Effective optimization of microstrip transformer using FDTD simulation and cascade connection of scattering matrices

In this paper, a new method which combines FDTD simulation with cascade connection of sub-circuit general scattering matrices (GSMs) is presented for optimizing circuit containing irregular structure. This method construct scattering matrix of global structure effectively and efficiently by using FDTD simulation extracted GSMs of sub-circuits instead of compact element model, which is difficult to be extracted. By comparing the S₁₁ of an optimized three-section microstrip transformer with the results from other methods, the accuracy of this method has been validated. The accuracy as well as the efficiency of this method makes extremely time-consuming direct electromagnetic optimization can also be avoided. Finally, the effectiveness of this method is further demonstrated by the optimization of a meandered UWB transformer.