An X-Band Dual-Mode Class-C VCO With a 45.27% Tuning Range in 55-nm CMOS

This paper introduces an X-band dual-mode Class-C voltage-controlled oscillator (VCO) in 55-nm CMOS process. An inductor-based resonator effectively reduces parasitic capacitance and design complexity compared to transformer-based oscillators. Moreover, using only a simple inductor-based resonator can effectively avoid frequency mismatch and magnetic coupling losses between coils. At the same time, it is biased in Class-C working mode to improve the current utilization efficiency. By using multi-mode switching technology, the proposed oscillator can achieve a wide range and better phase noise, simultaneously. The layout-based simulation results show that the VCO can cover a frequency range from 7.86 to 12.66 GHz achieving a 45.27% tuning range and the phase noise (PN) at 1-MHz offset is -121 dBc/Hz, while the carrier frequency is 8 GHz. It draws 15 mA from a 1.2 V supply. The size of the oscillator core area is 620 μm × 410 μm.