Low-Phase-Noise VCO using Cascode Q-enhancement Connection and Source-Damping- Resistance Technique

In this paper a cascode CMOS VCO with a source-damping-resistance technique is proposed to reach low phase noise. A cascode cross-coupling connection is able to enhance the quality factor (Q) of the tank. Furthermore, a source-damping-resistance technique is adopted to improve phase noise originating from different mechanism. An optimum damping resistance is studied for different offset of phase noise. Measured oscillation frequency is from 2.26 GHz to 2.14 GHz. The measured phase noise at 1 MHz offset is −125.9 dBc/Hz at 2.14 GHz, and the core power consumption is 3.0mW from a supply voltage of 1.5V. A FOM of −187.6 at 1MHz offset is obtained. Two different phase noise improvement techniques merged simultaneously are demonstrated.