| An 80 MHz bandpass filter with a tunable quality factor of 16∼44 using an improved transconductor circuit is presented. A noise optimized biquad structure for high-Q, high-frequency bandpass filter is proposed. The quality factor of the filter is tuned using a new quality factor locked loop algorithm. It was shown that a second-order quality factor locked loop is necessary and sufficient to tune the quality factor of a bandpass filter with zero steady state error. The accuracy, mismatch, and sensitivity analysis of the new tuning scheme was performed and analyzed. Based on the proposed noise optimized filter structure and new quality factor tuning scheme, a biquad filter was designed and fabricated in 025 mum BiCMOS process. The measured results show that the biquad filter achieves a SNR of 45 dB at IMD of 40 dB. The P-1dB compression point and IIP3 of the filter are -10 dBm and -2.68 dBm, respectively. The proposed biquad filter and quality factor tuning scheme consumes 58mW and 13 mW of power at 3.3 V supply. |
