Conformal Antenna Array Design Using Aperture Synthesis and On-Platform Modeling

Conformal antenna arrays have long represented an attractive solution to challenges imposed by an electromagnetic aperture on an aerospace platform. This allows designers to trade between array positioning and geometry, and avoids the significant aerodynamic drag of a planar array. This is hampered by the expense of the design and computational modelling required to ensure that a conformal array will meet its performance requirements. The proposed approach uses raycasting techniques to predict the rectilinear projection of a conformal aperture onto the farfield to calculate the maximum achievable beam coverage (aperture maximum directivity envelope). In order to compare aperture projection with the performance of the modelled arrays in a consistent manner, the steering efficiency (SE), which is the fraction of the farfield steerable to within 3dB of the maximum directivity, was calculated for the aperture, stacked patch, and conical monopole elements. The stacked patch elements demonstrated a SE of 18% over the steering plane compared with 40% for the arbitrary directional elements, and the optimum of 38% for the aperture overall. The Conical monopole elements achieved a SE of 8%, compared to 20% for the measured elements, and 33% achieved with arbitrary omnidirectional elements. These results demonstrate that, for both omnidirectional and directional elements, the aperture projection method offers a compelling tool for conformal array design, which is consistent with the achieved array performance for the stacked patch and conical monopole elements.