A Low-power Quadrature VCO Using Current-reused Technique and Back-gate Coupling

A novel quadrature voltage controlled oscillator (QVCO) using current-reused technique and back-gate coupling is presented. The QVCO realized with LC-tank is demonstrated in a 0.18 um RF CMOS 1P6M process. Using the current-reused technique efficiently reduces the power dissipation. However, by stacking switching transistors in series like a cascade, the architecture cannot perform well in phase noise. Through an improved circuit schematic with back-gate coupling, the phase noise of the circuit can be lowered. As a result of reducing four transistors in the circuit, the total power dissipation can be cut down even more. The simulation shows the phase noise is around −107 dBc/Hz at 1 MHz offset and the output frequency tuning range of the fabricated QVCO is 600 kHz ranging from 5.15 to 5.75 GHz for 802.11a. The circuit draws only 1.5 mA from a 1.8-V supply. Compared with the recent works, the proposed topologies show a better phase noise performance and can be adopted for low-power applications. DOI: 10.2529/PIERS060907041642