A conveyor system for processing items on which radio frequency identification tags are disposed includes a frame and a conveyor that is disposed moveably on the frame and that conveys items through a path of travel, each item having at least one respective radio frequency identification tag disposed thereon. An antenna is disposed on the frame with respect to the path of travel so that the antenna radiates radio frequency signals into a first area through which the items pass. The antenna comprises a substrate and a plurality of patch elements disposed on the substrate in respective positions that are sequential with respect to a direction transverse to the path of travel. An electric current at each patch element drives radiation of the radio frequency signals and defines a rotating electric current pattern. Respective rotational directions of the electric current pattern at two patch elements are opposite to each other. A radio frequency transmitter drives the antenna to admit the radio frequency signals into the first area.