A robust 43-GHz VCO in CMOS for OC-768 SONET applications

In this paper, we present a 43-GHz LC-VCO in 0.13-μm CMOS for use in SONET OC-768 optical networks. A tuned output buffer is used to provide 1.3 V_p-p (single-ended) into a 90-fF capacitive load as is required when the VCO is used in typical clock and data recovery (CDR) circuits. Phase noise is -90 dBc/Hz at a 1-MHz offset from the carrier; this meets SONET jitter specifications. The design has a tune range of 4.2%. The VCO, including output buffers, consumes 14 mA from a 1-V supply and occupies 0.06 mm² of die area. Modern CMOS process characteristics and the high center frequency of this design mean that the tank loss is not dominated by the integrated inductor, but rather by the tank capacitance. An area-efficient inductor design that does not require any optimization is used.