The complementary strip-slot radiating element and its applications are reviewed. The element is a modified version of the conventional microstrip-fed slot that presents very broad
matching. Its inherent lattice equivalent circuit, its use as unit-cell of artificial transmission lines and its utility as radiating element are described. Promising experimental results for prototypes of a phased uniform array, a sequentially-rotated ring array
and a log-periodic array based on the element for microwave frequencies are included.