Performance comparison of two wide-tuning-range 13-GHz CMOS LC-VCOs

In this paper, two wide-tuning-range CMOS LC voltage-controlled oscillator (LC-VCO) topologies are studied and their performance is compared. Proof-of-concept prototypes of each topology are implemented in a 90-nm CMOS technology. The first design incorporates multiple VCO cores with overlapping tuning ranges and has an extra buffer compared to the second design. The second design uses one VCO core and a switched-capacitor array. Based on measurement results they achieve a wide tuning range of 28.20% and 24.42% and dissipate 5.07 mW and 5.10 mW from a 1.2-V supply, respectively. Furthermore, the addition of the source-follower buffer to the first structure reduces the loading effect on the VCO core and thus facilitates higher oscillation frequency.