Space-Mapping Based Automatic Design of SIW-Based Directional Coupler With Arbitrary Power Ratio

In this paper, an automatic design method allowing efficient design of substrate integrated waveguide (SIW) directional coupler with any given power ratio between 3 dB and 20 dB has been proposed. Due to excessive electromagnetic (EM) simulation time of SIW structure, the space mapping technique is exploited to accelerate the design process. An EM-simulation based dielectric rectangular waveguide (RWG) model acts as the surrogate to reduce the simulation time. A two-stage optimization scheme including a differential evolution (DE) algorithm and a Nelder-Mead (NM) simplex algorithm is used to obtain initial surrogate design. Suitable objective functions are proposed for surrogate optimization and for parameter extraction procedure of space mapping technique. Our proposed method is verified with an X band SIW directional coupler with four different power ratio designs, which are 3 dB, 10 dB, 15 dB and 20 dB. The experimental results confirm the effectiveness and efficiency of the method.