Wide-Band, Multi-Beam, High Isolation, Multi-Mode Radial Vivaldi Antenna for Direction Finding

This paper presents the design and experimental verification of a low-cost, wideband, multi-mode antenna intended as a reflector feed for direction finding applications. The design consists of dual concentric radial arrays of interleaved Vivaldi elements, with a tilt and orientation optimized for use in an Axially Displaced Ellipse (ADE) dual-reflector antenna system. The central main array provides four wide-band, high efficiency beams (sum and difference right and left-handed polarizations), whereas the outer array provides an isolated, second set of independent beams. An advantage of the radial array is that it can be optimized to achieve a wide range of near-constant directivity and beamwidth values over a wide bandwidth, permitting its use as a feed to a reflector system where a wide range of F/D values can be accommodated. The linearly polarized Vivaldi elements are optimized to cover Ka-band, and they provide a very high frontend efficiency. The optimized feed is then integrated into a 70cm ADE deployable mesh reflector, where good agreement between modeled to measured primary feed and secondary patterns are reported.