A CMOS VCO with Optimized Tune Branches for Zero-IF CDMA Cellular Application in a 0.5μm BiCMOS process

A fully integrated, very-low phase-noise CMOS voltage controlled oscillator (VCO) has been implemented for zero-IF CDMA cellular receiver (Rx) using CMOS transistors in a 0.5mum SiGe BiCMOS process technology. To optimize the phase noise performance, the VCO used the proposed coarse and fine tune branch which employed high-Q accumulation-mode MOS (AMOS) varactors. The measured phase noise is below -133dBc/Hz at 900kHz offset frequency from a 1.762GHz carrier, which yields enough margin for the IS-98 single-tone test requirement. The integrated CDMA cellular Rx including this Rx VCO shows more than 2.5dB single-tone performance margin