Aplicación de la teoría del equilibrio de potencias en entornos reverberantes para el cálculo de la efectividad de apantallamiento

  1. FERNÁNDEZ ROMERO, SERGIO
Supervised by:
  1. Iván González Diego Director

Defence university: Universidad de Alcalá

Fecha de defensa: 16 June 2016

Committee:
  1. Francisco Manuel Sáez de Adana Herrero Chair
  2. Óscar Gutiérrez Blanco Secretary
  3. Antonio Jurado-Lucena Committee member
  4. David Escot Bocanegra Committee member
  5. Fernando Rivas Peña Committee member
Department:
  1. Ciencias de la Computación

Type: Thesis

Abstract

This thesis deals with the problem of electromagnetic (EM) shielding effectiveness (SE) estimation of a structure, fuselage or equipment case. SE means the ratio of the signal received (from a transmitter) without the shield, to the signal received inside the shield, and it is a main design parameter of aircrafts, vehicles, ships and satellites. In this study the problem is solved by a combination of methods based on the power balance theory present in reverberant environments. Therefore, the technique described in this thesis could be used in multipath environments where the EM signals could come from any direction and with any polarization. The application frequency range will depend on the object dimensions in comparison with the signal wavelength. Traditionally, an environment is reverberant when it is electrically large, that means, when it supports several modes at the lowest frequency of interest, and, for that reason, the signal electrical wavelength is much smaller than the object or cavity dimensions. The SE measurement procedure and the validation method of reverberation chambers have been deeply analyzed using the National Institute of Aerospace Technique (INTA) facilities. Thus, every theoretical concept, model or formalism implemented during this study has could be compared with experimental results. The method developed for SE prediction has been validated with real test case measurements using the nested reverberation chambers technique. The main parameters of the power balance theory in reverberant cavities, such as the energy leakage and dissipation mechanisms, the cavity quality factor, the average power density or the maximum electrical field level, have been exhaustively described. In addition, the relationships between these parameters have been analyzed in a very wide frequency range, which permit us to draw conclusions about how each parameter affects the final SE result at different frequency bands. Furthermore, the thesis makes progress in the important issue of calculating the average transmission cross section of an arbitrary shape aperture, which is a fundamental parameter for an accurate SE prediction of a complex and real structure. For that purpose, a methodology based on the image theory has been implemented in order to solve the dual problem of an aperture in a planar conducting screen of infinite extent, using the EM simulation code MONURBS of Alcala de Henares University. The final solution is the combination of a simplified microwave propagation model with the updated and more accurate formulation for energy leakage and dissipation mechanisms. The method is able to calculate the exchanges of EM energy between coupled spaces inreverberant environments. The theoretical models have been developed and implemented from a practical viewpoint in order to solve EM compatibility problems such as the interoperability between equipment which are installed at same cavity by means of the calculation of the maximum electrical field level due to an external or internal interference signal, the microwave signal propagation in a reverberant environment, or the accurate and reliable SE estimation of a structure, fuselage or equipment case