Modeling Of The Back-door Coupling Behavior Using Electromagnetic Topology

In the increasingly complex electromagnetic environment, modern electronic equipment inevitably will be affected by the external electromagnetic fields. External electromagnetic field coupling into the cabin through the external cables of equipment and the non-ideal shielding shell, then coupling with the equipment in the cabin is called the back-door coupling. Among this, the coupling through the non-ideal shielding shell mainly includes the coupling by the discontinuous place such as doors and Windows, apertures, slots on the shielding shell, the transmission caused by the bad conductivity of the shell material and the shielding failure caused by the imperfect grounding in low frequency. The back-door coupling widely exists in electronic equipments, and the field produced by the back-door coupling distributes in the whole system, and will form complex electromagnetic field distribution in the cavity. Therefore, it has important theoretical significance and research value to establish a quick and efficient method to analysis the back door coupling problems of the system.The cable coupling and the aperture coupling problems are researched as follows:1. The method of moment(MoM)based on dyadic green’s function of the cavity is used to analyse the electromagnetic coupling problem of slotted cavity illuminated by the external plane wave. First according to the equivalence principle, the aperture on the rectangular cavity is equivalent to an equivalent magnetic current, then the coupling field inside the cavity can be expressed by the radiation field of the equivalent magnetic current. The equivalent current on the aperture is determined by the triangular function and pulse function, and then the coupling field in the cavity can be calculated by the dyadic green’s function of the rectangular cavity. Afterwards, the aperture coupling problem of the thick wall cavity is analysed by the same method, and the coupling field in the cavity is calculated by introducing two equivalent magnetic current on both inside and outside of the aperture.2. Relative to the superimposed calculating of the coupling field inside the multi-slot cavity, the iterative method is used to modify the calculation of the equivalent magnetic current on the aperture and the coupling field in the cavity. The calculation results show that whether to modify iteration method has great influence to the calculation of coupling field, therefore the mutual coupling between multiple apertures can’t be ignored optionally. Then the coupling field in the multi-slot cavity is modified by the iterative method, and the accuracy of the iterative method is demonstrated by the calculation of the coupling field in the thick wall cavity.3. The joint modeling of the cable coupling and aperture coupling by the electromagnetic topology is studied. First the electromagnetic coupling problem of the transmission line in the slotted cavity is analysed. The coupling field in the cavity is calculated by the MoM based on dyadic green’s function of the cavity, and then the coupling field is used as excitation source, the BLT equation is used to analyse the current response of the transmission line load. Second and the load responses of the penetrating cable and the penetrating shielding cable are calculated. The electromagnetic coupling problem of the slotted cavity in two cases that the penetrating cable and the penetrating shielding cable coupling is analysed, and the the current response of the transmission line load is calculated.