Comparison of VCO Topology for Wideband Multi-Standard Applications

In this paper, three popular VCO topologies: cross-coupled, complementary cross-coupled, and differential Colpitts are investigated in terms of their performance for wideband wireless communication applications. Three VCOs, implemented in a standard 0.5 mum CMOS technology, are compared from the prospective of phase noise sensitivity to various noise sources, tuning range limitations, power dissipation, and design area. A new figure of merit (FOM) has been proposed to include tuning range into the overall performance metrics. Based on this metric, the experimental result shows that the differential Colpitts and cross-coupled VCO topologies can achieve the best FOM, wide tuning range (42%), and that they are therefore the best candidates for wide-band applications