Design of a low-phase-noise Ka-band GaAs HBT VCO

In this paper, the study of a Ka-band GaAs HBT VCO is reported with particular emphasis on achieving low-phase noise while using direct coupled varactor. A push-push cross-coupled VCO configuration is employed to achieve high oscillation frequency and low-phase noise. The measured oscillation bandwidth spans from 30.2 to 28.6 GHz with a tuning range of 1.6 GHz, while the phase noise at 1 MHz of frequency offset from the carrier at 29.3 GHz is -111.5 dBc/Hz. The VCO consumes 28.2 mW from 3 V supply and occupies an area of 0.82 mm x 0.62 mm. The FOM of the VCO achieves -186.3 dBc/Hz.