Design Techniques for a Low-Voltage VCO With Wide Tuning Range and Low Sensitivity to Environmental Variations

This paper presents design techniques for a low-voltage voltage-controlled oscillator (VCO) with a wide tuning range and low sensitivity to process, voltage, and temperature (PVT) variations. For wide tuning range, a switched tuning scheme is employed coupled with voltage-boosting techniques in a manner that improves the quality factor and tuning range of a switched capacitor array. To minimize the design overhead required for a robust VCO, an adaptive body-biasing technique is proposed, which relaxes the startup constraint and increases the VCO's immunity to PVT variations. The proposed VCO is implemented in 0.18-mu m CMOS technology and operates at 2.4 GHz. It achieves phase noise of -117 dBc/Hz at 1-MHz offset and a tuning range 20% while consuming 365 mu W of power. The figure-of-merit with the tuning range is -197 dBc/Hz, which is the lowest among recent state-of-the-art low-voltage VCOs.