Analysis And Design Of Low Phase-Noise Wide Tuning-Range Fully Integrated CMOS LC VCO

The explosive growth in wireless communications has driven universities and companies to produce wireless transceivers at low-cost, low-power, and compact size. Recently, all of RF components, such as low-noise amplifiers (LNA), mixer, local oscillators (LOs), and IF filter, seem possible to be integrated in CMOS scaled technology. On-chip passive elements such as spiral inductors and varactors make on-chip implementation of LC VCO feasible.In this thesis, the theory and design methodology of LC VCO are studied, and many key techniques in circuit implementation are discussed in a simple way. First of all, the foundations of oscillator's physical mechanism are briefly introduced. Then in chapter 3, characteristics of LC TANK, the most significant component are studied. For on chip passive devices, we only focus on spiral inductor and inversion-mode varactor. In chapter 4, the definition of Phase Noise, one of the most important performance specs of VCOs, are introduced. Its non-ideal impact on radio frequency communication system are also characterized, after which two widely used phase noise model are studied, the linear-time-invariant model (include its modification by Lesson) and phase linear-time-variant model. As for ultra wide band VCO design, the variation of oscillating frequency will introduce many serious problem, even resulted in VCOs'operation failure. In chapter 5, we will focus on this problem and frequency-dependence of start-up constraint and output amplitude will be discussed thoroughly. After this, a practical wide band LC VCO design will be introduced. This proposed LC VCO has been fabricated in TSMC commercial 0.18μm RF CMOS process. Using a combination of switched binary-weighted MIM capacitor array and MOS varactors, this VCO achieves a tuning range of 1.65GHz~2.45GHz, while maintaining VCO gain less than 100MHz/V over its entire frequency range. It only draws 3mA from a 1.8V supply and the measured single-sided phase noise is -87.88 dBc/Hz at a 20KHz offset from a 1.65GHz carrier. Finally, we discussed some application issues for ultra wide band VCO. An adaptive frequency calibration strategy is proposed and a veriloga model for wide band VCO is also provided.