Design of a near-field focused reflectarray antenna for RFID reader applications

An implementation of planar reflectarray antenna is presented in this paper to produce radiating fields that are focused in the near-zone of the array aperture. This work is motivated by the increasing interest in the applications of RFID [1,2,4], vital life-detection systems [3] and noncontact microwave detection system[3], where the objects under detection may locate in the near zone of the antenna. In this case, a focused field radiation in the target area helps to reduce the interferences resulted from the scattering due to the presence of neighborhood structures, and save the system power. In the past, most works employed phased array antennas [3,4] to produce near-field focused beams, which suffer from complicated beam-forming networks and higher power loss dissipated inside the circuits. The reflectarray antenna tends to improve these shortcomings because the sophisticated beam-forming RF circuits can be omitted. As a demonstration example, a prototype at 2.4GHz is realized for RFID reader applications, which is characterized via numerical and experimental measurements. © 2010 IEEE.