Methods and techniques for improving the figure of merit for wide tuning range quadrature voltage controlled oscillators

Abstract

Next generation wireless devices will be required to support a wide variety of commercial standards and operate over a wide range of frequency bands. Two examples that are already receiving a lot of attention are software-defined and cognitive radios. Therefore, components that are capable of operating over ultra-wide frequency ranges are required. Quadrature oscillators are a major component in any communication system. They are often needed in RF transceivers to support spectrally efficient modulation techniques. Furthermore, modern telecommunication standards require very low phase noise oscillators and because of their outstanding noise performance, LC-oscillators, are a popular choice. Hence, a lot of effort has been invested in studying and improving the figure of merit (FOM) of wide tuning range LC-Quadrature voltage controlled oscillators (QVCO). So far this effort has been primarily focused on three areas, expanding the tuning range, improving phase noise performance, and reducing the power consumption. Although many techniques have been proposed and used successfully in the literature, a lot of them lack sufficient theoretical analysis. First, the recently proposed, inductive current tuning methodology for expanding the tuning range of QVCO beyond capacitive tuning only is fully analyzed. In addition, a new low phase noise architecture that employs current tuning technique is proposed. The phase noise, tuning range and power consumption of two existing architectures and the proposed one are compared. The three designs are simulated and their FOMs are calculated and compared to identify the highest FOM architecture. Next, a popular architecture that is being utilized in the recent literature for the purpose of improving phase noise and expanding the tuning range, the transformer-based (T-based)