Efficient implementation of the Cauchy method for automated CAD-model construction

An efficient and stable implementation of the multidimensional Cauchy method for creating high quality multivariate models of microwave circuits from electromagnetic (EM) simulation data is presented in this paper. The algorithm uses the total least squares method to solve the ill-conditioned interpolation problem and automatically determines the model order and distribution of support points in the parameter space in such a manner that instabilities are prevented. Numerical tests show that the method requires fewer support points to achieve similar accuracy as the rational function models published previously. The utility and accuracy of the technique is demonstrated on a filter design example involving three- and fivedimensional models.