Concepts and methods in optimization of integrated LC VCOs

Underlying physical mechanisms controlling the noise properties of oscillat ors are studied, This treatment shows the importance of inductance selectio n for oscillator noise optimization. A design strategy centered around an i nductance selection scheme is executed using a practical graphical optimiza tion method to optimize phase noise subject to design constraints such as p ower dissipation, tank amplitude, tuning range, startup condition, and diam eters of spiral inductors, The optimization technique is demonstrated throu gh a design example, leading to a 2,4-GHz fully integrated, LC voltage-cont rolled oscillator (VCO) implemented using 0.35-mum MOS transistors. The mea sured phase-noise values are - 121, - 117, and - 115 dBc/Hz at 600-kHz offs et 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 compar ison of various oscillators are introduced and used to compare this work to previously reported results.