| In this thesis, recent increases in computational power are exploited to apply the technique of "high resolution spectral analysis" with the Numerical Electromagnetics Code to obtain a complete diagnosis of HF antenna-to-antenna coupling and antenna-to-airframe coupling on aircraft. The HF antenna installations on two large aircraft, namely, the EC-130/TACAMO and the CL-600/CHALLENGER, are studied. The unusually complex installation of five HF wire antennas on the EC-130 represents a unique challenge. An existing EC-130 wire-grid model is upgraded by removing all modelling errors, and refining the wire-grids representing the wings and stabilizers of the aircraft. The revised model is used to study the inter-antenna coupling and the antenna-to-airframe coupling modes on the EC-130. Results are presented which describe all the coupling modes that have been identified and their impact on radiation patterns and likely operational consequences. Antenna resonant lengths and the loading conditions for passive antennas are found to have significant influence on the inter-antenna coupling modes. The modelling of the notch HF antenna on the CL-600 aircraft reveals the radiation characteristics of this antenna, especially the antenna-to-airframe coupling for the first time. Three current paths are identified on the EC-130's airframe and two on the CL-600's. The information sets provided by this thesis are very difficult, if not impossible to obtain by any scale-model or full-scale measurement programs. |
