Design formula for band-switching capacitor array in wide tuning range low-phase-noise LC-VCO

  • Authors:

  • Hwann-Kaeo Chiou;Hsien-Jui Chen;Hsien-Yuan Liao;Shuw-Guann Lin;Yin-Cheng Chang

  • Affiliations:

  • Department of Electrical Engineering, National Central University, No. 300, Jhongda Road, Jhongli City, Taoyuan County 32001, Taiwan;Department of Electrical Engineering, National Central University, No. 300, Jhongda Road, Jhongli City, Taoyuan County 32001, Taiwan;Department of Electrical Engineering, National Central University, No. 300, Jhongda Road, Jhongli City, Taoyuan County 32001, Taiwan;Department of Electrical Engineering, National Central University, No. 300, Jhongda Road, Jhongli City, Taoyuan County 32001, Taiwan;Department of Electrical Engineering, National Central University, No. 300, Jhongda Road, Jhongli City, Taoyuan County 32001, Taiwan

  • Venue:
  • Microelectronics Journal
  • Year:
  • 2008

Quantified Score

Hi-index 0.00

Visualization

Abstract

A low phase noise with wide tuning range complementary LC cross-coupled voltage control oscillator (LC-VCO) using 0.18@mm CMOS technology is presented. This paper proposes a design formula for the choice of the value of varactor (@DC"v"a"r) and band switch capacitor (C"s) for the binary-weighted band-switching LC tank which is convenient to determine the proper tuning constant for wideband, low-phase-noise operations. This general formula considers the ratio of frequency overlap (ov) and all the parasitic effects from band-switching capacitor array and transistors. The designed VCO using a 4-bit band-switching capacitor array demonstrates the operating frequencies from 4.166 to 5.537GHz with an equivalent tuning bandwidth of 28.26%. The measured tuning range of all sub-bands is well agreed with that of the post-layout simulation results. The measured phase noise is -123.1dBc/Hz at 1MHz offset in the 5.2GHz band. The calculated figure-of-merit (FoM) of this VCO was as high as -187dB. When considering the tuning bandwidth the designed VCO obtains a FoM-bandwidth product of 52.83, which is much better than previously published works.