A 25.9-GHz voltage-controlled oscillator fabricated in a CMOS process

A 25.9-GHz voltage-controlled oscillator (VCO) has been demonstrated using 0.1-/spl mu/m NMOS transistors in a partially scaled CMOS process. The tuning range and output power level are 600 MHz and /spl sim/-22 dBm. The phase noise at a 3-MHz offset is -106 dBc/Hz when the VCO core consumes 24 mW from a 1.5-V supply. This VCO uses a MOS varactor with Q>20 at 26 GHz. Though Q is higher, due to the polysilicon gate depletion effect, the frequency tuning is not monotonic and a mechanism to limit the control voltage range is needed for phase-locked loop (PLL) applications.