An Automatic Synthesis Methodology for Synthesis of CMOS Ring VCOs

L. Wang and A. Nunez (USA)


Synthesis, VCO, Phase Noise


In general, the design process of analog and mixed-signal circuits is considered more challenging than designing dig ital circuits. Complex performance metrics and design con strains have to be taken into account while synthesizing analog and mixed-signal circuits. Moreover, the nonlin earity of the circuits and presence of noise also make the designing process of analog circuits more complex than their digital counterparts. On the other hand, while Com puter Automated Design (CAD) tools for digital circuits have reached high level of maturity; CAD tools for analog circuits are still in their early stage of development. There fore, automated synthesis tools for analog and mixed-signal circuits are highly necessitated. In particular, developing synthesis tools for RF circuits are even more challenging due to the extremely high frequency of operation and the effect of noise. In this paper, we present a methodology for automatically synthesizing CMOS ring Voltage Controlled Oscillators(VCOs). In particular, we take a four stage dif ferential ring VCO as a design example. The objective is to automatically size the devices while minimizing the phase noise effect produced by digital switching circuits. A Ge netic Algorithm is used in the synthesis process to find near optimal solutions in reasonable time.

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