The radiation characteristics of ellipsoidal reflector antennas in the near zone of antenna aperture are investigated using Physical Optics (PO) approximations. This antenna has potential applications in the near-field communications because its radiation focuses in the near zone. Analytical formulations to predict the radiation efficiency and exhibit field phenomena are developed. Its applications as a RFID reader antenna at 2.4 GHz are demonstrated by numerical simulations and measurements over a realistic implementation of offset reflector fed by a microstrip patch antenna. Both numerical and experimental studies are performed to validate this antenna design.