Method of TDIE for combination problems of electromagnetic field and circuit

Solving methods based on TDIE (time-domain integral equation) for field-circuit combination problems are studied, the main idea of which is “coupling current”. Circuit part and electromagnetic structure in the area are combined by the coupling current at the junction. Traditional current continuity equation is consummated by that result. Then TDIE and the simulation method for circuit-MNA (modified nodal analysis) is combined, and general KVL (Kirchoff´s voltage law) is used to connect electric potential both at node of the circuit and at port of the electromagnetic structure. When this method is applied to solve hybrid problems of field and circuit, port model is no longer needed, and the coupling equations are solved directly. Finally, an example of transmission line is presented to testify validity of the method.