A novel concept for RFID tag localization using a tunable near-field focused circular-phase array antenna working at 5.8 GHz is presented. It serves as the reader antenna and focuses the power into a small region, in the tag vicinity. By scanning the focal spot along one axis and monitoring the differential scattered power by a tag, its position along the axis is easily computed with good accuracy. This simple localization scheme is well adapted for specific localization scheme, for example for objects placed over a conveyor belt.