A transformer-based X-band CMOS quadrature VCO without current sources

Sangsoo Ko, Taeksang Song, Euisik Yoon, Songcheol Hong

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


An X-band quadrature voltage-controlled oscillator (QVCO) is fabricated using 0.18-μm CMOS technology. The high impedance of a current source allows a highly effective Q-factor of the LC tank [1]. The proposed X-band CMOS quadrature VCO has low phase noise of -117.5 dB/Hz at 1-MHz offset frequency, despite the absence of a current source, because a transformer can separate the gate bias of series-connected transistors from cross-coupled RF feedback. The VCO can operate under 1.8 V of power supply. The figure of merit (FOM) is 187.5 dB at a 10.3-GHz oscillation frequency, which is the best value among X-band VCOs.

Original languageEnglish
Pages (from-to)305-307
Number of pages3
JournalMicrowave and Optical Technology Letters
Issue number4
Publication statusPublished - 2005 Feb 20

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Electrical and Electronic Engineering


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