FEM-based hybrid methods for the analysis of antennas on electrically large structures

In this paper, in-house developed 3D FEM/PO and FEM/UTD hybrid methods are presented. These techniques are shown to be accurate and efficient when they are applied to analyze antennas mounted on a large complex structure. The equivalent sources are obtained by solving an FEM problem over the antenna and its vicinity in conjunction with an absorbing boundary condition (ABC) and/or an impedance boundary condition (IBC). Based on the equivalent sources, the secondary radiation effects arising from mounting structures, e.g. helicopter bodies, are calculated using physical optics (PO) or uniform theory of diffraction (UTD). To show the capability of the hybrid techniques, an antenna on various mounting structures, such as a plate, a cylinder and a helicopter airframe, are investigated. The radiation patterns predicted by the hybrid methods are compared very well with FDTD or measurements showing the validity of the codes