Comparison of Switched-capacitor Ladder and Ccd Transversal Filters

Switched-capacitor ladder f i l t e r s and CCD tr a n s v e r s a l f i l t e r s have developed i n t o two competitive approaches f o r implementing high p e r f o r mance f i l t e r s which can be f u l l y i n t e g r a t e d using MOS-LSI technology [1,2] I n some respects the two techniques are s i m i l a r since they are both analog sampled data f i l t e r s which make use of charge storage on capa c i t o r s . However, i n most other aspects, they are fundamentally very d i f f e r e n t since CCD t r a n s v e r s a l f i l t e r s use only t r a n s f e r f u n c t i o n zeros to shape the frequency response, whereas the switched capacitor ladders are r e c u r s i v e f i l t e r s which make use of both poles and zeros. For some a p p l i c a t i o n s a t r a n s v e r s a l , a l l zero f i l t e r must be used, such as when tr u e l i n e a r phase i s required or i n matched f i l t e r i n g . On the other hand, a very narrow bandpass f i l t e r can be r e a l i z e d using a simple p a i r of high Q poles, which i s much more e f f i c i e n t than using a CCD tr a n s v e r s a l f i l t e r which would r e q u i r e a l a r g e number of zeros and th e r e f o r e many CCD stages f o r a narrow passband response.