Pareto optimal design of ultra-wideband 3-dB directional coupler using generalized differential evolution algorithm

Broadband microwave directional couplers are a very important category of passive microwave circuits. A novel method for the design of the tapering shape of broadside-coupled directional couplers is presented. The design method is based on generalized differential evolution (GDE3), which is a multi-objective extension of differential evolution. Three objectives are considered in this design: the return loss, coupling and isolation. The achieved Pareto front presents optimal possible trade-offs among the three objectives. The results indicate the advantages of this approach and the applicability of this design method.