Aerospace Vehicle Geometry Effects On Omni-Directional Antenna Radiation Patterns
By David Farr and Ron Sisco
Ground plane geometry plays a major roll in determining antenna radiation pattern characteristics, especially for omni-directional radiators. The ground plane for antennas utilized on many aerospace vehicles is the vehicle itself which most often cannot be changed to accommodate the electrical needs of an antenna. The resultant ground plane may be, therefore, far from optimal.
Further, amplitude pattern characteristics are critical for any application. In recent years, with PSK modulation and similar techniques becoming more prevalent in missile applications as well as certain GPS determination schemes, phase pattern characteristics are also now of equal importance.
Utilizing Finite Difference Time Domain (FDTD) techniques, this paper considers and illustrates the effects that vehicle geometry has on radiation pattern characteristics (both amplitude and phase) for omni-spherical and hemi-spherical antennas mounted on cylindrical bodies with parasitic structures. The effect on the phase center and apparent phase center for both individual elements and multi-element arrays, such as Wraparound™ antennas, is also considered and explained. Finally, this paper outlines good engineering practices when utilizing omni-directional antennas in aerospace applications.