A constant output power Q-band VCO with distributed cross-coupled-G_m core and A-mode pMOS varactors

This paper presents a constant output power and low DC consumption VCO fabricated in tsmc™ 90 nm CMOS technology for Q-band applications. A two-pair nMOS cross-coupled transistors forms a distributed negative transconductance (-G_m) core to meet the start-up oscillation condition. The inductive routes of the distributed layout reduce the parasitic capacitances of the transistors and lower the DC consumption. By choosing the accumulation-mode pMOS varactors in LC-tank, the VCO has a nearly constant output power and phase noise under + 1 V tuning voltage. The oscillator achieves an output power of -15.83 ± 0.89 dBm from 47.16 to 48.47 GHz, while the varators tunes from -2.0 V to +1 V. The phase noise is -88.57 dBc/Hz@ 1-MHz at the 48-GHz free-frequency. The DC consumption is 9.5 mW at the 0.75-V power supply. The chip size including the buffer amplifiers and pads is only 0.776 × 0.719 mm².