  We report the first Vivaldi arrays monolithically fabricated exclusively
using commercial, low-cost, 3D metal printing (direct metal laser sintering).
Furthermore, we developed one of the first dual-polarized Vivaldi arrays on a
triangular lattice, and compare it to a square lattice array. The triangular
lattice is attractive because it has a 15.5% larger cell size compared to the
square lattice and can be more naturally truncated into a wide range of
aperture shapes such as a rectangle, hexagon, or triangle. Both arrays operate
at 3-20 GHz and scan angles out to 60 degree from normal. The fabrication
process is significantly simplified compared to previously published Vivaldi
arrays since the antenna is ready for use directly after the standard printing
process is complete. This rapid manufacturing is further expedited by printing
the 'Sub-Miniature Push-on, Micro' (SMPM) connectors directly onto the
radiating elements, which simplifies assembly and reduces cost compared to
utilizing discrete RF connectors. The arrays have a modular design that allow
for combining multiple sub-arrays together for arbitrarily increasing the
aperture size. Simulations and measurement show that our arrays have similar
performance as previously published Vivaldi arrays, but with simpler
fabrication.
