US Patent 7642917 Antenna arrangement

A network of antennas for contactless reading or writing of RFID tags in a detection volume, including three or four flat, independent antennas sequentially connected to a single reader by a switch, wherein planes of the antennas pass through a reading/writing/detection volume centered in the detection volume, for every pair of antennas, an intersection of their planes is included in the optimal reading/writing volume, and the antennas are arranged so that any direction in the optimal reading/writing volume forms an angle of about 45° or less with at least one of the planes of the antennas.