This letter describes the use of slot array equivalence of single square-shaped patch antenna for the generation of orbital angular momentum (OAM) wave. Single patch antenna with phase-shifted power divider network behaves as 4-element slot array and can generate +1 or -1 OAM mode. Design, analysis, and measurement of the proposed novel OAM antenna that resonates at frequency 5.5 GHz are presented. © 2002-2011 IEEE.