Phase noise optimization of integrated ring voltage-controlled oscillators by metaheuristics

Real applications of integrated circuits (ICs) require satisfying strong target specifications, which challenge is focused on trading off specifications that are in conflict, i.e. improving one characteristic can degrade other(s). This is the case of designing a ring voltage-controlled oscillator (VCO) using IC nanometer technology, with the goal to accomplish a wide frequency and voltage-control tuning range, low silicon area, among others. For real ring VCO applications, an open challenge is guaranteeing minimum phase noise, which is in conflict with main dynamical characteristics when maximizing frequency range, voltage-control range, gain, and minimizing silicon area and power consumption. To cope with these design problems, we show the minimization of the phase noise of a ring VCO applying two metaheuristics, namely: Differential evolution (DE) and particle swarm optimization (PSO), which have the ability to handle constraints that are relevant to generate optimal solutions. The results show that both DE and PSO are effective in the optimization of the ring VCO. The comparison of the best phase noise results obtained with DE (-129.01 dBc/Hz @1MHz) and PSO (-124.67 dBc/Hz @1MHz) algorithms, not only show that the DE solution being lower by 4.34 dBc/Hz with respect to the best solution provided by PSO, but also it is quite satisfactory in contrast to similar works. Finally, the optimized ring VCO characteristics are compared herein with several designs considering a figure of merit, gain, frequency and voltage-control ranges.