A 34.16-39.6 GHz low phase noise VCO for frequency-modulated continuous-wave radar in a 28-nm CMOS

A dual-core voltage-controlled oscillator (VCO) using harmonic resonance is presented in this letter. Without an additional switch capacitor bank, harmonic resonance implemented in VCO is realized by only a single control voltage, satisfying the requirement of frequency-modulated continuous-wave radar. Two pairs of varactors are added to the transformer-based tank, which ensures a constant ratio between the two resonant frequencies of the tank in the entire tuning range. Robustly single-frequency oscillation is obtained by increasing the coupling coefficient of the transformer and the coupling capacitor's capacitance. Implemented in a 28-nm complementary metal-oxide-semiconductor, the VCO shows a 14.75% frequency tuning range covering 34.16-39.6 GHz. The measured results show it exhibits -102.13 dBc/Hz phase noise at a 1 MHz offset from the 34.16 GHz. The oscillator core draws 21-28 mA from a 0.9 V supply.