Approximate LMS tuning of continuous time filters: convergence and sensitivity analysis

The quality factor of continuous time filters may be tuned using a master/slave arrangement in which an analogue implementation of the LMS algorithm is used to tune the master filter. Two such schemes are analysed, and their sensitivities to the effects of parasitic capacitances are determined theoretically and then compared. The two schemes are shown to have similar sensitivities to parasitically induced errors in the magnitude frequency response of the master filter, whereas only one of them is shown to be immune to phase errors in the master filter. The theoretical results are verified using a behavioural simulation. Approximate hardware costs of the two tuning schemes are also compared.