Bandwidth-enhancement gm-C filter with independent ωO and Q tuning mechanisms in both topology and control loops

This paper deals with the proposal of a new topology for a g_m-C continuous time filter which allows the adjustment and tuning of its characteristic parameters (ω_O and Q) in an independent way (without cross-tuning), thereby extending the Q range of the filter for a particular ω_O value. Additionally a comparison of three different Q-tuning algorithms is presented. It is shown that an LMS-based Q-control strategy allows to overcome the intrinsic dependence between the Q and ω_O tuning loops. The combination of both the proposed filter topology and the selected control loop algorithms results in an enhanced transient performance as well as an improvement in terms of cross-detuning.