Continuous-Time LMS Adaptive Recursive Filters

This paper presents an approach for implementing continuous-time adaptive recursive filters. The resulting filters should be capable of operating on much higher signal frequencies than their digital counterparts since no sampling is required. With respect to implementation problems, the effects of DC offsets is investigated and formulae derived so that these effects can be estimated and reduced. As well, it is shown that the DC offset performance is strongly affected by the choice of structure for the adaptive filter. Finally, experimental results from a discrete prototype are given where accurate adaptation is observed and DC offset effects are compared to theoretical predictions.