On the tuning of digitally programmable continuous-time filters

Abstract

Tuning strategies associated with a digitally programmable and reconfigurable continuous-time filter structure which is monolithically implementable and possesses potential for high-frequency precision application are presented. The filter structure is based on a universal biquadratic block realized by means of digitally controllable CMOS transconductance amplifiers and programmable capacitor arrays. Various system identification techniques are proposed to provide accurate performance measurements as required by the digital tuning algorithms which can be performed by an external tuning controller. With the specific CMOS implementation on a prototype experimental filter structure, the presented tuning algorithm can successfully tune a 2nd-order bandpass filter with less than 1% error on filter characteristics, namely resonant frequencies. 3dB bandwidths and the maximum gains. Tuning algorithms for general biquadratic filter functions are also discussed in this dissertation. Finally, future works are addressed by proposing the addition of automatic or semi-automatic analog tuning loops in the filter structure to compensate the deficiencies of digital tuning algorithms.