A 4∼7GHz ultra wideband VCO with tunable active inductor

An ultra-wideband CMOS VCO with tuning range of 3.8~7.4 GHz is presented, using tunable active inductor (TAI). The inductance of TAI can be tuned from 0.34~0.61 nH by active tunable resistor, and exhibits a quality factor of about 90. The VCO is designed in a 0.18 um CMOS technology with power dissipation of around 29.1 mW and phase noise (PN) of -92.05 dBc/Hz. PLL-based and LC-based phase noise reduction techniques are also examined. The former and latter reduces the phase noise by 1 dBC/Hz and 3 dBC/Hz, respectively.