Electromagnetic optimisation of microwave filters using an efficient model parameter extraction technique

An efficient model parameter extraction (PE) approach and a linear calibration method in the framework of the space mapping technique for electromagnetic (EM) optimisation of microwave filters is presented. A correct formulation for the PE is proposed that allows the use of simple approximate models. In this technique, knowledge of the reflection function of the EM model is efficiently used to iteratively calibrate an existing approximate model of the filter. The use of a reflection function in this approach eliminates the need for the direct modelling of all the complex unknown EM effects in the microwave filter during the PE step. A number of guidelines are also presented to improve the uniqueness of the solution. The validity of the method is verified by the design and optimisation of two filters. In all cases, very good convergence and robustness are achieved with a minimum number of EM simulations.