A ultra-low-voltage 6.9 GHz CMOS quadrature VCO with superharmonic and back-gate coupling

A 0.35V fully-integrated quadrature voltage-control oscillator (QVCO) is presented, which consists two LC-tank VCOs with superharmonic and back-gate coupling techniques to couple them to run in quadrature. The proposed QVCO is simulated in the 130 nm CMOS technology. All MOSFETs are designed in the deep n-well. Consuming the power of 3.4 mW from a 0.35 V supply voltage, the QVCO achieves a frequency tuning range from 6.54 GHz to 6.98 GHz as the tuning voltage is varied from 0 V to 0.4 V. The simulation result shows that the phase noise at 1 MHz offset is -108.1 dBc/Hz at the carrier frequency of 6.98 GHz and the figure of merit (FOM) of the QVCO is -180 dBc/Hz. It is comparable or better than that of other state-of-the-art QVCO designs operating at much higher supply voltage.