An active RFID indoor positioning system using analog phased array antennas

A complete active RFID indoor positioning system based on analog phased array antenna is presented. By steering the main beam of each reader´s phased array of 8 monopole elements, the angle of arrival of an active RFID tag can be obtained, from which an accurate position will be calculated by simple triangulation. To deal with multiple tag applications, CSMA-CD access mechanism is adopted to avoid collision between tags. Multipath effect has been accommodated using effective data filtering techniques. The position accuracy has been demonstrated as high as +/-1m in an indoor environment even when incoming signal is blocked by nearby obstacles.