An accurate automatic tuning scheme for high-Q continuous-time bandpass filters based on amplitude comparison

A new automatic tuning scheme for continuous-time high-Q bandpass filters is presented. It is conducted by amplitude comparison at three frequencies generated by an on-chip frequency synthesizer. Theoretical analysis and experimental results are provided. Analysis shows the tuning method is suitable for bandpass filters with Q>10. A g/sub m/-C second-order filter is designed to demonstrate the proposed tuning scheme. The test chip is fabricated in AMI 0.5 /spl mu/m process. The measured frequency tuning error is 0.25%, and Q-tuning error is 3% for a 200 MHz filter with a desired Q of 28.6.