A Design and Analysis of High Performance Voltage Controlled Oscillators

The voltage controlled oscillator (VCO) is one of the most important building blocks in modern communication applications such as microprocessor clock generation, wired and wireless communications, system synchronization, and frequency synthesis. The design of high performance VCOs has been increasingly more important and still is an active research area. Research on VCOs for the past decade has been concentrated in the areas of higher frequency, lower phase noise, low power, low operating voltage, and increased tuning range. However many of these objectives can be only achieved at the expense of some other objectives. This thesis analyzes the design of high performance of inductor-capacitor (LC) tank and ring VCOs. First the basics of both LC and ring VCOs are reviewed. Then through the basics, new LC VCO topologies and circuit tricks are derived and analyzed. The design, simulation, and layout guidelines are also provided. Finally, the circuit techniques used in both regular and quadrature VCOs and simulation results of regular inductor and symmetric inductor designs are compared. Next, the several single-ended and differential ring VCO topologies are reviewed and pros and cons for each type are provided. From the basic topologies, a new ring VCO cell topology is then introduced, along with the bias circuit, output buffers, and divider. A three stage VCO based on the new topology is designed and simulated in both thick-oxide and thin-oxide devices in 65nm CMOS SOI process. The results of thick and thin oxide devices are compared and confirmed the usability of the new ring VCO cell topology. Finally, a conclusion of the design of high performance LC and ring VCOs is drawn and new directions of research are predicted.