In this paper, a single elliptical patch antenna is proposed to generate double-deflection orbital angular momentum (OAM) vortex beams. The physical mechanism of an equivalent uniform elliptical array (UEA) is constructed and analyzed by using the theory of characteristic modes. The elliptical patch antenna can be fed with a 3dB directional coupler to generate the double-deflection vortex beams with single OAM mode or mixed OAM modes. The simulation and measurement results verify that the proposed single elliptical patch antenna is a simple, miniaturized, and multifunctional generator for OAM vortex beams.