1. THEORETISCHE ELEKTROTECHNIK Field Coupling into the A380 Aircraft Introduction The field equivalence principle Special consideration for slots Demonstration by means of a small example Numerical model of the A380 aircraft with back doors Fully discretized model, EFIE problem Coupling-in results based on the application of equivalent currents of magnetic type Conclusion Dietmar Leugner, H.-D. Brüns leugner@tu-harburg.de bruens@tu-harburg.de

2. THEORETISCHE ELEKTROTECHNIK Introduction Fully discretized MoM model 10219 unkowns Typical element dimensions from 2 cm² to 2500 cm²

3. THEORETISCHE ELEKTROTECHNIK Introduction Loop antenna, HF range Numerically critical because of very low radiation resistance Stable solution only with inserted wire grid Validation: power budget

4. THEORETISCHE ELEKTROTECHNIK Typcal results for the HF range (A380) Radiation diagram at 30 MHz Loop antenna input impedance

5. THEORETISCHE ELEKTROTECHNIK Huygens principle in electromagnetics

6. THEORETISCHE ELEKTROTECHNIK Transition slot / conducting part (problem of end charges) Possible solution: overlap and inclusion of into the system matrix as impressed current (to be done)

7. THEORETISCHE ELEKTROTECHNIK Illuminated sphere at 300 MHz Field vectors in log. scaleGeometry

8. THEORETISCHE ELEKTROTECHNIK Coupled-in E field

9. THEORETISCHE ELEKTROTECHNIK Discretization of back door (1) Door: 0.9m x 1.9m Slot width: 1 cm Surface currents at 30 MHz

10. THEORETISCHE ELEKTROTECHNIK Discretization of back door (2) Details of slot discretization

11. THEORETISCHE ELEKTROTECHNIK Failure of classical EFIE (1MHz, 0°) Closed ModelModel with door Cross section of empty aircraft

12. THEORETISCHE ELEKTROTECHNIK E field at 1 MHz generated by magnetic currents (phase 0°) Vectors are plotted in log. scale Cross section of empty aircraft

13. THEORETISCHE ELEKTROTECHNIK E field caused by magnetic slot currents Maximum magnitude of E in cross section of empty aircraft Aircraft structure completely neglected 1 MHz 30 MHz

14. THEORETISCHE ELEKTROTECHNIK Conclusion Small slots in large conducting bodies cannot be treated sufficiently by a MoM-EFIE approach Equivalent currents in slots and apertures acting as excitation sources provide an alternative Special treatment at the intersecting line of Huygens surfaces and MoM surfaces is necessary Application of purely magnetic slot currents give a first order solution The method works only if completely decoupled spaces are considered