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A continuous-time 7th-order Butterworth Gm–C low pass filter (LPF) with on-chip automatic tuning circuit has been implemented for a direct conversion DBS tuner in 0.35 μm SiGe BiCMOS technology. The filter’s -3 dB cutoff frequency f0 can be tuned from 4 to 40 MHz. A novel on-chip automatic tuning scheme has been successfully realized to tune and lock the filter’s cutoff frequency. Measurement results show that the filter has -0.5 dB passband gain,+/–5% bandwidth accuracy,30 nV/Hz1/2 input referred noise,?3 dBVrms passband IIP3,and 27 dBVrms stopband IIP3. The I/Q LPFs with the tuning circuit draw 13 mA (with f0 = 20 MHz) from 5 V supply,and occupy 0.5 mm2.
A continuous-time 7th-order Butterworth Gm-C low pass filter (LPF) with on-chip automatic tuning circuit has been implemented for a direct conversion DBS tuner in 0.35 μm SiGe BiCMOS technology. The filter’s -3 dB cutoff frequency f0 can be tuned from 4 to 40 MHz. A novel on-chip automatic tuning scheme has been successfully realized to tune and lock the filter’s cutoff frequency. Measurement results show that the filter has -0.5 dB passband gain, +/- 5% bandwidth accuracy, 30 The I / Q LPFs with the tuning circuit draw 13 mA (with f0 = 20 MHz) from 5 V supply, and occupy 0.5 mm2.