Phase noise analysis in CMOS LC Quadrature VCO

Shuguang Han , Baoyong Chi and Zhihua Wang Department of Electronic Engineering, Tsinghua University, Beijing 100084, P. R. China Institute of Microelectronics, Tsinghua University, Beijing 100084, P. R. China 2 Abstract: Based on a physical understanding of phase noise mechanisms in CMOS LC Quadrature voltage-controlled oscillator (QVCO), a quantitative analysis of phase noise in QVCO is developed. The noise of the coupling transistor is identified, and the relationship between the phase noise and the ratio of the width of coupling transistor to the width of switching transistor is analyzed. The prediction of the phase noise is in good agreement with the measurement results at 2 1/ f region. As a demonstration, a QVCO is implemented in a 0.25-um CMOS process using on-chip spiral inductors. Measurement results show that the QVCO can be tuned between 1.77 and 2.415GHz, has a phase noise of –117.17dBc/Hz at 1-MHz frequency offset for a 2.267GHz carrier, and dissipates 7.5mW from the 2.5-V power supply.