An UWB Hemispherical Vivaldi Array

We report the first conformal ultrawideband (UWB) array on a doubly curved surface for wide-angle electronic scanning. We use a quadrilateral mesh as the basis for systematically arraying UWB radiators on arbitrary surfaces. A prototype consisting of a 52-element, dual-polarized Vivaldi array arranged over a 181 mm diameter hemisphere is developed. The antennas and SMP connectors are 3-D printed out of titanium to allow for simple fabrication and assembly. We derive the theoretical gain of a hemispherical array based on the antenna size and number of elements. The measured realized gain of the prototype array is within 2 dB of the theoretical value from 2 to 18 GHz and scan angles out to 120° from the
${z}$
-axis. This field of view is twice that of a planar array with the same diameter in agreement with theory. This work provides a baseline performance for larger conformal arrays that have more uniform meshes. Furthermore, the basic concept can be extended to other UWB radiating elements.