o r in t h e model ing of t h e u n k n o w n s y s t e m . and t h e delay introduced in t h e s ignal p a t h , are s o m e of t h e disadvantages o f t e n encountered in m o s t of t h e proposed s t ruc tures . In th is paper , w e p r e s e n t t w o delayless m a x i m a l l y dec imated s t ruc tures where t h e o p t i m a l c h a n n e l f i l t ers are related t o t h e wideband s y s t e m in a closed f o r m . T h e y m a k e u s e of a special D F T analys i s f i l t er bank where t h e polyphase c o m p o n e n t s of t h e pro to type f i l t er represent f r a c t i o n a l delays s u c h t h a t al iasing i s cancelled w i t h n o need of adapt ive crossf i l ters .