TRANSIENT ELECTROMAGNETIC FIELD COUPLING TO A METALLIC ENCLOSURE USING N-PORT THEORY

THERE IS A NEED TO UNDERSTAND AND PREDICT THE COUPLING OF TRANSIENT ELECTROMAGNETIC FIELDS TO METALLIC ENCLOSURES. THIS ALLOWS US TO SAFEGUARD SENSITIVE ELECTRONIC EQUIPMENT FROM THE EFFECTS OF LARGE ELECTROMAGNETIC PULSES, WHOSE ORIGINS MAY BE NUCLEAR EXPLOSIONS PULSED MICROWAVES OR LIGHTNING. THE PROBLEM THAT WE PROPOSE TO INVESTIGATE INVOLVES THE COUPLING OF ELECTROMAGNETIC FIELDS TO A THIN WIRE THAT IS LOCATED INSIDE A METALLIC ENCLOSURE FORMED BY A THINWALLED BODY OF RECTANGULAR SHAPE. WE PROPOSE TO SOLVE THE PROBLEM BY RESORTING TO N-PORT THEORY, WHICH IS FAMILIAR TO ELECTRICAL ENGINEERS.IN THIS APPROACH THE STRUCTURE IS ISOLATED FROM ITS ENVIRONMENT AND IS REPLACED BY ITS EQUIVALENT IMMITTANCE MATRIX, WHICH WILL BE COMPUTED USING FINITE ELEMENTS. THE IMMITTANCE MATRIX FOR THE EXTERNAL WORLD WILL BE COMPUTED BY A BOUNDARY INTEGRAL EQUATION. TWO METHODS FOR OBTAINING THE TRANSIENT RESPONSE OF THE COUPLED SYSTEMS WILL BE STUDIED: (A) NUMERICAL INVERSION OF FOURIER OR LAPLACE TRANSFORMS, OR (B) DIRECT TIME-STEPPING.