Abstract
Abstract In recent years, due to the rapid development of the wireless communication systems, the specifications of the RF integrated circuits inside these systems become very rigorous. The frequency synthesizer plays a very important role in various communication ICs, in which the voltage controlled oscillator (VCO) is the key component for high performance frequency synthesizer. In this study, the main focus is about design of low phase noise and wide band VCO. The substrate noise coupling effect in VCO is also discussed. This thesis first introduces the fundamentals of VCO such as the design considerations of VCO and the modeling of the phase noise in a VCO. Next describes two wide band and low phase noise VCO structures, which can reduce phase noise by the differentially tuned varactors and the capacitors array and switches, respectively. Both these two VCOs are fabricated by TSMC 0.18□m CMOS process. The output frequency is from 3GHz to 5GHz, and the phase noise at 1MHz offset is -113dBc/Hz. Due to the trend of integrating the digital circuits and analog circuits on a single chip in recent years, substrate noise is being taken more and more seriously. This thesis investigates the effect of substrate noise on VCO, including the comparison of the VCO output performances with the noise injected via several different pads. Furthermore, the effect of the inductor grounded or floated on the VCO is compared and discussed in this thesis also. It is demonstrated the grounded inductor guard ring provides a better isolation from substrate noise than the floated one by 9.4dB.