70% Improvement in Q-factor of spiral inductor and its application in switched K-band VCO using 0.18 um CMOS technology

A novel technique for increasing the quality factor of the on-chip inductor is proposed in this paper. A high-quality factor shunt inductor is designed using the lower layers 5 and 3 in 0.18 um CMOS technology so the top layer is valid for other circuit components. The quality factor is improved by 70 % in the Ku, K and Ka-band compared to the single layer inductor. Furthermore, the proposed inductor has a compact area of about 0.0089 mm ² . This shunt inductor is used with a switched MOS varactor capacitors to construct a switched notch filter which has a sharp skirt characteristic and can be used in the VCO circuits. Using this switched shunt inductor resonator, the phase noise of the VCO is enhanced by 8 dB compared to single layer inductor resonator, moreover, the frequency tuning range is doubled. The VCO achieves a wide tuning range of 2.5 GHz, the first band from 18.8 to 19.97 GHz while the second band from 19.96 to 21.3 GHz. The phase noise at 1MHz is -112.4 and -112.5 dBc/Hz at the low and high band and this results FoM of-192.2 and -192.5 at 19.9 GHz and 21.3 GHz, respectively. The figure of merit considering the frequency tuning range (FoM ^T ) is -194.4 dBc/Hz and the active VCO core area is 0.039 mm ²