Design considerations for monolithic Si-based RF VCOs in wireless single-chip systems

The paper discusses a number of important considerations in the design of differential VCO known as -G/sub M/ LC-tank VCO in Si technologies. The availability of multiple interconnect layers, culminating in a thick electroplated Cu (bump) layer, has led to significant improvements in the Q-factor of tank circuit inductors. In addition, the use of symmetric differential inductor structures can result in substantial improvements in Q through the enhancement of mutual coupling.