Complete automatic Q tuning system on a chip

As the need for filters in high frequency applications increases so too are the requirements for high accuracy. Design of accurate filters requires some kind of tuning scheme to be added in the filter circuitry. In this paper we present an innovative approach to VLSI implementation of Q tuning of analog lowpass/highpass filters based on the magnitude locked loop method. The proposed method uses the LMS algorithm to adaptively compensate changes in input amplitude and frequency. A fully differential multiplier and a new linearly tuned OTA are designed to implement the automatic control loop in the integrated circuit. The tuning system was implemented in a CMOS 0.18 μm technology in a master-slave configuration.