A method for direct calculation of critical excitations in arbitrary two port systems

The inverse modified nodal analysis (IMNA) has been applied with success in past investigations to several EMC problems. Here a signal is defined at the system output, and the input signal necessary to produce this output signal is calculated. This way excitation signals complying with the EMC limits can be found. The method overcomes problems of typically used optimization algorithms. With a single simulation run a solution can be found. In the past the method was applied to simple passive coupling networks consisting of lumped elements. This paper deals with a significant extension. Scattering parameters matrices of two port systems have been integrated. The method, the needed date conversion algorithms and approximation procedures necessary to use S-parameter data sets in IMNA and MNA are shown. The method is applied to several test cases.