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Published June 2001 | public
Journal Article Open

Concepts and methods in optimization of integrated LC VCOs


Underlying physical mechanisms controlling the noise properties of oscillators are studied. This treatment shows the importance of inductance selection for oscillator noise optimization. A design strategy centered around an inductance selection scheme is executed using a practical graphical optimization method to optimize phase noise subject to design constraints such as power dissipation, tank amplitude, tuning range, startup condition, and diameters of spiral inductors. The optimization technique is demonstrated through a design example, leading to a 2.4-GHz fully integrated, LC voltage-controlled oscillator (VCO) implemented using 0.35-μm MOS transistors. The measured phase-noise values are -121, -117, and -115 dBc/Hz at 600-kHz offset from 1.91, 2.03, and 2.60-GHz carriers, respectively. The VCO dissipates 4 mA from a 2.5-V supply voltage. The inversion mode MOSCAP tuning is used to achieve 26% of tuning range. Two figures of merit for performance comparison of various oscillators are introduced and used to compare this work to previously reported results.

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"© 2001 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE." Manuscript received June 21, 2000; revised January 2, 2001. This work was supported in part by a fellowship from IBM Corporation. The authors would like to thank B. Analui and C. White of the California Institute of Technology for valuable discussions and suggestions on the theoretical aspects of this paper. They would also like to thank Conexant Systems for fabrication of the VCO, and particularly B. Bhattacharyya, F. In'tveld, and R. Magoon for consistent help and support. They would like to appreciate the help with the measurement provided by I. Aoki, H. Hashemi and H. Wu of California Institute of Technology and P. Vo of Massachusetts Institute of Technology.


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August 21, 2023
August 21, 2023