Design of CMOS LC voltage controlled oscillators

Abstract

This work presents the design and implementation of CMOS LC voltage controlled oscillators. On-chip planar spiral inductors and PMOS inversion mode varactors were utilized to implement the resonator. Two voltage controlled oscillators (VCOs) were realized as a part of this work, one designed to operate at 1.1 GHz while the second at 1.8 GHz. Both VCOs were implemented in a scalable digital CMOS process, with the former in a 1.5 micron CMOS process and the latter in a 0.5 micron technology. A simulation based methodology was adopted to arrive at a simple pi model used to model the metal and substrate related losses responsible for deteriorating the integrated inductor's performance. Geometry based optimization techniques were utilized to arrive at an inductor geometry that ensures reasonable quality factor. In addition to the core VCO structure a host of test structures have been incorporated in order to carry out two-port network measurements in the future. Such measurements should enable one to gain a greater insight into the integrated inductor and varactor's performance.