LC-VCOs using spiral inductors with single- and dual-layer patterned floating shields: a comparative study

• Published in: Analog integrated circuits and signal processing 2017-06, Vol.91 (3), p.497-502
• Main Authors: Lim, Chee Cheow, Ramiah, Harikrishnan, Yin, Jun, Mak, Pui-In, Martins, Rui P.
• Format: Article
• Language: English
• Subjects: Circuits and Systems; CMOS; Electrical Engineering; Engineering; Inductors; Mixed Signal Letter; Noise levels; Power consumption; Signal,Image and Speech Processing
• ISSN: 0925-1030; 1573-1979
• DOI: 10.1007/s10470-017-0958-7

This letter studies and compares class-B VCOs using spiral inductors with the proposed dual-layer patterned floating shield (DL-PFS) and conventional single-layer patterned floating shield (SL-PFS). The proposed DL-PFS technique utilizes two lowest metal layers to effectively reduce the capacitive induced current to the substrate in an on-chip spiral inductor, thereby boosts its Q-factor by 40% when compared with the conventional SL-PFS approach. We fabricated, as a proof of concept, the class-B LC-VCOs using the DL-PFS and SL-PFS in 0.13 µm CMOS. Operating at 10 GHz, the VCO with the DL-PFS inductor measures a 3.6 dB phase noise (PN) improvement at the same power consumption of 2.12 mW. Specifically, the VCO with DL-PFS inductor is tunable from 9.3-to-10.1 GHz and measured PN at 10 GHz is −132.5 dBc/Hz at 10 MHz offset while consuming 2.12 mW at the lowest 0.6 V supply. The achieved figure-of-merit (187.4 dBc/Hz@1 MHz offset) compares favorably with the recent state-of-the-art.