Abstract

Carbon-fiber composite (CFC) materials, due to their desirable mechanical and thermal properties, have been progressively replacing metallic structures in commercial aircraft. The electrical and electromagnetic properties of these materials, including their impact on antenna performance, have been the subject of research since their introduction in aeronautical applications. It has been shown that carbon-fibre composites form effective ground planes for antennas and the antenna performance at VHF and UHF frequencies is not essentially different from metal ground planes.

However, CFC materials are prone to cracking when used in aeronautical applications. Additionally, when CFC materials are used in aircraft, joints are inevitable. These joints can be between CFC panels or CFC and metal panels in partially composite aircraft. These cracks and joints alter the current density on the airframe surface. This alteration of current density impacts the antenna radiation performance.

In this thesis, the radiation of antennas on carbon-fibre composite aircraft is studied. The airframe scattering mechanism is analyzed and guidelines for developing simplified models of aircraft geometry for antenna analyses are provided. The utility of the leading numerical techniques suitable for analysis of aircraft antennas at VHF and UHF frequencies is studied and benchmark data on the computational resources required is provided. The impact of cracks, seams and panel joints on the antenna radiation is also studied.