VCO phase-noise improvement by gate-finger configuration of 0.13-μm CMOS transistors

Using a standard logic process, 0.13-μm RF CMOS devices with multifinger gate structure have been fabricated. The flicker noise and minimum noise figure characteristics have been investigated with different gate layout splits, where the device parasitic resistance is the determining factor in this issue. The stripe-shaped gate configuration demonstrates better noise performance, due to the reduction of device gate resistance. In addition, the MOS varactors designed with different gate layouts were used in a 5.2-GHz voltage-controlled oscillator (VCO) design, where the VCO with the stripe-shaped (2 μm × 36 fingers) gate varactor improved about 6 dB in phase-noise performance at 100-kHz offset frequency than that of square-shaped (8 μm × 9 fingers) gate varactor.