Design of LC VCO for optimal figure of merit performance using CMODE

FOM (Figure Of Merit) is a novel performance yardstick of VCOs. Designing LC VCO circuit with desired specifications is highly time consuming and tedious job. In this paper CMODE (Combining Multi objective Optimization with Differential Evolution) optimization technique is used to design an LC VCO of optimal FOM with a target frequency of 2.5 GHz. The design parameters of LC VCO are obtained from the CMODE algorithm used in the MATLAB environment to optimize FOM. By using these parameters the LC VCO circuit is designed and synthesized in 90 nm CMOS technology in the Cadence Spectre Analog Design Environment(ADE). This VCO achieves phase noise of -119.7 dBc/Hz at 1 MHz offset while consuming 515 uW power with a tuning range of 10.53%. The FOM is obtained to be -190.26 dBc/Hz at 1 MHz offset. Hence the best performance index meeting the desired specifications is obtained in a single run of the algorithm.