Maximizing the oscillation frequency of CMOS VCOs

Techniques for enhancing the operation frequency range for voltage controlled ring oscillators are discussed. It is shown that substantial improvement in speed is achievable with concentric layout techniques and with transconductance density optimization. Simulation results for a VCO designed in a 0.35 /spl mu/m CMOS process are presented which show a center frequency of 4.5 GHz and a tuning range of /spl plusmn/12%.