Integration of a 15-Element, VHF Bow-Tie Antenna Array into an Aerodynamic Fairing on a NASA P-3 Aircraft

Abstract

Radar depth sounding and imaging of deep glaciers in Antarctica and Greenland yield results for better understanding a changing climate and improving glacier modeling. A 15-element, airborne antenna array with an increased bandwidth was developed to advance the potential for radar measurements as part of NASA Operation IceBridge (OIB). These antennas were a planar, modified bow-tie antenna design. The antennas were fed using a custom ferrite, transmission line transformer balun capable of operating with high power signals and across a wide frequency range. An aerodynamic fairing enclosed the antennas and was required to achieve structural performance, but the structural design contradicted and imposed limitations on the antenna performance. Dielectric and parasitic conductors loaded the antenna, limited bandwidth and decreased return loss. Detailed analysis through full-wave simulations and measurements identified the structural effects on the antenna. Proper compensation techniques regarding antenna design and adaption of the surrounding structure improved the antenna performance. The original structure design rendered the antenna incapable of producing a return loss greater than 10 dB, and the final structure and antenna design achieved a bandwidth of 41% with a center frequency of 195 MHz in reference to a 10 dB return loss. The design also considered the mutual coupling between array elements, and this was reduced using unique modifications to the antenna ends.