Multiple-GHz ring and LC VCOs in 0.18 /spl mu/m CMOS

This work presents a comparison of the ring and LC VCOs to be used in multiple-GHz communication systems. Multiple-GHz CMOS ring and LC VCOs are implemented on the same chip and tested under similar conditions for a fair comparison. The prototype chip was fabricated using a 0.18 /spl mu/m CMOS process and includes three-stage ring and symmetrical LC VCOs aimed for this comparison. The ring VCO dissipates 50 mW at an oscillation frequency of 6.1 GHz, and exhibits -97.5 dBc/Hz phase noise (@ 1 MHz). The LC VCO has a maximum frequency of 3 GHz with a 46% tuning range and has -111.4dBc/Hz phase noise (@1 MHz) while using 3.6 mW.

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