Design of high-Q varactors for low-power wireless applications using a standard CMOS process

The power consumption of an LC-tank oscillator is strongly affected by the varactor quality factor, whether the inductor is on- or off-chip. This paper proposes a new solution to realize high-Q, highly tunable on-chip varactors in a standard CMOS process, achieving a quality factor higher than 100 at 1 GHz, for a tuning ratio of 2. Other solutions are described and their respective advantages compared, while their characteristics are measured for a 0.5 /spl mu/m process.