An antenna array for detecting a coded radio frequency identification (RFID) tag signal generated by a tag during passage of the tag through a detection volume, or portal. The array comprises at least first and second antennas disposed at different positions around the periphery of the detection volume,...http://www.google.de/patents/US6094173?utm_source=gb-gplus-sharePatent US6094173 - Method and apparatus for detecting an RFID tag signal
