A Low Power, Fully Integrated SiGe BiCMOS Baseband Circuitry for a Direct Conversion CMMB Tuner IC*

A fully integrated analog baseband circuitry for a China mobile multimedia broadcasting (CMMB) direct conversion tuner IC is proposed in this paper. It includes an 8th order Op-Amp-RC channel select filter with 1MHz or 4MHz bandwidth and 71dB stop-band rejection at $1.7f_{-3\text{dB}}$ to meet the stringent Adjacent channel rejection (ACR) specifications and utilizes a novel gain-bandwidth-product extension technique in designing the low power, high speed Operational amplifiers (Op-Amps) for the filter. A current steering type Variable gain amplifier (VGA) is adopted to provide 44dB variable gain range and an on-chip DC offset cancellation (DCOC) circuit is designed to prevent the baseband chain from saturation due to DC offsets. Fabricated in a $0.35\mu\mathrm{m}$ SiGe BiCMOS process, the proposed chip consumes only 6mA from a 3V supply.