Fully analogue LMS adaptive notch filter in BICMOS technology

A fully analogue adaptive notch filter for meter pulse applications in analogue subscriber line systems is presented. The filter is part of an integrated circuit which includes both low voltage subscriber line interface circuit- (SLIC)- and CODEC-filter functions. The effects of offset, noise, and transient behavior are investigated, and a linear model for stability analysis is derived. Fabricated in a 1 /spl mu/m BiCMOS technology this circuit uses the benefits of accurate SC-filters, low offset comparators, and linear multipliers. Due to the adaptive approach the performance of the filter is independent of process deviations and temperature effects. The filter has been designed for an attenuation of 50 dB @ 12 or 16 kHz, a dynamic range of 103 dB and a settling time of less than 5 ms.