In this paper, a very low power modified current-reused quadrature voltage-controlled oscillator (QVCO) is proposed with the back-gate coupling technique for the quadrature signal generation. By stacking switching transistors in series like a cascode, the modified current-reused QVCO can be constructed in a totem-pole manner to reuse the dc biasing current and lower the power consumption. By utilizing the back-gates of switching transistors as coupling terminals to achieve the quadrature outputs, the back-gate coupled QVCO improves the phase noise and reduces the power consumption compared to the conventional coupling transistor based topology. Together with the modified current-reuse and back-gate coupling techniques, the proposed QVCO can operate at reduced supply voltage and power consumption while maintaining remarkable circuit performance in terms of low phase noise and wide tuning range. With a dc power of 1.6[Formula: see text]mW under a 0.8[Formula: see text]V supply voltage, the simulation results show the tuning range of the QVCO is from 2.36 to 3.04[Formula: see text]GHz as the tuning voltage is varied from 0.8 to 0.0[Formula: see text]V. The phase noise is [Formula: see text]118.3[Formula: see text]dBc/Hz at 1[Formula: see text]MHz offset frequency from the carrier frequency of 2.36[Formula: see text]GHz and the corresponding figure-of-merit of the QVCO is [Formula: see text]183.7[Formula: see text]dBc/Hz.
A Quadrature VCO Exploiting Direct Back-Gate Second Harmonic Coupling
