Wideband CMOS LC VCOs for IEEE 802.15.4a Applications

Two wideband LC VCOs, customized for IEEE 802.15.4a applications, are presented in this paper. Both circuits have been designed and implemented in a 90-nm CMOS technology. The first VCO has been designed for the 3.1-5 GHz UWB band. It exhibits a tuning range of 40% from 3.2 GHz to 4.8 GHz with a tuning voltage of 1.2 V. The measured phase noise at 1-MHz offset from a 4-GHz carrier is -114 dBc/Hz. The 4-GHz VCO current consumption is only 1.5 mA from a 1.2-V supply voltage. The second VCO represents an improved design intended for the 6-10 GHz frequency operating range. By exploiting differentially tuned varactors, the proposed 8-GHz VCO is able to guarantee a 45% tuning range and a phase noise at 1-MHz offset frequency lower than -102 dBc/Hz. The 8-GHz VCO draws 2.6 mA from a 1.2-V supply voltage.