This paper describes digital auto-tuning schemes for second-order Gm-C bandpass filters which are suitable for fine CMOS implementation. We propose a switched Gm-C analog filter and two digital tuning schemes: a center frequency tuning scheme using the phase information and a Q factor tuning scheme using the magnitude information. We present circuits, describe their operations, and present SPICE simulation results.
A digital tuning scheme for digitally programmable integrated continuous-time filters and techniques for high-precision monolithic linear circuit design and implementation