Measurement of Seam Impedances of Tactical Shelters for Threat Level NEMP Simulation

These cases effectively can be reduced to two extremes, resistive seams and inductive slots. The excitation of these seams and slots occurs via the externally incident fields. Modeling of shelter shielding effectiveness and internal fields can then be viewed as a two stage process. First external incident fields and current densities are calculated for the 3D shelter and incident field waveform. Then the assumption for internal numerical modeling is that the excitation at any point along a seam is directly related to the current across the seam in the direction it would flow on a continuous sheet. The constant of proportionality being the seam impedance. Currents flowing horizontally along the seam are neglected.