A 12th order active-RC filter with automatic frequency tuning for DVB Tuner applications

A 12th order active-RC filter for DVB Tuner applications with automatic frequency tuning (AFT) is presented in this paper. The filter is implemented in Butterworth biquad structure. The AFT circuit is introduced to compensate the frequency variation by a 7-bits switched-capacitor array. The measurement results indicate that the precision of tuning circuit can be controlled less than plusmn2.3%, the in-band group delay variation is 70 ns, and the in-band IM3 achieves -60 dB with -27 dbm input power. This proposed filter circuit, fabricated in a SMIC 0.18 mum CMOS process, consumes 6 mA current with 1.8 V power supply.