A High Area Utilization Cross-Symmetric Main&Tail Inductor Applicable to Enhanced FoM LC-VCO

A cross-symmetric main&tail inductor with high area utilization is proposed originally. The designed inductor structure has advantages in both lower phase noise and area consumption when applied to LC-VCO. The inductor is composed of a pair of cross-symmetric octagonal main inductor and tail inductor. The tail inductor is used as noise filter, which can effectively suppress phase noise. Due to its cross-symmetric structural characteristics, the tail inductor will not generate obvious magnetic coupling interference with the main inductor. The proposed cross-symmetric main&tail inductor improves the area utilization by using the redundant area of the octagonal main inductor while optimizing the LC-VCO phase noise, without the obvious Q value changes of main inductor. Compared with the conventional inductor, the unit area utilization rate is increased from 82.84% to 87.13%. When the VCO output frequency is 2.669 GHz, phase noise \u2013is achieved as -129.5 dBc\/Hz over LC-VCO based on the cross-symmetric main&tail inductor, which is lower than -120.4 dBc\/Hz of the conventional inductor. The output frequency range of the LC-VCO is 2.295 GHz ~ 3.080 GHz, and FOM of LC-VCO is 193.8 dBc\/Hz.