Analytical approaches to calculating the parasitic coupling between packages and microwave circuits

The aim of this contribution is the derivation of a simple mathematical model to describe the electromagnetic interaction between the microstrip structure and the resonant modes of the metal shielding, in which the structure mentioned is built in either for avoiding the radiation or for suppressing electric coupling between adjacent circuit. By the help of this model based on the electromagnetic field equations equivalent electric circuits are extracted to consider the interaction between electric and magnetic surface currents and cavity modes in a commercially available circuit simulator. Several examples and their results show the applicability of the technique proposed.