| In this work, two types of automatic tuning systems, VCO based and VCF based, are studied in the context of integrated continuous-time LC filters with a Q-enhancement. Nonlinear effects in the VCO-based tuning system is found key to achieving stable quality factor control. Based on this analysis, a new VCO-based Q-tuning system using a conductance reference is presented. In addition, a VCF-based tuning system suitable for Q-enhanced LC filter is proposed. To demonstrate the feasibility of the proposed tuning techniques, both the VCO-based and VCF-based tuning systems were implemented for a 1.5-V, 6-GHz Q-enhanced LC filter on a UMC 0.18-mum standard CMOS process.; A contribution to the design of Q-enhanced LC filters is also made. A novel loss compensation technique for series-branch resonators in a bandpass filter is proposed. A test chip is implemented on Anadigics's InGap HBT GaAs process to validate the proposed technique. |
